[PATCH 3.10 28/29] btrfs: incorrect handling for fiemap_fill_next_extent return

[Greg Kroah-Hartman <gregkh@linuxfoundation.org>]

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

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

From: Chengyu Song <csong84@gatech.edu>

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 <csong84@gatech.edu>
Reviewed-by: David Sterba <dsterba@suse.cz>
Reviewed-by: Liu Bo <bo.li.liu@oracle.com>
Signed-off-by: Chris Mason <clm@fb.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

---
 fs/btrfs/extent_io.c |    5 ++++-
 1 file changed, 4 insertions(+), 1 deletion(-)

--- a/fs/btrfs/extent_io.c
+++ b/fs/btrfs/extent_io.c
@@ -4080,8 +4080,11 @@ int extent_fiemap(struct inode *inode, s
 		}
 		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);


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