diff --git a/TEST_MAPPING b/TEST_MAPPING
deleted file mode 100644
index da7fca1..0000000
--- a/TEST_MAPPING
+++ /dev/null
@@ -1,66 +0,0 @@
-{
-  "presubmit": [
-    {
-      "name": "adbd_test"
-    },
-    {
-      "name": "adb_crypto_test"
-    },
-    {
-      "name": "adb_pairing_auth_test"
-    },
-    {
-      "name": "adb_pairing_connection_test"
-    },
-    {
-      "name": "adb_tls_connection_test"
-    },
-    {
-      "name": "CtsFsMgrTestCases"
-    },
-    {
-      "name": "CtsInitTestCases"
-    },
-    {
-      "name": "debuggerd_test"
-    },
-    {
-      "name": "fs_mgr_vendor_overlay_test"
-    },
-    {
-      "name": "init_kill_services_test"
-    },
-    {
-      "name": "libpackagelistparser_test"
-    },
-    {
-      "name": "libcutils_test"
-    },
-    {
-      "name": "libmodprobe_tests"
-    },
-    {
-      "name": "libprocinfo_test"
-    },
-    {
-      "name": "libutils_test"
-    },
-    {
-      "name": "memunreachable_test"
-    },
-    {
-      "name": "memunreachable_unit_test"
-    },
-    {
-      "name": "memunreachable_binder_test"
-    },
-    {
-      "name": "propertyinfoserializer_tests"
-    }
-  ],
-  "imports": [
-    {
-      "path": "frameworks/base/tests/StagedInstallTest"
-    }
-  ]
-}
diff --git a/debuggerd/Android.bp b/debuggerd/Android.bp
index d7e8f32..9ca0eba 100644
--- a/debuggerd/Android.bp
+++ b/debuggerd/Android.bp
@@ -13,6 +13,7 @@
         "-Wno-unused-function",
         "-Wno-nullability-completeness",
         "-Os",
+        "-fno-finite-loops",
     ],
 
     local_include_dirs: ["include"],
@@ -209,6 +210,9 @@
         "libcutils",
         "liblog",
     ],
+    runtime_libs: [
+        "libdexfile",           // libdexfile_support dependency
+    ],
 
     whole_static_libs: [
         "libasync_safe",
@@ -224,11 +228,17 @@
             exclude_static_libs: [
                 "libdexfile_support",
             ],
+            exclude_runtime_libs: [
+                "libdexfile",
+            ],
         },
         vendor_ramdisk: {
             exclude_static_libs: [
                 "libdexfile_support",
             ],
+            exclude_runtime_libs: [
+                "libdexfile",
+            ],
         },
     },
 
diff --git a/debuggerd/OWNERS b/debuggerd/OWNERS
index bfeedca..6f7e4a3 100644
--- a/debuggerd/OWNERS
+++ b/debuggerd/OWNERS
@@ -1,2 +1 @@
 cferris@google.com
-jmgao@google.com
diff --git a/debuggerd/TEST_MAPPING b/debuggerd/TEST_MAPPING
new file mode 100644
index 0000000..d5327db
--- /dev/null
+++ b/debuggerd/TEST_MAPPING
@@ -0,0 +1,7 @@
+{
+  "presubmit": [
+    {
+      "name": "debuggerd_test"
+    }
+  ]
+}
diff --git a/debuggerd/debuggerd.cpp b/debuggerd/debuggerd.cpp
index 360ea95..e20e8d9 100644
--- a/debuggerd/debuggerd.cpp
+++ b/debuggerd/debuggerd.cpp
@@ -93,8 +93,18 @@
     errx(1, "process %d is a zombie", pid);
   }
 
-  if (kill(pid, 0) != 0) {
-    err(1, "cannot send signal to process %d", pid);
+  // Send a signal to the main thread pid, not a side thread. The signal
+  // handler always sets the crashing tid to the main thread pid when sent this
+  // signal. This is to avoid a problem where the signal is sent to a process,
+  // but happens on a side thread and the intercept mismatches since it
+  // is looking for the main thread pid, not the tid of this random thread.
+  // See b/194346289 for extra details.
+  if (kill(proc_info.pid, 0) != 0) {
+    if (pid == proc_info.pid) {
+      err(1, "cannot send signal to process %d", pid);
+    } else {
+      err(1, "cannot send signal to main thread %d (requested thread %d)", proc_info.pid, pid);
+    }
   }
 
   unique_fd piperead, pipewrite;
@@ -103,9 +113,13 @@
   }
 
   std::thread redirect_thread = spawn_redirect_thread(std::move(piperead));
-  if (!debuggerd_trigger_dump(pid, dump_type, 0, std::move(pipewrite))) {
+  if (!debuggerd_trigger_dump(proc_info.pid, dump_type, 0, std::move(pipewrite))) {
     redirect_thread.join();
-    errx(1, "failed to dump process %d", pid);
+    if (pid == proc_info.pid) {
+      errx(1, "failed to dump process %d", pid);
+    } else {
+      errx(1, "failed to dump main thread %d (requested thread %d)", proc_info.pid, pid);
+    }
   }
 
   redirect_thread.join();
diff --git a/debuggerd/debuggerd_test.cpp b/debuggerd/debuggerd_test.cpp
index abda071..68c9aca 100644
--- a/debuggerd/debuggerd_test.cpp
+++ b/debuggerd/debuggerd_test.cpp
@@ -961,6 +961,44 @@
   ASSERT_MATCH(result, R"(Abort message: 'x{4045}')");
 }
 
+TEST_F(CrasherTest, abort_message_newline_trimmed) {
+  int intercept_result;
+  unique_fd output_fd;
+  StartProcess([]() {
+    android_set_abort_message("Message with a newline.\n");
+    abort();
+  });
+  StartIntercept(&output_fd);
+  FinishCrasher();
+  AssertDeath(SIGABRT);
+  FinishIntercept(&intercept_result);
+
+  ASSERT_EQ(1, intercept_result) << "tombstoned reported failure";
+
+  std::string result;
+  ConsumeFd(std::move(output_fd), &result);
+  ASSERT_MATCH(result, R"(Abort message: 'Message with a newline.')");
+}
+
+TEST_F(CrasherTest, abort_message_multiple_newlines_trimmed) {
+  int intercept_result;
+  unique_fd output_fd;
+  StartProcess([]() {
+    android_set_abort_message("Message with multiple newlines.\n\n\n\n\n");
+    abort();
+  });
+  StartIntercept(&output_fd);
+  FinishCrasher();
+  AssertDeath(SIGABRT);
+  FinishIntercept(&intercept_result);
+
+  ASSERT_EQ(1, intercept_result) << "tombstoned reported failure";
+
+  std::string result;
+  ConsumeFd(std::move(output_fd), &result);
+  ASSERT_MATCH(result, R"(Abort message: 'Message with multiple newlines.')");
+}
+
 TEST_F(CrasherTest, abort_message_backtrace) {
   int intercept_result;
   unique_fd output_fd;
@@ -1825,3 +1863,204 @@
   ASSERT_TRUE(android::base::ReadFdToString(output_fd, &output));
   ASSERT_EQ("foo", output);
 }
+
+// Verify that when an intercept is present for the main thread, and the signal
+// is received on a different thread, the intercept still works.
+TEST_F(CrasherTest, intercept_for_main_thread_signal_on_side_thread) {
+  StartProcess([]() {
+    std::thread thread([]() {
+      // Raise the signal on the side thread.
+      raise_debugger_signal(kDebuggerdNativeBacktrace);
+    });
+    thread.join();
+    _exit(0);
+  });
+
+  unique_fd output_fd;
+  StartIntercept(&output_fd, kDebuggerdNativeBacktrace);
+  FinishCrasher();
+  AssertDeath(0);
+
+  int intercept_result;
+  FinishIntercept(&intercept_result);
+  ASSERT_EQ(1, intercept_result) << "tombstoned reported failure";
+
+  std::string result;
+  ConsumeFd(std::move(output_fd), &result);
+  ASSERT_BACKTRACE_FRAME(result, "raise_debugger_signal");
+}
+
+static std::string format_pointer(uintptr_t ptr) {
+#if defined(__LP64__)
+  return android::base::StringPrintf("%08x'%08x", static_cast<uint32_t>(ptr >> 32),
+                                     static_cast<uint32_t>(ptr & 0xffffffff));
+#else
+  return android::base::StringPrintf("%08x", static_cast<uint32_t>(ptr & 0xffffffff));
+#endif
+}
+
+static std::string format_pointer(void* ptr) {
+  return format_pointer(reinterpret_cast<uintptr_t>(ptr));
+}
+
+static std::string format_full_pointer(uintptr_t ptr) {
+#if defined(__LP64__)
+  return android::base::StringPrintf("%016" PRIx64, ptr);
+#else
+  return android::base::StringPrintf("%08x", ptr);
+#endif
+}
+
+static std::string format_full_pointer(void* ptr) {
+  return format_full_pointer(reinterpret_cast<uintptr_t>(ptr));
+}
+
+__attribute__((__noinline__)) int crash_call(uintptr_t ptr) {
+  int* crash_ptr = reinterpret_cast<int*>(ptr);
+  *crash_ptr = 1;
+  return *crash_ptr;
+}
+
+// Verify that a fault address before the first map is properly handled.
+TEST_F(CrasherTest, fault_address_before_first_map) {
+  StartProcess([]() {
+    ASSERT_EQ(0, crash_call(0x1024));
+    _exit(0);
+  });
+
+  unique_fd output_fd;
+  StartIntercept(&output_fd);
+  FinishCrasher();
+  AssertDeath(SIGSEGV);
+
+  int intercept_result;
+  FinishIntercept(&intercept_result);
+  ASSERT_EQ(1, intercept_result) << "tombstoned reported failure";
+
+  std::string result;
+  ConsumeFd(std::move(output_fd), &result);
+  ASSERT_MATCH(result, R"(signal 11 \(SIGSEGV\), code 1 \(SEGV_MAPERR\), fault addr 0x1024)");
+
+  ASSERT_MATCH(result, R"(\nmemory map \(.*\):\n)");
+
+  std::string match_str = android::base::StringPrintf(
+      R"(memory map .*:\n--->Fault address falls at %s before any mapped regions\n    )",
+      format_pointer(0x1024).c_str());
+  ASSERT_MATCH(result, match_str);
+}
+
+// Verify that a fault address after the last map is properly handled.
+TEST_F(CrasherTest, fault_address_after_last_map) {
+  uintptr_t crash_uptr = untag_address(UINTPTR_MAX - 15);
+  StartProcess([crash_uptr]() {
+    ASSERT_EQ(0, crash_call(crash_uptr));
+    _exit(0);
+  });
+
+  unique_fd output_fd;
+  StartIntercept(&output_fd);
+  FinishCrasher();
+  AssertDeath(SIGSEGV);
+
+  int intercept_result;
+  FinishIntercept(&intercept_result);
+  ASSERT_EQ(1, intercept_result) << "tombstoned reported failure";
+
+  std::string result;
+  ConsumeFd(std::move(output_fd), &result);
+
+  std::string match_str = R"(signal 11 \(SIGSEGV\), code 1 \(SEGV_MAPERR\), fault addr )";
+  match_str += android::base::StringPrintf("0x%" PRIxPTR, crash_uptr);
+  ASSERT_MATCH(result, match_str);
+
+  ASSERT_MATCH(result, R"(\nmemory map \(.*\): \(fault address prefixed with --->)\n)");
+
+  // Assumes that the open files section comes after the map section.
+  // If that assumption changes, the regex below needs to change.
+  match_str = android::base::StringPrintf(
+      R"(\n--->Fault address falls at %s after any mapped regions\n\nopen files:)",
+      format_pointer(crash_uptr).c_str());
+  ASSERT_MATCH(result, match_str);
+}
+
+// Verify that a fault address between maps is properly handled.
+TEST_F(CrasherTest, fault_address_between_maps) {
+  // Create a map before the fork so it will be present in the child.
+  void* start_ptr =
+      mmap(nullptr, 3 * getpagesize(), PROT_READ | PROT_WRITE, MAP_ANONYMOUS | MAP_PRIVATE, -1, 0);
+  ASSERT_NE(MAP_FAILED, start_ptr);
+  // Unmap the page in the middle.
+  void* middle_ptr =
+      reinterpret_cast<void*>(reinterpret_cast<uintptr_t>(start_ptr) + getpagesize());
+  ASSERT_EQ(0, munmap(middle_ptr, getpagesize()));
+
+  StartProcess([middle_ptr]() {
+    ASSERT_EQ(0, crash_call(reinterpret_cast<uintptr_t>(middle_ptr)));
+    _exit(0);
+  });
+
+  // Unmap the two maps.
+  ASSERT_EQ(0, munmap(start_ptr, getpagesize()));
+  void* end_ptr =
+      reinterpret_cast<void*>(reinterpret_cast<uintptr_t>(start_ptr) + 2 * getpagesize());
+  ASSERT_EQ(0, munmap(end_ptr, getpagesize()));
+
+  unique_fd output_fd;
+  StartIntercept(&output_fd);
+  FinishCrasher();
+  AssertDeath(SIGSEGV);
+
+  int intercept_result;
+  FinishIntercept(&intercept_result);
+  ASSERT_EQ(1, intercept_result) << "tombstoned reported failure";
+
+  std::string result;
+  ConsumeFd(std::move(output_fd), &result);
+
+  std::string match_str = R"(signal 11 \(SIGSEGV\), code 1 \(SEGV_MAPERR\), fault addr )";
+  match_str += android::base::StringPrintf("%p", middle_ptr);
+  ASSERT_MATCH(result, match_str);
+
+  ASSERT_MATCH(result, R"(\nmemory map \(.*\): \(fault address prefixed with --->)\n)");
+
+  match_str = android::base::StringPrintf(
+      R"(    %s.*\n--->Fault address falls at %s between mapped regions\n    %s)",
+      format_pointer(start_ptr).c_str(), format_pointer(middle_ptr).c_str(),
+      format_pointer(end_ptr).c_str());
+  ASSERT_MATCH(result, match_str);
+}
+
+// Verify that a fault address happens in the correct map.
+TEST_F(CrasherTest, fault_address_in_map) {
+  // Create a map before the fork so it will be present in the child.
+  void* ptr = mmap(nullptr, getpagesize(), 0, MAP_ANONYMOUS | MAP_PRIVATE, -1, 0);
+  ASSERT_NE(MAP_FAILED, ptr);
+
+  StartProcess([ptr]() {
+    ASSERT_EQ(0, crash_call(reinterpret_cast<uintptr_t>(ptr)));
+    _exit(0);
+  });
+
+  ASSERT_EQ(0, munmap(ptr, getpagesize()));
+
+  unique_fd output_fd;
+  StartIntercept(&output_fd);
+  FinishCrasher();
+  AssertDeath(SIGSEGV);
+
+  int intercept_result;
+  FinishIntercept(&intercept_result);
+  ASSERT_EQ(1, intercept_result) << "tombstoned reported failure";
+
+  std::string result;
+  ConsumeFd(std::move(output_fd), &result);
+
+  std::string match_str = R"(signal 11 \(SIGSEGV\), code 2 \(SEGV_ACCERR\), fault addr )";
+  match_str += android::base::StringPrintf("%p", ptr);
+  ASSERT_MATCH(result, match_str);
+
+  ASSERT_MATCH(result, R"(\nmemory map \(.*\): \(fault address prefixed with --->)\n)");
+
+  match_str = android::base::StringPrintf(R"(\n--->%s.*\n)", format_pointer(ptr).c_str());
+  ASSERT_MATCH(result, match_str);
+}
diff --git a/debuggerd/handler/debuggerd_handler.cpp b/debuggerd/handler/debuggerd_handler.cpp
index 375dbed..35be2bf 100644
--- a/debuggerd/handler/debuggerd_handler.cpp
+++ b/debuggerd/handler/debuggerd_handler.cpp
@@ -155,18 +155,14 @@
  * could allocate memory or hold a lock.
  */
 static void log_signal_summary(const siginfo_t* info) {
-  char thread_name[MAX_TASK_NAME_LEN + 1];  // one more for termination
-  if (prctl(PR_GET_NAME, reinterpret_cast<unsigned long>(thread_name), 0, 0, 0) != 0) {
-    strcpy(thread_name, "<name unknown>");
-  } else {
-    // short names are null terminated by prctl, but the man page
-    // implies that 16 byte names are not.
-    thread_name[MAX_TASK_NAME_LEN] = 0;
+  char main_thread_name[MAX_TASK_NAME_LEN + 1];
+  if (!get_main_thread_name(main_thread_name, sizeof(main_thread_name))) {
+    strncpy(main_thread_name, "<unknown>", sizeof(main_thread_name));
   }
 
   if (info->si_signo == BIONIC_SIGNAL_DEBUGGER) {
-    async_safe_format_log(ANDROID_LOG_INFO, "libc", "Requested dump for tid %d (%s)", __gettid(),
-                          thread_name);
+    async_safe_format_log(ANDROID_LOG_INFO, "libc", "Requested dump for pid %d (%s)", __getpid(),
+                          main_thread_name);
     return;
   }
 
@@ -181,9 +177,13 @@
     get_signal_sender(sender_desc, sizeof(sender_desc), info);
   }
 
-  char main_thread_name[MAX_TASK_NAME_LEN + 1];
-  if (!get_main_thread_name(main_thread_name, sizeof(main_thread_name))) {
-    strncpy(main_thread_name, "<unknown>", sizeof(main_thread_name));
+  char thread_name[MAX_TASK_NAME_LEN + 1];  // one more for termination
+  if (prctl(PR_GET_NAME, reinterpret_cast<unsigned long>(thread_name), 0, 0, 0) != 0) {
+    strcpy(thread_name, "<name unknown>");
+  } else {
+    // short names are null terminated by prctl, but the man page
+    // implies that 16 byte names are not.
+    thread_name[MAX_TASK_NAME_LEN] = 0;
   }
 
   async_safe_format_log(ANDROID_LOG_FATAL, "libc",
@@ -532,8 +532,13 @@
 
   log_signal_summary(info);
 
+  // If we got here due to the signal BIONIC_SIGNAL_DEBUGGER, it's possible
+  // this is not the main thread, which can cause the intercept logic to fail
+  // since the intercept is only looking for the main thread. In this case,
+  // setting crashing_tid to pid instead of the current thread's tid avoids
+  // the problem.
   debugger_thread_info thread_info = {
-      .crashing_tid = __gettid(),
+      .crashing_tid = (signal_number == BIONIC_SIGNAL_DEBUGGER) ? __getpid() : __gettid(),
       .pseudothread_tid = -1,
       .siginfo = info,
       .ucontext = context,
diff --git a/debuggerd/libdebuggerd/tombstone.cpp b/debuggerd/libdebuggerd/tombstone.cpp
index 9c01f15..ff03bcd 100644
--- a/debuggerd/libdebuggerd/tombstone.cpp
+++ b/debuggerd/libdebuggerd/tombstone.cpp
@@ -232,6 +232,12 @@
     return;
   }
 
+  // Remove any trailing newlines.
+  size_t index = length;
+  while (index > 0 && (msg[index - 1] == '\0' || msg[index - 1] == '\n')) {
+    --index;
+  }
+  msg[index] = '\0';
   _LOG(log, logtype::HEADER, "Abort message: '%s'\n", &msg[0]);
 }
 
diff --git a/debuggerd/libdebuggerd/tombstone_proto.cpp b/debuggerd/libdebuggerd/tombstone_proto.cpp
index ff12017..0c93c90 100644
--- a/debuggerd/libdebuggerd/tombstone_proto.cpp
+++ b/debuggerd/libdebuggerd/tombstone_proto.cpp
@@ -271,6 +271,13 @@
     return;
   }
 
+  // Remove any trailing newlines.
+  size_t index = msg.size();
+  while (index > 0 && (msg[index - 1] == '\0' || msg[index - 1] == '\n')) {
+    --index;
+  }
+  msg.resize(index);
+
   tombstone->set_abort_message(msg);
 }
 
diff --git a/debuggerd/libdebuggerd/tombstone_proto_to_text.cpp b/debuggerd/libdebuggerd/tombstone_proto_to_text.cpp
index 053299a..681b963 100644
--- a/debuggerd/libdebuggerd/tombstone_proto_to_text.cpp
+++ b/debuggerd/libdebuggerd/tombstone_proto_to_text.cpp
@@ -362,8 +362,13 @@
   print_thread_memory_dump(callback, tombstone, thread);
 
   CBS("");
-  CBS("memory map (%d %s):", tombstone.memory_mappings().size(),
-      tombstone.memory_mappings().size() == 1 ? "entry" : "entries");
+
+  // No memory maps to print.
+  if (tombstone.memory_mappings().empty()) {
+    CBS("No memory maps found");
+    return;
+  }
+
   int word_size = pointer_width(tombstone);
   const auto format_pointer = [word_size](uint64_t ptr) -> std::string {
     if (word_size == 8) {
@@ -375,8 +380,41 @@
     return StringPrintf("%0*" PRIx64, word_size * 2, ptr);
   };
 
+  std::string memory_map_header =
+      StringPrintf("memory map (%d %s):", tombstone.memory_mappings().size(),
+                   tombstone.memory_mappings().size() == 1 ? "entry" : "entries");
+
+  bool has_fault_address = signal_info.has_fault_address();
+  uint64_t fault_address = untag_address(signal_info.fault_address());
+  bool preamble_printed = false;
+  bool printed_fault_address_marker = false;
   for (const auto& map : tombstone.memory_mappings()) {
+    if (!preamble_printed) {
+      preamble_printed = true;
+      if (has_fault_address) {
+        if (fault_address < map.begin_address()) {
+          memory_map_header +=
+              StringPrintf("\n--->Fault address falls at %s before any mapped regions",
+                           format_pointer(fault_address).c_str());
+          printed_fault_address_marker = true;
+        } else {
+          memory_map_header += " (fault address prefixed with --->)";
+        }
+      }
+      CBS("%s", memory_map_header.c_str());
+    }
+
     std::string line = "    ";
+    if (has_fault_address && !printed_fault_address_marker) {
+      if (fault_address < map.begin_address()) {
+        printed_fault_address_marker = true;
+        CBS("--->Fault address falls at %s between mapped regions",
+            format_pointer(fault_address).c_str());
+      } else if (fault_address >= map.begin_address() && fault_address < map.end_address()) {
+        printed_fault_address_marker = true;
+        line = "--->";
+      }
+    }
     StringAppendF(&line, "%s-%s", format_pointer(map.begin_address()).c_str(),
                   format_pointer(map.end_address() - 1).c_str());
     StringAppendF(&line, " %s%s%s", map.read() ? "r" : "-", map.write() ? "w" : "-",
@@ -398,6 +436,11 @@
 
     CBS("%s", line.c_str());
   }
+
+  if (has_fault_address && !printed_fault_address_marker) {
+    CBS("--->Fault address falls at %s after any mapped regions",
+        format_pointer(fault_address).c_str());
+  }
 }
 
 void print_logs(CallbackType callback, const Tombstone& tombstone, int tail) {
diff --git a/debuggerd/tombstoned/tombstoned.cpp b/debuggerd/tombstoned/tombstoned.cpp
index 05d8050..02ded1e 100644
--- a/debuggerd/tombstoned/tombstoned.cpp
+++ b/debuggerd/tombstoned/tombstoned.cpp
@@ -448,8 +448,10 @@
     return;
   }
 
-  if (crash->output.text.fd == -1) {
-    LOG(WARNING) << "missing output fd";
+  if (crash->output.text.fd < 0) {
+    if (crash->output.text.fd == -1) {
+      LOG(WARNING) << "skipping tombstone file creation due to intercept";
+    }
     return;
   }
 
diff --git a/diagnose_usb/OWNERS b/diagnose_usb/OWNERS
index 643b448..fcd7757 100644
--- a/diagnose_usb/OWNERS
+++ b/diagnose_usb/OWNERS
@@ -1,2 +1 @@
-jmgao@google.com
 yabinc@google.com
diff --git a/fastboot/OWNERS b/fastboot/OWNERS
index a72ee07..58b2a81 100644
--- a/fastboot/OWNERS
+++ b/fastboot/OWNERS
@@ -1,4 +1,3 @@
 dvander@google.com
 hridya@google.com
 enh@google.com
-jmgao@google.com
diff --git a/fastboot/README.md b/fastboot/README.md
index c224448..d3b6c1a 100644
--- a/fastboot/README.md
+++ b/fastboot/README.md
@@ -27,16 +27,16 @@
 1. Host sends a command, which is an ascii string in a single
    packet no greater than 64 bytes.
 
