[PATCH 3/5] xfs: fix fork selection in xfs_find_trim_cow_extent

[Christoph Hellwig <hch@lst.de>]

We should want to write directly into the data fork for blocks that don't
have an extent in the COW fork covering them yet.

Signed-off-by: Christoph Hellwig <hch@lst.de>
---
 fs/xfs/xfs_reflink.c | 8 ++++++--
 1 file changed, 6 insertions(+), 2 deletions(-)

diff --git a/fs/xfs/xfs_reflink.c b/fs/xfs/xfs_reflink.c
index d1758771f21a..b25ea7a3a0e7 100644
--- a/fs/xfs/xfs_reflink.c
+++ b/fs/xfs/xfs_reflink.c
@@ -369,9 +369,13 @@ xfs_find_trim_cow_extent(
 	 * If we don't find an overlapping extent, trim the range we need to
 	 * allocate to fit the hole we found.
 	 */
-	if (!xfs_iext_lookup_extent(ip, ip->i_cowfp, offset_fsb, &icur, &got) ||
-	    got.br_startoff > offset_fsb)
+	if (!xfs_iext_lookup_extent(ip, ip->i_cowfp, offset_fsb, &icur, &got))
+		got.br_startoff = offset_fsb + count_fsb;
+	if (got.br_startoff > offset_fsb) {
+		xfs_trim_extent(imap, imap->br_startoff,
+				got.br_startoff - imap->br_startoff);
 		return xfs_reflink_trim_around_shared(ip, imap, shared);
+	}
 
 	*shared = true;
 	if (isnullstartblock(got.br_startblock)) {
-- 
2.18.0