xfs: check sb_meta_uuid for dabuf buffer recovery
Got a report that a repeated crash test of a container host would eventually fail with a log recovery error preventing the system from mounting the root filesystem. It manifested as a directory leaf node corruption on writeback like so: XFS (loop0): Mounting V5 Filesystem XFS (loop0): Starting recovery (logdev: internal) XFS (loop0): Metadata corruption detected at xfs_dir3_leaf_check_int+0x99/0xf0, xfs_dir3_leaf1 block 0x12faa158 XFS (loop0): Unmount and run xfs_repair XFS (loop0): First 128 bytes of corrupted metadata buffer: 00000000: 00 00 00 00 00 00 00 00 3d f1 00 00 e1 9e d5 8b ........=....... 00000010: 00 00 00 00 12 fa a1 58 00 00 00 29 00 00 1b cc .......X...).... 00000020: 91 06 78 ff f7 7e 4a 7d 8d 53 86 f2 ac 47 a8 23 ..x..~J}.S...G.# 00000030: 00 00 00 00 17 e0 00 80 00 43 00 00 00 00 00 00 .........C...... 00000040: 00 00 00 2e 00 00 00 08 00 00 17 2e 00 00 00 0a ................ 00000050: 02 35 79 83 00 00 00 30 04 d3 b4 80 00 00 01 50 .5y....0.......P 00000060: 08 40 95 7f 00 00 02 98 08 41 fe b7 00 00 02 d4 .@.......A...... 00000070: 0d 62 ef a7 00 00 01 f2 14 50 21 41 00 00 00 0c .b.......P!A.... XFS (loop0): Corruption of in-memory data (0x8) detected at xfs_do_force_shutdown+0x1a/0x20 (fs/xfs/xfs_buf.c:1514). Shutting down. XFS (loop0): Please unmount the filesystem and rectify the problem(s) XFS (loop0): log mount/recovery failed: error -117 XFS (loop0): log mount failed Tracing indicated that we were recovering changes from a transaction at LSN 0x29/0x1c16 into a buffer that had an LSN of 0x29/0x1d57. That is, log recovery was overwriting a buffer with newer changes on disk than was in the transaction. Tracing indicated that we were hitting the "recovery immediately" case in xfs_buf_log_recovery_lsn(), and hence it was ignoring the LSN in the buffer. The code was extracting the LSN correctly, then ignoring it because the UUID in the buffer did not match the superblock UUID. The problem arises because the UUID check uses the wrong UUID - it should be checking the sb_meta_uuid, not sb_uuid. This filesystem has sb_uuid != sb_meta_uuid (which is fine), and the buffer has the correct matching sb_meta_uuid in it, it's just the code checked it against the wrong superblock uuid. The is no corruption in the filesystem, and failing to recover the buffer due to a write verifier failure means the recovery bug did not propagate the corruption to disk. Hence there is no corruption before or after this bug has manifested, the impact is limited simply to an unmountable filesystem.... This was missed back in 2015 during an audit of incorrect sb_uuid usage that resulted in commit fcfbe2c4 ("xfs: log recovery needs to validate against sb_meta_uuid") that fixed the magic32 buffers to validate against sb_meta_uuid instead of sb_uuid. It missed the magicda buffers.... Fixes: ce748eaa ("xfs: create new metadata UUID field and incompat flag") Signed-off-by:Dave Chinner <dchinner@redhat.com> Reviewed-by: