diff --git a/init/README.md b/init/README.md
index b70366b..0dd1490 100644
--- a/init/README.md
+++ b/init/README.md
@@ -547,13 +547,16 @@
   * `ref`: use the systemwide DE key
   * `per_boot_ref`: use the key freshly generated on each boot.
 
-`mount_all <fstab> [ <path> ]\* [--<option>]`
+`mount_all [ <fstab> ] [--<option>]`
 > Calls fs\_mgr\_mount\_all on the given fs\_mgr-format fstab with optional
   options "early" and "late".
   With "--early" set, the init executable will skip mounting entries with
   "latemount" flag and triggering fs encryption state event. With "--late" set,
   init executable will only mount entries with "latemount" flag. By default,
   no option is set, and mount\_all will process all entries in the given fstab.
+  If the fstab parameter is not specified, fstab.${ro.boot.fstab_suffix},
+  fstab.${ro.hardware} or fstab.${ro.hardware.platform} will be scanned for
+  under /odm/etc, /vendor/etc, or / at runtime, in that order.
 
 `mount <type> <device> <dir> [ <flag>\* ] [<options>]`
 > Attempt to mount the named device at the directory _dir_
diff --git a/init/builtins.cpp b/init/builtins.cpp
index 149a766..e918e12 100644
--- a/init/builtins.cpp
+++ b/init/builtins.cpp
@@ -518,21 +518,21 @@
 
 /* Imports .rc files from the specified paths. Default ones are applied if none is given.
  *
- * start_index: index of the first path in the args list
+ * rc_paths: list of paths to rc files to import
  */
-static void import_late(const std::vector<std::string>& args, size_t start_index, size_t end_index) {
+static void import_late(const std::vector<std::string>& rc_paths) {
     auto& action_manager = ActionManager::GetInstance();
     auto& service_list = ServiceList::GetInstance();
     Parser parser = CreateParser(action_manager, service_list);
-    if (end_index <= start_index) {
+    if (rc_paths.empty()) {
         // Fallbacks for partitions on which early mount isn't enabled.
         for (const auto& path : late_import_paths) {
             parser.ParseConfig(path);
         }
         late_import_paths.clear();
     } else {
-        for (size_t i = start_index; i < end_index; ++i) {
-            parser.ParseConfig(args[i]);
+        for (const auto& rc_path : rc_paths) {
+            parser.ParseConfig(rc_path);
         }
     }
 
@@ -633,48 +633,44 @@
 
 static int initial_mount_fstab_return_code = -1;
 
-/* mount_all <fstab> [ <path> ]* [--<options>]*
+/* <= Q: mount_all <fstab> [ <path> ]* [--<options>]*
+ * >= R: mount_all [ <fstab> ] [--<options>]*
  *
  * This function might request a reboot, in which case it will
  * not return.
  */
 static Result<void> do_mount_all(const BuiltinArguments& args) {
-    std::size_t na = 0;
-    bool import_rc = true;
-    bool queue_event = true;
-    int mount_mode = MOUNT_MODE_DEFAULT;
-    const auto& fstab_file = args[1];
-    std::size_t path_arg_end = args.size();
-    const char* prop_post_fix = "default";
+    auto mount_all = ParseMountAll(args.args);
+    if (!mount_all.ok()) return mount_all.error();
 
-    for (na = args.size() - 1; na > 1; --na) {
-        if (args[na] == "--early") {
-            path_arg_end = na;
-            queue_event = false;
-            mount_mode = MOUNT_MODE_EARLY;
-            prop_post_fix = "early";
-        } else if (args[na] == "--late") {
-            path_arg_end = na;
-            import_rc = false;
-            mount_mode = MOUNT_MODE_LATE;
-            prop_post_fix = "late";
-        }
+    const char* prop_post_fix = "default";
+    bool queue_event = true;
+    if (mount_all->mode == MOUNT_MODE_EARLY) {
+        prop_post_fix = "early";
+        queue_event = false;
+    } else if (mount_all->mode == MOUNT_MODE_LATE) {
+        prop_post_fix = "late";
     }
 
     std::string prop_name = "ro.boottime.init.mount_all."s + prop_post_fix;
     android::base::Timer t;
 
     Fstab fstab;
-    if (!ReadFstabFromFile(fstab_file, &fstab)) {
-        return Error() << "Could not read fstab";
+    if (mount_all->fstab_path.empty()) {
+        if (!ReadDefaultFstab(&fstab)) {
+            return Error() << "Could not read default fstab";
+        }
+    } else {
+        if (!ReadFstabFromFile(mount_all->fstab_path, &fstab)) {
+            return Error() << "Could not read fstab";
+        }
     }
 
-    auto mount_fstab_return_code = fs_mgr_mount_all(&fstab, mount_mode);
+    auto mount_fstab_return_code = fs_mgr_mount_all(&fstab, mount_all->mode);
     SetProperty(prop_name, std::to_string(t.duration().count()));
 
-    if (import_rc && SelinuxGetVendorAndroidVersion() <= __ANDROID_API_Q__) {
-        /* Paths of .rc files are specified at the 2nd argument and beyond */
-        import_late(args.args, 2, path_arg_end);
+    if (mount_all->import_rc) {
+        import_late(mount_all->rc_paths);
     }
 
     if (queue_event) {
@@ -690,11 +686,20 @@
     return {};
 }
 
-/* umount_all <fstab> */
+/* umount_all [ <fstab> ] */
 static Result<void> do_umount_all(const BuiltinArguments& args) {
+    auto umount_all = ParseUmountAll(args.args);
+    if (!umount_all.ok()) return umount_all.error();
+
     Fstab fstab;
-    if (!ReadFstabFromFile(args[1], &fstab)) {
-        return Error() << "Could not read fstab";
+    if (umount_all->empty()) {
+        if (!ReadDefaultFstab(&fstab)) {
+            return Error() << "Could not read default fstab";
+        }
+    } else {
+        if (!ReadFstabFromFile(*umount_all, &fstab)) {
+            return Error() << "Could not read fstab";
+        }
     }
 
     if (auto result = fs_mgr_umount_all(&fstab); result != 0) {
@@ -1349,11 +1354,11 @@
         // mount_all is currently too complex to run in vendor_init as it queues action triggers,
         // imports rc scripts, etc.  It should be simplified and run in vendor_init context.
         // mount and umount are run in the same context as mount_all for symmetry.
-        {"mount_all",               {1,     kMax, {false,  do_mount_all}}},
+        {"mount_all",               {0,     kMax, {false,  do_mount_all}}},
         {"mount",                   {3,     kMax, {false,  do_mount}}},
         {"perform_apex_config",     {0,     0,    {false,  do_perform_apex_config}}},
         {"umount",                  {1,     1,    {false,  do_umount}}},
-        {"umount_all",              {1,     1,    {false,  do_umount_all}}},
+        {"umount_all",              {0,     1,    {false,  do_umount_all}}},
         {"update_linker_config",    {0,     0,    {false,  do_update_linker_config}}},
         {"readahead",               {1,     2,    {true,   do_readahead}}},
         {"remount_userdata",        {0,     0,    {false,  do_remount_userdata}}},
diff --git a/init/check_builtins.cpp b/init/check_builtins.cpp
index d1a84f3..450c079 100644
--- a/init/check_builtins.cpp
+++ b/init/check_builtins.cpp
@@ -123,6 +123,14 @@
     return {};
 }
 
+Result<void> check_mount_all(const BuiltinArguments& args) {
+    auto options = ParseMountAll(args.args);
+    if (!options.ok()) {
+        return options.error();
+    }
+    return {};
+}
+
 Result<void> check_mkdir(const BuiltinArguments& args) {
     auto options = ParseMkdir(args.args);
     if (!options.ok()) {
@@ -204,6 +212,14 @@
     return {};
 }
 
+Result<void> check_umount_all(const BuiltinArguments& args) {
+    auto options = ParseUmountAll(args.args);
+    if (!options.ok()) {
+        return options.error();
+    }
+    return {};
+}
+
 Result<void> check_wait(const BuiltinArguments& args) {
     if (args.size() == 3 && !args[2].empty()) {
         double timeout_double;
diff --git a/init/check_builtins.h b/init/check_builtins.h
index fb34556..725a6fd 100644
--- a/init/check_builtins.h
+++ b/init/check_builtins.h
@@ -32,11 +32,13 @@
 Result<void> check_load_system_props(const BuiltinArguments& args);
 Result<void> check_loglevel(const BuiltinArguments& args);
 Result<void> check_mkdir(const BuiltinArguments& args);
+Result<void> check_mount_all(const BuiltinArguments& args);
 Result<void> check_restorecon(const BuiltinArguments& args);
 Result<void> check_restorecon_recursive(const BuiltinArguments& args);
 Result<void> check_setprop(const BuiltinArguments& args);
 Result<void> check_setrlimit(const BuiltinArguments& args);
 Result<void> check_sysclktz(const BuiltinArguments& args);
+Result<void> check_umount_all(const BuiltinArguments& args);
 Result<void> check_wait(const BuiltinArguments& args);
 Result<void> check_wait_for_prop(const BuiltinArguments& args);
 
diff --git a/init/util.cpp b/init/util.cpp
index f9be055..40f24b1 100644
--- a/init/util.cpp
+++ b/init/util.cpp
@@ -572,6 +572,48 @@
     return MkdirOptions{args[1], mode, *uid, *gid, fscrypt_action, ref_option};
 }
 
+Result<MountAllOptions> ParseMountAll(const std::vector<std::string>& args) {
+    bool compat_mode = false;
+    bool import_rc = false;
+    if (SelinuxGetVendorAndroidVersion() <= __ANDROID_API_Q__) {
+        if (args.size() <= 1) {
+            return Error() << "mount_all requires at least 1 argument";
+        }
+        compat_mode = true;
+        import_rc = true;
+    }
+
+    std::size_t first_option_arg = args.size();
+    enum mount_mode mode = MOUNT_MODE_DEFAULT;
+
+    // If we are <= Q, then stop looking for non-fstab arguments at slot 2.
+    // Otherwise, stop looking at slot 1 (as the fstab path argument is optional >= R).
+    for (std::size_t na = args.size() - 1; na > (compat_mode ? 1 : 0); --na) {
+        if (args[na] == "--early") {
+            first_option_arg = na;
+            mode = MOUNT_MODE_EARLY;
+        } else if (args[na] == "--late") {
+            first_option_arg = na;
+            mode = MOUNT_MODE_LATE;
+            import_rc = false;
+        }
+    }
+
+    std::string fstab_path;
+    if (first_option_arg > 1) {
+        fstab_path = args[1];
+    } else if (compat_mode) {
+        return Error() << "mount_all argument 1 must be the fstab path";
+    }
+
+    std::vector<std::string> rc_paths;
+    for (std::size_t na = 2; na < first_option_arg; ++na) {
+        rc_paths.push_back(args[na]);
+    }
+
+    return MountAllOptions{rc_paths, fstab_path, mode, import_rc};
+}
+
 Result<std::pair<int, std::vector<std::string>>> ParseRestorecon(
         const std::vector<std::string>& args) {
     struct flag_type {
@@ -612,6 +654,15 @@
     return std::pair(flag, paths);
 }
 
+Result<std::string> ParseUmountAll(const std::vector<std::string>& args) {
+    if (SelinuxGetVendorAndroidVersion() <= __ANDROID_API_Q__) {
+        if (args.size() <= 1) {
+            return Error() << "umount_all requires at least 1 argument";
+        }
+    }
+    return args[1];
+}
+
 static void InitAborter(const char* abort_message) {
     // When init forks, it continues to use this aborter for LOG(FATAL), but we want children to
     // simply abort instead of trying to reboot the system.
diff --git a/init/util.h b/init/util.h
index 8167b02..28f6b18 100644
--- a/init/util.h
+++ b/init/util.h
@@ -22,6 +22,7 @@
 #include <chrono>
 #include <functional>
 #include <string>
+#include <vector>
 
 #include <android-base/chrono_utils.h>
 
@@ -33,6 +34,12 @@
 namespace android {
 namespace init {
 
+enum mount_mode {
+    MOUNT_MODE_DEFAULT = 0,
+    MOUNT_MODE_EARLY = 1,
+    MOUNT_MODE_LATE = 2,
+};
+
 static const char kColdBootDoneProp[] = "ro.cold_boot_done";
 
 extern void (*trigger_shutdown)(const std::string& command);
@@ -73,9 +80,20 @@
 
 Result<MkdirOptions> ParseMkdir(const std::vector<std::string>& args);
 
+struct MountAllOptions {
+    std::vector<std::string> rc_paths;
+    std::string fstab_path;
+    mount_mode mode;
+    bool import_rc;
+};
+
+Result<MountAllOptions> ParseMountAll(const std::vector<std::string>& args);
+
 Result<std::pair<int, std::vector<std::string>>> ParseRestorecon(
         const std::vector<std::string>& args);
 
+Result<std::string> ParseUmountAll(const std::vector<std::string>& args);
+
 void SetStdioToDevNull(char** argv);
 void InitKernelLogging(char** argv);
 void InitSecondStageLogging(char** argv);