btrfs: reloc: add backref_cache::fs_info member

Add this member so that we can grab fs_info without the help from
reloc_control.
Reviewed-by: Josef Bacik <josef@toxicpanda.com>
Signed-off-by: Qu Wenruo <wqu@suse.com>
Reviewed-by: David Sterba <dsterba@suse.com>
Signed-off-by: David Sterba <dsterba@suse.com>

fs/btrfs/relocation.c

@@ -164,6 +164,8 @@ struct backref_cache {
 
 	/* The list of useless backref nodes during backref cache build */
 	struct list_head useless_node;
+
+	struct btrfs_fs_info *fs_info;
 };
 
 /*
@@ -266,7 +268,8 @@ static void mapping_tree_init(struct mapping_tree *tree)
 	spin_lock_init(&tree->lock);
 }
 
-static void backref_cache_init(struct backref_cache *cache)
+static void backref_cache_init(struct btrfs_fs_info *fs_info,
+			       struct backref_cache *cache)
 {
 	int i;
 	cache->rb_root = RB_ROOT;
@@ -277,6 +280,7 @@ static void backref_cache_init(struct backref_cache *cache)
 	INIT_LIST_HEAD(&cache->leaves);
 	INIT_LIST_HEAD(&cache->pending_edge);
 	INIT_LIST_HEAD(&cache->useless_node);
+	cache->fs_info = fs_info;
 }
 
 static void backref_cache_cleanup(struct backref_cache *cache)
@@ -4188,7 +4192,7 @@ static struct reloc_control *alloc_reloc_control(struct btrfs_fs_info *fs_info)
 
 	INIT_LIST_HEAD(&rc->reloc_roots);
 	INIT_LIST_HEAD(&rc->dirty_subvol_roots);
-	backref_cache_init(&rc->backref_cache);
+	backref_cache_init(fs_info, &rc->backref_cache);
 	mapping_tree_init(&rc->reloc_root_tree);
 	extent_io_tree_init(fs_info, &rc->processed_blocks,
 			    IO_TREE_RELOC_BLOCKS, NULL);