diff --git a/Android.mk b/Android.mk
index a013511..2992f06 100644
--- a/Android.mk
+++ b/Android.mk
@@ -145,6 +145,7 @@
 
 LOCAL_SRC_FILES := \
     adb_install.cpp \
+    fsck_unshare_blocks.cpp \
     fuse_sdcard_provider.cpp \
     install.cpp \
     recovery.cpp \
@@ -205,6 +206,13 @@
 endif
 endif
 
+# e2fsck is needed for adb remount -R.
+ifeq ($(BOARD_EXT4_SHARE_DUP_BLOCKS),true)
+ifneq (,$(filter userdebug eng,$(TARGET_BUILD_VARIANT)))
+LOCAL_REQUIRED_MODULES += e2fsck_static
+endif
+endif
+
 ifeq ($(BOARD_CACHEIMAGE_PARTITION_SIZE),)
 LOCAL_REQUIRED_MODULES += \
     recovery-persist \
diff --git a/fsck_unshare_blocks.cpp b/fsck_unshare_blocks.cpp
new file mode 100644
index 0000000..a100368
--- /dev/null
+++ b/fsck_unshare_blocks.cpp
@@ -0,0 +1,163 @@
+/*
+ * Copyright (C) 2018 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 "fsck_unshare_blocks.h"
+
+#include <errno.h>
+#include <fcntl.h>
+#include <spawn.h>
+#include <string.h>
+#include <sys/mount.h>
+#include <sys/stat.h>
+#include <sys/types.h>
+#include <sys/wait.h>
+#include <unistd.h>
+
+#include <algorithm>
+#include <memory>
+#include <string>
+#include <vector>
+
+#include <android-base/logging.h>
+#include <android-base/properties.h>
+#include <android-base/unique_fd.h>
+#include <fstab/fstab.h>
+
+#include "roots.h"
+
+static constexpr const char* SYSTEM_E2FSCK_BIN = "/system/bin/e2fsck_static";
+static constexpr const char* TMP_E2FSCK_BIN = "/tmp/e2fsck.bin";
+
+static bool copy_file(const char* source, const char* dest) {
+  android::base::unique_fd source_fd(open(source, O_RDONLY));
+  if (source_fd < 0) {
+    PLOG(ERROR) << "open %s failed" << source;
+    return false;
+  }
+
+  android::base::unique_fd dest_fd(open(dest, O_CREAT | O_WRONLY, S_IRWXU));
+  if (dest_fd < 0) {
+    PLOG(ERROR) << "open %s failed" << dest;
+    return false;
+  }
+
+  for (;;) {
+    char buf[4096];
+    ssize_t rv = read(source_fd, buf, sizeof(buf));
+    if (rv < 0) {
+      PLOG(ERROR) << "read failed";
+      return false;
+    }
+    if (rv == 0) {
+      break;
+    }
+    if (write(dest_fd, buf, rv) != rv) {
+      PLOG(ERROR) << "write failed";
+      return false;
+    }
+  }
+  return true;
+}
+
+static bool run_e2fsck(const std::string& partition) {
+  Volume* volume = volume_for_mount_point(partition);
+  if (!volume) {
+    LOG(INFO) << "No fstab entry for " << partition << ", skipping.";
+    return true;
+  }
+
+  LOG(INFO) << "Running e2fsck on device " << volume->blk_device;
+
+  std::vector<std::string> args = { TMP_E2FSCK_BIN, "-p", "-E", "unshare_blocks",
+                                    volume->blk_device };
+  std::vector<char*> argv(args.size());
+  std::transform(args.cbegin(), args.cend(), argv.begin(),
+                 [](const std::string& arg) { return const_cast<char*>(arg.c_str()); });
+  argv.push_back(nullptr);
+
+  pid_t child;
+  char* env[] = { nullptr };
+  if (posix_spawn(&child, argv[0], nullptr, nullptr, argv.data(), env)) {
+    PLOG(ERROR) << "posix_spawn failed";
+    return false;
+  }
+
+  int status = 0;
+  int ret = TEMP_FAILURE_RETRY(waitpid(child, &status, 0));
+  if (ret < 0) {
+    PLOG(ERROR) << "waitpid failed";
+    return false;
+  }
+  if (!WIFEXITED(status)) {
+    LOG(ERROR) << "e2fsck exited abnormally: " << status;
+    return false;
+  }
+  int return_code = WEXITSTATUS(status);
+  if (return_code >= 8) {
+    LOG(ERROR) << "e2fsck could not unshare blocks: " << return_code;
+    return false;
+  }
+
+  LOG(INFO) << "Successfully unshared blocks on " << partition;
+  return true;
+}
+
+static const char* get_system_root() {
+  if (android::base::GetBoolProperty("ro.build.system_root_image", false)) {
+    return "/system_root";
+  } else {
+    return "/system";
+  }
+}
+
+bool do_fsck_unshare_blocks() {
+  // List of partitions we will try to e2fsck -E unshare_blocks.
+  std::vector<std::string> partitions = { "/odm", "/oem", "/product", "/vendor" };
+
+  // Temporarily mount system so we can copy e2fsck_static.
+  bool mounted = false;
+  if (android::base::GetBoolProperty("ro.build.system_root_image", false)) {
+    mounted = ensure_path_mounted_at("/", "/system_root") != -1;
+    partitions.push_back("/");
+  } else {
+    mounted = ensure_path_mounted("/system") != -1;
+    partitions.push_back("/system");
+  }
+  if (!mounted) {
+    LOG(ERROR) << "Failed to mount system image.";
+    return false;
+  }
+  if (!copy_file(SYSTEM_E2FSCK_BIN, TMP_E2FSCK_BIN)) {
+    LOG(ERROR) << "Could not copy e2fsck to /tmp.";
+    return false;
+  }
+  if (umount(get_system_root()) < 0) {
+    PLOG(ERROR) << "umount failed";
+    return false;
+  }
+
+  bool ok = true;
+  for (const auto& partition : partitions) {
+    ok &= run_e2fsck(partition);
+  }
+
+  if (ok) {
+    LOG(INFO) << "Finished running e2fsck.";
+  } else {
+    LOG(ERROR) << "Finished running e2fsck, but not all partitions succceeded.";
+  }
+  return ok;
+}
diff --git a/fsck_unshare_blocks.h b/fsck_unshare_blocks.h
new file mode 100644
index 0000000..9de8ef9
--- /dev/null
+++ b/fsck_unshare_blocks.h
@@ -0,0 +1,22 @@
+/*
+ * Copyright (C) 2018 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 _FILESYSTEM_CMDS_H
+#define _FILESYSTEM_CMDS_H
+
+bool do_fsck_unshare_blocks();
+
+#endif  // _FILESYSTEM_CMDS_H
diff --git a/recovery.cpp b/recovery.cpp
index 69b1499..8f39679 100644
--- a/recovery.cpp
+++ b/recovery.cpp
@@ -55,6 +55,7 @@
 #include "adb_install.h"
 #include "common.h"
 #include "device.h"
+#include "fsck_unshare_blocks.h"
 #include "fuse_sdcard_provider.h"
 #include "fuse_sideload.h"
 #include "install.h"
@@ -989,6 +990,7 @@
                  [](const std::string& arg) { return const_cast<char*>(arg.c_str()); });
 
   static constexpr struct option OPTIONS[] = {
+    { "fsck_unshare_blocks", no_argument, nullptr, 0 },
     { "just_exit", no_argument, nullptr, 'x' },
     { "locale", required_argument, nullptr, 0 },
     { "prompt_and_wipe_data", no_argument, nullptr, 0 },
@@ -1017,6 +1019,7 @@
   bool sideload_auto_reboot = false;
   bool just_exit = false;
   bool shutdown_after = false;
+  bool fsck_unshare_blocks = false;
   int retry_count = 0;
   bool security_update = false;
   std::string locale;
@@ -1034,7 +1037,9 @@
         break;
       case 0: {
         std::string option = OPTIONS[option_index].name;
-        if (option == "locale") {
+        if (option == "fsck_unshare_blocks") {
+          fsck_unshare_blocks = true;
+        } else if (option == "locale") {
           // Handled in recovery_main.cpp
         } else if (option == "prompt_and_wipe_data") {
           should_prompt_and_wipe_data = true;
@@ -1201,6 +1206,10 @@
     if (sideload_auto_reboot) {
       ui->Print("Rebooting automatically.\n");
     }
+  } else if (fsck_unshare_blocks) {
+    if (!do_fsck_unshare_blocks()) {
+      status = INSTALL_ERROR;
+    }
   } else if (!just_exit) {
     // If this is an eng or userdebug build, automatically turn on the text display if no command
     // is specified. Note that this should be called before setting the background to avoid