xfs: fix fork selection in xfs_find_trim_cow_extent

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>
Reviewed-by: Brian Foster <bfoster@redhat.com>
Signed-off-by: Dave Chinner <david@fromorbit.com>

1 files changed, 6 insertions, 2 deletions

diff --git a/fs/xfs/xfs_reflink.c b/fs/xfs/xfs_reflink.c
index 80e5e79b86b0..8eaeec9d58ed 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)) {