[PATCH 3.16.y-ckt 46/71] btrfs: incorrect handling for fiemap_fill_next_extent return

3.16.7-ckt14 -stable review patch.  If anyone has any objections, please let me know.

------------------

From: Chengyu Song <redacted>

commit 26e726afe01c1c82072cf23a5ed89ce25f39d9f2 upstream.

fiemap_fill_next_extent returns 0 on success, -errno on error, 1 if this was
the last extent that will fit in user array. If 1 is returned, the return
value may eventually returned to user space, which should not happen, according
to manpage of ioctl.

Signed-off-by: Chengyu Song <redacted>
Reviewed-by: David Sterba <redacted>
Reviewed-by: Liu Bo <redacted>
Signed-off-by: Chris Mason <clm@fb.com>
Signed-off-by: Luis Henriques <redacted>
---
 fs/btrfs/extent_io.c | 5 ++++-
 1 file changed, 4 insertions(+), 1 deletion(-)

diff --git a/fs/btrfs/extent_io.c b/fs/btrfs/extent_io.c
index 09b4e3165e2c..a7db105139d2 100644
--- a/fs/btrfs/extent_io.c
+++ b/fs/btrfs/extent_io.c

@@ -4359,8 +4359,11 @@ int extent_fiemap(struct inode *inode, struct fiemap_extent_info *fieinfo,
 		}
 		ret = fiemap_fill_next_extent(fieinfo, em_start, disko,
 					      em_len, flags);
-		if (ret)
+		if (ret) {
+			if (ret == 1)
+				ret = 0;
 			goto out_free;
+		}
 	}
 out_free:
 	free_extent_map(em);