btrfs: Factor out tree roots initialization during mount

The code responsible for reading and initializing tree roots is
scattered in open_ctree among 2 labels, emulating a loop. This is rather
confusing to reason about. Instead, factor the code to a new function,
init_tree_roots which implements the same logical flow.

There are a couple of notable differences, namely:

* Instead of using next_backup_root it's using the newly introduced
  read_backup_root.

* If read_backup_root returns an error init_tree_roots propagates the
  error and there is no special handling of that case e.g. the code jumps
  straight to 'fail_tree_roots' label. The old code, however, was
  (erroneously) jumping to 'fail_block_groups' label if next_backup_root
  did fail, this was unnecessary since the tree roots init logic doesn't
  modify the state of block groups.

Signed-off-by: Nikolay Borisov <nborisov@suse.com>
Reviewed-by: David Sterba <dsterba@suse.com>
Signed-off-by: David Sterba <dsterba@suse.com>

diff --git a/fs/btrfs/disk-io.c b/fs/btrfs/disk-io.c
index 4d061fa..1b1f051 100644 (file)
--- a/fs/btrfs/disk-io.c
+++ b/fs/btrfs/disk-io.c
@@ -2610,6 +2610,89 @@ out:
        return ret;
 }
 
+int __cold init_tree_roots(struct btrfs_fs_info *fs_info)
+{
+       struct btrfs_super_block *sb = fs_info->super_copy;
+       struct btrfs_root *tree_root = fs_info->tree_root;
+       bool handle_error = false;
+       int ret = 0;
+       int i;
+
+       for (i = 0; i < BTRFS_NUM_BACKUP_ROOTS; i++) {
+               u64 generation;
+               int level;
+
+               if (handle_error) {
+                       if (!IS_ERR(tree_root->node))
+                               free_extent_buffer(tree_root->node);
+                       tree_root->node = NULL;
+
+                       if (!btrfs_test_opt(fs_info, USEBACKUPROOT))
+                               break;
+
+                       free_root_pointers(fs_info, 0);
+
+                       /*
+                        * Don't use the log in recovery mode, it won't be
+                        * valid
+                        */
+                       btrfs_set_super_log_root(sb, 0);
+
+                       /* We can't trust the free space cache either */
+                       btrfs_set_opt(fs_info->mount_opt, CLEAR_CACHE);
+
+                       ret = read_backup_root(fs_info, i);
+                       if (ret < 0)
+                               return ret;
+               }
+               generation = btrfs_super_generation(sb);
+               level = btrfs_super_root_level(sb);
+               tree_root->node = read_tree_block(fs_info, btrfs_super_root(sb),
+                                                 generation, level, NULL);
+               if (IS_ERR(tree_root->node) ||
+                   !extent_buffer_uptodate(tree_root->node)) {
+                       handle_error = true;
+
+                       if (IS_ERR(tree_root->node))
+                               ret = PTR_ERR(tree_root->node);
+                       else if (!extent_buffer_uptodate(tree_root->node))
+                               ret = -EUCLEAN;
+
+                       btrfs_warn(fs_info, "failed to read tree root");
+                       continue;
+               }
+
+               btrfs_set_root_node(&tree_root->root_item, tree_root->node);
+               tree_root->commit_root = btrfs_root_node(tree_root);
+               btrfs_set_root_refs(&tree_root->root_item, 1);
+
+               mutex_lock(&tree_root->objectid_mutex);
+               ret = btrfs_find_highest_objectid(tree_root,
+                                               &tree_root->highest_objectid);
+               if (ret < 0) {
+                       mutex_unlock(&tree_root->objectid_mutex);
+                       handle_error = true;
+                       continue;
+               }
+
+               ASSERT(tree_root->highest_objectid <= BTRFS_LAST_FREE_OBJECTID);
+               mutex_unlock(&tree_root->objectid_mutex);
+
+               ret = btrfs_read_roots(fs_info);
+               if (ret < 0) {
+                       handle_error = true;
+                       continue;
+               }
+
+               /* All successful */
+               fs_info->generation = generation;
+               fs_info->last_trans_committed = generation;
+               break;
+       }
+
+       return ret;
+}
+
 int __cold open_ctree(struct super_block *sb,
               struct btrfs_fs_devices *fs_devices,
               char *options)
@@ -2628,8 +2711,6 @@ int __cold open_ctree(struct super_block *sb,
        struct btrfs_root *chunk_root;
        int ret;
        int err = -EINVAL;
-       int num_backups_tried = 0;
-       int backup_index = 0;
        int clear_free_space_tree = 0;
        int level;
 
@@ -3051,44 +3132,9 @@ int __cold open_ctree(struct super_block *sb,
                goto fail_tree_roots;
        }
 
-retry_root_backup:
-       generation = btrfs_super_generation(disk_super);
-       level = btrfs_super_root_level(disk_super);
-
-       tree_root->node = read_tree_block(fs_info,
-                                         btrfs_super_root(disk_super),
-                                         generation, level, NULL);
-       if (IS_ERR(tree_root->node) ||
-           !extent_buffer_uptodate(tree_root->node)) {
-               btrfs_warn(fs_info, "failed to read tree root");
-               if (!IS_ERR(tree_root->node))
-                       free_extent_buffer(tree_root->node);
-               tree_root->node = NULL;
-               goto recovery_tree_root;
-       }
-
-       btrfs_set_root_node(&tree_root->root_item, tree_root->node);
-       tree_root->commit_root = btrfs_root_node(tree_root);
-       btrfs_set_root_refs(&tree_root->root_item, 1);
-
-       mutex_lock(&tree_root->objectid_mutex);
-       ret = btrfs_find_highest_objectid(tree_root,
-                                       &tree_root->highest_objectid);
-       if (ret) {
-               mutex_unlock(&tree_root->objectid_mutex);
-               goto recovery_tree_root;
-       }
-
-       ASSERT(tree_root->highest_objectid <= BTRFS_LAST_FREE_OBJECTID);
-
-       mutex_unlock(&tree_root->objectid_mutex);
-
-       ret = btrfs_read_roots(fs_info);
+       ret = init_tree_roots(fs_info);
        if (ret)
-               goto recovery_tree_root;
-
-       fs_info->generation = generation;
-       fs_info->last_trans_committed = generation;
+               goto fail_tree_roots;
 
        ret = btrfs_verify_dev_extents(fs_info);
        if (ret) {
@@ -3383,24 +3429,6 @@ fail:
        btrfs_free_stripe_hash_table(fs_info);
        btrfs_close_devices(fs_info->fs_devices);
        return err;
-
-recovery_tree_root:
-       if (!btrfs_test_opt(fs_info, USEBACKUPROOT))
-               goto fail_tree_roots;
-
-       free_root_pointers(fs_info, false);
-
-       /* don't use the log in recovery mode, it won't be valid */
-       btrfs_set_super_log_root(disk_super, 0);
-
-       /* we can't trust the free space cache either */
-       btrfs_set_opt(fs_info->mount_opt, CLEAR_CACHE);
-
-       ret = next_root_backup(fs_info, fs_info->super_copy,
-                              &num_backups_tried, &backup_index);
-       if (ret == -1)
-               goto fail_block_groups;
-       goto retry_root_backup;
 }
 ALLOW_ERROR_INJECTION(open_ctree, ERRNO);