check_mft_mirror() still computes the number of bytes to validate in each
mirrored MFT record, but the actual comparison against $MFTMirr was dropped
when the superblock code was updated.

As a result, mount misses a stale or inconsistent $MFTMirr as long as both
records pass the structural baad-record checks. Restore the comparison and
log an error when the primary $MFT record differs from its mirror copy.

Returning false lets the existing mount error handling mark the volume as
having NTFS errors and, with on_errors=remount-ro, continue read-only. The
default on_errors=continue mount policy still allows the mount to proceed.

Fixes: 6251f0b0de7d ("ntfs: update super block operations")
Signed-off-by: DaeMyung Kang <charsyam@gmail.com>
---
 fs/ntfs/super.c | 7 +++++++
 1 file changed, 7 insertions(+)

diff --git a/fs/ntfs/super.c b/fs/ntfs/super.c
index 22dc786..e8ecc52 100644
--- a/fs/ntfs/super.c
+++ b/fs/ntfs/super.c
@@ -979,6 +979,13 @@ mft_unmap_out:
 			    ntfs_is_baad_recordp((__le32 *)kmirr))
 				bytes = vol->mft_record_size;
 		}
+		/* Compare the two records. */
+		if (memcmp(kmft, kmirr, bytes)) {
+			ntfs_error(sb,
+				   "$MFT and $MFTMirr record %i do not match.  Run chkdsk.",
+				   i);
+			goto mm_unmap_out;
+		}
 		kmft += vol->mft_record_size;
 		kmirr += vol->mft_record_size;
 	} while (++i < vol->mftmirr_size);
-- 
2.43.0

ntfs_sync_fs() can be called while the filesystem remains mounted
read-write, for example by sync(2) or periodic writeback. Clearing
VOLUME_IS_DIRTY from that path marks the volume clean before the mount
lifetime has ended.

If the system crashes after sync_fs() clears the bit but before unmount or
remount-read-only, the volume can be left looking clean even though a clean
shutdown did not happen. Keep the dirty bit set during sync_fs(); the
unmount and remount-read-only paths already clear it when no NTFS errors
were seen.

Fixes: 6251f0b0de7d ("ntfs: update super block operations")
Signed-off-by: DaeMyung Kang <charsyam@gmail.com>
---
 fs/ntfs/super.c | 8 +-------
 1 file changed, 1 insertion(+), 7 deletions(-)

diff --git a/fs/ntfs/super.c b/fs/ntfs/super.c
index e8ecc52..024d363 100644
--- a/fs/ntfs/super.c
+++ b/fs/ntfs/super.c
@@ -1895,7 +1895,6 @@ static void ntfs_shutdown(struct super_block *sb)
 static int ntfs_sync_fs(struct super_block *sb, int wait)
 {
 	struct ntfs_volume *vol = NTFS_SB(sb);
-	int err = 0;
 
 	if (NVolShutdown(vol))
 		return -EIO;
@@ -1903,15 +1902,10 @@ static int ntfs_sync_fs(struct super_block *sb, int wait)
 	if (!wait)
 		return 0;
 
-	/* If there are some dirty buffers in the bdev inode */
-	if (ntfs_clear_volume_flags(vol, VOLUME_IS_DIRTY)) {
-		ntfs_warning(sb, "Failed to clear dirty bit in volume information flags.  Run chkdsk.");
-		err = -EIO;
-	}
 	sync_inodes_sb(sb);
 	sync_blockdev(sb->s_bdev);
 	blkdev_issue_flush(sb->s_bdev);
-	return err;
+	return 0;
 }
 
 /*
-- 
2.43.0