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xfs: handle racy AIO in xfs_reflink_end_cow

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commit e12199f85d upstream.

If we got two AIO writes into a COW area the second one might not have any
COW extents left to convert.  Handle that case gracefully instead of
triggering an assert or accessing beyond the bounds of the extent list.

Signed-off-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>
This commit is contained in:
Christoph Hellwig
2017-10-03 08:58:33 -07:00
committed by Greg Kroah-Hartman
parent 002295a6be
commit 1b4998dced
1 changed files with 8 additions and 1 deletions
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9
fs/xfs/xfs_reflink.c
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@@ -767,7 +767,13 @@ xfs_reflink_end_cow(
/* If there is a hole at end_fsb - 1 go to the previous extent */
if (eof || got.br_startoff > end_fsb) {
ASSERT(idx > 0);
/*
* In case of racing, overlapping AIO writes no COW extents
* might be left by the time I/O completes for the loser of
* the race. In that case we are done.
*/
if (idx <= 0)
goto out_cancel;
xfs_bmbt_get_all(xfs_iext_get_ext(ifp, --idx), &got);
}
@@ -841,6 +847,7 @@ next_extent:
out_defer:
xfs_defer_cancel(&dfops);
out_cancel:
xfs_trans_cancel(tp);
xfs_iunlock(ip, XFS_ILOCK_EXCL);
out: