From: Long Li leo.lilong@huawei.com
commit e4c3b72a6ea93ed9c1815c74312eee9305638852 upstream.
While performing the IO fault injection test, I caught the following data corruption report:
XFS (dm-0): Internal error ltbno + ltlen > bno at line 1957 of file fs/xfs/libxfs/xfs_alloc.c. Caller xfs_free_ag_extent+0x79c/0x1130 CPU: 3 PID: 33 Comm: kworker/3:0 Not tainted 6.5.0-rc7-next-20230825-00001-g7f8666926889 #214 Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS ?-20190727_073836-buildvm-ppc64le-16.ppc.fedoraproject.org-3.fc31 04/01/2014 Workqueue: xfs-inodegc/dm-0 xfs_inodegc_worker Call Trace: <TASK> dump_stack_lvl+0x50/0x70 xfs_corruption_error+0x134/0x150 xfs_free_ag_extent+0x7d3/0x1130 __xfs_free_extent+0x201/0x3c0 xfs_trans_free_extent+0x29b/0xa10 xfs_extent_free_finish_item+0x2a/0xb0 xfs_defer_finish_noroll+0x8d1/0x1b40 xfs_defer_finish+0x21/0x200 xfs_itruncate_extents_flags+0x1cb/0x650 xfs_free_eofblocks+0x18f/0x250 xfs_inactive+0x485/0x570 xfs_inodegc_worker+0x207/0x530 process_scheduled_works+0x24a/0xe10 worker_thread+0x5ac/0xc60 kthread+0x2cd/0x3c0 ret_from_fork+0x4a/0x80 ret_from_fork_asm+0x11/0x20 </TASK> XFS (dm-0): Corruption detected. Unmount and run xfs_repair
After analyzing the disk image, it was found that the corruption was triggered by the fact that extent was recorded in both inode datafork and AGF btree blocks. After a long time of reproduction and analysis, we found that the reason of free sapce btree corruption was that the AGF btree was not recovered correctly.
Consider the following situation, Checkpoint A and Checkpoint B are in the same record and share the same start LSN1, buf items of same object (AGF btree block) is included in both Checkpoint A and Checkpoint B. If the buf item in Checkpoint A has been recovered and updates metadata LSN permanently, then the buf item in Checkpoint B cannot be recovered, because log recovery skips items with a metadata LSN >= the current LSN of the recovery item. If there is still an inode item in Checkpoint B that records the Extent X, the Extent X will be recorded in both inode datafork and AGF btree block after Checkpoint B is recovered. Such transaction can be seen when allocing enxtent for inode bmap, it record both the addition of extent to the inode extent list and the removing extent from the AGF.
|------------Record (LSN1)------------------|---Record (LSN2)---| |-------Checkpoint A----------|----------Checkpoint B-----------| | Buf Item(Extent X) | Buf Item / Inode item(Extent X) | | Extent X is freed | Extent X is allocated |
After commit 12818d24db8a ("xfs: rework log recovery to submit buffers on LSN boundaries") was introduced, we submit buffers on lsn boundaries during log recovery. The above problem can be avoided under normal paths, but it's not guaranteed under abnormal paths. Consider the following process, if an error was encountered after recover buf item in Checkpoint A and before recover buf item in Checkpoint B, buffers that have been added to the buffer_list will still be submitted, this violates the submits rule on lsn boundaries. So buf item in Checkpoint B cannot be recovered on the next mount due to current lsn of transaction equal to metadata lsn on disk. The detailed process of the problem is as follows.
First Mount:
xlog_do_recovery_pass error = xlog_recover_process xlog_recover_process_data xlog_recover_process_ophdr xlog_recovery_process_trans ... /* recover buf item in Checkpoint A */ xlog_recover_buf_commit_pass2 xlog_recover_do_reg_buffer /* add buffer of agf btree block to buffer_list */ xfs_buf_delwri_queue(bp, buffer_list) ... ==> Encounter read IO error and return /* submit buffers regardless of error */ if (!list_empty(&buffer_list)) xfs_buf_delwri_submit(&buffer_list);
<buf items of agf btree block in Checkpoint A recovery success>
Second Mount:
xlog_do_recovery_pass error = xlog_recover_process xlog_recover_process_data xlog_recover_process_ophdr xlog_recovery_process_trans ... /* recover buf item in Checkpoint B */ xlog_recover_buf_commit_pass2 /* buffer of agf btree block wouldn't added to buffer_list due to lsn equal to current_lsn */ if (XFS_LSN_CMP(lsn, current_lsn) >= 0) goto out_release
<buf items of agf btree block in Checkpoint B wouldn't recovery>
In order to make sure that submits buffers on lsn boundaries in the abnormal paths, we need to check error status before submit buffers that have been added from the last record processed. If error status exist, buffers in the bufffer_list should not be writen to disk.
Canceling the buffers in the buffer_list directly isn't correct, unlike any other place where write list was canceled, these buffers has been initialized by xfs_buf_item_init() during recovery and held by buf item, buf items will not be released in xfs_buf_delwri_cancel(), it's not easy to solve.
If the filesystem has been shut down, then delwri list submission will error out all buffers on the list via IO submission/completion and do all the correct cleanup automatically. So shutting down the filesystem could prevents buffers in the bufffer_list from being written to disk.
Fixes: 50d5c8d8e938 ("xfs: check LSN ordering for v5 superblocks during recovery") Signed-off-by: Long Li leo.lilong@huawei.com Reviewed-by: "Darrick J. Wong" djwong@kernel.org Signed-off-by: Chandan Babu R chandanbabu@kernel.org Signed-off-by: Catherine Hoang catherine.hoang@oracle.com Acked-by: Darrick J. Wong djwong@kernel.org --- fs/xfs/xfs_log_recover.c | 23 ++++++++++++++++++++--- 1 file changed, 20 insertions(+), 3 deletions(-)
diff --git a/fs/xfs/xfs_log_recover.c b/fs/xfs/xfs_log_recover.c index cc14cd1c2282..57f366c3d355 100644 --- a/fs/xfs/xfs_log_recover.c +++ b/fs/xfs/xfs_log_recover.c @@ -3203,11 +3203,28 @@ xlog_do_recovery_pass( kmem_free(hbp);
/* - * Submit buffers that have been added from the last record processed, - * regardless of error status. + * Submit buffers that have been dirtied by the last record recovered. */ - if (!list_empty(&buffer_list)) + if (!list_empty(&buffer_list)) { + if (error) { + /* + * If there has been an item recovery error then we + * cannot allow partial checkpoint writeback to + * occur. We might have multiple checkpoints with the + * same start LSN in this buffer list, and partial + * writeback of a checkpoint in this situation can + * prevent future recovery of all the changes in the + * checkpoints at this start LSN. + * + * Note: Shutting down the filesystem will result in the + * delwri submission marking all the buffers stale, + * completing them and cleaning up _XBF_LOGRECOVERY + * state without doing any IO. + */ + xlog_force_shutdown(log, SHUTDOWN_LOG_IO_ERROR); + } error2 = xfs_buf_delwri_submit(&buffer_list); + }
if (error && first_bad) *first_bad = rhead_blk;