btrfs: push __setup_root into btrfs_alloc_root

There's no reason to not init the root at alloc time, and with later
patches it actually causes problems if we error out mounting the fs
before the tree_root is init'ed because we expect it to have a valid ref
count.  Fix this by pushing __setup_root into btrfs_alloc_root.
Reviewed-by: Nikolay Borisov <nborisov@suse.com>
Signed-off-by: Josef Bacik <josef@toxicpanda.com>
Reviewed-by: David Sterba <dsterba@suse.com>
Signed-off-by: David Sterba <dsterba@suse.com>

fs/btrfs/disk-io.c

@@ -1130,6 +1130,7 @@ static void __setup_root(struct btrfs_root *root, struct btrfs_fs_info *fs_info,
 			 u64 objectid)
 {
 	bool dummy = test_bit(BTRFS_FS_STATE_DUMMY_FS_INFO, &fs_info->fs_state);
+	root->fs_info = fs_info;
 	root->node = NULL;
 	root->commit_root = NULL;
 	root->state = 0;
@@ -1198,11 +1199,11 @@ static void __setup_root(struct btrfs_root *root, struct btrfs_fs_info *fs_info,
 }
 
 static struct btrfs_root *btrfs_alloc_root(struct btrfs_fs_info *fs_info,
-		gfp_t flags)
+					   u64 objectid, gfp_t flags)
 {
 	struct btrfs_root *root = kzalloc(sizeof(*root), flags);
 	if (root)
-		root->fs_info = fs_info;
+		__setup_root(root, fs_info, objectid);
 	return root;
 }
 
@@ -1215,12 +1216,11 @@ struct btrfs_root *btrfs_alloc_dummy_root(struct btrfs_fs_info *fs_info)
 	if (!fs_info)
 		return ERR_PTR(-EINVAL);
 
-	root = btrfs_alloc_root(fs_info, GFP_KERNEL);
+	root = btrfs_alloc_root(fs_info, BTRFS_ROOT_TREE_OBJECTID, GFP_KERNEL);
 	if (!root)
 		return ERR_PTR(-ENOMEM);
 
 	/* We don't use the stripesize in selftest, set it as sectorsize */
-	__setup_root(root, fs_info, BTRFS_ROOT_TREE_OBJECTID);
 	root->alloc_bytenr = 0;
 
 	return root;
@@ -1244,12 +1244,11 @@ struct btrfs_root *btrfs_create_tree(struct btrfs_trans_handle *trans,
 	 * context to avoid deadlock if reclaim happens.
 	 */
 	nofs_flag = memalloc_nofs_save();
-	root = btrfs_alloc_root(fs_info, GFP_KERNEL);
+	root = btrfs_alloc_root(fs_info, objectid, GFP_KERNEL);
 	memalloc_nofs_restore(nofs_flag);
 	if (!root)
 		return ERR_PTR(-ENOMEM);
 
-	__setup_root(root, fs_info, objectid);
 	root->root_key.objectid = objectid;
 	root->root_key.type = BTRFS_ROOT_ITEM_KEY;
 	root->root_key.offset = 0;
@@ -1309,12 +1308,10 @@ static struct btrfs_root *alloc_log_tree(struct btrfs_trans_handle *trans,
 	struct btrfs_root *root;
 	struct extent_buffer *leaf;
 
-	root = btrfs_alloc_root(fs_info, GFP_NOFS);
+	root = btrfs_alloc_root(fs_info, BTRFS_TREE_LOG_OBJECTID, GFP_NOFS);
 	if (!root)
 		return ERR_PTR(-ENOMEM);
 
-	__setup_root(root, fs_info, BTRFS_TREE_LOG_OBJECTID);
-
 	root->root_key.objectid = BTRFS_TREE_LOG_OBJECTID;
 	root->root_key.type = BTRFS_ROOT_ITEM_KEY;
 	root->root_key.offset = BTRFS_TREE_LOG_OBJECTID;
@@ -1401,14 +1398,12 @@ static struct btrfs_root *btrfs_read_tree_root(struct btrfs_root *tree_root,
 	if (!path)
 		return ERR_PTR(-ENOMEM);
 
-	root = btrfs_alloc_root(fs_info, GFP_NOFS);
+	root = btrfs_alloc_root(fs_info, key->objectid, GFP_NOFS);
 	if (!root) {
 		ret = -ENOMEM;
 		goto alloc_fail;
 	}
 
-	__setup_root(root, fs_info, key->objectid);
-
 	ret = btrfs_find_root(tree_root, key, path,
 			      &root->root_item, &root->root_key);
 	if (ret) {
@@ -2208,12 +2203,11 @@ static int btrfs_replay_log(struct btrfs_fs_info *fs_info,
 		return -EIO;
 	}
 
-	log_tree_root = btrfs_alloc_root(fs_info, GFP_KERNEL);
+	log_tree_root = btrfs_alloc_root(fs_info, BTRFS_TREE_LOG_OBJECTID,
+					 GFP_KERNEL);
 	if (!log_tree_root)
 		return -ENOMEM;
 
-	__setup_root(log_tree_root, fs_info, BTRFS_TREE_LOG_OBJECTID);
-
 	log_tree_root->node = read_tree_block(fs_info, bytenr,
 					      fs_info->generation + 1,
 					      level, NULL);
@@ -2645,8 +2639,12 @@ int __cold open_ctree(struct super_block *sb,
 	int clear_free_space_tree = 0;
 	int level;
 
-	tree_root = fs_info->tree_root = btrfs_alloc_root(fs_info, GFP_KERNEL);
-	chunk_root = fs_info->chunk_root = btrfs_alloc_root(fs_info, GFP_KERNEL);
+	tree_root = btrfs_alloc_root(fs_info, BTRFS_ROOT_TREE_OBJECTID,
+				     GFP_KERNEL);
+	fs_info->tree_root = tree_root;
+	chunk_root = btrfs_alloc_root(fs_info, BTRFS_CHUNK_TREE_OBJECTID,
+				      GFP_KERNEL);
+	fs_info->chunk_root = chunk_root;
 	if (!tree_root || !chunk_root) {
 		err = -ENOMEM;
 		goto fail;
@@ -2824,8 +2822,6 @@ int __cold open_ctree(struct super_block *sb,
 		goto fail_alloc;
 	}
 
-	__setup_root(tree_root, fs_info, BTRFS_ROOT_TREE_OBJECTID);
-
 	invalidate_bdev(fs_devices->latest_bdev);
 
 	/*
@@ -3021,8 +3017,6 @@ int __cold open_ctree(struct super_block *sb,
 	generation = btrfs_super_chunk_root_generation(disk_super);
 	level = btrfs_super_chunk_root_level(disk_super);
 
-	__setup_root(chunk_root, fs_info, BTRFS_CHUNK_TREE_OBJECTID);
-
 	chunk_root->node = read_tree_block(fs_info,
 					   btrfs_super_chunk_root(disk_super),
 					   generation, level, NULL);