diff --git a/cmds/installd/Android.mk b/cmds/installd/Android.mk
index 6cd0689..d29e5ba 100644
--- a/cmds/installd/Android.mk
+++ b/cmds/installd/Android.mk
@@ -45,8 +45,8 @@
 LOCAL_MODULE_CLASS := EXECUTABLES
 LOCAL_SRC_FILES := otapreopt_script.sh
 
-# Let this depend on otapreopt and the chroot tool, so we just have to mention one in a
-# configuration.
-LOCAL_REQUIRED_MODULES := otapreopt otapreopt_chroot
+# Let this depend on otapreopt, the chroot tool and the slot script, so we just have to mention one
+# in a configuration.
+LOCAL_REQUIRED_MODULES := otapreopt otapreopt_chroot otapreopt_slot
 
 include $(BUILD_PREBUILT)
diff --git a/cmds/installd/commands.cpp b/cmds/installd/commands.cpp
index e6680ed..95451bf 100644
--- a/cmds/installd/commands.cpp
+++ b/cmds/installd/commands.cpp
@@ -18,6 +18,7 @@
 
 #include <errno.h>
 #include <inttypes.h>
+#include <regex>
 #include <stdlib.h>
 #include <sys/capability.h>
 #include <sys/file.h>
@@ -28,9 +29,9 @@
 #include <sys/xattr.h>
 #include <unistd.h>
 
+#include <android-base/logging.h>
 #include <android-base/stringprintf.h>
 #include <android-base/strings.h>
-#include <android-base/logging.h>
 #include <android-base/unique_fd.h>
 #include <cutils/fs.h>
 #include <cutils/log.h>               // TODO: Move everything to base/logging.
@@ -43,12 +44,14 @@
 
 #include <globals.h>
 #include <installd_deps.h>
+#include <otapreopt_utils.h>
 #include <utils.h>
 
 #ifndef LOG_TAG
 #define LOG_TAG "installd"
 #endif
 
+using android::base::EndsWith;
 using android::base::StringPrintf;
 
 namespace android {
@@ -57,6 +60,26 @@
 static constexpr const char* kCpPath = "/system/bin/cp";
 static constexpr const char* kXattrDefault = "user.default";
 
+static constexpr const char* PKG_LIB_POSTFIX = "/lib";
+static constexpr const char* CACHE_DIR_POSTFIX = "/cache";
+static constexpr const char* CODE_CACHE_DIR_POSTFIX = "/code_cache";
+
+static constexpr const char* IDMAP_PREFIX = "/data/resource-cache/";
+static constexpr const char* IDMAP_SUFFIX = "@idmap";
+
+// NOTE: keep in sync with StorageManager
+static constexpr int FLAG_STORAGE_DE = 1 << 0;
+static constexpr int FLAG_STORAGE_CE = 1 << 1;
+
+// NOTE: keep in sync with Installer
+static constexpr int FLAG_CLEAR_CACHE_ONLY = 1 << 8;
+static constexpr int FLAG_CLEAR_CODE_CACHE_ONLY = 1 << 9;
+
+/* dexopt needed flags matching those in dalvik.system.DexFile */
+static constexpr int DEXOPT_DEX2OAT_NEEDED       = 1;
+static constexpr int DEXOPT_PATCHOAT_NEEDED      = 2;
+static constexpr int DEXOPT_SELF_PATCHOAT_NEEDED = 3;
+
 #define MIN_RESTRICTED_HOME_SDK_VERSION 24 // > M
 
 typedef int fd_t;
@@ -754,6 +777,16 @@
         sprintf(image_format_arg, "--image-format=%s", app_image_format);
     }
 
+    char dex2oat_large_app_threshold[kPropertyValueMax];
+    bool have_dex2oat_large_app_threshold =
+            get_property("dalvik.vm.dex2oat-very-large", dex2oat_large_app_threshold, NULL) > 0;
+    char dex2oat_large_app_threshold_arg[strlen("--very-large-app-threshold=") + kPropertyValueMax];
+    if (have_dex2oat_large_app_threshold) {
+        sprintf(dex2oat_large_app_threshold_arg,
+                "--very-large-app-threshold=%s",
+                dex2oat_large_app_threshold);
+    }
+
     static const char* DEX2OAT_BIN = "/system/bin/dex2oat";
 
     static const char* RUNTIME_ARG = "--runtime-arg";
@@ -854,7 +887,8 @@
                      + (have_app_image_format ? 1 : 0)
                      + dex2oat_flags_count
                      + (profile_fd == -1 ? 0 : 1)
-                     + (shared_libraries != nullptr ? 4 : 0)];
+                     + (shared_libraries != nullptr ? 4 : 0)
+                     + (have_dex2oat_large_app_threshold ? 1 : 0)];
     int i = 0;
     argv[i++] = DEX2OAT_BIN;
     argv[i++] = zip_fd_arg;
@@ -897,6 +931,9 @@
     if (have_app_image_format) {
         argv[i++] = image_format_arg;
     }
+    if (have_dex2oat_large_app_threshold) {
+        argv[i++] = dex2oat_large_app_threshold_arg;
+    }
     if (dex2oat_flags_count) {
         i += split(dex2oat_flags, argv + i);
     }
@@ -1313,13 +1350,29 @@
     return true;
 }
 
-static void trim_extension(char* path) {
-  // Trim the extension.
-  int pos = strlen(path);
-  for (; pos >= 0 && path[pos] != '.'; --pos) {}
-  if (pos >= 0) {
-      path[pos] = '\0';  // Trim extension
+// Translate the given oat path to an art (app image) path. An empty string
+// denotes an error.
+static std::string create_image_filename(const std::string& oat_path) {
+  // A standard dalvik-cache entry. Replace ".dex" with ".art."
+  if (EndsWith(oat_path, ".dex")) {
+    std::string art_path = oat_path;
+    art_path.replace(art_path.length() - strlen("dex"), strlen("dex"), "art");
+    CHECK(EndsWith(art_path, ".art"));
+    return art_path;
   }
+
+  // An odex entry. Not that this may not be an extension, e.g., in the OTA
+  // case (where the base name will have an extension for the B artifact).
+  size_t odex_pos = oat_path.rfind(".odex");
+  if (odex_pos != std::string::npos) {
+    std::string art_path = oat_path;
+    art_path.replace(odex_pos, strlen(".odex"), ".art");
+    CHECK_NE(art_path.find(".art"), std::string::npos);
+    return art_path;
+  }
+
+  // Don't know how to handle this.
+  return "";
 }
 
 static bool add_extension_to_file_name(char* file_name, const char* extension) {
@@ -1330,7 +1383,7 @@
     return true;
 }
 
-static int open_output_file(char* file_name, bool recreate, int permissions) {
+static int open_output_file(const char* file_name, bool recreate, int permissions) {
     int flags = O_RDWR | O_CREAT;
     if (recreate) {
         if (unlink(file_name) < 0) {
@@ -1388,19 +1441,110 @@
     return analyse_profiles(uid, pkgname);
 }
 
+static const char* parse_null(const char* arg) {
+    if (strcmp(arg, "!") == 0) {
+        return nullptr;
+    } else {
+        return arg;
+    }
+}
+
+int dexopt(const char* const params[DEXOPT_PARAM_COUNT]) {
+    return dexopt(params[0],                    // apk_path
+                  atoi(params[1]),              // uid
+                  params[2],                    // pkgname
+                  params[3],                    // instruction_set
+                  atoi(params[4]),              // dexopt_needed
+                  params[5],                    // oat_dir
+                  atoi(params[6]),              // dexopt_flags
+                  params[7],                    // compiler_filter
+                  parse_null(params[8]),        // volume_uuid
+                  parse_null(params[9]));       // shared_libraries
+    static_assert(DEXOPT_PARAM_COUNT == 10U, "Unexpected dexopt param count");
+}
+
+// Helper for fd management. This is similar to a unique_fd in that it closes the file descriptor
+// on destruction. It will also run the given cleanup (unless told not to) after closing.
+//
+// Usage example:
+//
+//   Dex2oatFileWrapper<std::function<void ()>> file(open(...),
+//                                                   [name]() {
+//                                                       unlink(name.c_str());
+//                                                   });
+//   // Note: care needs to be taken about name, as it needs to have a lifetime longer than the
+//            wrapper if captured as a reference.
+//
+//   if (file.get() == -1) {
+//       // Error opening...
+//   }
+//
+//   ...
+//   if (error) {
+//       // At this point, when the Dex2oatFileWrapper is destructed, the cleanup function will run
+//       // and delete the file (after the fd is closed).
+//       return -1;
+//   }
+//
+//   (Success case)
+//   file.SetCleanup(false);
+//   // At this point, when the Dex2oatFileWrapper is destructed, the cleanup function will not run
+//   // (leaving the file around; after the fd is closed).
+//
+template <typename Cleanup>
+class Dex2oatFileWrapper {
+ public:
+    Dex2oatFileWrapper() : value_(-1), cleanup_(), do_cleanup_(true) {
+    }
+
+    Dex2oatFileWrapper(int value, Cleanup cleanup)
+            : value_(value), cleanup_(cleanup), do_cleanup_(true) {}
+
+    ~Dex2oatFileWrapper() {
+        reset(-1);
+    }
+
+    int get() {
+        return value_;
+    }
+
+    void SetCleanup(bool cleanup) {
+        do_cleanup_ = cleanup;
+    }
+
+    void reset(int new_value) {
+        if (value_ >= 0) {
+            close(value_);
+        }
+        if (do_cleanup_ && cleanup_ != nullptr) {
+            cleanup_();
+        }
+
+        value_ = new_value;
+    }
+
+    void reset(int new_value, Cleanup new_cleanup) {
+        if (value_ >= 0) {
+            close(value_);
+        }
+        if (do_cleanup_ && cleanup_ != nullptr) {
+            cleanup_();
+        }
+
+        value_ = new_value;
+        cleanup_ = new_cleanup;
+    }
+
+ private:
+    int value_;
+    Cleanup cleanup_;
+    bool do_cleanup_;
+};
+
 int dexopt(const char* apk_path, uid_t uid, const char* pkgname, const char* instruction_set,
            int dexopt_needed, const char* oat_dir, int dexopt_flags, const char* compiler_filter,
            const char* volume_uuid ATTRIBUTE_UNUSED, const char* shared_libraries)
 {
-    struct utimbuf ut;
-    struct stat input_stat;
-    char out_path[PKG_PATH_MAX];
-    char swap_file_name[PKG_PATH_MAX];
-    char image_path[PKG_PATH_MAX];
-    const char *input_file;
-    char in_odex_path[PKG_PATH_MAX];
-    int res;
-    fd_t input_fd=-1, out_fd=-1, image_fd=-1, swap_fd=-1;
     bool is_public = ((dexopt_flags & DEXOPT_PUBLIC) != 0);
     bool vm_safe_mode = (dexopt_flags & DEXOPT_SAFEMODE) != 0;
     bool debuggable = (dexopt_flags & DEXOPT_DEBUGGABLE) != 0;
@@ -1410,12 +1554,16 @@
     CHECK(pkgname != nullptr);
     CHECK(pkgname[0] != 0);
 
-    fd_t reference_profile_fd = -1;
     // Public apps should not be compiled with profile information ever. Same goes for the special
     // package '*' used for the system server.
+    Dex2oatFileWrapper<std::function<void ()>> reference_profile_fd;
     if (!is_public && pkgname[0] != '*') {
         // Open reference profile in read only mode as dex2oat does not get write permissions.
-        reference_profile_fd = open_reference_profile(uid, pkgname, /*read_write*/ false);
+        const std::string pkgname_str(pkgname);
+        reference_profile_fd.reset(open_reference_profile(uid, pkgname, /*read_write*/ false),
+                                   [pkgname_str]() {
+                                       clear_reference_profile(pkgname_str.c_str());
+                                   });
         // Note: it's OK to not find a profile here.
     }
 
@@ -1423,10 +1571,13 @@
         LOG_FATAL("dexopt flags contains unknown fields\n");
     }
 
+    char out_path[PKG_PATH_MAX];
     if (!create_oat_out_path(apk_path, instruction_set, oat_dir, out_path)) {
         return false;
     }
 
+    const char *input_file;
+    char in_odex_path[PKG_PATH_MAX];
     switch (dexopt_needed) {
         case DEXOPT_DEX2OAT_NEEDED:
             input_file = apk_path;
@@ -1445,35 +1596,41 @@
 
         default:
             ALOGE("Invalid dexopt needed: %d\n", dexopt_needed);
-            exit(72);
+            return 72;
     }
 
+    struct stat input_stat;
     memset(&input_stat, 0, sizeof(input_stat));
     stat(input_file, &input_stat);
 
-    input_fd = open(input_file, O_RDONLY, 0);
-    if (input_fd < 0) {
+    base::unique_fd input_fd(open(input_file, O_RDONLY, 0));
+    if (input_fd.get() < 0) {
         ALOGE("installd cannot open '%s' for input during dexopt\n", input_file);
         return -1;
     }
 
-    out_fd = open_output_file(out_path, /*recreate*/true, /*permissions*/0644);
-    if (out_fd < 0) {
+    const std::string out_path_str(out_path);
+    Dex2oatFileWrapper<std::function<void ()>> out_fd(
+            open_output_file(out_path, /*recreate*/true, /*permissions*/0644),
+            [out_path_str]() { unlink(out_path_str.c_str()); });
+    if (out_fd.get() < 0) {
         ALOGE("installd cannot open '%s' for output during dexopt\n", out_path);
-        goto fail;
+        return -1;
     }
-    if (!set_permissions_and_ownership(out_fd, is_public, uid, out_path)) {
-        goto fail;
+    if (!set_permissions_and_ownership(out_fd.get(), is_public, uid, out_path)) {
+        return -1;
     }
 
     // Create a swap file if necessary.
+    base::unique_fd swap_fd;
     if (ShouldUseSwapFileForDexopt()) {
         // Make sure there really is enough space.
+        char swap_file_name[PKG_PATH_MAX];
         strcpy(swap_file_name, out_path);
         if (add_extension_to_file_name(swap_file_name, ".swap")) {
-            swap_fd = open_output_file(swap_file_name, /*recreate*/true, /*permissions*/0600);
+            swap_fd.reset(open_output_file(swap_file_name, /*recreate*/true, /*permissions*/0600));
         }
-        if (swap_fd < 0) {
+        if (swap_fd.get() < 0) {
             // Could not create swap file. Optimistically go on and hope that we can compile
             // without it.
             ALOGE("installd could not create '%s' for swap during dexopt\n", swap_file_name);
@@ -1486,111 +1643,108 @@
     }
 
     // Avoid generating an app image for extract only since it will not contain any classes.
-    strcpy(image_path, out_path);
-    trim_extension(image_path);
-    if (add_extension_to_file_name(image_path, ".art")) {
-      char app_image_format[kPropertyValueMax];
-      bool have_app_image_format =
-              get_property("dalvik.vm.appimageformat", app_image_format, NULL) > 0;
-      // Use app images only if it is enabled (by a set image format) and we are compiling
-      // profile-guided (so the app image doesn't conservatively contain all classes).
-      if (profile_guided && have_app_image_format) {
-          // Recreate is true since we do not want to modify a mapped image. If the app is already
-          // running and we modify the image file, it can cause crashes (b/27493510).
-          image_fd = open_output_file(image_path, /*recreate*/true, /*permissions*/0600);
-          if (image_fd < 0) {
-              // Could not create application image file. Go on since we can compile without it.
-              ALOGE("installd could not create '%s' for image file during dexopt\n", image_path);
-          } else if (!set_permissions_and_ownership(image_fd, is_public, uid, image_path)) {
-              image_fd = -1;
-          }
-      }
-      // If we have a valid image file path but no image fd, erase the image file.
-      if (image_fd < 0) {
-          if (unlink(image_path) < 0) {
-              if (errno != ENOENT) {
-                  PLOG(ERROR) << "Couldn't unlink image file " << image_path;
-              }
-          }
-      }
+    Dex2oatFileWrapper<std::function<void ()>> image_fd;
+    const std::string image_path = create_image_filename(out_path);
+    if (!image_path.empty()) {
+        char app_image_format[kPropertyValueMax];
+        bool have_app_image_format =
+                get_property("dalvik.vm.appimageformat", app_image_format, NULL) > 0;
+        // Use app images only if it is enabled (by a set image format) and we are compiling
+        // profile-guided (so the app image doesn't conservatively contain all classes).
+        if (profile_guided && have_app_image_format) {
+            // Recreate is true since we do not want to modify a mapped image. If the app is
+            // already running and we modify the image file, it can cause crashes (b/27493510).
+            image_fd.reset(open_output_file(image_path.c_str(),
+                                            true /*recreate*/,
+                                            0600 /*permissions*/),
+                           [image_path]() { unlink(image_path.c_str()); }
+                           );
+            if (image_fd.get() < 0) {
+                // Could not create application image file. Go on since we can compile without
+                // it.
+                LOG(ERROR) << "installd could not create '"
+                        << image_path
+                        << "' for image file during dexopt";
+            } else if (!set_permissions_and_ownership(image_fd.get(),
+                                                      is_public,
+                                                      uid,
+                                                      image_path.c_str())) {
+                image_fd.reset(-1);
+            }
+        }
+        // If we have a valid image file path but no image fd, explicitly erase the image file.
+        if (image_fd.get() < 0) {
+            if (unlink(image_path.c_str()) < 0) {
+                if (errno != ENOENT) {
+                    PLOG(ERROR) << "Couldn't unlink image file " << image_path;
+                }
+            }
+        }
     }
 
     ALOGV("DexInv: --- BEGIN '%s' ---\n", input_file);
 
-    pid_t pid;
-    pid = fork();
+    pid_t pid = fork();
     if (pid == 0) {
         /* child -- drop privileges before continuing */
         drop_capabilities(uid);
 
         SetDex2OatAndPatchOatScheduling(boot_complete);
-        if (flock(out_fd, LOCK_EX | LOCK_NB) != 0) {
+        if (flock(out_fd.get(), LOCK_EX | LOCK_NB) != 0) {
             ALOGE("flock(%s) failed: %s\n", out_path, strerror(errno));
-            exit(67);
+            _exit(67);
         }
 
         if (dexopt_needed == DEXOPT_PATCHOAT_NEEDED
             || dexopt_needed == DEXOPT_SELF_PATCHOAT_NEEDED) {
-            run_patchoat(input_fd, out_fd, input_file, out_path, pkgname, instruction_set);
+            run_patchoat(input_fd.get(),
+                         out_fd.get(),
+                         input_file,
+                         out_path,
+                         pkgname,
+                         instruction_set);
         } else if (dexopt_needed == DEXOPT_DEX2OAT_NEEDED) {
             // Pass dex2oat the relative path to the input file.
             const char *input_file_name = get_location_from_path(input_file);
-            run_dex2oat(input_fd, out_fd, image_fd, input_file_name, out_path, swap_fd,
-                        instruction_set, compiler_filter, vm_safe_mode, debuggable, boot_complete,
-                        reference_profile_fd, shared_libraries);
+            run_dex2oat(input_fd.get(),
+                        out_fd.get(),
+                        image_fd.get(),
+                        input_file_name,
+                        out_path,
+                        swap_fd.get(),
+                        instruction_set,
+                        compiler_filter,
+                        vm_safe_mode,
+                        debuggable,
+                        boot_complete,
+                        reference_profile_fd.get(),
+                        shared_libraries);
         } else {
             ALOGE("Invalid dexopt needed: %d\n", dexopt_needed);
-            exit(73);
+            _exit(73);
         }
-        exit(68);   /* only get here on exec failure */
+        _exit(68);   /* only get here on exec failure */
     } else {
-        res = wait_child(pid);
+        int res = wait_child(pid);
         if (res == 0) {
             ALOGV("DexInv: --- END '%s' (success) ---\n", input_file);
         } else {
             ALOGE("DexInv: --- END '%s' --- status=0x%04x, process failed\n", input_file, res);
-            goto fail;
+            return -1;
         }
     }
 
+    struct utimbuf ut;
     ut.actime = input_stat.st_atime;
     ut.modtime = input_stat.st_mtime;
     utime(out_path, &ut);
 
-    close(out_fd);
-    close(input_fd);
-    if (swap_fd >= 0) {
-        close(swap_fd);
-    }
-    if (reference_profile_fd >= 0) {
-        close(reference_profile_fd);
-    }
-    if (image_fd >= 0) {
-        close(image_fd);
-    }
-    return 0;
+    // We've been successful, don't delete output.
+    out_fd.SetCleanup(false);
+    image_fd.SetCleanup(false);
+    reference_profile_fd.SetCleanup(false);
 
-fail:
-    if (out_fd >= 0) {
-        close(out_fd);
-        unlink(out_path);
-    }
-    if (input_fd >= 0) {
-        close(input_fd);
-    }
-    if (reference_profile_fd >= 0) {
-        close(reference_profile_fd);
-        // We failed to compile. Unlink the reference profile. Current profiles are already unlinked
-        // when profmoan advises compilation.
-        clear_reference_profile(pkgname);
-    }
-    if (swap_fd >= 0) {
-        close(swap_fd);
-    }
-    if (image_fd >= 0) {
-        close(image_fd);
-    }
-    return -1;
+    return 0;
 }
 
 int mark_boot_complete(const char* instruction_set)
@@ -1925,11 +2079,59 @@
     return true;
 }
 
+// Move/rename a B artifact (from) to an A artifact (to).
+static bool move_ab_path(const std::string& b_path, const std::string& a_path) {
+    // Check whether B exists.
+    {
+        struct stat s;
+        if (stat(b_path.c_str(), &s) != 0) {
+            // Silently ignore for now. The service calling this isn't smart enough to understand
+            // lack of artifacts at the moment.
+            return false;
+        }
+        if (!S_ISREG(s.st_mode)) {
+            LOG(ERROR) << "A/B artifact " << b_path << " is not a regular file.";
+            // Try to unlink, but swallow errors.
+            unlink(b_path.c_str());
+            return false;
+        }
+    }
+
+    // Rename B to A.
+    if (!unlink_and_rename(b_path.c_str(), a_path.c_str())) {
+        // Delete the b_path so we don't try again (or fail earlier).
+        if (unlink(b_path.c_str()) != 0) {
+            PLOG(ERROR) << "Could not unlink " << b_path;
+        }
+
+        return false;
+    }
+
+    return true;
+}
+
 int move_ab(const char* apk_path, const char* instruction_set, const char* oat_dir) {
     if (apk_path == nullptr || instruction_set == nullptr || oat_dir == nullptr) {
         LOG(ERROR) << "Cannot move_ab with null input";
         return -1;
     }
+
+    // Get the current slot suffix. No suffix, no A/B.
+    std::string slot_suffix;
+    {
+        char buf[kPropertyValueMax];
+        if (get_property("ro.boot.slot_suffix", buf, nullptr) <= 0) {
+            return -1;
+        }
+        slot_suffix = buf;
+
+        if (!ValidateTargetSlotSuffix(slot_suffix)) {
+            LOG(ERROR) << "Target slot suffix not legal: " << slot_suffix;
+            return -1;
+        }
+    }
+
+    // Validate other inputs.
     if (validate_apk_path(apk_path) != 0) {
         LOG(ERROR) << "invalid apk_path " << apk_path;
         return -1;
@@ -1943,37 +2145,37 @@
     if (!calculate_oat_file_path(a_path, oat_dir, apk_path, instruction_set)) {
         return -1;
     }
+    const std::string a_image_path = create_image_filename(a_path);
 
-    // B path = A path + ".b"
-    std::string b_path = StringPrintf("%s.b", a_path);
+    // B path = A path + slot suffix.
+    const std::string b_path = StringPrintf("%s.%s", a_path, slot_suffix.c_str());
+    const std::string b_image_path = StringPrintf("%s.%s",
+                                                  a_image_path.c_str(),
+                                                  slot_suffix.c_str());
 
-    // Check whether B exists.
-    {
-        struct stat s;
-        if (stat(b_path.c_str(), &s) != 0) {
-            // Silently ignore for now. The service calling this isn't smart enough to understand
-            // lack of artifacts at the moment.
-            return -1;
+    bool oat_success = move_ab_path(b_path, a_path);
+    bool success;
+
+    if (oat_success) {
+        // Note: we can live without an app image. As such, ignore failure to move the image file.
+        //       If we decide to require the app image, or the app image being moved correctly,
+        //       then change accordingly.
+        constexpr bool kIgnoreAppImageFailure = true;
+
+        bool art_success = true;
+        if (!a_image_path.empty()) {
+            art_success = move_ab_path(b_image_path, a_image_path);
         }
-        if (!S_ISREG(s.st_mode)) {
-            LOG(ERROR) << "A/B artifact " << b_path << " is not a regular file.";
-            // Try to unlink, but swallow errors.
-            unlink(b_path.c_str());
-            return -1;
-        }
+
+        success = art_success || kIgnoreAppImageFailure;
+    } else {
+        // Cleanup: delete B image, ignore errors.
+        unlink(b_image_path.c_str());
+
+        success = false;
     }
 
-    // Rename B to A.
-    if (!unlink_and_rename(b_path.c_str(), a_path)) {
-        // Delete the b_path so we don't try again (or fail earlier).
-        if (unlink(b_path.c_str()) != 0) {
-            PLOG(ERROR) << "Could not unlink " << b_path;
-        }
-
-        return -1;
-    }
-
-    return 0;
+    return success ? 0 : -1;
 }
 
 }  // namespace installd
diff --git a/cmds/installd/commands.h b/cmds/installd/commands.h
index 7a42c5c..e990f1b 100644
--- a/cmds/installd/commands.h
+++ b/cmds/installd/commands.h
@@ -28,6 +28,8 @@
 namespace android {
 namespace installd {
 
+static constexpr size_t DEXOPT_PARAM_COUNT = 10U;
+
 int create_app_data(const char *uuid, const char *pkgname, userid_t userid, int flags,
         appid_t appid, const char* seinfo, int target_sdk_version);
 int restorecon_app_data(const char* uuid, const char* pkgName, userid_t userid, int flags,
@@ -56,9 +58,21 @@
 
 bool dump_profile(uid_t uid, const char *pkgname, const char *dex_files);
 
-int dexopt(const char *apk_path, uid_t uid, const char *pkgName, const char *instruction_set,
-           int dexopt_needed, const char* oat_dir, int dexopt_flags, const char* compiler_filter,
-           const char* volume_uuid, const char* shared_libraries);
+int dexopt(const char *apk_path,
+           uid_t uid,
+           const char *pkgName,
+           const char *instruction_set,
+           int dexopt_needed,
+           const char* oat_dir,
+           int dexopt_flags,
+           const char* compiler_filter,
+           const char* volume_uuid,
+           const char* shared_libraries);
+static_assert(DEXOPT_PARAM_COUNT == 10U, "Unexpected dexopt param size");
+
+// Helper for the above, converting arguments.
+int dexopt(const char* const params[DEXOPT_PARAM_COUNT]);
+
 int mark_boot_complete(const char *instruction_set);
 int linklib(const char* uuid, const char* pkgname, const char* asecLibDir, int userId);
 int idmap(const char *target_path, const char *overlay_path, uid_t uid);
diff --git a/cmds/installd/globals.cpp b/cmds/installd/globals.cpp
index 6a67e29..93e1ce5 100644
--- a/cmds/installd/globals.cpp
+++ b/cmds/installd/globals.cpp
@@ -30,6 +30,22 @@
 namespace android {
 namespace installd {
 
+static constexpr const char* APP_SUBDIR = "app/"; // sub-directory under ANDROID_DATA
+
+static constexpr const char* PRIV_APP_SUBDIR = "priv-app/"; // sub-directory under ANDROID_DATA
+
+static constexpr const char* EPHEMERAL_APP_SUBDIR = "app-ephemeral/"; // sub-directory under
+                                                                      // ANDROID_DATA
+
+static constexpr const char* APP_LIB_SUBDIR = "app-lib/"; // sub-directory under ANDROID_DATA
+
+static constexpr const char* MEDIA_SUBDIR = "media/"; // sub-directory under ANDROID_DATA
+
+static constexpr const char* PROFILES_SUBDIR = "misc/profiles"; // sub-directory under ANDROID_DATA
+
+static constexpr const char* PRIVATE_APP_SUBDIR = "app-private/"; // sub-directory under
+                                                                  // ANDROID_DATA
+
 /* Directory records that are used in execution of commands. */
 dir_rec_t android_app_dir;
 dir_rec_t android_app_ephemeral_dir;
@@ -77,7 +93,7 @@
 
     // Get the android ephemeral app directory.
     if (copy_and_append(&android_app_ephemeral_dir, &android_data_dir, EPHEMERAL_APP_SUBDIR) < 0) {
-        return -1;
+        return false;
     }
 
     // Get the android app native library directory.
@@ -86,7 +102,7 @@
     }
 
     // Get the sd-card ASEC mount point.
-    if (get_path_from_env(&android_asec_dir, "ASEC_MOUNTPOINT") < 0) {
+    if (get_path_from_env(&android_asec_dir, ASEC_MOUNTPOINT_ENV_NAME) < 0) {
         return false;
     }
 
diff --git a/cmds/installd/globals.h b/cmds/installd/globals.h
index 3e52346..c90beec 100644
--- a/cmds/installd/globals.h
+++ b/cmds/installd/globals.h
@@ -23,6 +23,11 @@
 namespace android {
 namespace installd {
 
+/* constants */
+
+// Name of the environment variable that contains the asec mountpoint.
+static constexpr const char* ASEC_MOUNTPOINT_ENV_NAME = "ASEC_MOUNTPOINT";
+
 /* data structures */
 
 struct dir_rec_t {
diff --git a/cmds/installd/installd.cpp b/cmds/installd/installd.cpp
index d5c3ccd..531c6df 100644
--- a/cmds/installd/installd.cpp
+++ b/cmds/installd/installd.cpp
@@ -219,7 +219,8 @@
 // We use otapreopt_chroot to get into the chroot.
 static constexpr const char* kOtaPreopt = "/system/bin/otapreopt_chroot";
 
-static int do_ota_dexopt(char **arg, char reply[REPLY_MAX] ATTRIBUTE_UNUSED) {
+static int do_ota_dexopt(const char* args[DEXOPT_PARAM_COUNT],
+                         char reply[REPLY_MAX] ATTRIBUTE_UNUSED) {
     // Time to fork and run otapreopt.
 
     // Check that the tool exists.
@@ -231,12 +232,14 @@
 
     pid_t pid = fork();
     if (pid == 0) {
-        const char* argv[1 + 9 + 1];
+        const char* argv[1 + DEXOPT_PARAM_COUNT + 1];
         argv[0] = kOtaPreopt;
-        for (size_t i = 1; i <= 9; ++i) {
-            argv[i] = arg[i - 1];
+
+        for (size_t i = 0; i < DEXOPT_PARAM_COUNT; ++i) {
+            argv[i + 1] = args[i];
         }
-        argv[10] = nullptr;
+
+        argv[DEXOPT_PARAM_COUNT + 1] = nullptr;
 
         execv(argv[0], (char * const *)argv);
         PLOG(ERROR) << "execv(OTAPREOPT_CHROOT) failed";
@@ -252,22 +255,30 @@
     }
 }
 
+static int do_regular_dexopt(const char* args[DEXOPT_PARAM_COUNT],
+                             char reply[REPLY_MAX] ATTRIBUTE_UNUSED) {
+    return dexopt(args);
+}
+
+using DexoptFn = int (*)(const char* args[DEXOPT_PARAM_COUNT],
+                         char reply[REPLY_MAX]);
+
 static int do_dexopt(char **arg, char reply[REPLY_MAX])
 {
-    int dexopt_flags = atoi(arg[6]);
-    if ((dexopt_flags & DEXOPT_OTA) != 0) {
-      return do_ota_dexopt(arg, reply);
+    const char* args[DEXOPT_PARAM_COUNT];
+    for (size_t i = 0; i < DEXOPT_PARAM_COUNT; ++i) {
+        CHECK(arg[i] != nullptr);
+        args[i] = arg[i];
     }
-    return dexopt(arg[0],                      // apk_path
-                  atoi(arg[1]),                // uid
-                  arg[2],                      // pkgname
-                  arg[3],                      // instruction_set
-                  atoi(arg[4]),                // dexopt_needed
-                  arg[5],                      // oat_dir
-                  dexopt_flags,
-                  arg[7],                      // compiler_filter
-                  parse_null(arg[8]),          // volume_uuid
-                  parse_null(arg[9]));         // shared_libraries
+
+    int dexopt_flags = atoi(arg[6]);
+    DexoptFn dexopt_fn;
+    if ((dexopt_flags & DEXOPT_OTA) != 0) {
+        dexopt_fn = do_ota_dexopt;
+    } else {
+        dexopt_fn = do_regular_dexopt;
+    }
+    return dexopt_fn(args, reply);
 }
 
 static int do_merge_profiles(char **arg, char reply[REPLY_MAX])
@@ -546,7 +557,7 @@
     return 0;
 }
 
-bool initialize_globals() {
+static bool initialize_globals() {
     const char* data_path = getenv("ANDROID_DATA");
     if (data_path == nullptr) {
         ALOGE("Could not find ANDROID_DATA");
diff --git a/cmds/installd/installd_constants.h b/cmds/installd/installd_constants.h
index dfde727..b0bcce9 100644
--- a/cmds/installd/installd_constants.h
+++ b/cmds/installd/installd_constants.h
@@ -26,50 +26,13 @@
 constexpr const char* PRIMARY_USER_PREFIX = "data/";
 constexpr const char* SECONDARY_USER_PREFIX = "user/";
 
-constexpr const char* PKG_DIR_POSTFIX = "";
-
-constexpr const char* PKG_LIB_POSTFIX = "/lib";
-
-constexpr const char* CACHE_DIR_POSTFIX = "/cache";
-constexpr const char* CODE_CACHE_DIR_POSTFIX = "/code_cache";
-
-constexpr const char* APP_SUBDIR = "app/"; // sub-directory under ANDROID_DATA
-constexpr const char* PRIV_APP_SUBDIR = "priv-app/"; // sub-directory under ANDROID_DATA
-constexpr const char* EPHEMERAL_APP_SUBDIR = "app-ephemeral/"; // sub-directory under ANDROID_DATA
-
-constexpr const char* APP_LIB_SUBDIR = "app-lib/"; // sub-directory under ANDROID_DATA
-
-constexpr const char* MEDIA_SUBDIR = "media/"; // sub-directory under ANDROID_DATA
-
-constexpr const char* PROFILES_SUBDIR = "misc/profiles"; // sub-directory under ANDROID_DATA
-
-/* other handy constants */
-
-constexpr const char* PRIVATE_APP_SUBDIR = "app-private/"; // sub-directory under ANDROID_DATA
-
 // This is used as a string literal, can't be constants. TODO: std::string...
 #define DALVIK_CACHE "dalvik-cache"
 constexpr const char* DALVIK_CACHE_POSTFIX = "@classes.dex";
 
-constexpr const char* IDMAP_PREFIX = "/data/resource-cache/";
-constexpr const char* IDMAP_SUFFIX = "@idmap";
-
 constexpr size_t PKG_NAME_MAX = 128u;   /* largest allowed package name */
 constexpr size_t PKG_PATH_MAX = 256u;   /* max size of any path we use */
 
-// NOTE: keep in sync with StorageManager
-constexpr int FLAG_STORAGE_DE = 1 << 0;
-constexpr int FLAG_STORAGE_CE = 1 << 1;
-
-// NOTE: keep in sync with Installer
-constexpr int FLAG_CLEAR_CACHE_ONLY = 1 << 8;
-constexpr int FLAG_CLEAR_CODE_CACHE_ONLY = 1 << 9;
-
-/* dexopt needed flags matching those in dalvik.system.DexFile */
-constexpr int DEXOPT_DEX2OAT_NEEDED       = 1;
-constexpr int DEXOPT_PATCHOAT_NEEDED      = 2;
-constexpr int DEXOPT_SELF_PATCHOAT_NEEDED = 3;
-
 /****************************************************************************
  * IMPORTANT: These values are passed from Java code. Keep them in sync with
  * frameworks/base/services/core/java/com/android/server/pm/Installer.java
diff --git a/cmds/installd/installd_deps.h b/cmds/installd/installd_deps.h
index 5ff46e6..5093178 100644
--- a/cmds/installd/installd_deps.h
+++ b/cmds/installd/installd_deps.h
@@ -57,9 +57,6 @@
                               const char *src,
                               const char *instruction_set);
 
-// Initialize globals. May be implemented with the helper in globals.h.
-extern bool initialize_globals();
-
 }  // namespace installd
 }  // namespace android
 
diff --git a/cmds/installd/otapreopt.cpp b/cmds/installd/otapreopt.cpp
index 8b9c931..7e02b6b 100644
--- a/cmds/installd/otapreopt.cpp
+++ b/cmds/installd/otapreopt.cpp
@@ -30,6 +30,7 @@
 #include <android-base/logging.h>
 #include <android-base/macros.h>
 #include <android-base/stringprintf.h>
+#include <android-base/strings.h>
 #include <cutils/fs.h>
 #include <cutils/log.h>
 #include <cutils/properties.h>
@@ -39,7 +40,7 @@
 #include <file_parsing.h>
 #include <globals.h>
 #include <installd_deps.h>  // Need to fill in requirements of commands.
-#include <string_helpers.h>
+#include <otapreopt_utils.h>
 #include <system_properties.h>
 #include <utils.h>
 
@@ -51,16 +52,15 @@
 #define TOKEN_MAX     16    /* max number of arguments in buffer */
 #define REPLY_MAX     256   /* largest reply allowed */
 
+using android::base::EndsWith;
+using android::base::Join;
+using android::base::Split;
+using android::base::StartsWith;
 using android::base::StringPrintf;
 
 namespace android {
 namespace installd {
 
-static constexpr const char* kBootClassPathPropertyName = "BOOTCLASSPATH";
-static constexpr const char* kAndroidRootPathPropertyName = "ANDROID_ROOT";
-static constexpr const char* kOTARootDirectory = "/system-b";
-static constexpr size_t kISAIndex = 3;
-
 template<typename T>
 static constexpr T RoundDown(T x, typename std::decay<T>::type n) {
     return DCHECK_CONSTEXPR(IsPowerOfTwo(n), , T(0))(x & -n);
@@ -73,8 +73,6 @@
 
 class OTAPreoptService {
  public:
-    static constexpr const char* kOTADataDirectory = "/data/ota";
-
     // Main driver. Performs the following steps.
     //
     // 1) Parse options (read system properties etc from B partition).
@@ -87,26 +85,31 @@
     //
     // 5) Run update.
     int Main(int argc, char** argv) {
+        if (!ReadArguments(argc, argv)) {
+            LOG(ERROR) << "Failed reading command line.";
+            return 1;
+        }
+
         if (!ReadSystemProperties()) {
             LOG(ERROR)<< "Failed reading system properties.";
-            return 1;
+            return 2;
         }
 
         if (!ReadEnvironment()) {
             LOG(ERROR) << "Failed reading environment properties.";
-            return 2;
+            return 3;
         }
 
-        if (!ReadPackage(argc, argv)) {
-            LOG(ERROR) << "Failed reading command line file.";
-            return 3;
+        if (!CheckAndInitializeInstalldGlobals()) {
+            LOG(ERROR) << "Failed initializing globals.";
+            return 4;
         }
 
         PrepareEnvironment();
 
-        if (!PrepareBootImage()) {
+        if (!PrepareBootImage(/* force */ false)) {
             LOG(ERROR) << "Failed preparing boot image.";
-            return 4;
+            return 5;
         }
 
         int dexopt_retcode = RunPreopt();
@@ -114,7 +117,7 @@
         return dexopt_retcode;
     }
 
-    int GetProperty(const char* key, char* value, const char* default_value) {
+    int GetProperty(const char* key, char* value, const char* default_value) const {
         const std::string* prop_value = system_properties_.GetProperty(key);
         if (prop_value == nullptr) {
             if (default_value == nullptr) {
@@ -131,7 +134,16 @@
         return static_cast<int>(size);
     }
 
+    std::string GetOTADataDirectory() const {
+        return StringPrintf("%s/%s", GetOtaDirectoryPrefix().c_str(), target_slot_.c_str());
+    }
+
+    const std::string& GetTargetSlot() const {
+        return target_slot_;
+    }
+
 private:
+
     bool ReadSystemProperties() {
         static constexpr const char* kPropertyFiles[] = {
                 "/default.prop", "/system/build.prop"
@@ -173,27 +185,106 @@
             return false;
         }
 
-        // Check that we found important properties.
-        constexpr const char* kRequiredProperties[] = {
-                kBootClassPathPropertyName, kAndroidRootPathPropertyName
-        };
-        for (size_t i = 0; i < arraysize(kRequiredProperties); ++i) {
-            if (system_properties_.GetProperty(kRequiredProperties[i]) == nullptr) {
-                return false;
-            }
+        if (system_properties_.GetProperty(kAndroidDataPathPropertyName) == nullptr) {
+            return false;
+        }
+        android_data_ = *system_properties_.GetProperty(kAndroidDataPathPropertyName);
+
+        if (system_properties_.GetProperty(kAndroidRootPathPropertyName) == nullptr) {
+            return false;
+        }
+        android_root_ = *system_properties_.GetProperty(kAndroidRootPathPropertyName);
+
+        if (system_properties_.GetProperty(kBootClassPathPropertyName) == nullptr) {
+            return false;
+        }
+        boot_classpath_ = *system_properties_.GetProperty(kBootClassPathPropertyName);
+
+        if (system_properties_.GetProperty(ASEC_MOUNTPOINT_ENV_NAME) == nullptr) {
+            return false;
+        }
+        asec_mountpoint_ = *system_properties_.GetProperty(ASEC_MOUNTPOINT_ENV_NAME);
+
+        return true;
+    }
+
+    const std::string& GetAndroidData() const {
+        return android_data_;
+    }
+
+    const std::string& GetAndroidRoot() const {
+        return android_root_;
+    }
+
+    const std::string GetOtaDirectoryPrefix() const {
+        return GetAndroidData() + "/ota";
+    }
+
+    bool CheckAndInitializeInstalldGlobals() {
+        // init_globals_from_data_and_root requires "ASEC_MOUNTPOINT" in the environment. We
+        // do not use any datapath that includes this, but we'll still have to set it.
+        CHECK(system_properties_.GetProperty(ASEC_MOUNTPOINT_ENV_NAME) != nullptr);
+        int result = setenv(ASEC_MOUNTPOINT_ENV_NAME, asec_mountpoint_.c_str(), 0);
+        if (result != 0) {
+            LOG(ERROR) << "Could not set ASEC_MOUNTPOINT environment variable";
+            return false;
+        }
+
+        if (!init_globals_from_data_and_root(GetAndroidData().c_str(), GetAndroidRoot().c_str())) {
+            LOG(ERROR) << "Could not initialize globals; exiting.";
+            return false;
+        }
+
+        // This is different from the normal installd. We only do the base
+        // directory, the rest will be created on demand when each app is compiled.
+        if (access(GetOtaDirectoryPrefix().c_str(), R_OK) < 0) {
+            LOG(ERROR) << "Could not access " << GetOtaDirectoryPrefix();
+            return false;
         }
 
         return true;
     }
 
-    bool ReadPackage(int argc ATTRIBUTE_UNUSED, char** argv) {
+    bool ReadArguments(int argc ATTRIBUTE_UNUSED, char** argv) {
+        // Expected command line:
+        //   target-slot dexopt {DEXOPT_PARAMETERS}
+        // The DEXOPT_PARAMETERS are passed on to dexopt(), so we expect DEXOPT_PARAM_COUNT
+        // of them. We store them in package_parameters_ (size checks are done when
+        // parsing the special parameters and when copying into package_parameters_.
+
+        static_assert(DEXOPT_PARAM_COUNT == ARRAY_SIZE(package_parameters_),
+                      "Unexpected dexopt param count");
+
+        const char* target_slot_arg = argv[1];
+        if (target_slot_arg == nullptr) {
+            LOG(ERROR) << "Missing parameters";
+            return false;
+        }
+        // Sanitize value. Only allow (a-zA-Z0-9_)+.
+        target_slot_ = target_slot_arg;
+        if (!ValidateTargetSlotSuffix(target_slot_)) {
+            LOG(ERROR) << "Target slot suffix not legal: " << target_slot_;
+            return false;
+        }
+
+        // Check for "dexopt" next.
+        if (argv[2] == nullptr) {
+            LOG(ERROR) << "Missing parameters";
+            return false;
+        }
+        if (std::string("dexopt").compare(argv[2]) != 0) {
+            LOG(ERROR) << "Second parameter not dexopt: " << argv[2];
+            return false;
+        }
+
+        // Copy the rest into package_parameters_, but be careful about over- and underflow.
         size_t index = 0;
-        while (index < ARRAY_SIZE(package_parameters_) &&
-                argv[index + 1] != nullptr) {
-            package_parameters_[index] = argv[index + 1];
+        while (index < DEXOPT_PARAM_COUNT &&
+                argv[index + 3] != nullptr) {
+            package_parameters_[index] = argv[index + 3];
             index++;
         }
-        if (index != ARRAY_SIZE(package_parameters_)) {
+        if (index != ARRAY_SIZE(package_parameters_) || argv[index + 3] != nullptr) {
             LOG(ERROR) << "Wrong number of parameters";
             return false;
         }
@@ -202,15 +293,9 @@
     }
 
     void PrepareEnvironment() {
-        CHECK(system_properties_.GetProperty(kBootClassPathPropertyName) != nullptr);
-        const std::string& boot_cp =
-                *system_properties_.GetProperty(kBootClassPathPropertyName);
-        environ_.push_back(StringPrintf("BOOTCLASSPATH=%s", boot_cp.c_str()));
-        environ_.push_back(StringPrintf("ANDROID_DATA=%s", kOTADataDirectory));
-        CHECK(system_properties_.GetProperty(kAndroidRootPathPropertyName) != nullptr);
-        const std::string& android_root =
-                *system_properties_.GetProperty(kAndroidRootPathPropertyName);
-        environ_.push_back(StringPrintf("ANDROID_ROOT=%s", android_root.c_str()));
+        environ_.push_back(StringPrintf("BOOTCLASSPATH=%s", boot_classpath_.c_str()));
+        environ_.push_back(StringPrintf("ANDROID_DATA=%s", GetOTADataDirectory().c_str()));
+        environ_.push_back(StringPrintf("ANDROID_ROOT=%s", android_root_.c_str()));
 
         for (const std::string& e : environ_) {
             putenv(const_cast<char*>(e.c_str()));
@@ -219,7 +304,7 @@
 
     // Ensure that we have the right boot image. The first time any app is
     // compiled, we'll try to generate it.
-    bool PrepareBootImage() {
+    bool PrepareBootImage(bool force) const {
         if (package_parameters_[kISAIndex] == nullptr) {
             LOG(ERROR) << "Instruction set missing.";
             return false;
@@ -227,44 +312,114 @@
         const char* isa = package_parameters_[kISAIndex];
 
         // Check whether the file exists where expected.
-        std::string dalvik_cache = std::string(kOTADataDirectory) + "/" + DALVIK_CACHE;
+        std::string dalvik_cache = GetOTADataDirectory() + "/" + DALVIK_CACHE;
         std::string isa_path = dalvik_cache + "/" + isa;
         std::string art_path = isa_path + "/system@framework@boot.art";
         std::string oat_path = isa_path + "/system@framework@boot.oat";
-        if (access(art_path.c_str(), F_OK) == 0 &&
-                access(oat_path.c_str(), F_OK) == 0) {
-            // Files exist, assume everything is alright.
-            return true;
+        bool cleared = false;
+        if (access(art_path.c_str(), F_OK) == 0 && access(oat_path.c_str(), F_OK) == 0) {
+            // Files exist, assume everything is alright if not forced. Otherwise clean up.
+            if (!force) {
+                return true;
+            }
+            ClearDirectory(isa_path);
+            cleared = true;
         }
 
+        // Reset umask in otapreopt, so that we control the the access for the files we create.
+        umask(0);
+
         // Create the directories, if necessary.
         if (access(dalvik_cache.c_str(), F_OK) != 0) {
-            if (mkdir(dalvik_cache.c_str(), 0711) != 0) {
-                PLOG(ERROR) << "Could not create dalvik-cache dir";
+            if (!CreatePath(dalvik_cache)) {
+                PLOG(ERROR) << "Could not create dalvik-cache dir " << dalvik_cache;
                 return false;
             }
         }
         if (access(isa_path.c_str(), F_OK) != 0) {
-            if (mkdir(isa_path.c_str(), 0711) != 0) {
+            if (!CreatePath(isa_path)) {
                 PLOG(ERROR) << "Could not create dalvik-cache isa dir";
                 return false;
             }
         }
 
         // Prepare to create.
-        // TODO: Delete files, just for a blank slate.
-        const std::string& boot_cp = *system_properties_.GetProperty(kBootClassPathPropertyName);
+        if (!cleared) {
+            ClearDirectory(isa_path);
+        }
 
         std::string preopted_boot_art_path = StringPrintf("/system/framework/%s/boot.art", isa);
         if (access(preopted_boot_art_path.c_str(), F_OK) == 0) {
           return PatchoatBootImage(art_path, isa);
         } else {
           // No preopted boot image. Try to compile.
-          return Dex2oatBootImage(boot_cp, art_path, oat_path, isa);
+          return Dex2oatBootImage(boot_classpath_, art_path, oat_path, isa);
         }
     }
 
-    bool PatchoatBootImage(const std::string& art_path, const char* isa) {
+    static bool CreatePath(const std::string& path) {
+        // Create the given path. Use string processing instead of dirname, as dirname's need for
+        // a writable char buffer is painful.
+
+        // First, try to use the full path.
+        if (mkdir(path.c_str(), 0711) == 0) {
+            return true;
+        }
+        if (errno != ENOENT) {
+            PLOG(ERROR) << "Could not create path " << path;
+            return false;
+        }
+
+        // Now find the parent and try that first.
+        size_t last_slash = path.find_last_of('/');
+        if (last_slash == std::string::npos || last_slash == 0) {
+            PLOG(ERROR) << "Could not create " << path;
+            return false;
+        }
+
+        if (!CreatePath(path.substr(0, last_slash))) {
+            return false;
+        }
+
+        if (mkdir(path.c_str(), 0711) == 0) {
+            return true;
+        }
+        PLOG(ERROR) << "Could not create " << path;
+        return false;
+    }
+
+    static void ClearDirectory(const std::string& dir) {
+        DIR* c_dir = opendir(dir.c_str());
+        if (c_dir == nullptr) {
+            PLOG(WARNING) << "Unable to open " << dir << " to delete it's contents";
+            return;
+        }
+
+        for (struct dirent* de = readdir(c_dir); de != nullptr; de = readdir(c_dir)) {
+            const char* name = de->d_name;
+            if (strcmp(name, ".") == 0 || strcmp(name, "..") == 0) {
+                continue;
+            }
+            // We only want to delete regular files and symbolic links.
+            std::string file = StringPrintf("%s/%s", dir.c_str(), name);
+            if (de->d_type != DT_REG && de->d_type != DT_LNK) {
+                LOG(WARNING) << "Unexpected file "
+                             << file
+                             << " of type "
+                             << std::hex
+                             << de->d_type
+                             << " encountered.";
+            } else {
+                // Try to unlink the file.
+                if (unlink(file.c_str()) != 0) {
+                    PLOG(ERROR) << "Unable to unlink " << file;
+                }
+            }
+        }
+        CHECK_EQ(0, closedir(c_dir)) << "Unable to close directory.";
+    }
+
+    bool PatchoatBootImage(const std::string& art_path, const char* isa) const {
         // This needs to be kept in sync with ART, see art/runtime/gc/space/image_space.cc.
 
         std::vector<std::string> cmd;
@@ -290,12 +445,12 @@
     bool Dex2oatBootImage(const std::string& boot_cp,
                           const std::string& art_path,
                           const std::string& oat_path,
-                          const char* isa) {
+                          const char* isa) const {
         // This needs to be kept in sync with ART, see art/runtime/gc/space/image_space.cc.
         std::vector<std::string> cmd;
         cmd.push_back("/system/bin/dex2oat");
         cmd.push_back(StringPrintf("--image=%s", art_path.c_str()));
-        for (const std::string& boot_part : Split(boot_cp, ':')) {
+        for (const std::string& boot_part : Split(boot_cp, ":")) {
             cmd.push_back(StringPrintf("--dex-file=%s", boot_part.c_str()));
         }
         cmd.push_back(StringPrintf("--oat-file=%s", oat_path.c_str()));
@@ -324,7 +479,7 @@
         const std::string* extra_opts =
                 system_properties_.GetProperty("dalvik.vm.image-dex2oat-flags");
         if (extra_opts != nullptr) {
-            std::vector<std::string> extra_vals = Split(*extra_opts, ' ');
+            std::vector<std::string> extra_vals = Split(*extra_opts, " ");
             cmd.insert(cmd.end(), extra_vals.begin(), extra_vals.end());
         }
         // TODO: Should we lower this? It's usually set close to max, because
@@ -356,18 +511,81 @@
         return (strcmp(arg, "!") == 0) ? nullptr : arg;
     }
 
+    bool ShouldSkipPreopt() const {
+        // There's one thing we have to be careful about: we may/will be asked to compile an app
+        // living in the system image. This may be a valid request - if the app wasn't compiled,
+        // e.g., if the system image wasn't large enough to include preopted files. However, the
+        // data we have is from the old system, so the driver (the OTA service) can't actually
+        // know. Thus, we will get requests for apps that have preopted components. To avoid
+        // duplication (we'd generate files that are not used and are *not* cleaned up), do two
+        // simple checks:
+        //
+        // 1) Does the apk_path start with the value of ANDROID_ROOT? (~in the system image)
+        //    (For simplicity, assume the value of ANDROID_ROOT does not contain a symlink.)
+        //
+        // 2) If you replace the name in the apk_path with "oat," does the path exist?
+        //    (=have a subdirectory for preopted files)
+        //
+        // If the answer to both is yes, skip the dexopt.
+        //
+        // Note: while one may think it's OK to call dexopt and it will fail (because APKs should
+        //       be stripped), that's not true for APKs signed outside the build system (so the
+        //       jar content must be exactly the same).
+
+        //       (This is ugly as it's the only thing where we need to understand the contents
+        //        of package_parameters_, but it beats postponing the decision or using the call-
+        //        backs to do weird things.)
+        constexpr size_t kApkPathIndex = 0;
+        CHECK_GT(DEXOPT_PARAM_COUNT, kApkPathIndex);
+        CHECK(package_parameters_[kApkPathIndex] != nullptr);
+        if (StartsWith(package_parameters_[kApkPathIndex], android_root_.c_str())) {
+            const char* last_slash = strrchr(package_parameters_[kApkPathIndex], '/');
+            if (last_slash != nullptr) {
+                std::string path(package_parameters_[kApkPathIndex],
+                                 last_slash - package_parameters_[kApkPathIndex] + 1);
+                CHECK(EndsWith(path, "/"));
+                path = path + "oat";
+                if (access(path.c_str(), F_OK) == 0) {
+                    return true;
+                }
+            }
+        }
+
+        // Another issue is unavailability of files in the new system. If the partition
+        // layout changes, otapreopt_chroot may not know about this. Then files from that
+        // partition will not be available and fail to build. This is problematic, as
+        // this tool will wipe the OTA artifact cache and try again (for robustness after
+        // a failed OTA with remaining cache artifacts).
+        if (access(package_parameters_[kApkPathIndex], F_OK) != 0) {
+            LOG(WARNING) << "Skipping preopt of non-existing package "
+                         << package_parameters_[kApkPathIndex];
+            return true;
+        }
+
+        return false;
+    }
+
     int RunPreopt() {
-        int ret = dexopt(package_parameters_[0],          // apk_path
-                atoi(package_parameters_[1]),             // uid
-                package_parameters_[2],                   // pkgname
-                package_parameters_[3],                   // instruction_set
-                atoi(package_parameters_[4]),             // dexopt_needed
-                package_parameters_[5],                   // oat_dir
-                atoi(package_parameters_[6]),             // dexopt_flags
-                package_parameters_[7],                   // compiler_filter
-                ParseNull(package_parameters_[8]),        // volume_uuid
-                ParseNull(package_parameters_[9]));       // shared_libraries
-        return ret;
+        if (ShouldSkipPreopt()) {
+            return 0;
+        }
+
+        int dexopt_result = dexopt(package_parameters_);
+        if (dexopt_result == 0) {
+            return 0;
+        }
+
+        // If the dexopt failed, we may have a stale boot image from a previous OTA run.
+        // Try to delete and retry.
+
+        if (!PrepareBootImage(/* force */ true)) {
+            LOG(ERROR) << "Forced boot image creating failed. Original error return was "
+                         << dexopt_result;
+            return dexopt_result;
+        }
+
+        LOG(WARNING) << "Original dexopt failed, re-trying after boot image was regenerated.";
+        return dexopt(package_parameters_);
     }
 
     ////////////////////////////////////
@@ -375,8 +593,8 @@
     ////////////////////////////////////
 
     // Wrapper on fork/execv to run a command in a subprocess.
-    bool Exec(const std::vector<std::string>& arg_vector, std::string* error_msg) {
-        const std::string command_line(Join(arg_vector, ' '));
+    static bool Exec(const std::vector<std::string>& arg_vector, std::string* error_msg) {
+        const std::string command_line = Join(arg_vector, ' ');
 
         CHECK_GE(arg_vector.size(), 1U) << command_line;
 
@@ -465,9 +683,8 @@
     void AddCompilerOptionFromSystemProperty(const char* system_property,
             const char* prefix,
             bool runtime,
-            std::vector<std::string>& out) {
-        const std::string* value =
-        system_properties_.GetProperty(system_property);
+            std::vector<std::string>& out) const {
+        const std::string* value = system_properties_.GetProperty(system_property);
         if (value != nullptr) {
             if (runtime) {
                 out.push_back("--runtime-arg");
@@ -480,11 +697,25 @@
         }
     }
 
