Commit 4b674b9a authored Apr 12, 2020 by Brian Foster Committed by Darrick J. Wong Apr 13, 2020

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: d6b636eb ("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>

parent 8f3d9f35

fs/xfs/xfs_icache.c

+10 −0

Original line number	Diff line number	Diff line
		@@ -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);
		}

fs/xfs/xfs_ioctl.c

+4 −1

Original line number	Diff line number	Diff line
		@@ -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:

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