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xfs: acquire superblock freeze protection on eofblocks scans 

The filesystem freeze sequence in XFS waits on any background
eofblocks or cowblocks scans to complete before the filesystem is
quiesced. At this point, the freezer has already stopped the
transaction subsystem, however, which means a truncate or cowblock
cancellation in progress is likely blocked in transaction
allocation. This results in a deadlock between freeze and the
associated scanner.

Fix this problem by holding superblock write protection across calls
into the block reapers. Since protection for background scans is
acquired from the workqueue task context, trylock to avoid a similar
deadlock between freeze and blocking on the write lock.

Fixes: d6b636ebb1 ("xfs: halt auto-reclamation activities while rebuilding rmap")
Reported-by: Paul Furtado <paulfurtado91@gmail.com>
Signed-off-by: Brian Foster <bfoster@redhat.com>
Reviewed-by: Chandan Rajendra <chandanrlinux@gmail.com>
Reviewed-by: Christoph Hellwig <hch@lst.de>
Reviewed-by: Allison Collins <allison.henderson@oracle.com>
Reviewed-by: Darrick J. Wong <darrick.wong@oracle.com>
Signed-off-by: Darrick J. Wong <darrick.wong@oracle.com>
This commit is contained in:
Brian Foster 2020-04-12 13:11:10 -07:00 committed by Darrick J. Wong
parent 8f3d9f3542
commit 4b674b9ac8
2 changed files with 14 additions and 1 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

10
fs/xfs/xfs_icache.c
View File

@ -911,7 +911,12 @@ xfs_eofblocks_worker(
{
struct xfs_mount *mp = container_of(to_delayed_work(work),
struct xfs_mount, m_eofblocks_work);
if (!sb_start_write_trylock(mp->m_super))
return;
xfs_icache_free_eofblocks(mp, NULL);
sb_end_write(mp->m_super);
xfs_queue_eofblocks(mp);
}
@ -938,7 +943,12 @@ xfs_cowblocks_worker(
{
struct xfs_mount *mp = container_of(to_delayed_work(work),
struct xfs_mount, m_cowblocks_work);
if (!sb_start_write_trylock(mp->m_super))
return;
xfs_icache_free_cowblocks(mp, NULL);
sb_end_write(mp->m_super);
xfs_queue_cowblocks(mp);
}

5
fs/xfs/xfs_ioctl.c
View File

@ -2363,7 +2363,10 @@ xfs_file_ioctl(
if (error)
return error;
return xfs_icache_free_eofblocks(mp, &keofb);
sb_start_write(mp->m_super);
error = xfs_icache_free_eofblocks(mp, &keofb);
sb_end_write(mp->m_super);
return error;
}
default: