Btrfs-progs: make sure to save mirror_num only if it is set

If we are cycling through all of the mirrors trying to find the best one we need
to make sure we set best_mirror to an actual mirror number and not 0.  Otherwise
we could end up reading a mirror that wasn't the best and make everybody sad.
Thanks,

Signed-off-by: Josef Bacik <jbacik@fb.com>
Signed-off-by: David Sterba <dsterba@suse.cz>
Signed-off-by: Chris Mason <clm@fb.com>

1 files changed, 1 insertions, 1 deletions

diff --git a/disk-io.c b/disk-io.c
index e840177f..0bd1bb01 100644
--- a/disk-io.c
+++ b/disk-io.c
@@ -297,7 +297,7 @@ struct extent_buffer *read_tree_block(struct btrfs_root *root, u64 bytenr,
 			ignore = 1;
 			continue;
 		}
-		if (btrfs_header_generation(eb) > best_transid) {
+		if (btrfs_header_generation(eb) > best_transid && mirror_num) {
 			best_transid = btrfs_header_generation(eb);
 			good_mirror = mirror_num;
 		}