[PATCH] Btrfs: avoid I/O repair BUG() from btree_read_extent_buffer_pages()

From btree_read_extent_buffer_pages(), currently repair_io_failure()

can be called with mirror_num being zero when submit_one_bio() returned
an error before. This used to cause a BUG_ON(!mirror_num) in
repair_io_failure() and indeed this is not a case that needs the I/O
repair code to rewrite disk blocks.
This commit prevents calling repair_io_failure() in this case and thus
avoids the BUG_ON() and malfunction.

Signed-off-by: Stefan Behrens <redacted>
---
 fs/btrfs/disk-io.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/fs/btrfs/disk-io.c b/fs/btrfs/disk-io.c
index 8cc4710..0a7a99b 100644
--- a/fs/btrfs/disk-io.c
+++ b/fs/btrfs/disk-io.c

@@ -407,7 +407,7 @@ static int btree_read_extent_buffer_pages(struct btrfs_root *root,
 			break;
 	}
 
-	if (failed && !ret)
+	if (failed && !ret && failed_mirror)
 		repair_eb_io_failure(root, eb, failed_mirror);
 
 	return ret;

-- 
1.7.11.1