btrfs: reloc: pass essential members for alloc_backref_node()

Bytenr and level are essential parameters for backref_node, thus it
makes sense to initialize them at allocation time.
Reviewed-by: Josef Bacik <josef@toxicpanda.com>
Reviewed-by: Nikolay Borisov <nborisov@suse.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

@@ -339,18 +339,24 @@ static void backref_cache_cleanup(struct backref_cache *cache)
 	ASSERT(!cache->nr_edges);
 }
 
-static struct backref_node *alloc_backref_node(struct backref_cache *cache)
+static struct backref_node *alloc_backref_node(struct backref_cache *cache,
+						u64 bytenr, int level)
 {
 	struct backref_node *node;
 
+	ASSERT(level >= 0 && level < BTRFS_MAX_LEVEL);
 	node = kzalloc(sizeof(*node), GFP_NOFS);
-	if (node) {
+	if (!node)
+		return node;
+
 	INIT_LIST_HEAD(&node->list);
 	INIT_LIST_HEAD(&node->upper);
 	INIT_LIST_HEAD(&node->lower);
 	RB_CLEAR_NODE(&node->rb_node);
 	cache->nr_nodes++;
-	}
+	node->level = level;
+	node->bytenr = bytenr;
+
 	return node;
 }
 
@@ -775,13 +781,12 @@ static int handle_direct_tree_backref(struct backref_cache *cache,
 	rb_node = tree_search(&cache->rb_root, ref_key->offset);
 	if (!rb_node) {
 		/* Parent node not yet cached */
-		upper = alloc_backref_node(cache);
+		upper = alloc_backref_node(cache, ref_key->offset,
+					   cur->level + 1);
 		if (!upper) {
 			free_backref_edge(cache, edge);
 			return -ENOMEM;
 		}
-		upper->bytenr = ref_key->offset;
-		upper->level = cur->level + 1;
 
 		/*
 		 *  Backrefs for the upper level block isn't cached, add the
@@ -896,16 +901,15 @@ static int handle_indirect_tree_backref(struct backref_cache *cache,
 		eb = path->nodes[level];
 		rb_node = tree_search(&cache->rb_root, eb->start);
 		if (!rb_node) {
-			upper = alloc_backref_node(cache);
+			upper = alloc_backref_node(cache, eb->start,
+						   lower->level + 1);
 			if (!upper) {
 				btrfs_put_root(root);
 				free_backref_edge(cache, edge);
 				ret = -ENOMEM;
 				goto out;
 			}
-			upper->bytenr = eb->start;
 			upper->owner = btrfs_header_owner(eb);
-			upper->level = lower->level + 1;
 			if (!test_bit(BTRFS_ROOT_REF_COWS, &root->state))
 				upper->cowonly = 1;
 
@@ -996,14 +1000,12 @@ struct backref_node *build_backref_tree(struct reloc_control *rc,
 		goto out;
 	}
 
-	node = alloc_backref_node(cache);
+	node = alloc_backref_node(cache, bytenr, level);
 	if (!node) {
 		err = -ENOMEM;
 		goto out;
 	}
 
-	node->bytenr = bytenr;
-	node->level = level;
 	node->lowest = 1;
 	cur = node;
 again:
@@ -1346,12 +1348,10 @@ static int clone_backref_node(struct btrfs_trans_handle *trans,
 	if (!node)
 		return 0;
 
-	new_node = alloc_backref_node(cache);
+	new_node = alloc_backref_node(cache, dest->node->start, node->level);
 	if (!new_node)
 		return -ENOMEM;
 
-	new_node->bytenr = dest->node->start;
-	new_node->level = node->level;
 	new_node->lowest = node->lowest;
 	new_node->checked = 1;
 	new_node->root = btrfs_grab_root(dest);