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authorChristoph Hellwig <hch@lst.de>2018-09-29 13:49:58 +1000
committerDave Chinner <david@fromorbit.com>2018-09-29 13:49:58 +1000
commitf5f3f959b70b272dfe2d05758e43ae52f5ff7748 (patch)
tree993379f5bd715a61485c0ac9f966464222977151 /fs
parentf369a13cead821e679c7415dc66a17ec48cc26bf (diff)
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')
-rw-r--r--fs/xfs/xfs_reflink.c10
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. */