-2. Client response with a single packet no greater than 64 bytes.
+2. Client response with a single packet no greater than 256 bytes.
    The first four bytes of the response are "OKAY", "FAIL", "DATA",
    or "INFO".  Additional bytes may contain an (ascii) informative
    message.
 
-   a. INFO -> the remaining 60 bytes are an informative message
+   a. INFO -> the remaining 252 bytes are an informative message
       (providing progress or diagnostic messages).  They should
       be displayed and then step #2 repeats
 
-   b. FAIL -> the requested command failed.  The remaining 60 bytes
+   b. FAIL -> the requested command failed.  The remaining 252 bytes
       of the response (if present) provide a textual failure message
       to present to the user.  Stop.
 
@@ -53,13 +53,13 @@
    until the client has sent or received the number of bytes indicated
    in the "DATA" response above.
 
-4. Client responds with a single packet no greater than 64 bytes.
+4. Client responds with a single packet no greater than 256 bytes.
    The first four bytes of the response are "OKAY", "FAIL", or "INFO".
    Similar to #2:
 
-   a. INFO -> display the remaining 60 bytes and return to #4
+   a. INFO -> display the remaining 252 bytes and return to #4
 
-   b. FAIL -> display the remaining 60 bytes (if present) as a failure
+   b. FAIL -> display the remaining 252 bytes (if present) as a failure
       reason and consider the command failed.  Stop.
 
    c. OKAY -> success.  Go to #5
diff --git a/fastboot/device/flashing.cpp b/fastboot/device/flashing.cpp
index ee0aa58..9b5d2cd 100644
--- a/fastboot/device/flashing.cpp
+++ b/fastboot/device/flashing.cpp
@@ -187,11 +187,17 @@
                                  ", build may be missing broken or missing boot_devices");
     }
 
+    std::string slot_suffix = device->GetCurrentSlot();
+    uint32_t slot_number = SlotNumberForSlotSuffix(slot_suffix);
+
+    std::string other_slot_suffix;
+    if (!slot_suffix.empty()) {
+        other_slot_suffix = (slot_suffix == "_a") ? "_b" : "_a";
+    }
+
     // If we are unable to read the existing metadata, then the super partition
     // is corrupt. In this case we reflash the whole thing using the provided
     // image.
-    std::string slot_suffix = device->GetCurrentSlot();
-    uint32_t slot_number = SlotNumberForSlotSuffix(slot_suffix);
     std::unique_ptr<LpMetadata> old_metadata = ReadMetadata(super_name, slot_number);
     if (wipe || !old_metadata) {
         if (!FlashPartitionTable(super_name, *new_metadata.get())) {
@@ -203,11 +209,15 @@
     }
 
     std::set<std::string> partitions_to_keep;
+    bool virtual_ab = android::base::GetBoolProperty("ro.virtual_ab.enabled", false);
     for (const auto& partition : old_metadata->partitions) {
         // Preserve partitions in the other slot, but not the current slot.
         std::string partition_name = GetPartitionName(partition);
-        if (!slot_suffix.empty() && GetPartitionSlotSuffix(partition_name) == slot_suffix) {
-            continue;
+        if (!slot_suffix.empty()) {
+            auto part_suffix = GetPartitionSlotSuffix(partition_name);
+            if (part_suffix == slot_suffix || (part_suffix == other_slot_suffix && virtual_ab)) {
+                continue;
+            }
         }
         std::string group_name = GetPartitionGroupName(old_metadata->groups[partition.group_index]);
         // Skip partitions in the COW group
diff --git a/fastboot/fastboot.cpp b/fastboot/fastboot.cpp
index c87ce60..532b524 100644
--- a/fastboot/fastboot.cpp
+++ b/fastboot/fastboot.cpp
@@ -941,7 +941,8 @@
         // Tries to locate top-level vbmeta from boot.img footer.
         uint64_t footer_offset = buf->sz - AVB_FOOTER_SIZE;
         if (0 != data.compare(footer_offset, AVB_FOOTER_MAGIC_LEN, AVB_FOOTER_MAGIC)) {
-            die("Failed to find AVB_FOOTER at offset: %" PRId64, footer_offset);
+            die("Failed to find AVB_FOOTER at offset: %" PRId64 ", is BOARD_AVB_ENABLE true?",
+                footer_offset);
         }
         const AvbFooter* footer = reinterpret_cast<const AvbFooter*>(data.c_str() + footer_offset);
         vbmeta_offset = be64toh(footer->vbmeta_offset);
@@ -1021,6 +1022,24 @@
         return;
     }
 
+    // If overflows and negative, it should be < buf->sz.
+    int64_t partition_size = static_cast<int64_t>(get_partition_size(partition));
+
+    if (partition_size == buf->sz) {
+        return;
+    }
+    // Some device bootloaders might not implement `fastboot getvar partition-size:boot[_a|_b]`.
+    // In this case, partition_size will be zero.
+    if (partition_size < buf->sz) {
+        fprintf(stderr,
+                "Warning: skip copying boot image avb footer"
+                " (boot partition size: %" PRId64 ", boot image size: %" PRId64 ").\n",
+                partition_size, buf->sz);
+        return;
+    }
+
+    // IMPORTANT: after the following read, we need to reset buf->fd before return (if not die).
+    // Because buf->fd will still be used afterwards.
     std::string data;
     if (!android::base::ReadFdToString(buf->fd, &data)) {
         die("Failed reading from boot");
@@ -1028,17 +1047,9 @@
 
     uint64_t footer_offset = buf->sz - AVB_FOOTER_SIZE;
     if (0 != data.compare(footer_offset, AVB_FOOTER_MAGIC_LEN, AVB_FOOTER_MAGIC)) {
+        lseek(buf->fd.get(), 0, SEEK_SET);  // IMPORTANT: resets buf->fd before return.
         return;
     }
-    // If overflows and negative, it should be < buf->sz.
-    int64_t partition_size = static_cast<int64_t>(get_partition_size(partition));
-
-    if (partition_size == buf->sz) {
-        return;
-    }
-    if (partition_size < buf->sz) {
-        die("boot partition is smaller than boot image");
-    }
 
     unique_fd fd(make_temporary_fd("boot rewriting"));
     if (!android::base::WriteStringToFd(data, fd)) {
diff --git a/fastboot/fs.cpp b/fastboot/fs.cpp
index 458a7a1..d268a50 100644
--- a/fastboot/fs.cpp
+++ b/fastboot/fs.cpp
@@ -143,6 +143,13 @@
         mke2fs_args.push_back("512");
     }
 
+    if (fsOptions & (1 << FS_OPT_CASEFOLD)) {
+        mke2fs_args.push_back("-O");
+        mke2fs_args.push_back("casefold");
+        mke2fs_args.push_back("-E");
+        mke2fs_args.push_back("encoding=utf8");
+    }
+
     mke2fs_args.push_back(fileName);
 
     std::string size_str = std::to_string(partSize / block_size);
diff --git a/fastboot/socket.cpp b/fastboot/socket.cpp
index 5a14b63..3096905 100644
--- a/fastboot/socket.cpp
+++ b/fastboot/socket.cpp
@@ -28,6 +28,10 @@
 
 #include "socket.h"
 
+#ifndef _WIN32
+#include <sys/select.h>
+#endif
+
 #include <android-base/errors.h>
 #include <android-base/stringprintf.h>
 
diff --git a/fs_mgr/Android.bp b/fs_mgr/Android.bp
index d4fc2b9..cb74ae0 100644
--- a/fs_mgr/Android.bp
+++ b/fs_mgr/Android.bp
@@ -65,6 +65,7 @@
         "-D_FILE_OFFSET_BITS=64",
     ],
     srcs: [
+        "blockdev.cpp",
         "file_wait.cpp",
         "fs_mgr.cpp",
         "fs_mgr_format.cpp",
@@ -126,10 +127,19 @@
     export_header_lib_headers: [
         "libfiemap_headers",
     ],
-    required: [
-        "e2freefrag",
-        "e2fsdroid",
-    ],
+    target: {
+        platform: {
+            required: [
+                "e2freefrag",
+                "e2fsdroid",
+            ],
+        },
+        recovery: {
+            required: [
+                "e2fsdroid.recovery",
+            ],
+        },
+    },
 }
 
 // Two variants of libfs_mgr are provided: libfs_mgr and libfs_mgr_binder.
@@ -205,7 +215,6 @@
     static_libs: [
         "libavb_user",
         "libgsid",
-        "libutils",
         "libvold_binder",
     ],
     shared_libs: [
@@ -220,6 +229,7 @@
         "liblog",
         "liblp",
         "libselinux",
+        "libutils",
     ],
     header_libs: [
         "libcutils_headers",
diff --git a/fs_mgr/TEST_MAPPING b/fs_mgr/TEST_MAPPING
index 84709b6..432aa4f 100644
--- a/fs_mgr/TEST_MAPPING
+++ b/fs_mgr/TEST_MAPPING
@@ -1,6 +1,9 @@
 {
   "presubmit": [
     {
+      "name": "CtsFsMgrTestCases"
+    },
+    {
       "name": "libdm_test"
     },
     {
@@ -13,6 +16,9 @@
       "name": "fiemap_writer_test"
     },
     {
+      "name": "fs_mgr_vendor_overlay_test"
+    },
+    {
       "name": "vts_libsnapshot_test"
     },
     {
diff --git a/fs_mgr/blockdev.cpp b/fs_mgr/blockdev.cpp
new file mode 100644
index 0000000..14b217c
--- /dev/null
+++ b/fs_mgr/blockdev.cpp
@@ -0,0 +1,159 @@
+/*
+ * Copyright (C) 2021 The Android Open Source Project
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *      http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+#include <android-base/file.h>
+#include <android-base/logging.h>
+#include <android-base/stringprintf.h>
+#include <android-base/strings.h>
+
+#include <dirent.h>
+#include <libdm/dm.h>
+#include <sys/stat.h>
+#include <sys/sysmacros.h>
+#include <sys/types.h>
+#include "blockdev.h"
+
+using android::base::Basename;
+using android::base::ErrnoError;
+using android::base::Error;
+using android::base::Result;
+using android::base::ResultError;
+using android::base::StartsWith;
+using android::base::StringPrintf;
+using android::base::unique_fd;
+using android::dm::DeviceMapper;
+
+// Return the parent device of a partition. Converts e.g. "sda26" into "sda".
+static std::string PartitionParent(const std::string& blockdev) {
+    if (blockdev.find('/') != std::string::npos) {
+        LOG(ERROR) << __func__ << ": invalid argument " << blockdev;
+        return blockdev;
+    }
+    auto dir = std::unique_ptr<DIR, decltype(&closedir)>{opendir("/sys/class/block"), closedir};
+    if (!dir) {
+        return blockdev;
+    }
+    for (struct dirent* ent = readdir(dir.get()); ent; ent = readdir(dir.get())) {
+        if (ent->d_name[0] == '.') {
+            continue;
+        }
+        std::string path = StringPrintf("/sys/class/block/%s/%s", ent->d_name, blockdev.c_str());
+        struct stat statbuf;
+        if (stat(path.c_str(), &statbuf) >= 0) {
+            return ent->d_name;
+        }
+    }
+    return blockdev;
+}
+
+// Convert a major:minor pair into a block device name.
+static std::string BlockdevName(dev_t dev) {
+    auto dir = std::unique_ptr<DIR, decltype(&closedir)>{opendir("/dev/block"), closedir};
+    if (!dir) {
+        return {};
+    }
+    for (struct dirent* ent = readdir(dir.get()); ent; ent = readdir(dir.get())) {
+        if (ent->d_name[0] == '.') {
+            continue;
+        }
+        const std::string path = std::string("/dev/block/") + ent->d_name;
+        struct stat statbuf;
+        if (stat(path.c_str(), &statbuf) >= 0 && dev == statbuf.st_rdev) {
+            return ent->d_name;
+        }
+    }
+    return {};
+}
+
+// Trim whitespace from the end of a string.
+static void rtrim(std::string& s) {
+    s.erase(s.find_last_not_of('\n') + 1, s.length());
+}
+
+// For file `file_path`, retrieve the block device backing the filesystem on
+// which the file exists and return the queue depth of the block device.
+static Result<uint32_t> BlockDeviceQueueDepth(const std::string& file_path) {
+    struct stat statbuf;
+    int res = stat(file_path.c_str(), &statbuf);
+    if (res < 0) {
+        return ErrnoError() << "stat(" << file_path << ")";
+    }
+    std::string blockdev = "/dev/block/" + BlockdevName(statbuf.st_dev);
+    LOG(DEBUG) << __func__ << ": " << file_path << " -> " << blockdev;
+    if (blockdev.empty()) {
+        const std::string err_msg =
+                StringPrintf("Failed to convert %u:%u (path %s)", major(statbuf.st_dev),
+                             minor(statbuf.st_dev), file_path.c_str());
+        return ResultError(err_msg, 0);
+    }
+    auto& dm = DeviceMapper::Instance();
+    for (;;) {
+        std::optional<std::string> child = dm.GetParentBlockDeviceByPath(blockdev);
+        if (!child) {
+            break;
+        }
+        LOG(DEBUG) << __func__ << ": " << blockdev << " -> " << *child;
+        blockdev = *child;
+    }
+    std::optional<std::string> maybe_blockdev = android::dm::ExtractBlockDeviceName(blockdev);
+    if (!maybe_blockdev) {
+        return ResultError("Failed to remove /dev/block/ prefix from " + blockdev, 0);
+    }
+    blockdev = PartitionParent(*maybe_blockdev);
+    LOG(DEBUG) << __func__ << ": "
+               << "Partition parent: " << blockdev;
+    const std::string nr_tags_path =
+            StringPrintf("/sys/class/block/%s/mq/0/nr_tags", blockdev.c_str());
+    std::string nr_tags;
+    if (!android::base::ReadFileToString(nr_tags_path, &nr_tags)) {
+        return ResultError("Failed to read " + nr_tags_path, 0);
+    }
+    rtrim(nr_tags);
+    LOG(DEBUG) << __func__ << ": " << file_path << " is backed by /dev/" << blockdev
+               << " and that block device supports queue depth " << nr_tags;
+    return strtol(nr_tags.c_str(), NULL, 0);
+}
+
+// Set 'nr_requests' of `loop_device_path` to the queue depth of the block
+// device backing `file_path`.
+Result<void> ConfigureQueueDepth(const std::string& loop_device_path,
+                                 const std::string& file_path) {
+    if (!StartsWith(loop_device_path, "/dev/")) {
+        return Error() << "Invalid argument " << loop_device_path;
+    }
+
+    const std::string loop_device_name = Basename(loop_device_path);
+
+    const Result<uint32_t> qd = BlockDeviceQueueDepth(file_path);
+    if (!qd.ok()) {
+        LOG(DEBUG) << __func__ << ": "
+                   << "BlockDeviceQueueDepth() returned " << qd.error();
+        return ResultError(qd.error());
+    }
+    const std::string nr_requests = StringPrintf("%u", *qd);
+    const std::string sysfs_path =
+            StringPrintf("/sys/class/block/%s/queue/nr_requests", loop_device_name.c_str());
+    unique_fd sysfs_fd(open(sysfs_path.c_str(), O_RDWR | O_CLOEXEC));
+    if (sysfs_fd == -1) {
+        return ErrnoError() << "Failed to open " << sysfs_path;
+    }
+
+    const int res = write(sysfs_fd.get(), nr_requests.data(), nr_requests.length());
+    if (res < 0) {
+        return ErrnoError() << "Failed to write to " << sysfs_path;
+    }
+    return {};
+}
diff --git a/fs_mgr/blockdev.h b/fs_mgr/blockdev.h
new file mode 100644
index 0000000..2c0d68a
--- /dev/null
+++ b/fs_mgr/blockdev.h
@@ -0,0 +1,21 @@
+/*
+ * Copyright (C) 2021 The Android Open Source Project
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *      http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+#include <android-base/result.h>
+#include <string>
+
+android::base::Result<void> ConfigureQueueDepth(const std::string& loop_device_path,
+                                                const std::string& file_path);
diff --git a/fs_mgr/fs_mgr.cpp b/fs_mgr/fs_mgr.cpp
index 4826ccf..5f15aad 100644
--- a/fs_mgr/fs_mgr.cpp
+++ b/fs_mgr/fs_mgr.cpp
@@ -34,11 +34,13 @@
 #include <time.h>
 #include <unistd.h>
 
+#include <array>
 #include <chrono>
 #include <functional>
 #include <map>
 #include <memory>
 #include <string>
+#include <string_view>
 #include <thread>
 #include <utility>
 #include <vector>
@@ -70,6 +72,7 @@
 #include <log/log_properties.h>
 #include <logwrap/logwrap.h>
 
+#include "blockdev.h"
 #include "fs_mgr_priv.h"
 
 #define KEY_LOC_PROP   "ro.crypto.keyfile.userdata"
@@ -101,6 +104,7 @@
 using android::base::Realpath;
 using android::base::SetProperty;
 using android::base::StartsWith;
+using android::base::StringPrintf;
 using android::base::Timer;
 using android::base::unique_fd;
 using android::dm::DeviceMapper;
@@ -2044,6 +2048,35 @@
     return 0;
 }
 
+static bool ConfigureIoScheduler(const std::string& device_path) {
+    if (!StartsWith(device_path, "/dev/")) {
+        LERROR << __func__ << ": invalid argument " << device_path;
+        return false;
+    }
+
+    const std::string iosched_path =
+            StringPrintf("/sys/block/%s/queue/scheduler", Basename(device_path).c_str());
+    unique_fd iosched_fd(open(iosched_path.c_str(), O_RDWR | O_CLOEXEC));
+    if (iosched_fd.get() == -1) {
+        PERROR << __func__ << ": failed to open " << iosched_path;
+        return false;
+    }
+
+    // Kernels before v4.1 only support 'noop'. Kernels [v4.1, v5.0) support
+    // 'noop' and 'none'. Kernels v5.0 and later only support 'none'.
+    static constexpr const std::array<std::string_view, 2> kNoScheduler = {"none", "noop"};
+
+    for (const std::string_view& scheduler : kNoScheduler) {
+        int ret = write(iosched_fd.get(), scheduler.data(), scheduler.size());
+        if (ret > 0) {
+            return true;
+        }
+    }
+
+    PERROR << __func__ << ": failed to write to " << iosched_path;
+    return false;
+}
+
 static bool InstallZramDevice(const std::string& device) {
     if (!android::base::WriteStringToFile(device, ZRAM_BACK_DEV)) {
         PERROR << "Cannot write " << device << " in: " << ZRAM_BACK_DEV;
@@ -2071,22 +2104,26 @@
 
     // Allocate loop device and attach it to file_path.
     LoopControl loop_control;
-    std::string device;
-    if (!loop_control.Attach(target_fd.get(), 5s, &device)) {
+    std::string loop_device;
+    if (!loop_control.Attach(target_fd.get(), 5s, &loop_device)) {
         return false;
     }
 
+    ConfigureIoScheduler(loop_device);
+
+    ConfigureQueueDepth(loop_device, "/");
+
     // set block size & direct IO
-    unique_fd device_fd(TEMP_FAILURE_RETRY(open(device.c_str(), O_RDWR | O_CLOEXEC)));
-    if (device_fd.get() == -1) {
-        PERROR << "Cannot open " << device;
+    unique_fd loop_fd(TEMP_FAILURE_RETRY(open(loop_device.c_str(), O_RDWR | O_CLOEXEC)));
+    if (loop_fd.get() == -1) {
+        PERROR << "Cannot open " << loop_device;
         return false;
     }
-    if (!LoopControl::EnableDirectIo(device_fd.get())) {
+    if (!LoopControl::EnableDirectIo(loop_fd.get())) {
         return false;
     }
 
-    return InstallZramDevice(device);
+    return InstallZramDevice(loop_device);
 }
 
 bool fs_mgr_swapon_all(const Fstab& fstab) {
@@ -2328,7 +2365,24 @@
         return false;
     }
 
-    auto options = "lowerdir=" + entry.lowerdir;
+    auto lowerdir = entry.lowerdir;
+    if (entry.fs_mgr_flags.overlayfs_remove_missing_lowerdir) {
+        bool removed_any = false;
+        std::vector<std::string> lowerdirs;
+        for (const auto& dir : android::base::Split(entry.lowerdir, ":")) {
+            if (access(dir.c_str(), F_OK)) {
+                PWARNING << __FUNCTION__ << "(): remove missing lowerdir '" << dir << "'";
+                removed_any = true;
+            } else {
+                lowerdirs.push_back(dir);
+            }
+        }
+        if (removed_any) {
+            lowerdir = android::base::Join(lowerdirs, ":");
+        }
+    }
+
+    auto options = "lowerdir=" + lowerdir;
     if (overlayfs_valid_result == OverlayfsValidResult::kOverrideCredsRequired) {
         options += ",override_creds=off";
     }
diff --git a/fs_mgr/fs_mgr_fstab.cpp b/fs_mgr/fs_mgr_fstab.cpp
index d0c89b9..9b6c3dd 100644
--- a/fs_mgr/fs_mgr_fstab.cpp
+++ b/fs_mgr/fs_mgr_fstab.cpp
@@ -181,6 +181,7 @@
         CheckFlag("fsverity", fs_verity);
         CheckFlag("metadata_csum", ext_meta_csum);
         CheckFlag("fscompress", fs_compress);
+        CheckFlag("overlayfs_remove_missing_lowerdir", overlayfs_remove_missing_lowerdir);
 
