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| author | Christoph Hellwig <hch@lst.de> | 2018-09-29 13:49:58 +1000 |
|---|---|---|
| committer | Dave Chinner <david@fromorbit.com> | 2018-09-29 13:49:58 +1000 |
| commit | f5f3f959b70b272dfe2d05758e43ae52f5ff7748 (patch) | |
| tree | 993379f5bd715a61485c0ac9f966464222977151 /fs/xfs/xfs_reflink.c | |
| parent | f369a13cead821e679c7415dc66a17ec48cc26bf (diff) | |
| download | lwn-f5f3f959b70b272dfe2d05758e43ae52f5ff7748.tar.gz lwn-f5f3f959b70b272dfe2d05758e43ae52f5ff7748.zip | |
xfs: skip delalloc COW blocks in xfs_reflink_end_cow
The iomap direct I/O code issues a single ->end_io call for the whole
I/O request, and if some of the extents cowered needed a COW operation
it will call xfs_reflink_end_cow over the whole range.
When we do AIO writes we drop the iolock after doing the initial setup,
but before the I/O completion. Between dropping the lock and completing
the I/O we can have a racing buffered write create new delalloc COW fork
extents in the region covered by the outstanding direct I/O write, and
thus see delalloc COW fork extents in xfs_reflink_end_cow. As
concurrent writes are fundamentally racy and no guarantees are given we
can simply skip those.
This can be easily reproduced with xfstests generic/208 in always_cow
mode.
Signed-off-by: Christoph Hellwig <hch@lst.de>
Reviewed-by: Darrick J. Wong <darrick.wong@oracle.com>
Signed-off-by: Dave Chinner <david@fromorbit.com>
Diffstat (limited to 'fs/xfs/xfs_reflink.c')
| -rw-r--r-- | fs/xfs/xfs_reflink.c | 10 |
1 files changed, 4 insertions, 6 deletions
diff --git a/fs/xfs/xfs_reflink.c b/fs/xfs/xfs_reflink.c index d60d0eeed7b9..5289e22cb081 100644 --- a/fs/xfs/xfs_reflink.c +++ b/fs/xfs/xfs_reflink.c @@ -693,14 +693,12 @@ xfs_reflink_end_cow( if (!del.br_blockcount) goto prev_extent; - ASSERT(!isnullstartblock(got.br_startblock)); - /* - * Don't remap unwritten extents; these are - * speculatively preallocated CoW extents that have been - * allocated but have not yet been involved in a write. + * Only remap real extent that contain data. With AIO + * speculatively preallocations can leak into the range we + * are called upon, and we need to skip them. */ - if (got.br_state == XFS_EXT_UNWRITTEN) + if (!xfs_bmap_is_real_extent(&got)) goto prev_extent; /* Unmap the old blocks in the data fork. */ |