From: Darrick J. Wong <djwong@xxxxxxxxxx>
For an unshare request, we only have to take action if the data fork has
a shared mapping. We don't care if someone else set up a cow operation.
If we find nothing in the data fork, return a hole to avoid allocating
space.
Note that fallocate will replace the delalloc reservation with an
unwritten extent anyway, so this has no user-visible effects outside of
avoiding unnecessary updates.
Signed-off-by: Darrick J. Wong <djwong@xxxxxxxxxx>
Reviewed-by: Dave Chinner <dchinner@xxxxxxxxxx>
---
fs/xfs/xfs_iomap.c | 5 +++--
1 file changed, 3 insertions(+), 2 deletions(-)
diff --git a/fs/xfs/xfs_iomap.c b/fs/xfs/xfs_iomap.c
index 285885c308bd..18c8f168b153 100644
--- a/fs/xfs/xfs_iomap.c
+++ b/fs/xfs/xfs_iomap.c
@@ -1006,8 +1006,9 @@ xfs_buffered_write_iomap_begin(
if (eof)
imap.br_startoff = end_fsb; /* fake hole until the end */
- /* We never need to allocate blocks for zeroing a hole. */
- if ((flags & IOMAP_ZERO) && imap.br_startoff > offset_fsb) {
+ /* We never need to allocate blocks for zeroing or unsharing a hole. */
+ if ((flags & (IOMAP_UNSHARE | IOMAP_ZERO)) &&
+ imap.br_startoff > offset_fsb) {
xfs_hole_to_iomap(ip, iomap, offset_fsb, imap.br_startoff);
goto out_unlock;
}
