From 2b3f004d3d518ec7a392066d935fd85c81412e33 Mon Sep 17 00:00:00 2001 From: "Darrick J. Wong" Date: Tue, 21 May 2024 23:01:45 -0700 Subject: [PATCH] xfs: drop xfarray sortinfo folio on error Chandan Babu reports the following livelock in xfs/708: run fstests xfs/708 at 2024-05-04 15:35:29 XFS (loop16): EXPERIMENTAL online scrub feature in use. Use at your own risk! XFS (loop5): Mounting V5 Filesystem e96086f0-a2f9-4424-a1d5-c75d53d823be XFS (loop5): Ending clean mount XFS (loop5): Quotacheck needed: Please wait. XFS (loop5): Quotacheck: Done. XFS (loop5): EXPERIMENTAL online scrub feature in use. Use at your own risk! INFO: task xfs_io:143725 blocked for more than 122 seconds. Not tainted 6.9.0-rc4+ #1 "echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message. task:xfs_io state:D stack:0 pid:143725 tgid:143725 ppid:117661 flags:0x00004006 Call Trace: __schedule+0x69c/0x17a0 schedule+0x74/0x1b0 io_schedule+0xc4/0x140 folio_wait_bit_common+0x254/0x650 shmem_undo_range+0x9d5/0xb40 shmem_evict_inode+0x322/0x8f0 evict+0x24e/0x560 __dentry_kill+0x17d/0x4d0 dput+0x263/0x430 __fput+0x2fc/0xaa0 task_work_run+0x132/0x210 get_signal+0x1a8/0x1910 arch_do_signal_or_restart+0x7b/0x2f0 syscall_exit_to_user_mode+0x1c2/0x200 do_syscall_64+0x72/0x170 entry_SYSCALL_64_after_hwframe+0x76/0x7e The shmem code is trying to drop all the folios attached to a shmem file and gets stuck on a locked folio after a bnobt repair. It looks like the process has a signal pending, so I started looking for places where we lock an xfile folio and then deal with a fatal signal. I found a bug in xfarray_sort_scan via code inspection. This function is called to set up the scanning phase of a quicksort operation, which may involve grabbing a locked xfile folio. If we exit the function with an error code, the caller does not call xfarray_sort_scan_done to put the xfile folio. If _sort_scan returns an error code while si->folio is set, we leak the reference and never unlock the folio. Therefore, change xfarray_sort to call _scan_done on exit. This is safe to call multiple times because it sets si->folio to NULL and ignores a NULL si->folio. Also change _sort_scan to use an intermediate variable so that we never pollute si->folio with an errptr. Fixes: 232ea052775f9 ("xfs: enable sorting of xfile-backed arrays") Reported-by: Chandan Babu R Signed-off-by: "Darrick J. Wong" Reviewed-by: Christoph Hellwig Signed-off-by: Chandan Babu R --- fs/xfs/scrub/xfarray.c | 9 ++++++--- 1 file changed, 6 insertions(+), 3 deletions(-) diff --git a/fs/xfs/scrub/xfarray.c b/fs/xfs/scrub/xfarray.c index 9185ae7088d4..cdd13ed9c569 100644 --- a/fs/xfs/scrub/xfarray.c +++ b/fs/xfs/scrub/xfarray.c @@ -822,12 +822,14 @@ xfarray_sort_scan( /* Grab the first folio that backs this array element. */ if (!si->folio) { + struct folio *folio; loff_t next_pos; - si->folio = xfile_get_folio(si->array->xfile, idx_pos, + folio = xfile_get_folio(si->array->xfile, idx_pos, si->array->obj_size, XFILE_ALLOC); - if (IS_ERR(si->folio)) - return PTR_ERR(si->folio); + if (IS_ERR(folio)) + return PTR_ERR(folio); + si->folio = folio; si->first_folio_idx = xfarray_idx(si->array, folio_pos(si->folio) + si->array->obj_size - 1); @@ -1048,6 +1050,7 @@ xfarray_sort( out_free: trace_xfarray_sort_stats(si, error); + xfarray_sort_scan_done(si); kvfree(si); return error; }