+    static constexpr const char* kBootClassPathPropertyName = "BOOTCLASSPATH";
+    static constexpr const char* kAndroidRootPathPropertyName = "ANDROID_ROOT";
+    static constexpr const char* kAndroidDataPathPropertyName = "ANDROID_DATA";
+    // The index of the instruction-set string inside the package parameters. Needed for
+    // some special-casing that requires knowledge of the instruction-set.
+    static constexpr size_t kISAIndex = 3;
+
     // Stores the system properties read out of the B partition. We need to use these properties
     // to compile, instead of the A properties we could get from init/get_property.
     SystemProperties system_properties_;
 
-    const char* package_parameters_[10];
+    // Some select properties that are always needed.
+    std::string target_slot_;
+    std::string android_root_;
+    std::string android_data_;
+    std::string boot_classpath_;
+    std::string asec_mountpoint_;
+
+    const char* package_parameters_[DEXOPT_PARAM_COUNT];
 
     // Store environment values we need to set.
     std::vector<std::string> environ_;
@@ -497,7 +728,6 @@
 ////////////////////////
 
 int get_property(const char *key, char *value, const char *default_value) {
-    // TODO: Replace with system-properties map.
     return gOps.GetProperty(key, value, default_value);
 }
 
@@ -505,7 +735,6 @@
 bool calculate_oat_file_path(char path[PKG_PATH_MAX], const char *oat_dir,
                              const char *apk_path,
                              const char *instruction_set) {
-    // TODO: Insert B directory.
     const char *file_name_start;
     const char *file_name_end;
 
@@ -526,8 +755,13 @@
     std::string file_name(file_name_start, file_name_len);
 
     // <apk_parent_dir>/oat/<isa>/<file_name>.odex.b
-    snprintf(path, PKG_PATH_MAX, "%s/%s/%s.odex.b", oat_dir, instruction_set,
-             file_name.c_str());
+    snprintf(path,
+             PKG_PATH_MAX,
+             "%s/%s/%s.odex.%s",
+             oat_dir,
+             instruction_set,
+             file_name.c_str(),
+             gOps.GetTargetSlot().c_str());
     return true;
 }
 
@@ -539,11 +773,6 @@
  */
 bool calculate_odex_file_path(char path[PKG_PATH_MAX], const char *apk_path,
                               const char *instruction_set) {
-    if (StringPrintf("%soat/%s/odex.b", apk_path, instruction_set).length() + 1 > PKG_PATH_MAX) {
-        ALOGE("apk_path '%s' may be too long to form odex file path.\n", apk_path);
-        return false;
-    }
-
     const char *path_end = strrchr(apk_path, '/');
     if (path_end == nullptr) {
         ALOGE("apk_path '%s' has no '/'s in it?!\n", apk_path);
@@ -559,11 +788,15 @@
     }
     std::string name_component(name_begin, extension_start - name_begin);
 
-    std::string new_path = StringPrintf("%s/oat/%s/%s.odex.b",
+    std::string new_path = StringPrintf("%s/oat/%s/%s.odex.%s",
                                         path_component.c_str(),
                                         instruction_set,
-                                        name_component.c_str());
-    CHECK_LT(new_path.length(), PKG_PATH_MAX);
+                                        name_component.c_str(),
+                                        gOps.GetTargetSlot().c_str());
+    if (new_path.length() >= PKG_PATH_MAX) {
+        LOG(ERROR) << "apk_path of " << apk_path << " is too long: " << new_path;
+        return false;
+    }
     strcpy(path, new_path.c_str());
     return true;
 }
@@ -586,7 +819,7 @@
     std::replace(from_src.begin(), from_src.end(), '/', '@');
 
     std::string assembled_path = StringPrintf("%s/%s/%s/%s%s",
-                                              OTAPreoptService::kOTADataDirectory,
+                                              gOps.GetOTADataDirectory().c_str(),
                                               DALVIK_CACHE,
                                               instruction_set,
                                               from_src.c_str(),
@@ -600,27 +833,6 @@
     return true;
 }
 
-bool initialize_globals() {
-    const char* data_path = getenv("ANDROID_DATA");
-    if (data_path == nullptr) {
-        ALOGE("Could not find ANDROID_DATA");
-        return false;
-    }
-    return init_globals_from_data_and_root(data_path, kOTARootDirectory);
-}
-
-static bool initialize_directories() {
-    // This is different from the normal installd. We only do the base
-    // directory, the rest will be created on demand when each app is compiled.
-    mode_t old_umask = umask(0);
-    LOG(INFO) << "Old umask: " << old_umask;
-    if (access(OTAPreoptService::kOTADataDirectory, R_OK) < 0) {
-        ALOGE("Could not access %s\n", OTAPreoptService::kOTADataDirectory);
-        return false;
-    }
-    return true;
-}
-
 static int log_callback(int type, const char *fmt, ...) {
     va_list ap;
     int priority;
@@ -648,8 +860,6 @@
     setenv("ANDROID_LOG_TAGS", "*:v", 1);
     android::base::InitLogging(argv);
 
-    ALOGI("otapreopt firing up\n");
-
     if (argc < 2) {
         ALOGE("Expecting parameters");
         exit(1);
@@ -659,16 +869,6 @@
     cb.func_log = log_callback;
     selinux_set_callback(SELINUX_CB_LOG, cb);
 
-    if (!initialize_globals()) {
-        ALOGE("Could not initialize globals; exiting.\n");
-        exit(1);
-    }
-
-    if (!initialize_directories()) {
-        ALOGE("Could not create directories; exiting.\n");
-        exit(1);
-    }
-
     if (selinux_enabled && selinux_status_open(true) < 0) {
         ALOGE("Could not open selinux status; exiting.\n");
         exit(1);
diff --git a/cmds/installd/otapreopt.rc b/cmds/installd/otapreopt.rc
new file mode 100644
index 0000000..059ae75
--- /dev/null
+++ b/cmds/installd/otapreopt.rc
@@ -0,0 +1,8 @@
+# When /data is available, look for A/B artifacts for the current slot and move them
+# into the dalvik-cache (relabeling them).
+on post-fs-data
+    exec - root -- /system/bin/otapreopt_slot
+    # The dalvik-cache was not moved itself, so as to restrict the rights of otapreopt_slot.
+    # But now the relabeling is annoying as there is no force option available here. So
+    # explicitly list all the ISAs we know.
+    restorecon_recursive /data/dalvik-cache/arm /data/dalvik-cache/arm64 /data/dalvik-cache/mips /data/dalvik-cache/mips64 /data/dalvik-cache/x86 /data/dalvik-cache/x86_64
diff --git a/cmds/installd/otapreopt_chroot.cpp b/cmds/installd/otapreopt_chroot.cpp
index f7f69a9..5ea89e6 100644
--- a/cmds/installd/otapreopt_chroot.cpp
+++ b/cmds/installd/otapreopt_chroot.cpp
@@ -14,14 +14,20 @@
  ** limitations under the License.
  */
 
+#include <fcntl.h>
 #include <linux/unistd.h>
 #include <sys/mount.h>
 #include <sys/wait.h>
 
+#include <sstream>
+
 #include <android-base/logging.h>
 #include <android-base/macros.h>
 #include <android-base/stringprintf.h>
 
+#include <commands.h>
+#include <otapreopt_utils.h>
+
 #ifndef LOG_TAG
 #define LOG_TAG "otapreopt"
 #endif
@@ -31,7 +37,37 @@
 namespace android {
 namespace installd {
 
+static void CloseDescriptor(int fd) {
+    if (fd >= 0) {
+        int result = close(fd);
+        UNUSED(result);  // Ignore result. Printing to logcat will open a new descriptor
+                         // that we do *not* want.
+    }
+}
+
+static void CloseDescriptor(const char* descriptor_string) {
+    int fd = -1;
+    std::istringstream stream(descriptor_string);
+    stream >> fd;
+    if (!stream.fail()) {
+        CloseDescriptor(fd);
+    }
+}
+
+// Entry for otapreopt_chroot. Expected parameters are:
+//   [cmd] [status-fd] [target-slot] "dexopt" [dexopt-params]
+// The file descriptor denoted by status-fd will be closed. The rest of the parameters will
+// be passed on to otapreopt in the chroot.
 static int otapreopt_chroot(const int argc, char **arg) {
+    // Close all file descriptors. They are coming from the caller, we do not want to pass them
+    // on across our fork/exec into a different domain.
+    // 1) Default descriptors.
+    CloseDescriptor(STDIN_FILENO);
+    CloseDescriptor(STDOUT_FILENO);
+    CloseDescriptor(STDERR_FILENO);
+    // 2) The status channel.
+    CloseDescriptor(arg[1]);
+
     // We need to run the otapreopt tool from the postinstall partition. As such, set up a
     // mount namespace and change root.
 
@@ -59,6 +95,28 @@
         }
     }
 
+    // Try to mount the vendor partition. update_engine doesn't do this for us, but we
+    // want it for vendor APKs.
+    // Notes:
+    //  1) We pretty much guess a name here and hope to find the partition by name.
+    //     It is just as complicated and brittle to scan /proc/mounts. But this requires
+    //     validating the target-slot so as not to try to mount some totally random path.
+    //  2) We're in a mount namespace here, so when we die, this will be cleaned up.
+    //  3) Ignore errors. Printing anything at this stage will open a file descriptor
+    //     for logging.
+    if (!ValidateTargetSlotSuffix(arg[2])) {
+        LOG(ERROR) << "Target slot suffix not legal: " << arg[2];
+        exit(207);
+    }
+    std::string vendor_partition = StringPrintf("/dev/block/bootdevice/by-name/vendor%s",
+                                                arg[2]);
+    int vendor_result = mount(vendor_partition.c_str(),
+                              "/postinstall/vendor",
+                              "ext4",
+                              MS_RDONLY,
+                              /* data */ nullptr);
+    UNUSED(vendor_result);
+
     // Chdir into /postinstall.
     if (chdir("/postinstall") != 0) {
         PLOG(ERROR) << "Unable to chdir into /postinstall.";
@@ -78,13 +136,42 @@
 
     // Now go on and run otapreopt.
 
-    const char* argv[1 + 9 + 1];
-    CHECK_EQ(argc, 10);
-    argv[0] = "/system/bin/otapreopt";
-    for (size_t i = 1; i <= 9; ++i) {
-        argv[i] = arg[i];
+    // Incoming:  cmd + status-fd + target-slot + "dexopt" + dexopt-params + null
+    // Outgoing:  cmd             + target-slot + "dexopt" + dexopt-params + null
+    constexpr size_t kInArguments =   1                       // Binary name.
+                                    + 1                       // status file descriptor.
+                                    + 1                       // target-slot.
+                                    + 1                       // "dexopt."
+                                    + DEXOPT_PARAM_COUNT      // dexopt parameters.
+                                    + 1;                      // null termination.
+    constexpr size_t kOutArguments =   1                       // Binary name.
+                                     + 1                       // target-slot.
+                                     + 1                       // "dexopt."
+                                     + DEXOPT_PARAM_COUNT      // dexopt parameters.
+                                     + 1;                      // null termination.
+    const char* argv[kOutArguments];
+    if (static_cast<size_t>(argc) !=  kInArguments - 1 /* null termination */) {
+        LOG(ERROR) << "Unexpected argument size "
+                   << argc
+                   << " vs "
+                   << (kInArguments - 1);
+        for (size_t i = 0; i < static_cast<size_t>(argc); ++i) {
+            if (arg[i] == nullptr) {
+                LOG(ERROR) << "(null)";
+            } else {
+                LOG(ERROR) << "\"" << arg[i] << "\"";
+            }
+        }
+        exit(206);
     }
-    argv[10] = nullptr;
+    argv[0] = "/system/bin/otapreopt";
+
+    // The first parameter is the status file descriptor, skip.
+
+    for (size_t i = 1; i <= kOutArguments - 2 /* cmd + null */; ++i) {
+        argv[i] = arg[i + 1];
+    }
+    argv[kOutArguments - 1] = nullptr;
 
     execv(argv[0], (char * const *)argv);
     PLOG(ERROR) << "execv(OTAPREOPT) failed.";
diff --git a/cmds/installd/otapreopt_script.sh b/cmds/installd/otapreopt_script.sh
index a31734a..f950276 100644
--- a/cmds/installd/otapreopt_script.sh
+++ b/cmds/installd/otapreopt_script.sh
@@ -18,24 +18,62 @@
 
 # This script will run as a postinstall step to drive otapreopt.
 
+TARGET_SLOT="$1"
+STATUS_FD="$2"
+
 # Maximum number of packages/steps.
 MAXIMUM_PACKAGES=1000
 
-PREPARE=$(cmd otadexopt prepare)
-if [ "$PREPARE" != "Success" ] ; then
-  echo "Failed to prepare."
+# First ensure the system is booted. This is to work around issues when cmd would
+# infinitely loop trying to get a service manager (which will never come up in that
+# mode). b/30797145
+BOOT_PROPERTY_NAME="dev.bootcomplete"
+
+BOOT_COMPLETE=$(getprop $BOOT_PROPERTY_NAME)
+if [ "$BOOT_COMPLETE" != "1" ] ; then
+  echo "Error: boot-complete not detected."
+  # We must return 0 to not block sideload.
+  exit 0
+fi
+
+
+# Compute target slot suffix.
+# TODO: Once bootctl is not restricted, we should query from there. Or get this from
+#       update_engine as a parameter.
+if [ "$TARGET_SLOT" = "0" ] ; then
+  TARGET_SLOT_SUFFIX="_a"
+elif [ "$TARGET_SLOT" = "1" ] ; then
+  TARGET_SLOT_SUFFIX="_b"
+else
+  echo "Unknown target slot $TARGET_SLOT"
   exit 1
 fi
 
+
+PREPARE=$(cmd otadexopt prepare)
+# Note: Ignore preparation failures. Step and done will fail and exit this.
+#       This is necessary to support suspends - the OTA service will keep
+#       the state around for us.
+
+PROGRESS=$(cmd otadexopt progress)
+print -u${STATUS_FD} "global_progress $PROGRESS"
+
 i=0
 while ((i<MAXIMUM_PACKAGES)) ; do
-  cmd otadexopt step
+  DEXOPT_PARAMS=$(cmd otadexopt next)
+
+  /system/bin/otapreopt_chroot $STATUS_FD $TARGET_SLOT_SUFFIX $DEXOPT_PARAMS >&- 2>&-
+
+  PROGRESS=$(cmd otadexopt progress)
+  print -u${STATUS_FD} "global_progress $PROGRESS"
+
   DONE=$(cmd otadexopt done)
-  if [ "$DONE" = "OTA complete." ] ; then
-    break
+  if [ "$DONE" = "OTA incomplete." ] ; then
+    sleep 1
+    i=$((i+1))
+    continue
   fi
-  sleep 1
-  i=$((i+1))
+  break
 done
 
 DONE=$(cmd otadexopt done)
@@ -45,6 +83,7 @@
   echo "Complete or error."
 fi
 
+print -u${STATUS_FD} "global_progress 1.0"
 cmd otadexopt cleanup
 
 exit 0
diff --git a/cmds/installd/otapreopt_slot.sh b/cmds/installd/otapreopt_slot.sh
new file mode 100644
index 0000000..b5786e9
--- /dev/null
+++ b/cmds/installd/otapreopt_slot.sh
@@ -0,0 +1,39 @@
+#!/system/bin/sh
+
+#
+# Copyright (C) 2016 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.
+#
+
+# This script will move artifacts for the currently active slot.
+
+SLOT_SUFFIX=$(getprop ro.boot.slot_suffix)
+if test -n "$SLOT_SUFFIX" ; then
+  if test -d /data/ota/$SLOT_SUFFIX/dalvik-cache ; then
+    log -p i -t otapreopt_slot "Moving A/B artifacts for slot ${SLOT_SUFFIX}."
+    OLD_SIZE=$(du -h -s /data/dalvik-cache)
+    rm -rf /data/dalvik-cache/*
+    NEW_SIZE=$(du -h -s /data/ota/$SLOT_SUFFIX/dalvik-cache)
+    mv /data/ota/$SLOT_SUFFIX/dalvik-cache/* /data/dalvik-cache/
+    rmdir /data/ota/$SLOT_SUFFIX/dalvik-cache
+    rmdir /data/ota/$SLOT_SUFFIX
+    log -p i -t otapreopt_slot "Moved ${NEW_SIZE} over ${OLD_SIZE}"
+  else
+    log -p i -t otapreopt_slot "No A/B artifacts found for slot ${SLOT_SUFFIX}."
+  fi
+  exit 0
+else
+  log -p w -t otapreopt_slot "Slot property empty."
+  exit 1
+fi
diff --git a/cmds/installd/otapreopt_utils.h b/cmds/installd/otapreopt_utils.h
new file mode 100644
index 0000000..436e554
--- /dev/null
+++ b/cmds/installd/otapreopt_utils.h
@@ -0,0 +1,34 @@
+/*
+ * Copyright (C) 2016 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.
+ */
+
+#ifndef OTAPREOPT_UTILS_H_
+#define OTAPREOPT_UTILS_H_
+
+#include <regex>
+
+namespace android {
+namespace installd {
+
+static inline bool ValidateTargetSlotSuffix(const std::string& input) {
+    std::regex slot_suffix_regex("[a-zA-Z0-9_]+");
+    std::smatch slot_suffix_match;
+    return std::regex_match(input, slot_suffix_match, slot_suffix_regex);
+}
+
+}  // namespace installd
+}  // namespace android
+
+#endif  // OTAPREOPT_UTILS_H_
diff --git a/cmds/installd/string_helpers.h b/cmds/installd/string_helpers.h
deleted file mode 100644
index e8fcdef..0000000
--- a/cmds/installd/string_helpers.h
+++ /dev/null
@@ -1,67 +0,0 @@
-/*
- * Copyright (C) 2015 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.
- */
-
-#ifndef ART_OTAPREOPT_STRING_HELPERS_H_
-#define ART_OTAPREOPT_STRING_HELPERS_H_
-
-#include <sstream>
-#include <string>
-
-#include <android-base/macros.h>
-
-namespace android {
-namespace installd {
-
-static inline bool StringStartsWith(const std::string& target,
-                                    const char* prefix) {
-    return target.compare(0, strlen(prefix), prefix) == 0;
-}
-
-// Split the input according to the separator character. Doesn't honor quotation.
-static inline std::vector<std::string> Split(const std::string& in, const char separator) {
-    if (in.empty()) {
-        return std::vector<std::string>();
-    }
-
-    std::vector<std::string> ret;
-    std::stringstream strstr(in);
-    std::string token;
-
-    while (std::getline(strstr, token, separator)) {
-        ret.push_back(token);
-    }
-
-    return ret;
-}
-
-template <typename StringT>
-static inline std::string Join(const std::vector<StringT>& strings, char separator) {
-    if (strings.empty()) {
-        return "";
-    }
-
-    std::string result(strings[0]);
-    for (size_t i = 1; i < strings.size(); ++i) {
-        result += separator;
-        result += strings[i];
-    }
-    return result;
-}
-
-}  // namespace installd
-}  // namespace android
-
-#endif  // ART_OTAPREOPT_STRING_HELPERS_H_