fs_mgr: overlay check shared blocks for / if /system is not

For bringup devices that do not have right-sized partition, and if
/system is now root, check / to be sure.

Consider unshare blocks for ext4 as dead code, provide a strong
message to caller to provide all the dependencies to overlayfs.

Test: adb-remount-test.sh
Bug: 130327601
Change-Id: Iffa7c5f24d8f409e71f89fe9ece274d8c476f6fc
Merged-In: Iffa7c5f24d8f409e71f89fe9ece274d8c476f6fc

2 files changed, 8 insertions, 9 deletions

diff --git a/fs_mgr/fs_mgr_overlayfs.cpp b/fs_mgr/fs_mgr_overlayfs.cpp
index 730d3db68..012abd4dc 100644
--- a/fs_mgr/fs_mgr_overlayfs.cpp
+++ b/fs_mgr/fs_mgr_overlayfs.cpp
@@ -159,6 +159,9 @@ bool fs_mgr_overlayfs_enabled(FstabEntry* entry) {
     auto save_errno = errno;
     errno = 0;
     auto has_shared_blocks = fs_mgr_has_shared_blocks(entry->mount_point, entry->blk_device);
+    if (!has_shared_blocks && (entry->mount_point == "/system")) {
+        has_shared_blocks = fs_mgr_has_shared_blocks("/", entry->blk_device);
+    }
     // special case for first stage init for system as root (taimen)
     if (!has_shared_blocks && (errno == ENOENT) && (entry->blk_device == "/dev/root")) {
         has_shared_blocks = true;
diff --git a/fs_mgr/fs_mgr_remount.cpp b/fs_mgr/fs_mgr_remount.cpp
index 093d44d41..cbe2008a0 100644
--- a/fs_mgr/fs_mgr_remount.cpp
+++ b/fs_mgr/fs_mgr_remount.cpp
@@ -371,17 +371,13 @@ int main(int argc, char* argv[]) {
                 continue;
             }
         }
-        PLOG(WARNING) << "failed to remount partition dev:" << blk_device << " mnt:" << mount_point;
-        // If errno = EROFS at this point, we are dealing with r/o
+        PLOG(ERROR) << "failed to remount partition dev:" << blk_device << " mnt:" << mount_point;
+        // If errno is EROFS at this point, we are dealing with r/o
         // filesystem types like squashfs, erofs or ext4 dedupe. We will
         // consider such a device that does not have CONFIG_OVERLAY_FS
-        // in the kernel as a misconfigured; except for ext4 dedupe.
-        if ((errno == EROFS) && can_reboot) {
-            const std::vector<std::string> msg = {"--fsck_unshare_blocks"};
-            std::string err;
-            if (write_bootloader_message(msg, &err)) reboot(true);
-            LOG(ERROR) << "Failed to set bootloader message: " << err;
-            errno = EROFS;
+        // in the kernel as a misconfigured.
+        if (errno == EROFS) {
+            LOG(ERROR) << "Consider providing all the dependencies to enable overlayfs";
         }
         retval = REMOUNT_FAILED;
     }