[PATCH 3/3] btrfs: Jump to correct label on init_root_trees failure

[Nikolay Borisov <nborisov@suse.com>]

During the refactoring and introduction of init_root_trees the code
retained the special handling of 'next_root_backup' failure by returning
-ESPIPE from init_root_trees and jumping to fail_block_groups.

This is wrong because next_root_backup doesn't tinker with blockgroups
at all and so any failure in it should be handled the same way as
failures from its sole caller (init_root_trees) - jumping to
fail_tree_roots. This was introduced in the original commit which
implemented backup roots af31f5e5b84b ("Btrfs: add a log of past tree
roots").

Fix it by always jumping to fail_tree_roots. While at it put some
sanity into next_root_backup by returning -EINVAL.

Signed-off-by: Nikolay Borisov <nborisov@suse.com>
---
 fs/btrfs/disk-io.c | 15 ++++++---------
 1 file changed, 6 insertions(+), 9 deletions(-)

diff --git a/fs/btrfs/disk-io.c b/fs/btrfs/disk-io.c
index 72580eb6b706..1eed0de4020f 100644
--- a/fs/btrfs/disk-io.c
+++ b/fs/btrfs/disk-io.c
@@ -1913,7 +1913,7 @@ static void backup_super_roots(struct btrfs_fs_info *info)
  * the array, so you send it the number of backups you've already
  * tried and the last backup index you used.
  *
- * this returns -1 when it has tried all the backups
+ * Returns EINVAL when it has tried all the backups
  */
 static noinline int next_root_backup(struct btrfs_fs_info *info,
 				     struct btrfs_super_block *super,
@@ -1927,13 +1927,13 @@ static noinline int next_root_backup(struct btrfs_fs_info *info,
 
 		newest = find_newest_super_backup(info, gen);
 		if (newest == -1)
-			return -1;
+			return -EINVAL;
 
 		*backup_index = newest;
 		*num_backups_tried = 1;
 	} else if (*num_backups_tried == BTRFS_NUM_BACKUP_ROOTS) {
 		/* we've tried all the backups, all done */
-		return -1;
+		return -EINVAL;
 	} else {
 		/* jump to the next oldest backup */
 		newest = (*backup_index + BTRFS_NUM_BACKUP_ROOTS - 1) %
@@ -2585,8 +2585,8 @@ int __cold init_tree_roots(struct btrfs_fs_info *fs_info)
 
 			ret = next_root_backup(fs_info, sb, &num_backups_tried,
 					       &backup_index);
-			if (ret == -1)
-				return -ESPIPE;
+			if (ret)
+				return ret;
 		}
 		generation = btrfs_super_generation(sb);
 		level = btrfs_super_root_level(sb);
@@ -3067,11 +3067,8 @@ int __cold open_ctree(struct super_block *sb,
 	}
 
 	ret = init_tree_roots(fs_info);
-	if (ret) {
-		if (ret == -ESPIPE)
-			goto fail_block_groups;
+	if (ret)
 		goto fail_tree_roots;
-	}
 
 	ret = btrfs_verify_dev_extents(fs_info);
 	if (ret) {
-- 
2.17.1