 #undef CheckFlag
 
@@ -413,17 +414,24 @@
     return fstab_result;
 }
 
-// Identify path to fstab file. Lookup is based on pattern
-// fstab.<fstab_suffix>, fstab.<hardware>, fstab.<hardware.platform> in
-// folders /odm/etc, vendor/etc, or /.
+// Return the path to the fstab file.  There may be multiple fstab files; the
+// one that is returned will be the first that exists of fstab.<fstab_suffix>,
+// fstab.<hardware>, and fstab.<hardware.platform>.  The fstab is searched for
+// in /odm/etc/ and /vendor/etc/, as well as in the locations where it may be in
+// the first stage ramdisk during early boot.  Previously, the first stage
+// ramdisk's copy of the fstab had to be located in the root directory, but now
+// the system/etc directory is supported too and is the preferred location.
 std::string GetFstabPath() {
     for (const char* prop : {"fstab_suffix", "hardware", "hardware.platform"}) {
         std::string suffix;
 
         if (!fs_mgr_get_boot_config(prop, &suffix)) continue;
 
-        for (const char* prefix :
-             {"/odm/etc/fstab.", "/vendor/etc/fstab.", "/fstab.", "/first_stage_ramdisk/fstab."}) {
+        for (const char* prefix : {// late-boot/post-boot locations
+                                   "/odm/etc/fstab.", "/vendor/etc/fstab.",
+                                   // early boot locations
+                                   "/system/etc/fstab.", "/first_stage_ramdisk/system/etc/fstab.",
+                                   "/fstab.", "/first_stage_ramdisk/fstab."}) {
             std::string fstab_path = prefix + suffix;
             if (access(fstab_path.c_str(), F_OK) == 0) {
                 return fstab_path;
diff --git a/fs_mgr/fs_mgr_overlayfs.cpp b/fs_mgr/fs_mgr_overlayfs.cpp
index 4d32bda..0522ac5 100644
--- a/fs_mgr/fs_mgr_overlayfs.cpp
+++ b/fs_mgr/fs_mgr_overlayfs.cpp
@@ -1133,7 +1133,7 @@
         return false;
     }
     if (!images->BackingImageExists(partition_name)) {
-        static constexpr uint64_t kMinimumSize = 16_MiB;
+        static constexpr uint64_t kMinimumSize = 64_MiB;
         static constexpr uint64_t kMaximumSize = 2_GiB;
 
         uint64_t size = std::clamp(info.size / 2, kMinimumSize, kMaximumSize);
diff --git a/fs_mgr/fs_mgr_roots.cpp b/fs_mgr/fs_mgr_roots.cpp
index fdaffbe..d275320 100644
--- a/fs_mgr/fs_mgr_roots.cpp
+++ b/fs_mgr/fs_mgr_roots.cpp
@@ -14,6 +14,7 @@
  * limitations under the License.
  */
 
+#include "android-base/file.h"
 #include "fs_mgr/roots.h"
 
 #include <sys/mount.h>
@@ -39,18 +40,26 @@
     while (true) {
         auto entry = GetEntryForMountPoint(fstab, str);
         if (entry != nullptr) return entry;
-        if (str == "/") break;
-        auto slash = str.find_last_of('/');
-        if (slash == std::string::npos) break;
-        if (slash == 0) {
-            str = "/";
-        } else {
-            str = str.substr(0, slash);
-        }
+        str = android::base::Dirname(str);
+        if (!str.compare(".") || !str.compare("/")) break;
     }
     return nullptr;
 }
 
+std::vector<FstabEntry*> GetEntriesForPath(Fstab* fstab, const std::string& path) {
+    std::vector<FstabEntry*> entries;
+    if (path.empty()) return entries;
+
+    std::string str(path);
+    while (true) {
+        entries = GetEntriesForMountPoint(fstab, str);
+        if (!entries.empty()) return entries;
+        str = android::base::Dirname(str);
+        if (!str.compare(".") || !str.compare("/")) break;
+    }
+    return entries;
+}
+
 enum class MountState {
     ERROR = -1,
     NOT_MOUNTED = 0,
@@ -71,12 +80,7 @@
     return MountState::NOT_MOUNTED;
 }
 
-bool EnsurePathMounted(Fstab* fstab, const std::string& path, const std::string& mount_pt) {
-    auto rec = GetEntryForPath(fstab, path);
-    if (rec == nullptr) {
-        LERROR << "unknown volume for path [" << path << "]";
-        return false;
-    }
+bool TryPathMount(FstabEntry* rec, const std::string& mount_pt) {
     if (rec->fs_type == "ramdisk") {
         // The ramdisk is always mounted.
         return true;
@@ -136,6 +140,21 @@
     return true;
 }
 
+bool EnsurePathMounted(Fstab* fstab, const std::string& path, const std::string& mount_point) {
+    auto entries = GetEntriesForPath(fstab, path);
+    if (entries.empty()) {
+        LERROR << "unknown volume for path [" << path << "]";
+        return false;
+    }
+
+    for (auto entry : entries) {
+        if (TryPathMount(entry, mount_point)) return true;
+    }
+
+    LERROR << "Failed to mount for path [" << path << "]";
+    return false;
+}
+
 bool EnsurePathUnmounted(Fstab* fstab, const std::string& path) {
     auto rec = GetEntryForPath(fstab, path);
     if (rec == nullptr) {
diff --git a/fs_mgr/include_fstab/fstab/fstab.h b/fs_mgr/include_fstab/fstab/fstab.h
index f33768b..9a4ed46 100644
--- a/fs_mgr/include_fstab/fstab/fstab.h
+++ b/fs_mgr/include_fstab/fstab/fstab.h
@@ -86,6 +86,7 @@
         bool fs_verity : 1;
         bool ext_meta_csum : 1;
         bool fs_compress : 1;
+        bool overlayfs_remove_missing_lowerdir : 1;
     } fs_mgr_flags = {};
 
     bool is_encryptable() const {
diff --git a/fs_mgr/libdm/dm.cpp b/fs_mgr/libdm/dm.cpp
index a5eda29..4034e30 100644
--- a/fs_mgr/libdm/dm.cpp
+++ b/fs_mgr/libdm/dm.cpp
@@ -578,34 +578,30 @@
     return std::string{spec.target_type, sizeof(spec.target_type)};
 }
 
-static bool ExtractBlockDeviceName(const std::string& path, std::string* name) {
+std::optional<std::string> ExtractBlockDeviceName(const std::string& path) {
     static constexpr std::string_view kDevBlockPrefix("/dev/block/");
     if (android::base::StartsWith(path, kDevBlockPrefix)) {
-        *name = path.substr(kDevBlockPrefix.length());
-        return true;
+        return path.substr(kDevBlockPrefix.length());
     }
-    return false;
+    return {};
 }
 
 bool DeviceMapper::IsDmBlockDevice(const std::string& path) {
-    std::string name;
-    if (!ExtractBlockDeviceName(path, &name)) {
-        return false;
-    }
-    return android::base::StartsWith(name, "dm-");
+    std::optional<std::string> name = ExtractBlockDeviceName(path);
+    return name && android::base::StartsWith(*name, "dm-");
 }
 
 std::optional<std::string> DeviceMapper::GetDmDeviceNameByPath(const std::string& path) {
-    std::string name;
-    if (!ExtractBlockDeviceName(path, &name)) {
+    std::optional<std::string> name = ExtractBlockDeviceName(path);
+    if (!name) {
         LOG(WARNING) << path << " is not a block device";
         return std::nullopt;
     }
-    if (!android::base::StartsWith(name, "dm-")) {
+    if (!android::base::StartsWith(*name, "dm-")) {
         LOG(WARNING) << path << " is not a dm device";
         return std::nullopt;
     }
-    std::string dm_name_file = "/sys/block/" + name + "/dm/name";
+    std::string dm_name_file = "/sys/block/" + *name + "/dm/name";
     std::string dm_name;
     if (!android::base::ReadFileToString(dm_name_file, &dm_name)) {
         PLOG(ERROR) << "Failed to read file " << dm_name_file;
@@ -616,16 +612,16 @@
 }
 
 std::optional<std::string> DeviceMapper::GetParentBlockDeviceByPath(const std::string& path) {
-    std::string name;
-    if (!ExtractBlockDeviceName(path, &name)) {
+    std::optional<std::string> name = ExtractBlockDeviceName(path);
+    if (!name) {
         LOG(WARNING) << path << " is not a block device";
         return std::nullopt;
     }
-    if (!android::base::StartsWith(name, "dm-")) {
+    if (!android::base::StartsWith(*name, "dm-")) {
         // Reached bottom of the device mapper stack.
         return std::nullopt;
     }
-    auto slaves_dir = "/sys/block/" + name + "/slaves";
+    auto slaves_dir = "/sys/block/" + *name + "/slaves";
     auto dir = std::unique_ptr<DIR, decltype(&closedir)>(opendir(slaves_dir.c_str()), closedir);
     if (dir == nullptr) {
         PLOG(ERROR) << "Failed to open: " << slaves_dir;
@@ -651,5 +647,61 @@
     return spec.target_type == "snapshot"s && data == "Overflow"s;
 }
 
+// Find directories in format of "/sys/block/dm-X".
+static int DmNameFilter(const dirent* de) {
+    if (android::base::StartsWith(de->d_name, "dm-")) {
+        return 1;
+    }
+    return 0;
+}
+
+std::map<std::string, std::string> DeviceMapper::FindDmPartitions() {
+    static constexpr auto DM_PATH_PREFIX = "/sys/block/";
+    dirent** namelist;
+    int n = scandir(DM_PATH_PREFIX, &namelist, DmNameFilter, alphasort);
+    if (n == -1) {
+        PLOG(ERROR) << "Failed to scan dir " << DM_PATH_PREFIX;
+        return {};
+    }
+    if (n == 0) {
+        LOG(ERROR) << "No dm block device found.";
+        free(namelist);
+        return {};
+    }
+
+    static constexpr auto DM_PATH_SUFFIX = "/dm/name";
+    static constexpr auto DEV_PATH = "/dev/block/";
+    std::map<std::string, std::string> dm_block_devices;
+    while (n--) {
+        std::string path = DM_PATH_PREFIX + std::string(namelist[n]->d_name) + DM_PATH_SUFFIX;
+        std::string content;
+        if (!android::base::ReadFileToString(path, &content)) {
+            PLOG(WARNING) << "Failed to read " << path;
+        } else {
+            std::string dm_block_name = android::base::Trim(content);
+            // AVB is using 'vroot' for the root block device but we're expecting 'system'.
+            if (dm_block_name == "vroot") {
+                dm_block_name = "system";
+            } else if (android::base::EndsWith(dm_block_name, "-verity")) {
+                auto npos = dm_block_name.rfind("-verity");
+                dm_block_name = dm_block_name.substr(0, npos);
+            } else if (!android::base::GetProperty("ro.boot.avb_version", "").empty()) {
+                // Verified Boot 1.0 doesn't add a -verity suffix. On AVB 2 devices,
+                // if DAP is enabled, then a -verity suffix must be used to
+                // differentiate between dm-linear and dm-verity devices. If we get
+                // here, we're AVB 2 and looking at a non-verity partition.
+                free(namelist[n]);
+                continue;
+            }
+
+            dm_block_devices.emplace(dm_block_name, DEV_PATH + std::string(namelist[n]->d_name));
+        }
+        free(namelist[n]);
+    }
+    free(namelist);
+
+    return dm_block_devices;
+}
+
 }  // namespace dm
 }  // namespace android
diff --git a/fs_mgr/libdm/include/libdm/dm.h b/fs_mgr/libdm/include/libdm/dm.h
index 8fcdf74..7e01b85 100644
--- a/fs_mgr/libdm/include/libdm/dm.h
+++ b/fs_mgr/libdm/include/libdm/dm.h
@@ -17,6 +17,7 @@
 #ifndef _LIBDM_DM_H_
 #define _LIBDM_DM_H_
 
+#include <dirent.h>
 #include <fcntl.h>
 #include <linux/dm-ioctl.h>
 #include <linux/kdev_t.h>
@@ -26,6 +27,7 @@
 #include <unistd.h>
 
 #include <chrono>
+#include <map>
 #include <memory>
 #include <optional>
 #include <string>
@@ -49,6 +51,10 @@
 
 static constexpr uint64_t kSectorSize = 512;
 
+// Returns `path` without /dev/block prefix if and only if `path` starts with
+// that prefix.
+std::optional<std::string> ExtractBlockDeviceName(const std::string& path);
+
 class DeviceMapper final {
   public:
     class DmBlockDevice final {
@@ -255,6 +261,12 @@
     //  * A failure occurred.
     std::optional<std::string> GetParentBlockDeviceByPath(const std::string& path);
 
+    // Iterate the content over "/sys/block/dm-x/dm/name" and find
+    // all the dm-wrapped block devices.
+    //
+    // Returns mapping <partition-name, /dev/block/dm-x>
+    std::map<std::string, std::string> FindDmPartitions();
+
   private:
     // Maximum possible device mapper targets registered in the kernel.
     // This is only used to read the list of targets from kernel so we allocate
diff --git a/fs_mgr/libsnapshot/Android.bp b/fs_mgr/libsnapshot/Android.bp
index 1c44e53..df00f45 100644
--- a/fs_mgr/libsnapshot/Android.bp
+++ b/fs_mgr/libsnapshot/Android.bp
@@ -504,3 +504,13 @@
         "inspect_cow.cpp",
     ],
 }
+
+python_library_host {
+    name: "snapshot_proto_python",
+    srcs: [
+        "android/snapshot/snapshot.proto",
+    ],
+    proto: {
+        canonical_path_from_root: false,
+    },
+}
diff --git a/fs_mgr/libsnapshot/cow_api_test.cpp b/fs_mgr/libsnapshot/cow_api_test.cpp
index ecfdefe..6066309 100644
--- a/fs_mgr/libsnapshot/cow_api_test.cpp
+++ b/fs_mgr/libsnapshot/cow_api_test.cpp
@@ -140,6 +140,85 @@
     ASSERT_TRUE(iter->Done());
 }
 
+TEST_F(CowTest, ReadWriteXor) {
+    CowOptions options;
+    options.cluster_ops = 0;
+    CowWriter writer(options);
+
+    ASSERT_TRUE(writer.Initialize(cow_->fd));
+
+    std::string data = "This is some data, believe it";
+    data.resize(options.block_size, '\0');
+
+    ASSERT_TRUE(writer.AddCopy(10, 20));
+    ASSERT_TRUE(writer.AddXorBlocks(50, data.data(), data.size(), 24, 10));
+    ASSERT_TRUE(writer.AddZeroBlocks(51, 2));
+    ASSERT_TRUE(writer.Finalize());
+
+    ASSERT_EQ(lseek(cow_->fd, 0, SEEK_SET), 0);
+
+    CowReader reader;
+    CowHeader header;
+    CowFooter footer;
+    ASSERT_TRUE(reader.Parse(cow_->fd));
+    ASSERT_TRUE(reader.GetHeader(&header));
+    ASSERT_TRUE(reader.GetFooter(&footer));
+    ASSERT_EQ(header.magic, kCowMagicNumber);
+    ASSERT_EQ(header.major_version, kCowVersionMajor);
+    ASSERT_EQ(header.minor_version, kCowVersionMinor);
+    ASSERT_EQ(header.block_size, options.block_size);
+    ASSERT_EQ(footer.op.num_ops, 4);
+
+    auto iter = reader.GetOpIter();
+    ASSERT_NE(iter, nullptr);
+    ASSERT_FALSE(iter->Done());
+    auto op = &iter->Get();
+
+    ASSERT_EQ(op->type, kCowCopyOp);
+    ASSERT_EQ(op->compression, kCowCompressNone);
+    ASSERT_EQ(op->data_length, 0);
+    ASSERT_EQ(op->new_block, 10);
+    ASSERT_EQ(op->source, 20);
+
+    StringSink sink;
+
+    iter->Next();
+    ASSERT_FALSE(iter->Done());
+    op = &iter->Get();
+
+    ASSERT_EQ(op->type, kCowXorOp);
+    ASSERT_EQ(op->compression, kCowCompressNone);
+    ASSERT_EQ(op->data_length, 4096);
+    ASSERT_EQ(op->new_block, 50);
+    ASSERT_EQ(op->source, 98314);  // 4096 * 24 + 10
+    ASSERT_TRUE(reader.ReadData(*op, &sink));
+    ASSERT_EQ(sink.stream(), data);
+
+    iter->Next();
+    ASSERT_FALSE(iter->Done());
+    op = &iter->Get();
+
+    // Note: the zero operation gets split into two blocks.
+    ASSERT_EQ(op->type, kCowZeroOp);
+    ASSERT_EQ(op->compression, kCowCompressNone);
+    ASSERT_EQ(op->data_length, 0);
+    ASSERT_EQ(op->new_block, 51);
+    ASSERT_EQ(op->source, 0);
+
+    iter->Next();
+    ASSERT_FALSE(iter->Done());
+    op = &iter->Get();
+
+    ASSERT_EQ(op->type, kCowZeroOp);
+    ASSERT_EQ(op->compression, kCowCompressNone);
+    ASSERT_EQ(op->data_length, 0);
+    ASSERT_EQ(op->new_block, 52);
+    ASSERT_EQ(op->source, 0);
+
+    iter->Next();
+    ASSERT_TRUE(iter->Done());
+}
+
 TEST_F(CowTest, CompressGz) {
     CowOptions options;
     options.cluster_ops = 0;
@@ -1034,6 +1113,54 @@
     ASSERT_FALSE(reader.Parse(cow_->fd));
 }
 
+TEST_F(CowTest, ResumeSeqOp) {
+    CowOptions options;
+    auto writer = std::make_unique<CowWriter>(options);
+    const int seq_len = 10;
+    uint32_t sequence[seq_len];
+    for (int i = 0; i < seq_len; i++) {
+        sequence[i] = i + 1;
+    }
+
+    ASSERT_TRUE(writer->Initialize(cow_->fd));
+
+    ASSERT_TRUE(writer->AddSequenceData(seq_len, sequence));
+    ASSERT_TRUE(writer->AddZeroBlocks(1, seq_len / 2));
+    ASSERT_TRUE(writer->AddLabel(1));
+    ASSERT_TRUE(writer->AddZeroBlocks(1 + seq_len / 2, 1));
+
+    ASSERT_EQ(lseek(cow_->fd, 0, SEEK_SET), 0);
+    auto reader = std::make_unique<CowReader>();
+    ASSERT_TRUE(reader->Parse(cow_->fd, 1));
+    auto itr = reader->GetRevMergeOpIter();
+    ASSERT_TRUE(itr->Done());
+
+    writer = std::make_unique<CowWriter>(options);
+    ASSERT_TRUE(writer->InitializeAppend(cow_->fd, 1));
+    ASSERT_TRUE(writer->AddZeroBlocks(1 + seq_len / 2, seq_len / 2));
+    ASSERT_TRUE(writer->Finalize());
+
+    ASSERT_EQ(lseek(cow_->fd, 0, SEEK_SET), 0);
+
+    reader = std::make_unique<CowReader>();
+    ASSERT_TRUE(reader->Parse(cow_->fd));
+
+    auto iter = reader->GetRevMergeOpIter();
+
+    uint64_t expected_block = 10;
+    while (!iter->Done() && expected_block > 0) {
+        ASSERT_FALSE(iter->Done());
+        const auto& op = iter->Get();
+
+        ASSERT_EQ(op.new_block, expected_block);
+
+        iter->Next();
+        expected_block--;
+    }
+    ASSERT_EQ(expected_block, 0);
+    ASSERT_TRUE(iter->Done());
+}
+
 TEST_F(CowTest, RevMergeOpItrTest) {
     CowOptions options;
     options.cluster_ops = 5;
diff --git a/fs_mgr/libsnapshot/cow_format.cpp b/fs_mgr/libsnapshot/cow_format.cpp
index 3085f80..8e6bec7 100644
--- a/fs_mgr/libsnapshot/cow_format.cpp
+++ b/fs_mgr/libsnapshot/cow_format.cpp
@@ -37,6 +37,8 @@
         os << "kCowLabelOp,   ";
     else if (op.type == kCowClusterOp)
         os << "kCowClusterOp  ";
+    else if (op.type == kCowXorOp)
+        os << "kCowXorOp      ";
     else if (op.type == kCowSequenceOp)
         os << "kCowSequenceOp ";
     else if (op.type == kCowFooterOp)
@@ -61,7 +63,7 @@
 int64_t GetNextOpOffset(const CowOperation& op, uint32_t cluster_ops) {
     if (op.type == kCowClusterOp) {
         return op.source;
-    } else if (op.type == kCowReplaceOp && cluster_ops == 0) {
+    } else if ((op.type == kCowReplaceOp || op.type == kCowXorOp) && cluster_ops == 0) {
         return op.data_length;
     } else {
         return 0;
@@ -93,6 +95,7 @@
 bool IsOrderedOp(const CowOperation& op) {
     switch (op.type) {
         case kCowCopyOp:
+        case kCowXorOp:
             return true;
         default:
             return false;
diff --git a/fs_mgr/libsnapshot/cow_reader.cpp b/fs_mgr/libsnapshot/cow_reader.cpp
index ace6f59..773d978 100644
--- a/fs_mgr/libsnapshot/cow_reader.cpp
+++ b/fs_mgr/libsnapshot/cow_reader.cpp
@@ -34,7 +34,11 @@
 namespace android {
 namespace snapshot {
 
-CowReader::CowReader() : fd_(-1), header_(), fd_size_(0) {}
+CowReader::CowReader()
+    : fd_(-1),
+      header_(),
+      fd_size_(0),
+      merge_op_blocks_(std::make_shared<std::vector<uint32_t>>()) {}
 
 static void SHA256(const void*, size_t, uint8_t[]) {
 #if 0
@@ -45,6 +49,23 @@
 #endif
 }
 
+std::unique_ptr<CowReader> CowReader::CloneCowReader() {
+    auto cow = std::make_unique<CowReader>();
+    cow->owned_fd_.reset();
+    cow->header_ = header_;
+    cow->footer_ = footer_;
+    cow->fd_size_ = fd_size_;
+    cow->last_label_ = last_label_;
+    cow->ops_ = ops_;
+    cow->merge_op_blocks_ = merge_op_blocks_;
+    cow->block_map_ = block_map_;
+    cow->num_total_data_ops_ = num_total_data_ops_;
+    cow->num_ordered_ops_to_merge_ = num_ordered_ops_to_merge_;
+    cow->has_seq_ops_ = has_seq_ops_;
+    cow->data_loc_ = data_loc_;
+    return cow;
+}
+
 bool CowReader::InitForMerge(android::base::unique_fd&& fd) {
     owned_fd_ = std::move(fd);
     fd_ = owned_fd_.get();
@@ -133,11 +154,14 @@
     if (!ParseOps(label)) {
         return false;
     }
+    // If we're resuming a write, we're not ready to merge
+    if (label.has_value()) return true;
     return PrepMergeOps();
 }
 
 bool CowReader::ParseOps(std::optional<uint64_t> label) {
     uint64_t pos;
+    auto data_loc = std::make_shared<std::unordered_map<uint64_t, uint64_t>>();
 
     // Skip the scratch space
     if (header_.major_version >= 2 && (header_.buffer_size > 0)) {
@@ -157,6 +181,13 @@
         // Reading a v1 version of COW which doesn't have buffer_size.
         header_.buffer_size = 0;
     }
+    uint64_t data_pos = 0;
+
+    if (header_.cluster_ops) {
+        data_pos = pos + header_.cluster_ops * sizeof(CowOperation);
+    } else {
+        data_pos = pos + sizeof(CowOperation);
+    }
 
     auto ops_buffer = std::make_shared<std::vector<CowOperation>>();
     uint64_t current_op_num = 0;
@@ -177,7 +208,11 @@
         while (current_op_num < ops_buffer->size()) {
             auto& current_op = ops_buffer->data()[current_op_num];
             current_op_num++;
+            if (current_op.type == kCowXorOp) {
+                data_loc->insert({current_op.new_block, data_pos});
+            }
             pos += sizeof(CowOperation) + GetNextOpOffset(current_op, header_.cluster_ops);
+            data_pos += current_op.data_length + GetNextDataOffset(current_op, header_.cluster_ops);
 
             if (current_op.type == kCowClusterOp) {
                 break;
@@ -268,6 +303,7 @@
 
     ops_ = ops_buffer;
     ops_->shrink_to_fit();
+    data_loc_ = data_loc;
 
     return true;
 }
@@ -606,7 +642,13 @@
             return false;
     }
 
-    CowDataStream stream(this, op.source, op.data_length);
+    uint64_t offset;
+    if (op.type == kCowXorOp) {
+        offset = data_loc_->at(op.new_block);
+    } else {
+        offset = op.source;
+    }
+    CowDataStream stream(this, offset, op.data_length);
     decompressor->set_stream(&stream);
     decompressor->set_sink(sink);
     return decompressor->Decompress(header_.block_size);
diff --git a/fs_mgr/libsnapshot/cow_writer.cpp b/fs_mgr/libsnapshot/cow_writer.cpp
index ef30e32..5ce1d3b 100644
--- a/fs_mgr/libsnapshot/cow_writer.cpp
+++ b/fs_mgr/libsnapshot/cow_writer.cpp
@@ -58,10 +58,24 @@
     return EmitRawBlocks(new_block_start, data, size);
 }
 
-bool ICowWriter::AddXorBlocks(uint32_t /*new_block_start*/, const void* /*data*/, size_t /*size*/,
-                              uint32_t /*old_block*/, uint16_t /*offset*/) {
-    LOG(ERROR) << "AddXorBlocks not yet implemented";
-    return false;
+bool ICowWriter::AddXorBlocks(uint32_t new_block_start, const void* data, size_t size,
+                              uint32_t old_block, uint16_t offset) {
+    if (size % options_.block_size != 0) {
+        LOG(ERROR) << "AddRawBlocks: size " << size << " is not a multiple of "
+                   << options_.block_size;
+        return false;
+    }
+
+    uint64_t num_blocks = size / options_.block_size;
+    uint64_t last_block = new_block_start + num_blocks - 1;
+    if (!ValidateNewBlock(last_block)) {
+        return false;
+    }
+    if (offset >= options_.block_size) {
+        LOG(ERROR) << "AddXorBlocks: offset " << offset << " is not less than "
+                   << options_.block_size;
+    }
+    return EmitXorBlocks(new_block_start, data, size, old_block, offset);
 }
 
 bool ICowWriter::AddZeroBlocks(uint64_t new_block_start, uint64_t num_blocks) {
@@ -278,13 +292,27 @@
 }
 
 bool CowWriter::EmitRawBlocks(uint64_t new_block_start, const void* data, size_t size) {
+    return EmitBlocks(new_block_start, data, size, 0, 0, kCowReplaceOp);
+}
+
+bool CowWriter::EmitXorBlocks(uint32_t new_block_start, const void* data, size_t size,
+                              uint32_t old_block, uint16_t offset) {
+    return EmitBlocks(new_block_start, data, size, old_block, offset, kCowXorOp);
+}
+
+bool CowWriter::EmitBlocks(uint64_t new_block_start, const void* data, size_t size,
+                           uint64_t old_block, uint16_t offset, uint8_t type) {
     const uint8_t* iter = reinterpret_cast<const uint8_t*>(data);
     CHECK(!merge_in_progress_);
     for (size_t i = 0; i < size / header_.block_size; i++) {
         CowOperation op = {};
-        op.type = kCowReplaceOp;
         op.new_block = new_block_start + i;
-        op.source = next_data_pos_;
+        op.type = type;
+        if (type == kCowXorOp) {
+            op.source = (old_block + i) * header_.block_size + offset;
+        } else {
+            op.source = next_data_pos_;
+        }
 
         if (compression_) {
             auto data = Compress(iter, header_.block_size);
diff --git a/fs_mgr/libsnapshot/dm_snapshot_internals.h b/fs_mgr/libsnapshot/dm_snapshot_internals.h
index ed77c15..4a36251 100644
--- a/fs_mgr/libsnapshot/dm_snapshot_internals.h
+++ b/fs_mgr/libsnapshot/dm_snapshot_internals.h
@@ -17,8 +17,9 @@
 #include <android-base/logging.h>
 #include <stdint.h>
 
+#include <limits>
 #include <optional>
-#include <vector>
+#include <unordered_set>
 
 namespace android {
 namespace snapshot {
@@ -37,21 +38,16 @@
             return;
         }
 
-        if (modified_chunks_.size() <= chunk_id) {
-            if (modified_chunks_.max_size() <= chunk_id) {
-                LOG(ERROR) << "Invalid COW size, chunk_id is too large.";
-                valid_ = false;
-                return;
-            }
-            modified_chunks_.resize(chunk_id + 1, false);
-            if (modified_chunks_.size() <= chunk_id) {
-                LOG(ERROR) << "Invalid COW size, chunk_id is too large.";
-                valid_ = false;
-                return;
-            }
+        if (chunk_id > std::numeric_limits<uint32_t>::max()) {
+            LOG(ERROR) << "Chunk exceeds maximum size: " << chunk_id;
+            valid_ = false;
+            return;
+        }
+        if (modified_chunks_.count(chunk_id) > 0) {
+            return;
         }
 
-        modified_chunks_[chunk_id] = true;
+        modified_chunks_.emplace(chunk_id);
     }
 
     std::optional<uint64_t> cow_size_bytes() const {
@@ -91,23 +87,16 @@
             return std::nullopt;
         }
 
-        uint64_t modified_chunks_count = 0;
         uint64_t cow_chunks = 0;
 
-        for (const auto& c : modified_chunks_) {
-            if (c) {
-                ++modified_chunks_count;
-            }
-        }
-
         /* disk header + padding = 1 chunk */
         cow_chunks += 1;
 
         /* snapshot modified chunks */
-        cow_chunks += modified_chunks_count;
+        cow_chunks += modified_chunks_.size();
 
         /* snapshot chunks index metadata */
-        cow_chunks += 1 + modified_chunks_count / exceptions_per_chunk;
+        cow_chunks += 1 + modified_chunks_.size() / exceptions_per_chunk;
 
         return cow_chunks;
     }
@@ -150,30 +139,8 @@
     /*
      * |modified_chunks_| is a container that keeps trace of the modified
      * chunks.
-     * Multiple options were considered when choosing the most appropriate data
-     * structure for this container. Here follows a summary of why vector<bool>
-     * has been chosen, taking as a reference a snapshot partition of 4 GiB and
-     * chunk size of 4 KiB.
-     * - std::set<uint64_t> is very space-efficient for a small number of
-     *   operations, but if the whole snapshot is changed, it would need to
-     *   store
-     *     4 GiB / 4 KiB * (64 bit / 8) = 8 MiB
-     *   just for the data, plus the additional data overhead for the red-black
-     *   tree used for data sorting (if each rb-tree element stores 3 address
-     *   and the word-aligne color, the total size grows to 32 MiB).
-     * - std::bitset<N> is not a good fit because requires a priori knowledge,
-     *   at compile time, of the bitset size.
-     * - std::vector<bool> is a special case of vector, which uses a data
-     *   compression that allows reducing the space utilization of each element
-     *   to 1 bit. In detail, this data structure is composed of a resizable
-     *   array of words, each of them representing a bitmap. On a 64 bit
-     *   device, modifying the whole 4 GiB snapshot grows this container up to
-     *     4 * GiB / 4 KiB / 64 = 64 KiB
-     *   that, even if is the same space requirement to change a single byte at
-     *   the highest address of the snapshot, is a very affordable space
-     *   requirement.
      */
-    std::vector<bool> modified_chunks_;
+    std::unordered_set<uint32_t> modified_chunks_;
 };
 
 }  // namespace snapshot
diff --git a/fs_mgr/libsnapshot/include/libsnapshot/cow_format.h b/fs_mgr/libsnapshot/include/libsnapshot/cow_format.h
index 464046b..c15682a 100644
--- a/fs_mgr/libsnapshot/include/libsnapshot/cow_format.h
+++ b/fs_mgr/libsnapshot/include/libsnapshot/cow_format.h
@@ -138,6 +138,8 @@
     // For Label operations, this is the value of the applied label.
     //
     // For Cluster operations, this is the length of the following data region
+    //
+    // For Xor operations, this is the byte location in the source image.
     uint64_t source;
 } __attribute__((packed));
 
@@ -148,6 +150,7 @@
 static constexpr uint8_t kCowZeroOp = 3;
 static constexpr uint8_t kCowLabelOp = 4;
 static constexpr uint8_t kCowClusterOp = 5;
+static constexpr uint8_t kCowXorOp = 6;
 static constexpr uint8_t kCowSequenceOp = 7;
 static constexpr uint8_t kCowFooterOp = -1;
 
diff --git a/fs_mgr/libsnapshot/include/libsnapshot/cow_reader.h b/fs_mgr/libsnapshot/include/libsnapshot/cow_reader.h
index 6c3059c..0786e82 100644
--- a/fs_mgr/libsnapshot/include/libsnapshot/cow_reader.h
+++ b/fs_mgr/libsnapshot/include/libsnapshot/cow_reader.h
@@ -136,6 +136,9 @@
 
     void CloseCowFd() { owned_fd_ = {}; }
 
+    // Creates a clone of the current CowReader without the file handlers
+    std::unique_ptr<CowReader> CloneCowReader();
+
   private:
     bool ParseOps(std::optional<uint64_t> label);
     bool PrepMergeOps();
@@ -153,6 +156,7 @@
     uint64_t num_total_data_ops_;
     uint64_t num_ordered_ops_to_merge_;
     bool has_seq_ops_;
+    std::shared_ptr<std::unordered_map<uint64_t, uint64_t>> data_loc_;
 };
 
 }  // namespace snapshot
diff --git a/fs_mgr/libsnapshot/include/libsnapshot/cow_writer.h b/fs_mgr/libsnapshot/include/libsnapshot/cow_writer.h
index 4a807fb..e17b5c6 100644
--- a/fs_mgr/libsnapshot/include/libsnapshot/cow_writer.h
+++ b/fs_mgr/libsnapshot/include/libsnapshot/cow_writer.h
@@ -86,6 +86,8 @@
   protected:
     virtual bool EmitCopy(uint64_t new_block, uint64_t old_block) = 0;
     virtual bool EmitRawBlocks(uint64_t new_block_start, const void* data, size_t size) = 0;
+    virtual bool EmitXorBlocks(uint32_t new_block_start, const void* data, size_t size,
+                               uint32_t old_block, uint16_t offset) = 0;
     virtual bool EmitZeroBlocks(uint64_t new_block_start, uint64_t num_blocks) = 0;
     virtual bool EmitLabel(uint64_t label) = 0;
     virtual bool EmitSequenceData(size_t num_ops, const uint32_t* data) = 0;
@@ -122,6 +124,8 @@
   protected:
     virtual bool EmitCopy(uint64_t new_block, uint64_t old_block) override;
     virtual bool EmitRawBlocks(uint64_t new_block_start, const void* data, size_t size) override;
+    virtual bool EmitXorBlocks(uint32_t new_block_start, const void* data, size_t size,
+                               uint32_t old_block, uint16_t offset) override;
     virtual bool EmitZeroBlocks(uint64_t new_block_start, uint64_t num_blocks) override;
     virtual bool EmitLabel(uint64_t label) override;
     virtual bool EmitSequenceData(size_t num_ops, const uint32_t* data) override;
@@ -129,6 +133,8 @@
   private:
     bool EmitCluster();
     bool EmitClusterIfNeeded();
+    bool EmitBlocks(uint64_t new_block_start, const void* data, size_t size, uint64_t old_block,
+                    uint16_t offset, uint8_t type);
     void SetupHeaders();
     bool ParseOptions();
     bool OpenForWrite();
diff --git a/fs_mgr/libsnapshot/include/libsnapshot/mock_snapshot_writer.h b/fs_mgr/libsnapshot/include/libsnapshot/mock_snapshot_writer.h
index 0457986..3655c01 100644
--- a/fs_mgr/libsnapshot/include/libsnapshot/mock_snapshot_writer.h
+++ b/fs_mgr/libsnapshot/include/libsnapshot/mock_snapshot_writer.h
@@ -36,6 +36,8 @@
 
     MOCK_METHOD(bool, EmitCopy, (uint64_t, uint64_t), (override));
     MOCK_METHOD(bool, EmitRawBlocks, (uint64_t, const void*, size_t), (override));
+    MOCK_METHOD(bool, EmitXorBlocks, (uint32_t, const void*, size_t, uint32_t, uint16_t),
+                (override));
     MOCK_METHOD(bool, EmitZeroBlocks, (uint64_t, uint64_t), (override));
     MOCK_METHOD(bool, EmitLabel, (uint64_t), (override));
     MOCK_METHOD(bool, EmitSequenceData, (size_t, const uint32_t*), (override));
diff --git a/fs_mgr/libsnapshot/include/libsnapshot/snapshot.h b/fs_mgr/libsnapshot/include/libsnapshot/snapshot.h
index e60da31..d9a0cd9 100644
--- a/fs_mgr/libsnapshot/include/libsnapshot/snapshot.h
+++ b/fs_mgr/libsnapshot/include/libsnapshot/snapshot.h
@@ -399,6 +399,7 @@
     FRIEND_TEST(SnapshotTest, MergeFailureCode);
     FRIEND_TEST(SnapshotTest, NoMergeBeforeReboot);
     FRIEND_TEST(SnapshotTest, UpdateBootControlHal);
+    FRIEND_TEST(SnapshotUpdateTest, AddPartition);
     FRIEND_TEST(SnapshotUpdateTest, DaemonTransition);
     FRIEND_TEST(SnapshotUpdateTest, DataWipeAfterRollback);
     FRIEND_TEST(SnapshotUpdateTest, DataWipeRollbackInRecovery);
diff --git a/fs_mgr/libsnapshot/include/libsnapshot/snapshot_writer.h b/fs_mgr/libsnapshot/include/libsnapshot/snapshot_writer.h
index c00dafa..b09e1ae 100644
--- a/fs_mgr/libsnapshot/include/libsnapshot/snapshot_writer.h
+++ b/fs_mgr/libsnapshot/include/libsnapshot/snapshot_writer.h
@@ -74,6 +74,8 @@
   protected:
     bool EmitCopy(uint64_t new_block, uint64_t old_block) override;
     bool EmitRawBlocks(uint64_t new_block_start, const void* data, size_t size) override;
+    bool EmitXorBlocks(uint32_t new_block_start, const void* data, size_t size, uint32_t old_block,
+                       uint16_t offset) override;
     bool EmitZeroBlocks(uint64_t new_block_start, uint64_t num_blocks) override;
     bool EmitLabel(uint64_t label) override;
     bool EmitSequenceData(size_t num_ops, const uint32_t* data) override;
@@ -102,6 +104,8 @@
   protected:
     bool EmitRawBlocks(uint64_t new_block_start, const void* data, size_t size) override;
     bool EmitZeroBlocks(uint64_t new_block_start, uint64_t num_blocks) override;
+    bool EmitXorBlocks(uint32_t new_block_start, const void* data, size_t size, uint32_t old_block,
+                       uint16_t offset) override;
     bool EmitCopy(uint64_t new_block, uint64_t old_block) override;
     bool EmitLabel(uint64_t label) override;
     bool EmitSequenceData(size_t num_ops, const uint32_t* data) override;
diff --git a/fs_mgr/libsnapshot/scripts/Android.bp b/fs_mgr/libsnapshot/scripts/Android.bp
new file mode 100644
index 0000000..3e09cc3
--- /dev/null
+++ b/fs_mgr/libsnapshot/scripts/Android.bp
@@ -0,0 +1,26 @@
+//
+// Copyright (C) 2021 The Android Open Source Project
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//      http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+//
+
+python_binary_host {
+    name: "dump_snapshot_proto",
+    main: "dump_snapshot_proto.py",
+    srcs: [
+        "dump_snapshot_proto.py",
+    ],
+    libs: [
+        "snapshot_proto_python",
+    ],
+}
diff --git a/fs_mgr/libsnapshot/scripts/dump_snapshot_proto.py b/fs_mgr/libsnapshot/scripts/dump_snapshot_proto.py
new file mode 100644
index 0000000..566108d
--- /dev/null
+++ b/fs_mgr/libsnapshot/scripts/dump_snapshot_proto.py
@@ -0,0 +1,39 @@
+# Copyright (C) 2021 The Android Open Source Project
+#
+# Licensed under the Apache License, Version 2.0 (the "License");
+# you may not use this file except in compliance with the License.
+# You may obtain a copy of the License at
+#
+#      http://www.apache.org/licenses/LICENSE-2.0
+#
+# Unless required by applicable law or agreed to in writing, software
+# distributed under the License is distributed on an "AS IS" BASIS,
+# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+# See the License for the specific language governing permissions and
+# limitations under the License.
+
+import argparse
+
+from android.snapshot import snapshot_pb2
+
+def main():
+    parser = argparse.ArgumentParser()
+    parser.add_argument('type', type = str, help = 'Type (snapshot or update)')
+    parser.add_argument('file', type = str, help = 'Input file')
+    args = parser.parse_args()
+
+    with open(args.file, 'rb') as fp:
+        data = fp.read()
+
+    if args.type == 'snapshot':
+        msg = snapshot_pb2.SnapshotStatus()
+    elif args.type == 'update':
+        msg = snapshot_pb2.SnapshotUpdateStatus()
+    else:
+        raise Exception('Unknown proto type')
+
+    msg.ParseFromString(data)
+    print(msg)
+
+if __name__ == '__main__':
+    main()
diff --git a/fs_mgr/libsnapshot/snapshot.cpp b/fs_mgr/libsnapshot/snapshot.cpp
index c3db32e..52324ba 100644
--- a/fs_mgr/libsnapshot/snapshot.cpp
+++ b/fs_mgr/libsnapshot/snapshot.cpp
@@ -2087,14 +2087,18 @@
     if (live_snapshot_status->compression_enabled()) {
         // Get the source device (eg the view of the partition from before it was resized).
         std::string source_device_path;
-        if (!MapSourceDevice(lock, params.GetPartitionName(), remaining_time,
-                             &source_device_path)) {
-            LOG(ERROR) << "Could not map source device for: " << cow_name;
-            return false;
-        }
+        if (live_snapshot_status->old_partition_size() > 0) {
+            if (!MapSourceDevice(lock, params.GetPartitionName(), remaining_time,
+                                 &source_device_path)) {
+                LOG(ERROR) << "Could not map source device for: " << cow_name;
+                return false;
+            }
 
-        auto source_device = GetSourceDeviceName(params.GetPartitionName());
-        created_devices.EmplaceBack<AutoUnmapDevice>(&dm, source_device);
+            auto source_device = GetSourceDeviceName(params.GetPartitionName());
+            created_devices.EmplaceBack<AutoUnmapDevice>(&dm, source_device);
+        } else {
+            source_device_path = base_path;
+        }
 
         if (!WaitForDevice(source_device_path, remaining_time)) {
             return false;
diff --git a/fs_mgr/libsnapshot/snapshot_reader.cpp b/fs_mgr/libsnapshot/snapshot_reader.cpp
index 5ee8e25..6546c2a 100644
--- a/fs_mgr/libsnapshot/snapshot_reader.cpp
+++ b/fs_mgr/libsnapshot/snapshot_reader.cpp
@@ -221,7 +221,7 @@
 
   private:
     size_t ignore_start_;
-    char discard_[4096];
+    char discard_[BLOCK_SZ];
 };
 
 ssize_t CompressedSnapshotReader::ReadBlock(uint64_t chunk, IByteSink* sink, size_t start_offset,
@@ -277,6 +277,29 @@
             errno = EIO;
             return -1;
         }
+    } else if (op->type == kCowXorOp) {
+        borrowed_fd fd = GetSourceFd();
+        if (fd < 0) {
+            // GetSourceFd sets errno.
+            return -1;
+        }
+
+        off64_t offset = op->source + start_offset;
+        char data[BLOCK_SZ];
+        if (!android::base::ReadFullyAtOffset(fd, &data, bytes_to_read, offset)) {
+            PLOG(ERROR) << "read " << *source_device_;
+            // ReadFullyAtOffset sets errno.
+            return -1;
+        }
+        PartialSink partial_sink(buffer, bytes_to_read, start_offset);
+        if (!cow_->ReadData(*op, &partial_sink)) {
+            LOG(ERROR) << "CompressedSnapshotReader failed to read xor op";
+            errno = EIO;
+            return -1;
+        }
+        for (size_t i = 0; i < bytes_to_read; i++) {
+            ((char*)buffer)[i] ^= data[i];
+        }
     } else {
         LOG(ERROR) << "CompressedSnapshotReader unknown op type: " << uint32_t(op->type);
         errno = EINVAL;
diff --git a/fs_mgr/libsnapshot/snapshot_reader_test.cpp b/fs_mgr/libsnapshot/snapshot_reader_test.cpp
index 9373059..078f16e 100644
--- a/fs_mgr/libsnapshot/snapshot_reader_test.cpp
+++ b/fs_mgr/libsnapshot/snapshot_reader_test.cpp
@@ -63,7 +63,9 @@
 
     void WriteCow(ISnapshotWriter* writer) {
         std::string new_block = MakeNewBlockString();
+        std::string xor_block = MakeXorBlockString();
 
+        ASSERT_TRUE(writer->AddXorBlocks(1, xor_block.data(), xor_block.size(), 0, kBlockSize / 2));
         ASSERT_TRUE(writer->AddCopy(3, 0));
         ASSERT_TRUE(writer->AddRawBlocks(5, new_block.data(), new_block.size()));
         ASSERT_TRUE(writer->AddZeroBlocks(7, 2));
@@ -75,7 +77,7 @@
         ASSERT_NE(reader, nullptr);
 
         // Test that unchanged blocks are not modified.
-        std::unordered_set<size_t> changed_blocks = {3, 5, 7, 8};
+        std::unordered_set<size_t> changed_blocks = {1, 3, 5, 7, 8};
         for (size_t i = 0; i < kBlockCount; i++) {
             if (changed_blocks.count(i)) {
                 continue;
@@ -88,6 +90,17 @@
         }
 
         // Test that we can read back our modified blocks.
+        std::string data(kBlockSize, 0);
+        std::string offsetblock = base_blocks_[0].substr(kBlockSize / 2, kBlockSize / 2) +
+                                  base_blocks_[1].substr(0, kBlockSize / 2);
+        ASSERT_EQ(offsetblock.size(), kBlockSize);
+        ASSERT_EQ(reader->Seek(1 * kBlockSize, SEEK_SET), 1 * kBlockSize);
+        ASSERT_EQ(reader->Read(data.data(), data.size()), kBlockSize);
+        for (int i = 0; i < 100; i++) {
+            data[i] = (char)~(data[i]);
+        }
+        ASSERT_EQ(data, offsetblock);
+
         std::string block(kBlockSize, 0);
         ASSERT_EQ(reader->Seek(3 * kBlockSize, SEEK_SET), 3 * kBlockSize);
         ASSERT_EQ(reader->Read(block.data(), block.size()), kBlockSize);
@@ -141,6 +154,12 @@
         return new_block;
     }
 
+    std::string MakeXorBlockString() {
+        std::string data(100, -1);
+        data.resize(kBlockSize, 0);
+        return data;
+    }
+
     std::unique_ptr<TemporaryFile> base_;
     std::unique_ptr<TemporaryFile> cow_;
     std::vector<std::string> base_blocks_;
diff --git a/fs_mgr/libsnapshot/snapshot_test.cpp b/fs_mgr/libsnapshot/snapshot_test.cpp
index b2203fe..057e5b19a 100644
--- a/fs_mgr/libsnapshot/snapshot_test.cpp
+++ b/fs_mgr/libsnapshot/snapshot_test.cpp
@@ -963,7 +963,7 @@
     }
 
     AssertionResult UnmapAll() {
-        for (const auto& name : {"sys", "vnd", "prd"}) {
+        for (const auto& name : {"sys", "vnd", "prd", "dlkm"}) {
             if (!dm_.DeleteDeviceIfExists(name + "_a"s)) {
                 return AssertionFailure() << "Cannot unmap " << name << "_a";
             }
@@ -2073,6 +2073,70 @@
     ASSERT_LT(res.required_size(), 40_MiB);
 }
 
+TEST_F(SnapshotUpdateTest, AddPartition) {
+    // OTA client blindly unmaps all partitions that are possibly mapped.
+    for (const auto& name : {"sys_b", "vnd_b", "prd_b"}) {
+        ASSERT_TRUE(sm->UnmapUpdateSnapshot(name));
+    }
+
+    group_->add_partition_names("dlkm");
+
+    auto dlkm = manifest_.add_partitions();
+    dlkm->set_partition_name("dlkm");
+    dlkm->set_estimate_cow_size(2_MiB);
+    SetSize(dlkm, 3_MiB);
+
+    // Grow all partitions. Set |prd| large enough that |sys| and |vnd|'s COWs
+    // fit in super, but not |prd|.
+    constexpr uint64_t partition_size = 3788_KiB;
+    SetSize(sys_, partition_size);
+    SetSize(vnd_, partition_size);
+    SetSize(prd_, partition_size);
+    SetSize(dlkm, partition_size);
+
+    AddOperationForPartitions({sys_, vnd_, prd_, dlkm});
+
+    // Execute the update.
+    ASSERT_TRUE(sm->BeginUpdate());
+    ASSERT_TRUE(sm->CreateUpdateSnapshots(manifest_));
+
+    // Write some data to target partitions.
+    for (const auto& name : {"sys_b", "vnd_b", "prd_b", "dlkm_b"}) {
+        ASSERT_TRUE(WriteSnapshotAndHash(name));
+    }
+
+    // Assert that source partitions aren't affected.
+    for (const auto& name : {"sys_a", "vnd_a", "prd_a"}) {
+        ASSERT_TRUE(IsPartitionUnchanged(name));
+    }
+
+    ASSERT_TRUE(sm->FinishedSnapshotWrites(false));
+
+    // Simulate shutting down the device.
+    ASSERT_TRUE(UnmapAll());
+
+    // After reboot, init does first stage mount.
+    auto init = NewManagerForFirstStageMount("_b");
+    ASSERT_NE(init, nullptr);
+    ASSERT_TRUE(init->NeedSnapshotsInFirstStageMount());
+    ASSERT_TRUE(init->CreateLogicalAndSnapshotPartitions("super", snapshot_timeout_));
+
+    // Check that the target partitions have the same content.
+    for (const auto& name : {"sys_b", "vnd_b", "prd_b", "dlkm_b"}) {
+        ASSERT_TRUE(IsPartitionUnchanged(name));
+    }
+
+    // Initiate the merge and wait for it to be completed.
+    ASSERT_TRUE(init->InitiateMerge());
+    ASSERT_EQ(UpdateState::MergeCompleted, init->ProcessUpdateState());
+
+    // Check that the target partitions have the same content after the merge.
+    for (const auto& name : {"sys_b", "vnd_b", "prd_b", "dlkm_b"}) {
+        ASSERT_TRUE(IsPartitionUnchanged(name))
+                << "Content of " << name << " changes after the merge";
+    }
+}
+
 class AutoKill final {
   public:
     explicit AutoKill(pid_t pid) : pid_(pid) {}
diff --git a/fs_mgr/libsnapshot/snapshot_writer.cpp b/fs_mgr/libsnapshot/snapshot_writer.cpp
index 34b3e87..3eda08e 100644
--- a/fs_mgr/libsnapshot/snapshot_writer.cpp
+++ b/fs_mgr/libsnapshot/snapshot_writer.cpp
@@ -106,6 +106,11 @@
     return cow_->AddRawBlocks(new_block_start, data, size);
 }
 
+bool CompressedSnapshotWriter::EmitXorBlocks(uint32_t new_block_start, const void* data,
+                                             size_t size, uint32_t old_block, uint16_t offset) {
+    return cow_->AddXorBlocks(new_block_start, data, size, old_block, offset);
+}
+
 bool CompressedSnapshotWriter::EmitZeroBlocks(uint64_t new_block_start, uint64_t num_blocks) {
     return cow_->AddZeroBlocks(new_block_start, num_blocks);
 }
@@ -157,6 +162,11 @@
     return true;
 }
 
+bool OnlineKernelSnapshotWriter::EmitXorBlocks(uint32_t, const void*, size_t, uint32_t, uint16_t) {
+    LOG(ERROR) << "EmitXorBlocks not implemented.";
+    return false;
+}
+
 bool OnlineKernelSnapshotWriter::EmitZeroBlocks(uint64_t new_block_start, uint64_t num_blocks) {
     std::string zeroes(options_.block_size, 0);
     for (uint64_t i = 0; i < num_blocks; i++) {
diff --git a/fs_mgr/libsnapshot/snapuserd/Android.bp b/fs_mgr/libsnapshot/snapuserd/Android.bp
index bc97afc..47268d4 100644
--- a/fs_mgr/libsnapshot/snapuserd/Android.bp
+++ b/fs_mgr/libsnapshot/snapuserd/Android.bp
@@ -78,6 +78,7 @@
         "liblog",
         "libsnapshot_cow",
         "libz",
+        "libext4_utils",
     ],
 }
 
@@ -121,6 +122,7 @@
         "libz",
         "libfs_mgr",
         "libdm",
+        "libext4_utils",
     ],
     header_libs: [
         "libstorage_literals_headers",
diff --git a/fs_mgr/libsnapshot/snapuserd/cow_snapuserd_test.cpp b/fs_mgr/libsnapshot/snapuserd/cow_snapuserd_test.cpp
index a718328..f4aef44 100644
--- a/fs_mgr/libsnapshot/snapuserd/cow_snapuserd_test.cpp
+++ b/fs_mgr/libsnapshot/snapuserd/cow_snapuserd_test.cpp
@@ -259,7 +259,7 @@
 void CowSnapuserdTest::CreateBaseDevice() {
     unique_fd rnd_fd;
 
-    total_base_size_ = (size_ * 4);
+    total_base_size_ = (size_ * 5);
     base_fd_ = CreateTempFile("base_device", total_base_size_);
     ASSERT_GE(base_fd_, 0);
 
@@ -304,6 +304,11 @@
     offset += size_;
     ASSERT_EQ(ReadFullyAtOffset(snapshot_fd, snapuserd_buffer.get(), size_, offset), true);
     ASSERT_EQ(memcmp(snapuserd_buffer.get(), (char*)orig_buffer_.get() + (size_ * 3), size_), 0);
+
+    // XOR
+    offset += size_;
+    ASSERT_EQ(ReadFullyAtOffset(snapshot_fd, snapuserd_buffer.get(), size_, offset), true);
+    ASSERT_EQ(memcmp(snapuserd_buffer.get(), (char*)orig_buffer_.get() + (size_ * 4), size_), 0);
 }
 
 void CowSnapuserdTest::CreateCowDeviceWithCopyOverlap_2() {
@@ -428,9 +433,10 @@
     ASSERT_TRUE(writer.Initialize(cow_system_->fd));
 
     size_t num_blocks = size_ / options.block_size;
-    size_t blk_end_copy = num_blocks * 2;
+    size_t blk_end_copy = num_blocks * 3;
     size_t source_blk = num_blocks - 1;
     size_t blk_src_copy = blk_end_copy - 1;
+    uint16_t xor_offset = 5;
 
     size_t x = num_blocks;
     while (1) {
@@ -443,6 +449,11 @@
         blk_src_copy -= 1;
     }
 
+    for (size_t i = num_blocks; i > 0; i--) {
+        ASSERT_TRUE(writer.AddXorBlocks(num_blocks + i - 1,
+                                        &random_buffer_1_.get()[options.block_size * (i - 1)],
+                                        options.block_size, 2 * num_blocks + i - 1, xor_offset));
+    }
     // Flush operations
     ASSERT_TRUE(writer.Finalize());
     // Construct the buffer required for validation
@@ -451,7 +462,11 @@
     ASSERT_EQ(android::base::ReadFullyAtOffset(base_fd_, orig_buffer_.get(), total_base_size_, 0),
               true);
     // Merged Buffer
-    memmove(orig_buffer_.get(), (char*)orig_buffer_.get() + size_, size_);
+    memmove(orig_buffer_.get(), (char*)orig_buffer_.get() + 2 * size_, size_);
+    memmove(orig_buffer_.get() + size_, (char*)orig_buffer_.get() + 2 * size_ + xor_offset, size_);
+    for (int i = 0; i < size_; i++) {
+        orig_buffer_.get()[size_ + i] ^= random_buffer_1_.get()[i];
+    }
 }
 
 void CowSnapuserdTest::CreateCowDeviceOrderedOps() {
@@ -473,6 +488,7 @@
 
         offset += 1_MiB;
     }
+    memset(random_buffer_1_.get(), 0, size_);
 
     CowOptions options;
     options.compression = "gz";
@@ -483,7 +499,8 @@
     size_t num_blocks = size_ / options.block_size;
     size_t x = num_blocks;
     size_t source_blk = 0;
-    size_t blk_src_copy = num_blocks;
+    size_t blk_src_copy = 2 * num_blocks;
+    uint16_t xor_offset = 5;
 
     while (1) {
         ASSERT_TRUE(writer.AddCopy(source_blk, blk_src_copy));
@@ -496,6 +513,8 @@
         blk_src_copy += 1;
     }
 
+    ASSERT_TRUE(writer.AddXorBlocks(num_blocks, random_buffer_1_.get(), size_, 2 * num_blocks,
+                                    xor_offset));
     // Flush operations
     ASSERT_TRUE(writer.Finalize());
     // Construct the buffer required for validation
@@ -504,7 +523,11 @@
     ASSERT_EQ(android::base::ReadFullyAtOffset(base_fd_, orig_buffer_.get(), total_base_size_, 0),
               true);
     // Merged Buffer
-    memmove(orig_buffer_.get(), (char*)orig_buffer_.get() + size_, size_);
+    memmove(orig_buffer_.get(), (char*)orig_buffer_.get() + 2 * size_, size_);
+    memmove(orig_buffer_.get() + size_, (char*)orig_buffer_.get() + 2 * size_ + xor_offset, size_);
+    for (int i = 0; i < size_; i++) {
+        orig_buffer_.get()[size_ + i] ^= random_buffer_1_.get()[i];
+    }
 }
 
 void CowSnapuserdTest::CreateCowDevice() {
@@ -538,6 +561,17 @@
     size_t source_blk = num_blocks - 1;
     size_t blk_src_copy = blk_end_copy - 1;
 
+    uint32_t sequence[num_blocks * 2];
+    // Sequence for Copy ops
+    for (int i = 0; i < num_blocks; i++) {
+        sequence[i] = num_blocks - 1 - i;
+    }
+    // Sequence for Xor ops
+    for (int i = 0; i < num_blocks; i++) {
+        sequence[num_blocks + i] = 5 * num_blocks - 1 - i;
+    }
+    ASSERT_TRUE(writer.AddSequenceData(2 * num_blocks, sequence));
+
     size_t x = num_blocks;
     while (1) {
         ASSERT_TRUE(writer.AddCopy(source_blk, blk_src_copy));
@@ -563,6 +597,11 @@
 
     ASSERT_TRUE(writer.AddRawBlocks(blk_random2_replace_start, random_buffer_1_.get(), size_));
 
+    size_t blk_xor_start = blk_random2_replace_start + num_blocks;
+    size_t xor_offset = BLOCK_SZ / 2;
+    ASSERT_TRUE(writer.AddXorBlocks(blk_xor_start, random_buffer_1_.get(), size_, num_blocks,
+                                    xor_offset));
+
     // Flush operations
     ASSERT_TRUE(writer.Finalize());
     // Construct the buffer required for validation
@@ -572,6 +611,13 @@
     memcpy((char*)orig_buffer_.get() + size_, random_buffer_1_.get(), size_);
     memcpy((char*)orig_buffer_.get() + (size_ * 2), (void*)zero_buffer.c_str(), size_);
     memcpy((char*)orig_buffer_.get() + (size_ * 3), random_buffer_1_.get(), size_);
+    ASSERT_EQ(android::base::ReadFullyAtOffset(base_fd_, &orig_buffer_.get()[size_ * 4], size_,
+                                               size_ + xor_offset),
+              true);
+    for (int i = 0; i < size_; i++) {
+        orig_buffer_.get()[(size_ * 4) + i] =
+                (uint8_t)(orig_buffer_.get()[(size_ * 4) + i] ^ random_buffer_1_.get()[i]);
+    }
 }
 
 void CowSnapuserdTest::InitCowDevice() {
@@ -1039,6 +1085,35 @@
     }
 }
 
+TEST(Snapuserd_Test, xor_buffer) {
+    std::string data = "Test String";
+    std::string jumbled = {0x0C, 0x2A, 0x21, 0x54, 0x73, 0x27, 0x06, 0x1B, 0x07, 0x09, 0x46};
+    std::string result = "XOR String!";
+
+    BufferSink sink;
+    XorSink xor_sink;
+    sink.Initialize(sizeof(struct dm_user_header) + 10);
+    int buffsize = 5;
+    xor_sink.Initialize(&sink, buffsize);
+
+    void* buff = sink.GetPayloadBuffer(data.length());
+    memcpy(buff, data.data(), data.length());
+
+    size_t actual;
+    size_t count = 0;
+    while (count < data.length()) {
+        void* xor_buff = xor_sink.GetBuffer(10, &actual);
+        ASSERT_EQ(actual, buffsize);
+        ASSERT_NE(xor_buff, nullptr);
+        memcpy(xor_buff, jumbled.data() + count, buffsize);
+        xor_sink.ReturnData(xor_buff, actual);
+        count += actual;
+    }
+
+    std::string answer = reinterpret_cast<char*>(sink.GetPayloadBufPtr());
+    ASSERT_EQ(answer, result);
+}
+
 TEST(Snapuserd_Test, Snapshot_Metadata) {
     CowSnapuserdMetadataTest harness;
     harness.Setup();
diff --git a/fs_mgr/libsnapshot/snapuserd/include/snapuserd/snapuserd_kernel.h b/fs_mgr/libsnapshot/snapuserd/include/snapuserd/snapuserd_kernel.h
index 6bb7a39..c592257 100644
--- a/fs_mgr/libsnapshot/snapuserd/include/snapuserd/snapuserd_kernel.h
+++ b/fs_mgr/libsnapshot/snapuserd/include/snapuserd/snapuserd_kernel.h
@@ -47,8 +47,6 @@
 static constexpr uint32_t CHUNK_SIZE = 8;
 static constexpr uint32_t CHUNK_SHIFT = (__builtin_ffs(CHUNK_SIZE) - 1);
 
-#define DIV_ROUND_UP(n, d) (((n) + (d)-1) / (d))
-
 // This structure represents the kernel COW header.
 // All the below fields should be in Little Endian format.
 struct disk_header {
diff --git a/fs_mgr/libsnapshot/snapuserd/snapuserd.cpp b/fs_mgr/libsnapshot/snapuserd/snapuserd.cpp
index 31d0221..5f4d706 100644
--- a/fs_mgr/libsnapshot/snapuserd/snapuserd.cpp
+++ b/fs_mgr/libsnapshot/snapuserd/snapuserd.cpp
@@ -16,10 +16,22 @@
 
 #include "snapuserd.h"
 
+#include <dirent.h>
+#include <fcntl.h>
+#include <linux/fs.h>
+#include <unistd.h>
+#include <algorithm>
+
 #include <csignal>
 #include <optional>
 #include <set>
 
+#include <android-base/file.h>
+#include <android-base/logging.h>
+#include <android-base/parseint.h>
+#include <android-base/properties.h>
+#include <android-base/strings.h>
+#include <android-base/unique_fd.h>
 #include <snapuserd/snapuserd_client.h>
 
 namespace android {
@@ -53,6 +65,10 @@
     return true;
 }
 
+std::unique_ptr<CowReader> Snapuserd::CloneReaderForWorker() {
+    return reader_->CloneCowReader();
+}
+
 bool Snapuserd::CommitMerge(int num_merge_ops) {
     struct CowHeader* ch = reinterpret_cast<struct CowHeader*>(mapped_addr_);
     ch->num_merge_ops += num_merge_ops;
@@ -334,7 +350,7 @@
     CowHeader header;
     CowOptions options;
     bool metadata_found = false;
-    int replace_ops = 0, zero_ops = 0, copy_ops = 0;
+    int replace_ops = 0, zero_ops = 0, copy_ops = 0, xor_ops = 0;
 
     SNAP_LOG(DEBUG) << "ReadMetadata: Parsing cow file";
 
@@ -439,12 +455,12 @@
     std::vector<const CowOperation*> vec;
     std::set<uint64_t> dest_blocks;
     std::set<uint64_t> source_blocks;
-    size_t pending_copy_ops = exceptions_per_area_ - num_ops;
-    uint64_t total_copy_ops = reader_->get_num_ordered_ops_to_merge();
+    size_t pending_ordered_ops = exceptions_per_area_ - num_ops;
+    uint64_t total_ordered_ops = reader_->get_num_ordered_ops_to_merge();
 
     SNAP_LOG(DEBUG) << " Processing copy-ops at Area: " << vec_.size()
                     << " Number of replace/zero ops completed in this area: " << num_ops
-                    << " Pending copy ops for this area: " << pending_copy_ops;
+                    << " Pending copy ops for this area: " << pending_ordered_ops;
 
     while (!cowop_rm_iter->Done()) {
         do {
@@ -497,24 +513,34 @@
             // the merge of operations are done based on the ops present
             // in the file.
             //===========================================================
+            uint64_t block_source = cow_op->source;
+            uint64_t block_offset = 0;
+            if (cow_op->type == kCowXorOp) {
+                block_source /= BLOCK_SZ;
+                block_offset = cow_op->source % BLOCK_SZ;
+            }
             if (prev_id.has_value()) {
-                if (dest_blocks.count(cow_op->new_block) || source_blocks.count(cow_op->source)) {
+                if (dest_blocks.count(cow_op->new_block) || source_blocks.count(block_source) ||
+                    (block_offset > 0 && source_blocks.count(block_source + 1))) {
                     break;
                 }
             }
             metadata_found = true;
-            pending_copy_ops -= 1;
+            pending_ordered_ops -= 1;
             vec.push_back(cow_op);
-            dest_blocks.insert(cow_op->source);
+            dest_blocks.insert(block_source);
+            if (block_offset > 0) {
+                dest_blocks.insert(block_source + 1);
+            }
             source_blocks.insert(cow_op->new_block);
             prev_id = cow_op->new_block;
             cowop_rm_iter->Next();
-        } while (!cowop_rm_iter->Done() && pending_copy_ops);
+        } while (!cowop_rm_iter->Done() && pending_ordered_ops);
 
         data_chunk_id = GetNextAllocatableChunkId(data_chunk_id);
-        SNAP_LOG(DEBUG) << "Batch Merge copy-ops of size: " << vec.size()
+        SNAP_LOG(DEBUG) << "Batch Merge copy-ops/xor-ops of size: " << vec.size()
                         << " Area: " << vec_.size() << " Area offset: " << offset
-                        << " Pending-copy-ops in this area: " << pending_copy_ops;
+                        << " Pending-ordered-ops in this area: " << pending_ordered_ops;
 
         for (size_t i = 0; i < vec.size(); i++) {
             struct disk_exception* de =
@@ -528,13 +554,18 @@
             chunk_vec_.push_back(std::make_pair(ChunkToSector(data_chunk_id), cow_op));
             offset += sizeof(struct disk_exception);
             num_ops += 1;
-            copy_ops++;
+            if (cow_op->type == kCowCopyOp) {
+                copy_ops++;
+            } else {  // it->second->type == kCowXorOp
+                xor_ops++;
+            }
+
             if (read_ahead_feature_) {
                 read_ahead_ops_.push_back(cow_op);
             }
 
             SNAP_LOG(DEBUG) << num_ops << ":"
-                            << " Copy-op: "
+                            << " Ordered-op: "
                             << " Old-chunk: " << de->old_chunk << " New-chunk: " << de->new_chunk;
 
             if (num_ops == exceptions_per_area_) {
@@ -554,22 +585,22 @@
                     SNAP_LOG(DEBUG) << "ReadMetadata() completed; Number of Areas: " << vec_.size();
                 }
 
-                if (!(pending_copy_ops == 0)) {
-                    SNAP_LOG(ERROR)
-                            << "Invalid pending_copy_ops: expected: 0 found: " << pending_copy_ops;
+                if (!(pending_ordered_ops == 0)) {
+                    SNAP_LOG(ERROR) << "Invalid pending_ordered_ops: expected: 0 found: "
+                                    << pending_ordered_ops;
                     return false;
                 }
-                pending_copy_ops = exceptions_per_area_;
+                pending_ordered_ops = exceptions_per_area_;
             }
 
             data_chunk_id = GetNextAllocatableChunkId(data_chunk_id);
-            total_copy_ops -= 1;
+            total_ordered_ops -= 1;
             /*
              * Split the number of ops based on the size of read-ahead buffer
              * region. We need to ensure that kernel doesn't issue IO on blocks
              * which are not read by the read-ahead thread.
              */
-            if (read_ahead_feature_ && (total_copy_ops % num_ra_ops_per_iter == 0)) {
+            if (read_ahead_feature_ && (total_ordered_ops % num_ra_ops_per_iter == 0)) {
                 data_chunk_id = GetNextAllocatableChunkId(data_chunk_id);
             }
         }
@@ -598,8 +629,8 @@
     SNAP_LOG(INFO) << "ReadMetadata completed. Final-chunk-id: " << data_chunk_id
                    << " Num Sector: " << ChunkToSector(data_chunk_id)
                    << " Replace-ops: " << replace_ops << " Zero-ops: " << zero_ops
-                   << " Copy-ops: " << copy_ops << " Areas: " << vec_.size()
-                   << " Num-ops-merged: " << header.num_merge_ops
+                   << " Copy-ops: " << copy_ops << " Xor-ops: " << xor_ops
+                   << " Areas: " << vec_.size() << " Num-ops-merged: " << header.num_merge_ops
                    << " Total-data-ops: " << reader_->get_num_total_data_ops();
 
