xfs: acquire superblock freeze protection on eofblocks scans
authorBrian Foster <bfoster@redhat.com>
Sun, 12 Apr 2020 20:11:10 +0000 (13:11 -0700)
committerGreg Kroah-Hartman <gregkh@linuxfoundation.org>
Sat, 2 May 2020 06:48:48 +0000 (08:48 +0200)
commitccd3b4bb9944f0538884d7396246273d8361996d
treed4404e14d57eaa92e0f982fdd85fca3970093611
parent62f1cb49155211818c88a719c48bc01596071e8f
xfs: acquire superblock freeze protection on eofblocks scans

commit 4b674b9ac852937af1f8c62f730c325fb6eadcdb upstream.

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: d6b636ebb1c9f ("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>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
fs/xfs/xfs_icache.c
fs/xfs/xfs_ioctl.c