On Tue, Oct 03, 2017 at 04:34:16PM +0200, Christoph Hellwig wrote:
> 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@xxxxxx>
Looks ok, will test.
Reviewed-by: Darrick J. Wong <darrick.wong@xxxxxxxxxx>
> ---
> fs/xfs/xfs_reflink.c | 9 ++++++++-
> 1 file changed, 8 insertions(+), 1 deletion(-)
>
> diff --git a/fs/xfs/xfs_reflink.c b/fs/xfs/xfs_reflink.c
> index 3246815c24d6..37e603bf1591 100644
> --- a/fs/xfs/xfs_reflink.c
> +++ b/fs/xfs/xfs_reflink.c
> @@ -736,7 +736,13 @@ xfs_reflink_end_cow(
> /* If there is a hole at end_fsb - 1 go to the previous extent */
> if (!xfs_iext_lookup_extent(ip, ifp, end_fsb - 1, &idx, &got) ||
> 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_iext_get_extent(ifp, --idx, &got);
> }
>
> @@ -809,6 +815,7 @@ xfs_reflink_end_cow(
>
> out_defer:
> xfs_defer_cancel(&dfops);
> +out_cancel:
> xfs_trans_cancel(tp);
> xfs_iunlock(ip, XFS_ILOCK_EXCL);
> out:
> --
> 2.14.1
>
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