     // Total number of sectors required for creating dm-user device
@@ -659,6 +690,74 @@
     return ReadMetadata();
 }
 
+void Snapuserd::ReadBlocksToCache(const std::string& dm_block_device,
+                                  const std::string& partition_name, off_t offset, size_t size) {
+    android::base::unique_fd fd(TEMP_FAILURE_RETRY(open(dm_block_device.c_str(), O_RDONLY)));
+    if (fd.get() == -1) {
+        SNAP_PLOG(ERROR) << "Error reading " << dm_block_device
+                         << " partition-name: " << partition_name;
+        return;
+    }
+
+    size_t remain = size;
+    off_t file_offset = offset;
+    // We pick 4M I/O size based on the fact that the current
+    // update_verifier has a similar I/O size.
+    size_t read_sz = 1024 * BLOCK_SZ;
+    std::vector<uint8_t> buf(read_sz);
+
+    while (remain > 0) {
+        size_t to_read = std::min(remain, read_sz);
+
+        if (!android::base::ReadFullyAtOffset(fd.get(), buf.data(), to_read, file_offset)) {
+            SNAP_PLOG(ERROR) << "Failed to read block from block device: " << dm_block_device
+                             << " at offset: " << file_offset
+                             << " partition-name: " << partition_name << " total-size: " << size
+                             << " remain_size: " << remain;
+            return;
+        }
+
+        file_offset += to_read;
+        remain -= to_read;
+    }
+
+    SNAP_LOG(INFO) << "Finished reading block-device: " << dm_block_device
+                   << " partition: " << partition_name << " size: " << size
+                   << " offset: " << offset;
+}
+
+void Snapuserd::ReadBlocks(const std::string& partition_name, const std::string& dm_block_device) {
+    SNAP_LOG(DEBUG) << "Reading partition: " << partition_name
+                    << " Block-Device: " << dm_block_device;
+
+    uint64_t dev_sz = 0;
+
+    unique_fd fd(TEMP_FAILURE_RETRY(open(dm_block_device.c_str(), O_RDONLY | O_CLOEXEC)));
+    if (fd < 0) {
+        SNAP_LOG(ERROR) << "Cannot open block device";
+        return;
+    }
+
+    dev_sz = get_block_device_size(fd.get());
+    if (!dev_sz) {
+        SNAP_PLOG(ERROR) << "Could not determine block device size: " << dm_block_device;
+        return;
+    }
+
+    int num_threads = 2;
+    size_t num_blocks = dev_sz >> BLOCK_SHIFT;
+    size_t num_blocks_per_thread = num_blocks / num_threads;
+    size_t read_sz_per_thread = num_blocks_per_thread << BLOCK_SHIFT;
+    off_t offset = 0;
+
+    for (int i = 0; i < num_threads; i++) {
+        std::async(std::launch::async, &Snapuserd::ReadBlocksToCache, this, dm_block_device,
+                   partition_name, offset, read_sz_per_thread);
+
+        offset += read_sz_per_thread;
+    }
+}
+
 /*
  * Entry point to launch threads
  */
@@ -687,6 +786,39 @@
                 std::async(std::launch::async, &WorkerThread::RunThread, worker_threads_[i].get()));
     }
 
+    bool second_stage_init = true;
+
+    // We don't want to read the blocks during first stage init.
+    if (android::base::EndsWith(misc_name_, "-init") || is_socket_present_) {
+        second_stage_init = false;
+    }
+
+    if (second_stage_init) {
+        SNAP_LOG(INFO) << "Reading blocks to cache....";
+        auto& dm = DeviceMapper::Instance();
+        auto dm_block_devices = dm.FindDmPartitions();
+        if (dm_block_devices.empty()) {
+            SNAP_LOG(ERROR) << "No dm-enabled block device is found.";
+        } else {
+            auto parts = android::base::Split(misc_name_, "-");
+            std::string partition_name = parts[0];
+
+            const char* suffix_b = "_b";
+            const char* suffix_a = "_a";
+
+            partition_name.erase(partition_name.find_last_not_of(suffix_b) + 1);
+            partition_name.erase(partition_name.find_last_not_of(suffix_a) + 1);
+
+            if (dm_block_devices.find(partition_name) == dm_block_devices.end()) {
+                SNAP_LOG(ERROR) << "Failed to find dm block device for " << partition_name;
+            } else {
+                ReadBlocks(partition_name, dm_block_devices.at(partition_name));
+            }
+        }
+    } else {
+        SNAP_LOG(INFO) << "Not reading block device into cache";
+    }
+
     bool ret = true;
     for (auto& t : threads) {
         ret = t.get() && ret;
diff --git a/fs_mgr/libsnapshot/snapuserd/snapuserd.h b/fs_mgr/libsnapshot/snapuserd/snapuserd.h
index 95d2f77..6388a83 100644
--- a/fs_mgr/libsnapshot/snapuserd/snapuserd.h
+++ b/fs_mgr/libsnapshot/snapuserd/snapuserd.h
@@ -38,6 +38,7 @@
 #include <android-base/logging.h>
 #include <android-base/stringprintf.h>
 #include <android-base/unique_fd.h>
+#include <ext4_utils/ext4_utils.h>
 #include <libdm/dm.h>
 #include <libsnapshot/cow_reader.h>
 #include <libsnapshot/cow_writer.h>
@@ -107,6 +108,20 @@
     size_t buffer_size_;
 };
 
+class XorSink : public IByteSink {
+  public:
+    void Initialize(BufferSink* sink, size_t size);
+    void Reset();
+    void* GetBuffer(size_t requested, size_t* actual) override;
+    bool ReturnData(void* buffer, size_t len) override;
+
+  private:
+    BufferSink* bufsink_;
+    std::unique_ptr<uint8_t[]> buffer_;
+    size_t buffer_size_;
+    size_t returned_;
+};
+
 class Snapuserd;
 
 class ReadAheadThread {
@@ -116,10 +131,10 @@
     bool RunThread();
 
   private:
-    void InitializeIter();
-    bool IterDone();
-    void IterNext();
-    const CowOperation* GetIterOp();
+    void InitializeRAIter();
+    bool RAIterDone();
+    void RAIterNext();
+    const CowOperation* GetRAOpIter();
     void InitializeBuffer();
 
     bool InitializeFds();
@@ -129,7 +144,7 @@
     }
 
     bool ReadAheadIOStart();
-    void PrepareReadAhead(uint64_t* source_block, int* pending_ops, std::vector<uint64_t>& blocks);
+    void PrepareReadAhead(uint64_t* source_offset, int* pending_ops, std::vector<uint64_t>& blocks);
     bool ReconstructDataFromCow();
     void CheckOverlap(const CowOperation* cow_op);
 
@@ -187,7 +202,9 @@
     // Processing COW operations
     bool ProcessCowOp(const CowOperation* cow_op);
     bool ProcessReplaceOp(const CowOperation* cow_op);
+    // Handles Copy and Xor
     bool ProcessCopyOp(const CowOperation* cow_op);
+    bool ProcessXorOp(const CowOperation* cow_op);
     bool ProcessZeroOp();
 
     bool ReadFromBaseDevice(const CowOperation* cow_op);
@@ -206,6 +223,7 @@
 
     std::unique_ptr<CowReader> reader_;
     BufferSink bufsink_;
+    XorSink xorsink_;
 
     std::string cow_device_;
     std::string backing_store_device_;
@@ -244,6 +262,7 @@
     void* GetExceptionBuffer(size_t i) { return vec_[i].get(); }
 
     bool InitializeWorkers();
+    std::unique_ptr<CowReader> CloneReaderForWorker();
     std::shared_ptr<Snapuserd> GetSharedPtr() { return shared_from_this(); }
 
     std::vector<std::pair<sector_t, const CowOperation*>>& GetChunkVec() { return chunk_vec_; }
@@ -284,6 +303,7 @@
     // Total number of blocks to be merged in a given read-ahead buffer region
     void SetTotalRaBlocksMerged(int x) { total_ra_blocks_merged_ = x; }
     int GetTotalRaBlocksMerged() { return total_ra_blocks_merged_; }
+    void SetSocketPresent(bool socket) { is_socket_present_ = socket; }
 
   private:
     bool IsChunkIdMetadata(chunk_t chunk);
@@ -296,6 +316,10 @@
     bool IsBlockAligned(int read_size) { return ((read_size & (BLOCK_SZ - 1)) == 0); }
     struct BufferState* GetBufferState();
 
+    void ReadBlocks(const std::string& partition_name, const std::string& dm_block_device);
+    void ReadBlocksToCache(const std::string& dm_block_device, const std::string& partition_name,
+                           off_t offset, size_t size);
+
     std::string cow_device_;
     std::string backing_store_device_;
     std::string control_device_;
@@ -335,6 +359,7 @@
 
     bool merge_initiated_ = false;
     bool attached_ = false;
+    bool is_socket_present_;
 };
 
 }  // namespace snapshot
diff --git a/fs_mgr/libsnapshot/snapuserd/snapuserd.rc b/fs_mgr/libsnapshot/snapuserd/snapuserd.rc
index 02fda8d..2750096 100644
--- a/fs_mgr/libsnapshot/snapuserd/snapuserd.rc
+++ b/fs_mgr/libsnapshot/snapuserd/snapuserd.rc
@@ -14,3 +14,6 @@
     user root
     group root system
     seclabel u:r:snapuserd:s0
+
+on property:init.svc.snapuserd=stopped
+    setprop snapuserd.ready false
diff --git a/fs_mgr/libsnapshot/snapuserd/snapuserd_client.cpp b/fs_mgr/libsnapshot/snapuserd/snapuserd_client.cpp
index 81e9228..1ea05a3 100644
--- a/fs_mgr/libsnapshot/snapuserd/snapuserd_client.cpp
+++ b/fs_mgr/libsnapshot/snapuserd/snapuserd_client.cpp
@@ -42,13 +42,15 @@
 using android::base::unique_fd;
 
 bool EnsureSnapuserdStarted() {
-    if (android::base::GetProperty("init.svc.snapuserd", "") == "running") {
-        return true;
+    if (android::base::GetProperty("init.svc.snapuserd", "") != "running") {
+        android::base::SetProperty("ctl.start", "snapuserd");
+        if (!android::base::WaitForProperty("init.svc.snapuserd", "running", 10s)) {
+            LOG(ERROR) << "Timed out waiting for snapuserd to start.";
+            return false;
+        }
     }
-
-    android::base::SetProperty("ctl.start", "snapuserd");
-    if (!android::base::WaitForProperty("init.svc.snapuserd", "running", 10s)) {
-        LOG(ERROR) << "Timed out waiting for snapuserd to start.";
+    if (!android::base::WaitForProperty("snapuserd.ready", "true", 10s)) {
+        LOG(ERROR) << "Timed out waiting for snapuserd to be ready.";
         return false;
     }
     return true;
diff --git a/fs_mgr/libsnapshot/snapuserd/snapuserd_readahead.cpp b/fs_mgr/libsnapshot/snapuserd/snapuserd_readahead.cpp
index 6fc26a6..b868eed 100644
--- a/fs_mgr/libsnapshot/snapuserd/snapuserd_readahead.cpp
+++ b/fs_mgr/libsnapshot/snapuserd/snapuserd_readahead.cpp
@@ -172,24 +172,37 @@
 }
 
 void ReadAheadThread::CheckOverlap(const CowOperation* cow_op) {
-    if (dest_blocks_.count(cow_op->new_block) || source_blocks_.count(cow_op->source)) {
+    uint64_t source_block = cow_op->source;
+    uint64_t source_offset = 0;
+    if (cow_op->type == kCowXorOp) {
+        source_block /= BLOCK_SZ;
+        source_offset = cow_op->source % BLOCK_SZ;
+    }
+    if (dest_blocks_.count(cow_op->new_block) || source_blocks_.count(source_block) ||
+        (source_offset > 0 && source_blocks_.count(source_block + 1))) {
         overlap_ = true;
     }
 
-    dest_blocks_.insert(cow_op->source);
+    dest_blocks_.insert(source_block);
+    if (source_offset > 0) {
+        dest_blocks_.insert(source_block + 1);
+    }
     source_blocks_.insert(cow_op->new_block);
 }
 
-void ReadAheadThread::PrepareReadAhead(uint64_t* source_block, int* pending_ops,
+void ReadAheadThread::PrepareReadAhead(uint64_t* source_offset, int* pending_ops,
                                        std::vector<uint64_t>& blocks) {
     int num_ops = *pending_ops;
     int nr_consecutive = 0;
 
-    if (!IterDone() && num_ops) {
-        // Get the first block
-        const CowOperation* cow_op = GetIterOp();
-        *source_block = cow_op->source;
-        IterNext();
+    if (!RAIterDone() && num_ops) {
+        // Get the first block with offset
+        const CowOperation* cow_op = GetRAOpIter();
+        *source_offset = cow_op->source;
+        if (cow_op->type == kCowCopyOp) {
+            *source_offset *= BLOCK_SZ;
+        }
+        RAIterNext();
         num_ops -= 1;
         nr_consecutive = 1;
         blocks.push_back(cow_op->new_block);
@@ -201,15 +214,19 @@
         /*
          * Find number of consecutive blocks working backwards.
          */
-        while (!IterDone() && num_ops) {
-            const CowOperation* op = GetIterOp();
-            if (op->source != (*source_block - nr_consecutive)) {
+        while (!RAIterDone() && num_ops) {
+            const CowOperation* op = GetRAOpIter();
+            uint64_t next_offset = op->source;
+            if (cow_op->type == kCowCopyOp) {
+                next_offset *= BLOCK_SZ;
+            }
+            if (next_offset != (*source_offset - nr_consecutive * BLOCK_SZ)) {
                 break;
             }
             nr_consecutive += 1;
             num_ops -= 1;
             blocks.push_back(op->new_block);
-            IterNext();
+            RAIterNext();
 
             if (!overlap_) {
                 CheckOverlap(op);
@@ -247,12 +264,12 @@
     // We are done re-constructing the mapping; however, we need to make sure
     // all the COW operations to-be merged are present in the re-constructed
     // mapping.
-    while (!IterDone()) {
-        const CowOperation* op = GetIterOp();
+    while (!RAIterDone()) {
+        const CowOperation* op = GetRAOpIter();
         if (read_ahead_buffer_map.find(op->new_block) != read_ahead_buffer_map.end()) {
             num_ops -= 1;
             snapuserd_->SetFinalBlockMerged(op->new_block);
-            IterNext();
+            RAIterNext();
         } else {
             // Verify that we have covered all the ops which were re-constructed
             // from COW device - These are the ops which are being
@@ -312,10 +329,10 @@
     source_blocks_.clear();
 
     while (true) {
-        uint64_t source_block;
+        uint64_t source_offset;
         int linear_blocks;
 
-        PrepareReadAhead(&source_block, &num_ops, blocks);
+        PrepareReadAhead(&source_offset, &num_ops, blocks);
         linear_blocks = blocks.size();
         if (linear_blocks == 0) {
             // No more blocks to read
@@ -324,7 +341,7 @@
         }
 
         // Get the first block in the consecutive set of blocks
-        source_block = source_block + 1 - linear_blocks;
+        source_offset = source_offset - (linear_blocks - 1) * BLOCK_SZ;
         size_t io_size = (linear_blocks * BLOCK_SZ);
         num_ops -= linear_blocks;
         total_blocks_merged += linear_blocks;
@@ -358,10 +375,12 @@
         // Read from the base device consecutive set of blocks in one shot
         if (!android::base::ReadFullyAtOffset(backing_store_fd_,
                                               (char*)read_ahead_buffer_ + buffer_offset, io_size,
-                                              source_block * BLOCK_SZ)) {
-            SNAP_PLOG(ERROR) << "Copy-op failed. Read from backing store: " << backing_store_device_
-                             << "at block :" << source_block << " buffer_offset : " << buffer_offset
-                             << " io_size : " << io_size << " buf-addr : " << read_ahead_buffer_;
+                                              source_offset)) {
+            SNAP_PLOG(ERROR) << "Ordered-op failed. Read from backing store: "
+                             << backing_store_device_ << "at block :" << source_offset / BLOCK_SZ
+                             << " offset :" << source_offset % BLOCK_SZ
+                             << " buffer_offset : " << buffer_offset << " io_size : " << io_size
+                             << " buf-addr : " << read_ahead_buffer_;
 
             snapuserd_->ReadAheadIOFailed();
             return false;
@@ -394,10 +413,10 @@
         return false;
     }
 
-    InitializeIter();
+    InitializeRAIter();
     InitializeBuffer();
 
-    while (!IterDone()) {
+    while (!RAIterDone()) {
         if (!ReadAheadIOStart()) {
             return false;
         }
@@ -433,21 +452,21 @@
     return true;
 }
 
-void ReadAheadThread::InitializeIter() {
+void ReadAheadThread::InitializeRAIter() {
     std::vector<const CowOperation*>& read_ahead_ops = snapuserd_->GetReadAheadOpsVec();
     read_ahead_iter_ = read_ahead_ops.rbegin();
 }
 
-bool ReadAheadThread::IterDone() {
+bool ReadAheadThread::RAIterDone() {
     std::vector<const CowOperation*>& read_ahead_ops = snapuserd_->GetReadAheadOpsVec();
     return read_ahead_iter_ == read_ahead_ops.rend();
 }
 
-void ReadAheadThread::IterNext() {
+void ReadAheadThread::RAIterNext() {
     read_ahead_iter_++;
 }
 
-const CowOperation* ReadAheadThread::GetIterOp() {
+const CowOperation* ReadAheadThread::GetRAOpIter() {
     return *read_ahead_iter_;
 }
 
diff --git a/fs_mgr/libsnapshot/snapuserd/snapuserd_server.cpp b/fs_mgr/libsnapshot/snapuserd/snapuserd_server.cpp
index a29b19b..2f87557 100644
--- a/fs_mgr/libsnapshot/snapuserd/snapuserd_server.cpp
+++ b/fs_mgr/libsnapshot/snapuserd/snapuserd_server.cpp
@@ -227,6 +227,7 @@
 void SnapuserdServer::RunThread(std::shared_ptr<DmUserHandler> handler) {
     LOG(INFO) << "Entering thread for handler: " << handler->misc_name();
 
+    handler->snapuserd()->SetSocketPresent(is_socket_present_);
     if (!handler->snapuserd()->Start()) {
         LOG(ERROR) << " Failed to launch all worker threads";
     }
@@ -290,6 +291,15 @@
     }
 
     AddWatchedFd(sockfd_, POLLIN);
+    is_socket_present_ = true;
+
+    // If started in first-stage init, the property service won't be online.
+    if (access("/dev/socket/property_service", F_OK) == 0) {
+        if (!android::base::SetProperty("snapuserd.ready", "true")) {
+            LOG(ERROR) << "Failed to set snapuserd.ready property";
+            return false;
+        }
+    }
 
     LOG(DEBUG) << "Snapuserd server now accepting connections";
     return true;
diff --git a/fs_mgr/libsnapshot/snapuserd/snapuserd_server.h b/fs_mgr/libsnapshot/snapuserd/snapuserd_server.h
index 846f848..3b6ff15 100644
--- a/fs_mgr/libsnapshot/snapuserd/snapuserd_server.h
+++ b/fs_mgr/libsnapshot/snapuserd/snapuserd_server.h
@@ -96,6 +96,7 @@
     bool terminating_;
     volatile bool received_socket_signal_ = false;
     std::vector<struct pollfd> watched_fds_;
+    bool is_socket_present_ = false;
 
     std::mutex lock_;
 
diff --git a/fs_mgr/libsnapshot/snapuserd/snapuserd_worker.cpp b/fs_mgr/libsnapshot/snapuserd/snapuserd_worker.cpp
index 13d45fe..cdf9fe7 100644
--- a/fs_mgr/libsnapshot/snapuserd/snapuserd_worker.cpp
+++ b/fs_mgr/libsnapshot/snapuserd/snapuserd_worker.cpp
@@ -71,6 +71,39 @@
     return msg->payload.buf;
 }
 
+void XorSink::Initialize(BufferSink* sink, size_t size) {
+    bufsink_ = sink;
+    buffer_size_ = size;
+    returned_ = 0;
+    buffer_ = std::make_unique<uint8_t[]>(size);
+}
+
+void XorSink::Reset() {
+    returned_ = 0;
+}
+
+void* XorSink::GetBuffer(size_t requested, size_t* actual) {
+    if (requested > buffer_size_) {
+        *actual = buffer_size_;
+    } else {
+        *actual = requested;
+    }
+    return buffer_.get();
+}
+
+bool XorSink::ReturnData(void* buffer, size_t len) {
+    uint8_t* xor_data = reinterpret_cast<uint8_t*>(buffer);
+    uint8_t* buff = reinterpret_cast<uint8_t*>(bufsink_->GetPayloadBuffer(len + returned_));
+    if (buff == nullptr) {
+        return false;
+    }
+    for (size_t i = 0; i < len; i++) {
+        buff[returned_ + i] ^= xor_data[i];
+    }
+    returned_ += len;
+    return true;
+}
+
 WorkerThread::WorkerThread(const std::string& cow_device, const std::string& backing_device,
                            const std::string& control_device, const std::string& misc_name,
                            std::shared_ptr<Snapuserd> snapuserd) {
@@ -105,11 +138,11 @@
 }
 
 bool WorkerThread::InitReader() {
-    reader_ = std::make_unique<CowReader>();
+    reader_ = snapuserd_->CloneReaderForWorker();
+
     if (!reader_->InitForMerge(std::move(cow_fd_))) {
         return false;
     }
-
     return true;
 }
 
@@ -150,10 +183,19 @@
     }
     SNAP_LOG(DEBUG) << " ReadFromBaseDevice...: new-block: " << cow_op->new_block
                     << " Source: " << cow_op->source;
-    if (!android::base::ReadFullyAtOffset(backing_store_fd_, buffer, BLOCK_SZ,
-                                          cow_op->source * BLOCK_SZ)) {
-        SNAP_PLOG(ERROR) << "Copy-op failed. Read from backing store: " << backing_store_device_
-                         << "at block :" << cow_op->source;
+    uint64_t offset = cow_op->source;
+    if (cow_op->type == kCowCopyOp) {
+        offset *= BLOCK_SZ;
+    }
+    if (!android::base::ReadFullyAtOffset(backing_store_fd_, buffer, BLOCK_SZ, offset)) {
+        std::string op;
+        if (cow_op->type == kCowCopyOp)
+            op = "Copy-op";
+        else {
+            op = "Xor-op";
+        }
+        SNAP_PLOG(ERROR) << op << " failed. Read from backing store: " << backing_store_device_
+                         << "at block :" << offset / BLOCK_SZ << " offset:" << offset % BLOCK_SZ;
         return false;
     }
 
@@ -188,6 +230,23 @@
     return true;
 }
 
+bool WorkerThread::ProcessXorOp(const CowOperation* cow_op) {
+    if (!GetReadAheadPopulatedBuffer(cow_op)) {
+        SNAP_LOG(DEBUG) << " GetReadAheadPopulatedBuffer failed..."
+                        << " new_block: " << cow_op->new_block;
+        if (!ReadFromBaseDevice(cow_op)) {
+            return false;
+        }
+    }
+    xorsink_.Reset();
+    if (!reader_->ReadData(*cow_op, &xorsink_)) {
+        SNAP_LOG(ERROR) << "ProcessXorOp failed for block " << cow_op->new_block;
+        return false;
+    }
+
+    return true;
+}
+
 bool WorkerThread::ProcessZeroOp() {
     // Zero out the entire block
     void* buffer = bufsink_.GetPayloadBuffer(BLOCK_SZ);
@@ -219,6 +278,10 @@
             return ProcessCopyOp(cow_op);
         }
 
+        case kCowXorOp: {
+            return ProcessXorOp(cow_op);
+        }
+
         default: {
             SNAP_LOG(ERROR) << "Unknown operation-type found: " << cow_op->type;
         }
@@ -470,10 +533,10 @@
 }
 
 int WorkerThread::GetNumberOfMergedOps(void* merged_buffer, void* unmerged_buffer, loff_t offset,
-                                       int unmerged_exceptions, bool* copy_op, bool* commit) {
+                                       int unmerged_exceptions, bool* ordered_op, bool* commit) {
     int merged_ops_cur_iter = 0;
     std::unordered_map<uint64_t, void*>& read_ahead_buffer_map = snapuserd_->GetReadAheadMap();
-    *copy_op = false;
+    *ordered_op = false;
     std::vector<std::pair<sector_t, const CowOperation*>>& chunk_vec = snapuserd_->GetChunkVec();
 
     // Find the operations which are merged in this cycle.
@@ -511,9 +574,9 @@
             }
             const CowOperation* cow_op = it->second;
 
-            if (snapuserd_->IsReadAheadFeaturePresent() && cow_op->type == kCowCopyOp) {
-                *copy_op = true;
-                // Every single copy operation has to come from read-ahead
+            if (snapuserd_->IsReadAheadFeaturePresent() && IsOrderedOp(*cow_op)) {
+                *ordered_op = true;
+                // Every single ordered operation has to come from read-ahead
                 // cache.
                 if (read_ahead_buffer_map.find(cow_op->new_block) == read_ahead_buffer_map.end()) {
                     SNAP_LOG(ERROR)
@@ -557,7 +620,7 @@
 bool WorkerThread::ProcessMergeComplete(chunk_t chunk, void* buffer) {
     uint32_t stride = exceptions_per_area_ + 1;
     const std::vector<std::unique_ptr<uint8_t[]>>& vec = snapuserd_->GetMetadataVec();
-    bool copy_op = false;
+    bool ordered_op = false;
     bool commit = false;
 
     // ChunkID to vector index
@@ -582,7 +645,7 @@
     }
 
     int merged_ops_cur_iter = GetNumberOfMergedOps(buffer, vec[divresult.quot].get(), offset,
-                                                   unmerged_exceptions, &copy_op, &commit);
+                                                   unmerged_exceptions, &ordered_op, &commit);
 
     // There should be at least one operation merged in this cycle
     if (!(merged_ops_cur_iter > 0)) {
@@ -590,7 +653,7 @@
         return false;
     }
 
-    if (copy_op) {
+    if (ordered_op) {
         if (commit) {
             // Push the flushing logic to read-ahead thread so that merge thread
             // can make forward progress. Sync will happen in the background
@@ -819,6 +882,7 @@
 
 bool WorkerThread::RunThread() {
     InitializeBufsink();
+    xorsink_.Initialize(&bufsink_, BLOCK_SZ);
 
     if (!InitializeFds()) {
         return false;
diff --git a/gatekeeperd/Android.bp b/gatekeeperd/Android.bp
index 95e814b..a7f0c0e 100644
--- a/gatekeeperd/Android.bp
+++ b/gatekeeperd/Android.bp
@@ -43,8 +43,8 @@
         "libhidlbase",
         "android.hardware.gatekeeper@1.0",
         "libgatekeeper_aidl",
-        "android.hardware.security.keymint-V1-ndk_platform",
-        "android.security.authorization-ndk_platform",
+        "android.hardware.security.keymint-V1-ndk",
+        "android.security.authorization-ndk",
     ],
 
     static_libs: ["libscrypt_static"],
diff --git a/init/Android.bp b/init/Android.bp
index a04d2db..5d09687 100644
--- a/init/Android.bp
+++ b/init/Android.bp
@@ -236,6 +236,7 @@
                 "init.rc",
                 "ueventd.rc",
                 "e2fsdroid",
+                "extra_free_kbytes.sh",
                 "make_f2fs",
                 "mke2fs",
                 "sload_f2fs",
@@ -552,3 +553,8 @@
         },
     },
 }
+
+sh_binary {
+    name: "extra_free_kbytes.sh",
+    src: "extra_free_kbytes.sh",
+}
diff --git a/init/TEST_MAPPING b/init/TEST_MAPPING
new file mode 100644
index 0000000..03b9eaa
--- /dev/null
+++ b/init/TEST_MAPPING
@@ -0,0 +1,13 @@
+{
+  "presubmit": [
+    {
+      "name": "CtsInitTestCases"
+    },
+    {
+      "name": "init_kill_services_test"
+    },
+    {
+      "name": "MicrodroidHostTestCases"
+    }
+  ]
+}
diff --git a/init/block_dev_initializer.cpp b/init/block_dev_initializer.cpp
index 9c2a7bb..05e00ed 100644
--- a/init/block_dev_initializer.cpp
+++ b/init/block_dev_initializer.cpp
@@ -87,7 +87,13 @@
 
     auto iter = devices->find(name);
     if (iter == devices->end()) {
-        return ListenerAction::kContinue;
+        auto partition_name = DeviceHandler::GetPartitionNameForDevice(uevent.device_name);
+        if (!partition_name.empty()) {
+            iter = devices->find(partition_name);
+        }
+        if (iter == devices->end()) {
+            return ListenerAction::kContinue;
+        }
     }
 
     LOG(VERBOSE) << __PRETTY_FUNCTION__ << ": found partition: " << name;
diff --git a/init/builtins.cpp b/init/builtins.cpp
index 035038f..7633d9c 100644
--- a/init/builtins.cpp
+++ b/init/builtins.cpp
@@ -1305,20 +1305,8 @@
 
     return {};
 }
-
-static bool IsApexUpdatable() {
-    static bool updatable = android::sysprop::ApexProperties::updatable().value_or(false);
-    return updatable;
-}
-
 static Result<void> do_update_linker_config(const BuiltinArguments&) {
-    // If APEX is not updatable, then all APEX information are already included in the first
-    // linker config generation, so there is no need to update linker configuration again.
-    if (IsApexUpdatable()) {
-        return GenerateLinkerConfiguration();
-    }
-
-    return {};
+    return GenerateLinkerConfiguration();
 }
 
 static Result<void> parse_apex_configs() {
diff --git a/init/devices.cpp b/init/devices.cpp
index 56c6623..d4a3cb9 100644
--- a/init/devices.cpp
+++ b/init/devices.cpp
@@ -46,6 +46,7 @@
 using android::base::ReadFileToString;
 using android::base::Readlink;
 using android::base::Realpath;
+using android::base::Split;
 using android::base::StartsWith;
 using android::base::StringPrintf;
 using android::base::Trim;
@@ -187,6 +188,36 @@
     }
 }
 
+std::string DeviceHandler::GetPartitionNameForDevice(const std::string& query_device) {
+    static const auto partition_map = [] {
+        std::vector<std::pair<std::string, std::string>> partition_map;
+        auto parser = [&partition_map](const std::string& key, const std::string& value) {
+            if (key != "androidboot.partition_map") {
+                return;
+            }
+            for (const auto& map : Split(value, ";")) {
+                auto map_pieces = Split(map, ",");
+                if (map_pieces.size() != 2) {
+                    LOG(ERROR) << "Expected a comma separated device,partition mapping, but found '"
+                               << map << "'";
+                    continue;
+                }
+                partition_map.emplace_back(map_pieces[0], map_pieces[1]);
+            }
+        };
+        ImportKernelCmdline(parser);
+        ImportBootconfig(parser);
+        return partition_map;
+    }();
+
+    for (const auto& [device, partition] : partition_map) {
+        if (query_device == device) {
+            return partition;
+        }
+    }
+    return {};
+}
+
 // Given a path that may start with a platform device, find the parent platform device by finding a
 // parent directory with a 'subsystem' symlink that points to the platform bus.
 // If it doesn't start with a platform device, return false
@@ -389,6 +420,10 @@
         // If we don't have a partition name but we are a partition on a boot device, create a
         // symlink of /dev/block/by-name/<device_name> for symmetry.
         links.emplace_back("/dev/block/by-name/" + uevent.device_name);
+        auto partition_name = GetPartitionNameForDevice(uevent.device_name);
+        if (!partition_name.empty()) {
+            links.emplace_back("/dev/block/by-name/" + partition_name);
+        }
     }
 
     auto last_slash = uevent.path.rfind('/');
diff --git a/init/devices.h b/init/devices.h
index d70d746..f9f4d79 100644
--- a/init/devices.h
+++ b/init/devices.h
@@ -122,6 +122,12 @@
 
     std::vector<std::string> GetBlockDeviceSymlinks(const Uevent& uevent) const;
 
+    // `androidboot.partition_map` allows associating a partition name for a raw block device
+    // through a comma separated and semicolon deliminated list. For example,
+    // `androidboot.partition_map=vdb,metadata;vdc,userdata` maps `vdb` to `metadata` and `vdc` to
+    // `userdata`.
+    static std::string GetPartitionNameForDevice(const std::string& device);
+
   private:
     bool FindPlatformDevice(std::string path, std::string* platform_device_path) const;
     std::tuple<mode_t, uid_t, gid_t> GetDevicePermissions(
diff --git a/init/extra_free_kbytes.sh b/init/extra_free_kbytes.sh
new file mode 100755
index 0000000..aeaa912
--- /dev/null
+++ b/init/extra_free_kbytes.sh
@@ -0,0 +1,136 @@
+#!/bin/sh
+
+# Script implements watermark_scale calculation which results in the same low
+# watermark as if extra_free_kbytes tunable were to be used.
+#
+# Usage: extra_free_kbytes.sh <extra_free_kbytes value>
+#
+# extra_free_kbytes is distributed between zones based on
+# zone.managed_pages/vm_total_pages ratio, where vm_total_pages is the sum of
+# zone.managed_pages for all zones (zone.high used in this calculation is 0
+# when this is calculated). Therefore for each zone its share is calculated as:
+#
+# extra_free_pages = extra_free_kbytes / page_size
+# extra_share = extra_free_pages * managed_pages / vm_total_pages
+#
+# This extra_share is added to the low and high watermarks:
+#
+# low = min + max(min / 4, managed_pages * (watermark_scale / 10000)) + extra_share
+# high = min + 2 * max(min / 4, managed_pages * (watermark_scale / 10000)) + extra_share
+#
+# Because Android uses extra_free_kbytes to adjust the low watermark, we ignore
+# the difference in how watermark_scale and extra_free_kbytes affect the high
+# watermark and will match the low watermark only.
+#
+# To eliminate extra_share and compansate the difference with watermark_scale,
+# a new watermark_scale_new is calculated as:
+#
+# (1) max(min / 4, managed_pages * (watermark_scale / 10000)) + extra_share =
+#   max(min / 4, managed_pages * (watermark_scale_new / 10000))
+#
+# Two cases to consider:
+# A. managed_pages * (watermark_scale / 10000) > min / 4
+# The formula (1) becomes:
+#
+# managed_pages * (watermark_scale / 10000) + extra_share =
+#   managed_pages * (watermark_scale_new / 10000)
+#
+# after simplifying and substituting extra_share formula becomes:
+#
+# (2) watermark_scale_new = watermark_scale + extra_free_pages / vm_total_pages * 10000
+#
+# B. managed_pages * (watermark_scale / 10000) < min / 4
+# The formula (1) becomes:
+#
+# min / 4 + extra_share = max(min / 4, managed_pages * (watermark_scale_new / 10000))
+#
+# after calculating watermark_scale_new, if (managed_pages * (watermark_scale_new / 10000))
+# is still smaller than min / 4 then we can't compensate extra_share with
+# watermark_scale anyway. Therefore calculation becomes:
+#
+# watermark_scale_new = (min / 4 + extra_share) / managed_pages * 10000
+#
+# after simplifying and substituting extra_share formula becomes:
+#
+# (3) watermark_scale_new = (min / 4) * 10000 / managed_pages + extra_free_pages / vm_total_pages * 10000
+#
+# After defining watermark_delta = extra_free_pages / vm_total_pages * 10000:
+#
+# if (managed_pages * (watermark_scale / 10000) > min / 4)
+#     watermark_scale_new = watermark_scale + watermark_delta
+# else
+#     watermark_scale_new = (min / 4) * 10000 / managed_pages + watermark_delta
+#
+
+if [ "$#" -ne 1 ]
+then
+    echo "Usage: $0 <extra_free_kbytes value>"
+    exit
+fi
+
+extra_free_kbytes=$1
+
+# if extra_free_kbytes knob exists, use it and exit
+if [ -e /proc/sys/vm/extra_free_kbytes ]
+then
+    echo $extra_free_kbytes > /proc/sys/vm/extra_free_kbytes
+    exit
+fi
+
+watermark_scale=`cat /proc/sys/vm/watermark_scale_factor`
+
+# convert extra_free_kbytes to pages
+page_size=$(getconf PAGESIZE)
+page_size_kb=$((page_size/1024))
+extra_free_pg=$((extra_free_kbytes/page_size_kb))
+
+managed=($(grep managed /proc/zoneinfo | awk '{print $2}'))
+length=${#managed[@]}
+min=($(grep "min" /proc/zoneinfo | awk '{print $2}'))
+
+# calculate vm_total_pages.
+# WARNING: if the final low watermark differs from the original, the source of
+# the error is likely vm_total_pages which is impossible to get exact from the
+# userspace. Grep for "Total pages" in the kernel logs to see the actual
+# vm_total_pages and plug it in the calculation to confirm the source of the
+# error. Error caused by this inaccuracy is normally within 1% range.
+vm_total_pages=0
+i=0
+while [ $i -lt $length ]
+do
+    vm_total_pages=$((vm_total_pages + managed[i]))
+    i=$((i+1))
+done
+
+# calculate watermark_scale_new for each zone and choose the max
+max_watermark_scale=0
+i=0
+while [ $i -lt $length ]
+do
+    # skip unmanaged zones
+    if [ ${managed[i]} -eq 0 ]
+    then
+        i=$((i+1))
+        continue
+    fi
+
+    base_margin=$((min[i] / 4))
+    calc_margin=$(echo "${managed[i]} * $watermark_scale / 10000" | bc)
+    # round the value by adding 0.5 and truncating the decimal part
+    watermark_delta=$(echo "x=($extra_free_pg / ($vm_total_pages / 10000) + 0.5); scale = 0; x/1" | bc -l)
+    if [ $calc_margin -gt $base_margin ]
+    then
+        watermark_scale_new=$(echo "$watermark_scale + $watermark_delta" | bc)
+    else
+        watermark_scale_new=$(echo "$base_margin / (${managed[i]} / 10000) + $watermark_delta" | bc)
+    fi
+
+    if [ $max_watermark_scale -lt $watermark_scale_new ]
+    then
+        max_watermark_scale=$watermark_scale_new
+    fi
+
+    i=$((i+1))
+done
+
+echo $max_watermark_scale > /proc/sys/vm/watermark_scale_factor
diff --git a/init/first_stage_console.cpp b/init/first_stage_console.cpp
index e2ea0ab..67cac19 100644
--- a/init/first_stage_console.cpp
+++ b/init/first_stage_console.cpp
@@ -85,7 +85,10 @@
 
 void StartConsole(const std::string& cmdline) {
     bool console = KernelConsolePresent(cmdline);
+    // Use a simple sigchld handler -- first_stage_console doesn't need to track or log zombies
+    const struct sigaction chld_act { .sa_handler = SIG_DFL, .sa_flags = SA_NOCLDWAIT };
 
+    sigaction(SIGCHLD, &chld_act, nullptr);
     pid_t pid = fork();
     if (pid != 0) {
         int status;
diff --git a/init/host_builtin_map.py b/init/host_builtin_map.py
index 6afcb17..41c86ac 100755
--- a/init/host_builtin_map.py
+++ b/init/host_builtin_map.py
@@ -1,4 +1,4 @@
-#!/usr/bin/env python
+#!/usr/bin/env python3
 """Generates the builtins map to be used by host_init_verifier.
 
 It copies the builtin function map from builtins.cpp, then replaces do_xxx() functions with the
@@ -39,8 +39,7 @@
   match = DO_REGEX.match(line)
   if match:
     if match.group(1) in check_functions:
-      print line.replace('do_', 'check_'),
+      line = line.replace('do_', 'check_')
     else:
-      print FUNCTION_REGEX.sub('check_stub', line),
-  else:
-    print line,
+      line = FUNCTION_REGEX.sub('check_stub', line)
+  print(line, end=' ')
diff --git a/init/mount_namespace.cpp b/init/mount_namespace.cpp
index 575cae9..593e5ae 100644
--- a/init/mount_namespace.cpp
+++ b/init/mount_namespace.cpp
@@ -97,110 +97,6 @@
     return true;
 }
 
-#ifdef ACTIVATE_FLATTENED_APEX
-
-static Result<void> MountDir(const std::string& path, const std::string& mount_path) {
-    if (int ret = mkdir(mount_path.c_str(), 0755); ret != 0 && errno != EEXIST) {
-        return ErrnoError() << "Could not create mount point " << mount_path;
-    }
-    if (mount(path.c_str(), mount_path.c_str(), nullptr, MS_BIND, nullptr) != 0) {
-        return ErrnoError() << "Could not bind mount " << path << " to " << mount_path;
-    }
-    return {};
-}
-
-static Result<apex::proto::ApexManifest> GetApexManifest(const std::string& apex_dir) {
-    const std::string manifest_path = apex_dir + "/apex_manifest.pb";
-    std::string content;
-    if (!android::base::ReadFileToString(manifest_path, &content)) {
-        return Error() << "Failed to read manifest file: " << manifest_path;
-    }
-    apex::proto::ApexManifest manifest;
-    if (!manifest.ParseFromString(content)) {
-        return Error() << "Can't parse manifest file: " << manifest_path;
-    }
-    return manifest;
-}
-
-template <typename Fn>
-static Result<void> ActivateFlattenedApexesFrom(const std::string& from_dir,
-                                                const std::string& to_dir, Fn on_activate) {
-    std::unique_ptr<DIR, decltype(&closedir)> dir(opendir(from_dir.c_str()), closedir);
-    if (!dir) {
-        return {};
-    }
-    dirent* entry;
-    std::vector<std::string> entries;
-
-    while ((entry = readdir(dir.get())) != nullptr) {
-        if (entry->d_name[0] == '.') continue;
-        if (entry->d_type == DT_DIR) {
-            entries.push_back(entry->d_name);
-        }
-    }
-
-    std::sort(entries.begin(), entries.end());
-    for (const auto& name : entries) {
-        const std::string apex_path = from_dir + "/" + name;
-        const auto apex_manifest = GetApexManifest(apex_path);
-        if (!apex_manifest.ok()) {
-            LOG(ERROR) << apex_path << " is not an APEX directory: " << apex_manifest.error();
-            continue;
-        }
-        const std::string mount_path = to_dir + "/" + apex_manifest->name();
-        if (auto result = MountDir(apex_path, mount_path); !result.ok()) {
-            return result;
-        }
-        on_activate(apex_path, *apex_manifest);
-    }
-    return {};
-}
-
-static bool ActivateFlattenedApexesIfPossible() {
-    if (IsRecoveryMode() || IsApexUpdatable()) {
-        return true;
-    }
-
-    const std::string kApexTop = "/apex";
-    const std::vector<std::string> kBuiltinDirsForApexes = {
-            "/system/apex",
-            "/system_ext/apex",
-            "/product/apex",
-            "/vendor/apex",
-    };
-
-    std::vector<com::android::apex::ApexInfo> apex_infos;
-    auto on_activate = [&](const std::string& apex_path,
-                           const apex::proto::ApexManifest& apex_manifest) {
-        apex_infos.emplace_back(apex_manifest.name(), apex_path, apex_path, apex_manifest.version(),
-                                apex_manifest.versionname(), /*isFactory=*/true, /*isActive=*/true,
-                                /* lastUpdateMillis= */ 0);
-    };
-
-    for (const auto& dir : kBuiltinDirsForApexes) {
-        if (auto result = ActivateFlattenedApexesFrom(dir, kApexTop, on_activate); !result.ok()) {
-            LOG(ERROR) << result.error();
-            return false;
-        }
-    }
-
-    std::ostringstream oss;
-    com::android::apex::ApexInfoList apex_info_list(apex_infos);
-    com::android::apex::write(oss, apex_info_list);
-    const std::string kApexInfoList = kApexTop + "/apex-info-list.xml";
-    if (!android::base::WriteStringToFile(oss.str(), kApexInfoList)) {
-        PLOG(ERROR) << "Failed to write " << kApexInfoList;
-        return false;
-    }
-    if (selinux_android_restorecon(kApexInfoList.c_str(), 0) != 0) {
-        PLOG(ERROR) << "selinux_android_restorecon(" << kApexInfoList << ") failed";
-    }
-
-    return true;
-}
-
-#endif  // ACTIVATE_FLATTENED_APEX
-
 static android::base::unique_fd bootstrap_ns_fd;
 static android::base::unique_fd default_ns_fd;
 
@@ -294,9 +190,7 @@
         default_ns_fd.reset(OpenMountNamespace());
         default_ns_id = GetMountNamespaceId();
     }
-#ifdef ACTIVATE_FLATTENED_APEX
-    success &= ActivateFlattenedApexesIfPossible();
-#endif
+
     LOG(INFO) << "SetupMountNamespaces done";
     return success;
 }
diff --git a/init/reboot.cpp b/init/reboot.cpp
index 0e788e4..1681627 100644
--- a/init/reboot.cpp
+++ b/init/reboot.cpp
@@ -639,6 +639,7 @@
         abort();
     }
 
+    bool do_shutdown_animation = GetBoolProperty("ro.init.shutdown_animation", false);
     // watchdogd is a vendor specific component but should be alive to complete shutdown safely.
     const std::set<std::string> to_starts{"watchdogd"};
     std::set<std::string> stop_first;
@@ -652,6 +653,8 @@
                            << "': " << result.error();
             }
             s->SetShutdownCritical();
+        } else if (do_shutdown_animation) {
+            continue;
         } else if (s->IsShutdownCritical()) {
             // Start shutdown critical service if not started.
             if (auto result = s->Start(); !result.ok()) {
@@ -664,14 +667,13 @@
     }
 
     // remaining operations (specifically fsck) may take a substantial duration
-    if (cmd == ANDROID_RB_POWEROFF || is_thermal_shutdown) {
+    if (!do_shutdown_animation && (cmd == ANDROID_RB_POWEROFF || is_thermal_shutdown)) {
         TurnOffBacklight();
     }
 
     Service* boot_anim = ServiceList::GetInstance().FindService("bootanim");
     Service* surface_flinger = ServiceList::GetInstance().FindService("surfaceflinger");
     if (boot_anim != nullptr && surface_flinger != nullptr && surface_flinger->IsRunning()) {
-        bool do_shutdown_animation = GetBoolProperty("ro.init.shutdown_animation", false);
 
         if (do_shutdown_animation) {
             SetProperty("service.bootanim.exit", "0");
@@ -1035,6 +1037,20 @@
                         return;
                     }
                 }
+            } else if (reboot_target == "quiescent") {
+                bootloader_message boot = {};
+                if (std::string err; !read_bootloader_message(&boot, &err)) {
+                    LOG(ERROR) << "Failed to read bootloader message: " << err;
+                }
+                // Update the boot command field if it's empty, and preserve
+                // the other arguments in the bootloader message.
+                if (!CommandIsPresent(&boot)) {
+                    strlcpy(boot.command, "boot-quiescent", sizeof(boot.command));
+                    if (std::string err; !write_bootloader_message(boot, &err)) {
+                        LOG(ERROR) << "Failed to set bootloader message: " << err;
+                        return;
+                    }
+                }
             } else if (reboot_target == "sideload" || reboot_target == "sideload-auto-reboot" ||
                        reboot_target == "fastboot") {
                 std::string arg = reboot_target == "sideload-auto-reboot" ? "sideload_auto_reboot"
diff --git a/libcutils/Android.bp b/libcutils/Android.bp
index 68b21c6..0d9f2c7 100644
--- a/libcutils/Android.bp
+++ b/libcutils/Android.bp
@@ -354,18 +354,3 @@
     defaults: ["libcutils_test_static_defaults"],
     test_config: "KernelLibcutilsTest.xml",
 }
-
-rust_bindgen {
-    name: "libcutils_bindgen",
-    wrapper_src: "rust/cutils.h",
-    crate_name: "cutils_bindgen",
-    source_stem: "bindings",
-    local_include_dirs: ["include"],
-    bindgen_flags: [
-        "--allowlist-function", "multiuser_get_app_id",
-        "--allowlist-function", "multiuser_get_uid",
-        "--allowlist-function", "multiuser_get_user_id",
-        "--allowlist-var", "AID_KEYSTORE",
-        "--allowlist-var", "AID_USER_OFFSET",
-    ],
-}
diff --git a/libcutils/TEST_MAPPING b/libcutils/TEST_MAPPING
new file mode 100644
index 0000000..e512ab7
--- /dev/null
+++ b/libcutils/TEST_MAPPING
@@ -0,0 +1,7 @@
+{
+  "presubmit": [
+    {
+      "name": "libcutils_test"
+    }
+  ]
+}
diff --git a/libcutils/rust/cutils.h b/libcutils/rust/cutils.h
deleted file mode 100644
index 9b78af6..0000000
--- a/libcutils/rust/cutils.h
+++ /dev/null
@@ -1,4 +0,0 @@
-#pragma once
-
-#include <cutils/multiuser.h>
-#include <private/android_filesystem_config.h>
diff --git a/libmodprobe/TEST_MAPPING b/libmodprobe/TEST_MAPPING
new file mode 100644
index 0000000..526b1e4
--- /dev/null
+++ b/libmodprobe/TEST_MAPPING
@@ -0,0 +1,7 @@
+{
+  "presubmit": [
+    {
+      "name": "libmodprobe_tests"
+    }
+  ]
+}
diff --git a/libpackagelistparser/TEST_MAPPING b/libpackagelistparser/TEST_MAPPING
new file mode 100644
index 0000000..51773f9
--- /dev/null
+++ b/libpackagelistparser/TEST_MAPPING
@@ -0,0 +1,7 @@
+{
+  "presubmit": [
+    {
+      "name": "libpackagelistparser_test"
+    }
+  ]
+}
diff --git a/libprocessgroup/cgroup_map.cpp b/libprocessgroup/cgroup_map.cpp
index 5ca0967..0734f25 100644
--- a/libprocessgroup/cgroup_map.cpp
+++ b/libprocessgroup/cgroup_map.cpp
@@ -43,6 +43,7 @@
 using android::base::GetBoolProperty;
 using android::base::StringPrintf;
 using android::base::unique_fd;
+using android::base::WriteStringToFile;
 
 static constexpr const char* CGROUP_PROCS_FILE = "/cgroup.procs";
 static constexpr const char* CGROUP_TASKS_FILE = "/tasks";
@@ -202,3 +203,21 @@
 
     return CgroupController(nullptr);
 }
+
+int CgroupMap::ActivateControllers(const std::string& path) const {
+    if (__builtin_available(android 30, *)) {
+        auto controller_count = ACgroupFile_getControllerCount();
+        for (uint32_t i = 0; i < controller_count; ++i) {
+            const ACgroupController* controller = ACgroupFile_getController(i);
+            if (ACgroupController_getFlags(controller) &
+                CGROUPRC_CONTROLLER_FLAG_NEEDS_ACTIVATION) {
+                std::string str = std::string("+") + ACgroupController_getName(controller);
+                if (!WriteStringToFile(str, path + "/cgroup.subtree_control")) {
+                    return -errno;
+                }
+            }
+        }
+        return 0;
+    }
+    return -ENOSYS;
+}
diff --git a/libprocessgroup/cgroup_map.h b/libprocessgroup/cgroup_map.h
index 427d71b..22d717b 100644
--- a/libprocessgroup/cgroup_map.h
+++ b/libprocessgroup/cgroup_map.h
@@ -62,6 +62,7 @@
 
     static CgroupMap& GetInstance();
     CgroupController FindController(const std::string& name) const;
+    int ActivateControllers(const std::string& path) const;
 
   private:
     bool loaded_ = false;
diff --git a/libprocessgroup/processgroup.cpp b/libprocessgroup/processgroup.cpp
index c824376..faf945c 100644
--- a/libprocessgroup/processgroup.cpp
+++ b/libprocessgroup/processgroup.cpp
@@ -416,13 +416,15 @@
     return KillProcessGroup(uid, initialPid, signal, 0 /*retries*/, max_processes);
 }
 
-static int createProcessGroupInternal(uid_t uid, int initialPid, std::string cgroup) {
+static int createProcessGroupInternal(uid_t uid, int initialPid, std::string cgroup,
+                                      bool activate_controllers) {
     auto uid_path = ConvertUidToPath(cgroup.c_str(), uid);
 
     struct stat cgroup_stat;
     mode_t cgroup_mode = 0750;
     gid_t cgroup_uid = AID_SYSTEM;
     uid_t cgroup_gid = AID_SYSTEM;
+    int ret = 0;
 
     if (stat(cgroup.c_str(), &cgroup_stat) == 1) {
         PLOG(ERROR) << "Failed to get stats for " << cgroup;
@@ -436,6 +438,13 @@
         PLOG(ERROR) << "Failed to make and chown " << uid_path;
         return -errno;
     }
+    if (activate_controllers) {
+        ret = CgroupMap::GetInstance().ActivateControllers(uid_path);
+        if (ret) {
+            LOG(ERROR) << "Failed to activate controllers in " << uid_path;
+            return ret;
+        }
+    }
 
     auto uid_pid_path = ConvertUidPidToPath(cgroup.c_str(), uid, initialPid);
 
@@ -446,7 +455,6 @@
 
     auto uid_pid_procs_file = uid_pid_path + PROCESSGROUP_CGROUP_PROCS_FILE;
 
-    int ret = 0;
     if (!WriteStringToFile(std::to_string(initialPid), uid_pid_procs_file)) {
         ret = -errno;
         PLOG(ERROR) << "Failed to write '" << initialPid << "' to " << uid_pid_procs_file;
@@ -466,14 +474,14 @@
     if (isMemoryCgroupSupported() && UsePerAppMemcg()) {
         CgroupGetControllerPath("memory", &cgroup);
         cgroup += "/apps";
-        int ret = createProcessGroupInternal(uid, initialPid, cgroup);
+        int ret = createProcessGroupInternal(uid, initialPid, cgroup, false);
         if (ret != 0) {
             return ret;
         }
     }
 
     CgroupGetControllerPath(CGROUPV2_CONTROLLER_NAME, &cgroup);
-    return createProcessGroupInternal(uid, initialPid, cgroup);
+    return createProcessGroupInternal(uid, initialPid, cgroup, true);
 }
 
 static bool SetProcessGroupValue(int tid, const std::string& attr_name, int64_t value) {
diff --git a/libsparse/Android.bp b/libsparse/Android.bp
index 0b4b640..3f9aeb2 100644
--- a/libsparse/Android.bp
+++ b/libsparse/Android.bp
@@ -85,11 +85,11 @@
     srcs: ["simg_dump.py"],
     version: {
         py2: {
-            embedded_launcher: true,
-            enabled: true,
+            enabled: false,
         },
         py3: {
-            enabled: false,
+            embedded_launcher: true,
+            enabled: true,
         },
     },
 }
diff --git a/libsparse/simg_dump.py b/libsparse/simg_dump.py
index 82a03ad..b0b3b22 100755
--- a/libsparse/simg_dump.py
+++ b/libsparse/simg_dump.py
@@ -1,4 +1,4 @@
-#! /usr/bin/env python
+#! /usr/bin/env python3
 
 # Copyright (C) 2012 The Android Open Source Project
 #
@@ -14,7 +14,6 @@
 # See the License for the specific language governing permissions and
 # limitations under the License.
 
-from __future__ import print_function
 import csv
 import getopt
 import hashlib
@@ -47,7 +46,7 @@
     opts, args = getopt.getopt(sys.argv[1:],
                                "vsc:",
                                ["verbose", "showhash", "csvfile"])
-  except getopt.GetoptError, e:
+  except getopt.GetoptError as e:
     print(e)
     usage(me)
   for o, a in opts:
diff --git a/libstats/pull_rust/Android.bp b/libstats/pull_rust/Android.bp
index 2a89e29..f07e32b 100644
--- a/libstats/pull_rust/Android.bp
+++ b/libstats/pull_rust/Android.bp
@@ -57,3 +57,13 @@
         "libstatspull_bindgen",
     ],
 }
+
+rust_test {
+    name: "libstatspull_bindgen_test",
+    srcs: [":libstatspull_bindgen"],
+    crate_name: "statspull_bindgen_test",
+    test_suites: ["general-tests"],
+    auto_gen_config: true,
+    clippy_lints: "none",
+    lints: "none",
+}
diff --git a/libutils/RefBase.cpp b/libutils/RefBase.cpp
index b57e287..0518927 100644
--- a/libutils/RefBase.cpp
+++ b/libutils/RefBase.cpp
@@ -170,7 +170,7 @@
         : mStrong(INITIAL_STRONG_VALUE)
         , mWeak(0)
         , mBase(base)
-        , mFlags(0)
+        , mFlags(OBJECT_LIFETIME_STRONG)
     {
     }
 
@@ -189,7 +189,7 @@
         : mStrong(INITIAL_STRONG_VALUE)
         , mWeak(0)
         , mBase(base)
-        , mFlags(0)
+        , mFlags(OBJECT_LIFETIME_STRONG)
         , mStrongRefs(NULL)
         , mWeakRefs(NULL)
         , mTrackEnabled(!!DEBUG_REFS_ENABLED_BY_DEFAULT)
diff --git a/libutils/TEST_MAPPING b/libutils/TEST_MAPPING
new file mode 100644
index 0000000..c8ef45c
--- /dev/null
+++ b/libutils/TEST_MAPPING
@@ -0,0 +1,7 @@
+{
+  "presubmit": [
+    {
+      "name": "libutils_test"
+    }
+  ]
+}
diff --git a/property_service/TEST_MAPPING b/property_service/TEST_MAPPING
new file mode 100644
index 0000000..fcdc86a
--- /dev/null
+++ b/property_service/TEST_MAPPING
@@ -0,0 +1,7 @@
+{
+  "presubmit": [
+    {
+      "name": "propertyinfoserializer_tests"
+    }
+  ]
+}
diff --git a/rootdir/init.rc b/rootdir/init.rc
index a7322fa..9371617 100644
--- a/rootdir/init.rc
+++ b/rootdir/init.rc
@@ -591,9 +591,10 @@
     # Load trusted keys from dm-verity protected partitions
     exec -- /system/bin/fsverity_init --load-verified-keys
 
+on late-fs && property:ro.product.cpu.abilist64=*
     # Set up a tracing instance for system_server to monitor error_report_end events.
     # These are sent by kernel tools like KASAN and KFENCE when a memory corruption
-    # is detected.
+    # is detected. This is only needed for 64-bit systems.
     mkdir /sys/kernel/tracing/instances/bootreceiver 0700 system system
     restorecon_recursive /sys/kernel/tracing/instances/bootreceiver
     write /sys/kernel/tracing/instances/bootreceiver/buffer_size_kb 1
@@ -1137,7 +1138,7 @@
 # and chown/chmod does not work for /proc/sys/ entries.
 # So proxy writes through init.
 on property:sys.sysctl.extra_free_kbytes=*
-    write /proc/sys/vm/extra_free_kbytes ${sys.sysctl.extra_free_kbytes}
+    exec -- /system/bin/extra_free_kbytes.sh ${sys.sysctl.extra_free_kbytes}
 
 # Allow users to drop caches
 on property:perf.drop_caches=3
diff --git a/toolbox/generate-input.h-labels.py b/toolbox/generate-input.h-labels.py
index c0e9fce..20db638 100755
--- a/toolbox/generate-input.h-labels.py
+++ b/toolbox/generate-input.h-labels.py
@@ -1,4 +1,4 @@
-#!/usr/bin/env python
+#!/usr/bin/env python3
 #
 # Copyright (C) 2015 The Android Open Source Project
 #
@@ -16,7 +16,7 @@
 #
 # pylint: disable=bad-indentation,bad-continuation
 
-from __future__ import print_function
+
 import os
 import re
 import sys
diff --git a/trusty/keymaster/Android.bp b/trusty/keymaster/Android.bp
index ff6460d..155363c 100644
--- a/trusty/keymaster/Android.bp
+++ b/trusty/keymaster/Android.bp
@@ -106,9 +106,9 @@
         "keymint/service.cpp",
     ],
     shared_libs: [
-        "android.hardware.security.keymint-V1-ndk_platform",
-        "android.hardware.security.secureclock-V1-ndk_platform",
-        "android.hardware.security.sharedsecret-V1-ndk_platform",
+        "android.hardware.security.keymint-V1-ndk",
+        "android.hardware.security.secureclock-V1-ndk",
+        "android.hardware.security.sharedsecret-V1-ndk",
         "lib_android_keymaster_keymint_utils",
         "libbase",
         "libbinder_ndk",
diff --git a/trusty/keymaster/ipc/trusty_keymaster_ipc.cpp b/trusty/keymaster/ipc/trusty_keymaster_ipc.cpp
index 0956fe6..2d44009 100644
--- a/trusty/keymaster/ipc/trusty_keymaster_ipc.cpp
+++ b/trusty/keymaster/ipc/trusty_keymaster_ipc.cpp
@@ -25,6 +25,8 @@
 #include <unistd.h>
 
 #include <algorithm>
+#include <variant>
+#include <vector>
 
 #include <log/log.h>
 #include <trusty/tipc.h>
@@ -46,8 +48,27 @@
     return 0;
 }
 
-int trusty_keymaster_call(uint32_t cmd, void* in, uint32_t in_size, uint8_t* out,
-                          uint32_t* out_size) {
+class VectorEraser {
+  public:
+    VectorEraser(std::vector<uint8_t>* v) : _v(v) {}
+    ~VectorEraser() {
+        if (_v) {
+            std::fill(const_cast<volatile uint8_t*>(_v->data()),
+                      const_cast<volatile uint8_t*>(_v->data() + _v->size()), 0);
+        }
+    }
+    void disarm() { _v = nullptr; }
+    VectorEraser(const VectorEraser&) = delete;
+    VectorEraser& operator=(const VectorEraser&) = delete;
+    VectorEraser(VectorEraser&& other) = delete;
+    VectorEraser& operator=(VectorEraser&&) = delete;
+
+  private:
+    std::vector<uint8_t>* _v;
+};
+
+std::variant<int, std::vector<uint8_t>> trusty_keymaster_call_2(uint32_t cmd, void* in,
+                                                                uint32_t in_size) {
     if (handle_ < 0) {
         ALOGE("not connected\n");
         return -EINVAL;
@@ -70,15 +91,38 @@
         ALOGE("failed to send cmd (%d) to %s: %s\n", cmd, KEYMASTER_PORT, strerror(errno));
         return -errno;
     }
-    size_t out_max_size = *out_size;
-    *out_size = 0;
+
+    std::vector<uint8_t> out(TRUSTY_KEYMASTER_RECV_BUF_SIZE);
+    VectorEraser out_eraser(&out);
+    uint8_t* write_pos = out.data();
+    uint8_t* out_end = out.data() + out.size();
+
     struct iovec iov[2];
     struct keymaster_message header;
     iov[0] = {.iov_base = &header, .iov_len = sizeof(struct keymaster_message)};
     while (true) {
-        iov[1] = {.iov_base = out + *out_size,
-                  .iov_len = std::min<uint32_t>(KEYMASTER_MAX_BUFFER_LENGTH,
-                                                out_max_size - *out_size)};
+        if (out_end - write_pos < KEYMASTER_MAX_BUFFER_LENGTH) {
+            // In stead of using std::vector.resize(), allocate a new one to have chance
+            // at zeroing the old buffer.
+            std::vector<uint8_t> new_out(out.size() + KEYMASTER_MAX_BUFFER_LENGTH);
+            // After the swap below this erases the old out buffer.
+            VectorEraser new_out_eraser(&new_out);
+            std::copy(out.data(), write_pos, new_out.begin());
+
+            auto write_offset = write_pos - out.data();
+
+            std::swap(new_out, out);
+
+            write_pos = out.data() + write_offset;
+            out_end = out.data() + out.size();
+        }
+        size_t buffer_size = 0;
+        if (__builtin_sub_overflow(reinterpret_cast<uintptr_t>(out_end),
+                                   reinterpret_cast<uintptr_t>(write_pos), &buffer_size)) {
+            return -EOVERFLOW;
+        }
+        iov[1] = {.iov_base = write_pos, .iov_len = buffer_size};
+
         rc = readv(handle_, iov, 2);
         if (rc < 0) {
             ALOGE("failed to retrieve response for cmd (%d) to %s: %s\n", cmd, KEYMASTER_PORT,
@@ -95,13 +139,36 @@
             ALOGE("invalid command (%d)", header.cmd);
             return -EINVAL;
         }
-        *out_size += ((size_t)rc - sizeof(struct keymaster_message));
+        write_pos += ((size_t)rc - sizeof(struct keymaster_message));
         if (header.cmd & KEYMASTER_STOP_BIT) {
             break;
         }
     }
 
-    return rc;
+    out.resize(write_pos - out.data());
+    out_eraser.disarm();
+    return out;
+}
+
+int trusty_keymaster_call(uint32_t cmd, void* in, uint32_t in_size, uint8_t* out,
+                          uint32_t* out_size) {
+    auto result = trusty_keymaster_call_2(cmd, in, in_size);
+    if (auto out_buffer = std::get_if<std::vector<uint8_t>>(&result)) {
+        if (out_buffer->size() <= *out_size) {
+            std::copy(out_buffer->begin(), out_buffer->end(), out);
+            std::fill(const_cast<volatile uint8_t*>(&*out_buffer->begin()),
+                      const_cast<volatile uint8_t*>(&*out_buffer->end()), 0);
+
+            *out_size = out_buffer->size();
+            return 0;
+        } else {
+            ALOGE("Message was to large (%zu) for the provided buffer (%u)", out_buffer->size(),
+                  *out_size);
+            return -EMSGSIZE;
+        }
+    } else {
+        return std::get<int>(result);
+    }
 }
 
 void trusty_keymaster_disconnect() {
@@ -155,28 +222,27 @@
     req.Serialize(send_buf, send_buf + req_size);
 
     // Send it
-    uint8_t recv_buf[TRUSTY_KEYMASTER_RECV_BUF_SIZE];
-    keymaster::Eraser recv_buf_eraser(recv_buf, TRUSTY_KEYMASTER_RECV_BUF_SIZE);
-    uint32_t rsp_size = TRUSTY_KEYMASTER_RECV_BUF_SIZE;
-    int rc = trusty_keymaster_call(command, send_buf, req_size, recv_buf, &rsp_size);
-    if (rc < 0) {
+    auto response = trusty_keymaster_call_2(command, send_buf, req_size);
+    if (auto response_buffer = std::get_if<std::vector<uint8_t>>(&response)) {
+        keymaster::Eraser response_buffer_erasor(response_buffer->data(), response_buffer->size());
+        ALOGV("Received %zu byte response\n", response_buffer->size());
+
+        const uint8_t* p = response_buffer->data();
+        if (!rsp->Deserialize(&p, p + response_buffer->size())) {
+            ALOGE("Error deserializing response of size %zu\n", response_buffer->size());
+            return KM_ERROR_UNKNOWN_ERROR;
+        } else if (rsp->error != KM_ERROR_OK) {
+            ALOGE("Response of size %zu contained error code %d\n", response_buffer->size(),
+                  (int)rsp->error);
+        }
+        return rsp->error;
+    } else {
+        auto rc = std::get<int>(response);
         // Reset the connection on tipc error
         trusty_keymaster_disconnect();
         trusty_keymaster_connect();
         ALOGE("tipc error: %d\n", rc);
         // TODO(swillden): Distinguish permanent from transient errors and set error_ appropriately.
         return translate_error(rc);
-    } else {
-        ALOGV("Received %d byte response\n", rsp_size);
     }
-
-    const uint8_t* p = recv_buf;
-    if (!rsp->Deserialize(&p, p + rsp_size)) {
-        ALOGE("Error deserializing response of size %d\n", (int)rsp_size);
-        return KM_ERROR_UNKNOWN_ERROR;
-    } else if (rsp->error != KM_ERROR_OK) {
-        ALOGE("Response of size %d contained error code %d\n", (int)rsp_size, (int)rsp->error);
-        return rsp->error;
-    }
-    return rsp->error;
 }
diff --git a/trusty/storage/proxy/storage.c b/trusty/storage/proxy/storage.c
index 5b83e21..2fde30f 100644
--- a/trusty/storage/proxy/storage.c
+++ b/trusty/storage/proxy/storage.c
@@ -477,7 +477,6 @@
     if (ssdir_fd < 0) {
         ALOGE("failed to open ss root dir \"%s\": %s\n",
                dirname, strerror(errno));
-        return -1;
     }
     ssdir_name = dirname;
     return 0;