diff options
| author | Brian Foster <bfoster@redhat.com> | 2017-01-27 23:22:57 -0800 |
|---|---|---|
| committer | Greg Kroah-Hartman <gregkh@linuxfoundation.org> | 2017-04-08 09:30:30 +0200 |
| commit | 4127a5d9fb89fd74d2816456e309eb82a3d375a9 (patch) | |
| tree | f7bdd2b2175c0b63f0a37c113d2d39bfa6d98bdb /fs/xfs/xfs_bmap_util.c | |
| parent | 4d725d7474dfddea00dca26f14b052c40d3444b0 (diff) | |
xfs: fix eofblocks race with file extending async dio writes
commit e4229d6b0bc9280f29624faf170cf76a9f1ca60e upstream.
It's possible for post-eof blocks to end up being used for direct I/O
writes. dio write performs an upfront unwritten extent allocation, sends
the dio and then updates the inode size (if necessary) on write
completion. If a file release occurs while a file extending dio write is
in flight, it is possible to mistake the post-eof blocks for speculative
preallocation and incorrectly truncate them from the inode. This means
that the resulting dio write completion can discover a hole and allocate
new blocks rather than perform unwritten extent conversion.
This requires a strange mix of I/O and is thus not likely to reproduce
in real world workloads. It is intermittently reproduced by generic/299.
The error manifests as an assert failure due to transaction overrun
because the aforementioned write completion transaction has only
reserved enough blocks for btree operations:
XFS: Assertion failed: tp->t_blk_res_used <= tp->t_blk_res, \
file: fs/xfs//xfs_trans.c, line: 309
The root cause is that xfs_free_eofblocks() uses i_size to truncate
post-eof blocks from the inode, but async, file extending direct writes
do not update i_size until write completion, long after inode locks are
dropped. Therefore, xfs_free_eofblocks() effectively truncates the inode
to the incorrect size.
Update xfs_free_eofblocks() to serialize against dio similar to how
extending writes are serialized against i_size updates before post-eof
block zeroing. Specifically, wait on dio while under the iolock. This
ensures that dio write completions have updated i_size before post-eof
blocks are processed.
Signed-off-by: Brian Foster <bfoster@redhat.com>
Reviewed-by: Christoph Hellwig <hch@lst.de>
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>
Diffstat (limited to 'fs/xfs/xfs_bmap_util.c')
| -rw-r--r-- | fs/xfs/xfs_bmap_util.c | 3 |
1 files changed, 3 insertions, 0 deletions
diff --git a/fs/xfs/xfs_bmap_util.c b/fs/xfs/xfs_bmap_util.c index d8ac76ca05a2..fd459b69161e 100644 --- a/fs/xfs/xfs_bmap_util.c +++ b/fs/xfs/xfs_bmap_util.c @@ -959,6 +959,9 @@ xfs_free_eofblocks( if (error) return error; + /* wait on dio to ensure i_size has settled */ + inode_dio_wait(VFS_I(ip)); + error = xfs_trans_alloc(mp, &M_RES(mp)->tr_itruncate, 0, 0, 0, &tp); if (error) { |