[v4,1/4] btrfs: allocate inode outside of btrfs_new_inode()

Commit Message

Omar Sandoval March 15, 2022, 1:12 a.m. UTC

From: Omar Sandoval <[e-mail]>

Instead of calling new_inode() and inode_init_owner() inside of
btrfs_new_inode(), do it in the callers. This allows us to pass in just
the inode instead of the mnt_userns and mode and removes the need for
memalloc_nofs_{save,restores}() since we do it before starting a
transaction. In create_subvol(), it also means we no longer have to look
up the inode again to instantiate it. This also paves the way for some
more cleanups in later patches.

This also removes the comments about Smack checking i_op, which are no
longer true since commit 5d6c31910bc0 ("xattr: Add
__vfs_{get,set,remove}xattr helpers"). Now it checks inode->i_opflags &
IOP_XATTR, which is set based on sb->s_xattr.

Signed-off-by: Omar Sandoval <[e-mail]>
---
 fs/btrfs/ctree.h |   5 +-
 fs/btrfs/inode.c | 287 +++++++++++++++++++++++++----------------------
 fs/btrfs/ioctl.c |  22 ++--
 3 files changed, 169 insertions(+), 145 deletions(-)

Patch

diff --git a/fs/btrfs/ctree.h b/fs/btrfs/ctree.h
index 4db17bd05a21..f39730420e8a 100644
--- a/fs/btrfs/ctree.h
+++ b/fs/btrfs/ctree.h
@@ -3254,10 +3254,11 @@  int btrfs_start_delalloc_roots(struct btrfs_fs_info *fs_info, long nr,
 int btrfs_set_extent_delalloc(struct btrfs_inode *inode, u64 start, u64 end,
 			      unsigned int extra_bits,
 			      struct extent_state **cached_state);
+struct inode *btrfs_new_subvol_inode(struct user_namespace *mnt_userns,
+				     struct inode *dir);
 int btrfs_create_subvol_root(struct btrfs_trans_handle *trans,
-			     struct btrfs_root *new_root,
 			     struct btrfs_root *parent_root,
-			     struct user_namespace *mnt_userns);
+			     struct inode *inode);
  void btrfs_set_delalloc_extent(struct inode *inode, struct extent_state *state,
 			       unsigned *bits);
 void btrfs_clear_delalloc_extent(struct inode *inode,
diff --git a/fs/btrfs/inode.c b/fs/btrfs/inode.c
index c47bdada2440..d616a3a35e83 100644
--- a/fs/btrfs/inode.c
+++ b/fs/btrfs/inode.c
@@ -6090,15 +6090,12 @@  static void btrfs_inherit_iflags(struct inode *inode, struct inode *dir)
 	btrfs_sync_inode_flags_to_i_flags(inode);
 }
 
-static struct inode *btrfs_new_inode(struct btrfs_trans_handle *trans,
-				     struct btrfs_root *root,
-				     struct user_namespace *mnt_userns,
-				     struct inode *dir,
-				     const char *name, int name_len,
-				     umode_t mode, u64 *index)
+static int btrfs_new_inode(struct btrfs_trans_handle *trans,
+			   struct btrfs_root *root, struct inode *inode,
+			   struct inode *dir, const char *name, int name_len,
+			   u64 *index)
 {
 	struct btrfs_fs_info *fs_info = root->fs_info;
-	struct inode *inode;
 	struct btrfs_inode_item *inode_item;
 	struct btrfs_key *location;
 	struct btrfs_path *path;
@@ -6108,20 +6105,11 @@  static struct inode *btrfs_new_inode(struct btrfs_trans_handle *trans,
 	u32 sizes[2];
 	struct btrfs_item_batch batch;
 	unsigned long ptr;
-	unsigned int nofs_flag;
 	int ret;
 
 	path = btrfs_alloc_path();
 	if (!path)
-		return ERR_PTR(-ENOMEM);
-
-	nofs_flag = memalloc_nofs_save();
-	inode = new_inode(fs_info->sb);
-	memalloc_nofs_restore(nofs_flag);
-	if (!inode) {
-		btrfs_free_path(path);
-		return ERR_PTR(-ENOMEM);
-	}
+		return -ENOMEM;
 
 	/*
 	 * O_TMPFILE, set link count to 0, so that after this point,
@@ -6133,8 +6121,7 @@  static struct inode *btrfs_new_inode(struct btrfs_trans_handle *trans,
 	ret = btrfs_get_free_objectid(root, &objectid);
 	if (ret) {
 		btrfs_free_path(path);
-		iput(inode);
-		return ERR_PTR(ret);
+		return ret;
 	}
 	inode->i_ino = objectid;
 
@@ -6144,8 +6131,7 @@  static struct inode *btrfs_new_inode(struct btrfs_trans_handle *trans,
 		ret = btrfs_set_inode_index(BTRFS_I(dir), index);
 		if (ret) {
 			btrfs_free_path(path);
-			iput(inode);
-			return ERR_PTR(ret);
+			return ret;
 		}
 	} else if (dir) {
 		*index = 0;
@@ -6157,13 +6143,14 @@  static struct inode *btrfs_new_inode(struct btrfs_trans_handle *trans,
 	 */
 	BTRFS_I(inode)->index_cnt = 2;
 	BTRFS_I(inode)->dir_index = *index;
-	BTRFS_I(inode)->root = btrfs_grab_root(root);
+	if (!BTRFS_I(inode)->root)
+		BTRFS_I(inode)->root = btrfs_grab_root(root);
 	BTRFS_I(inode)->generation = trans->transid;
 	inode->i_generation = BTRFS_I(inode)->generation;
 
 	btrfs_inherit_iflags(inode, dir);
 
-	if (S_ISREG(mode)) {
+	if (S_ISREG(inode->i_mode)) {
 		if (btrfs_test_opt(fs_info, NODATASUM))
 			BTRFS_I(inode)->flags |= BTRFS_INODE_NODATASUM;
 		if (btrfs_test_opt(fs_info, NODATACOW))
@@ -6208,10 +6195,8 @@  static struct inode *btrfs_new_inode(struct btrfs_trans_handle *trans,
 	location->type = BTRFS_INODE_ITEM_KEY;
 
 	ret = btrfs_insert_inode_locked(inode);
-	if (ret < 0) {
-		iput(inode);
+	if (ret < 0)
 		goto fail;
-	}
 
 	batch.keys = &key[0];
 	batch.data_sizes = &sizes[0];
@@ -6221,8 +6206,6 @@  static struct inode *btrfs_new_inode(struct btrfs_trans_handle *trans,
 	if (ret != 0)
 		goto fail_unlock;
 
-	inode_init_owner(mnt_userns, inode, dir, mode);
-
 	inode->i_mtime = current_time(inode);
 	inode->i_atime = inode->i_mtime;
 	inode->i_ctime = inode->i_mtime;
@@ -6259,15 +6242,20 @@  static struct inode *btrfs_new_inode(struct btrfs_trans_handle *trans,
 			  "error inheriting props for ino %llu (root %llu): %d",
 			btrfs_ino(BTRFS_I(inode)), root->root_key.objectid, ret);
 
-	return inode;
+	return 0;
 
 fail_unlock:
+	/*
+	 * discard_new_inode() calls iput(), but the caller owns the reference
+	 * to the inode.
+	 */
+	ihold(inode);
 	discard_new_inode(inode);
 fail:
 	if (dir && name)
 		BTRFS_I(dir)->index_cnt--;
 	btrfs_free_path(path);
-	return ERR_PTR(ret);
+	return ret;
 }
 
 /*
@@ -6365,37 +6353,36 @@  static int btrfs_mknod(struct user_namespace *mnt_userns, struct inode *dir,
 	struct btrfs_fs_info *fs_info = btrfs_sb(dir->i_sb);
 	struct btrfs_trans_handle *trans;
 	struct btrfs_root *root = BTRFS_I(dir)->root;
-	struct inode *inode = NULL;
+	struct inode *inode;
 	int err;
 	u64 index = 0;
 
+	inode = new_inode(dir->i_sb);
+	if (!inode)
+		return -ENOMEM;
+	inode_init_owner(mnt_userns, inode, dir, mode);
+	inode->i_op = &btrfs_special_inode_operations;
+	init_special_inode(inode, inode->i_mode, rdev);
+
 	/*
 	 * 2 for inode item and ref
 	 * 2 for dir items
 	 * 1 for xattr if selinux is on
 	 */
 	trans = btrfs_start_transaction(root, 5);
-	if (IS_ERR(trans))
+	if (IS_ERR(trans)) {
+		iput(inode);
 		return PTR_ERR(trans);
+	}
 
-	inode = btrfs_new_inode(trans, root, mnt_userns, dir,
-			dentry->d_name.name, dentry->d_name.len,
-			mode, &index);
-	if (IS_ERR(inode)) {
-		err = PTR_ERR(inode);
+	err = btrfs_new_inode(trans, root, inode, dir, dentry->d_name.name,
+			      dentry->d_name.len, &index);
+	if (err) {
+		iput(inode);
 		inode = NULL;
 		goto out_unlock;
 	}
 
-	/*
-	* If the active LSM wants to access the inode during
-	* d_instantiate it needs these. Smack checks to see
-	* if the filesystem supports xattrs by looking at the
-	* ops vector.
-	*/
-	inode->i_op = &btrfs_special_inode_operations;
-	init_special_inode(inode, inode->i_mode, rdev);
-
 	err = btrfs_init_inode_security(trans, inode, dir, &dentry->d_name);
 	if (err)
 		goto out_unlock;
@@ -6424,36 +6411,36 @@  static int btrfs_create(struct user_namespace *mnt_userns, struct inode *dir,
 	struct btrfs_fs_info *fs_info = btrfs_sb(dir->i_sb);
 	struct btrfs_trans_handle *trans;
 	struct btrfs_root *root = BTRFS_I(dir)->root;
-	struct inode *inode = NULL;
+	struct inode *inode;
 	int err;
 	u64 index = 0;
 
+	inode = new_inode(dir->i_sb);
+	if (!inode)
+		return -ENOMEM;
+	inode_init_owner(mnt_userns, inode, dir, mode);
+	inode->i_fop = &btrfs_file_operations;
+	inode->i_op = &btrfs_file_inode_operations;
+	inode->i_mapping->a_ops = &btrfs_aops;
+
 	/*
 	 * 2 for inode item and ref
 	 * 2 for dir items
 	 * 1 for xattr if selinux is on
 	 */
 	trans = btrfs_start_transaction(root, 5);
-	if (IS_ERR(trans))
+	if (IS_ERR(trans)) {
+		iput(inode);
 		return PTR_ERR(trans);
+	}
 
-	inode = btrfs_new_inode(trans, root, mnt_userns, dir,
-			dentry->d_name.name, dentry->d_name.len,
-			mode, &index);
-	if (IS_ERR(inode)) {
-		err = PTR_ERR(inode);
+	err = btrfs_new_inode(trans, root, inode, dir, dentry->d_name.name,
+			      dentry->d_name.len, &index);
+	if (err) {
+		iput(inode);
 		inode = NULL;
 		goto out_unlock;
 	}
-	/*
-	* If the active LSM wants to access the inode during
-	* d_instantiate it needs these. Smack checks to see
-	* if the filesystem supports xattrs by looking at the
-	* ops vector.
-	*/
-	inode->i_fop = &btrfs_file_operations;
-	inode->i_op = &btrfs_file_inode_operations;
-	inode->i_mapping->a_ops = &btrfs_aops;
 
 	err = btrfs_init_inode_security(trans, inode, dir, &dentry->d_name);
 	if (err)
@@ -6562,34 +6549,38 @@  static int btrfs_mkdir(struct user_namespace *mnt_userns, struct inode *dir,
 		       struct dentry *dentry, umode_t mode)
 {
 	struct btrfs_fs_info *fs_info = btrfs_sb(dir->i_sb);
-	struct inode *inode = NULL;
+	struct inode *inode;
 	struct btrfs_trans_handle *trans;
 	struct btrfs_root *root = BTRFS_I(dir)->root;
-	int err = 0;
+	int err;
 	u64 index = 0;
 
+	inode = new_inode(dir->i_sb);
+	if (!inode)
+		return -ENOMEM;
+	inode_init_owner(mnt_userns, inode, dir, S_IFDIR | mode);
+	inode->i_op = &btrfs_dir_inode_operations;
+	inode->i_fop = &btrfs_dir_file_operations;
+
 	/*
 	 * 2 items for inode and ref
 	 * 2 items for dir items
 	 * 1 for xattr if selinux is on
 	 */
 	trans = btrfs_start_transaction(root, 5);
-	if (IS_ERR(trans))
+	if (IS_ERR(trans)) {
+		iput(inode);
 		return PTR_ERR(trans);
+	}
 
-	inode = btrfs_new_inode(trans, root, mnt_userns, dir,
-			dentry->d_name.name, dentry->d_name.len,
-			S_IFDIR | mode, &index);
-	if (IS_ERR(inode)) {
-		err = PTR_ERR(inode);
+	err = btrfs_new_inode(trans, root, inode, dir, dentry->d_name.name,
+			      dentry->d_name.len, &index);
+	if (err) {
+		iput(inode);
 		inode = NULL;
 		goto out_fail;
 	}
 
-	/* these must be set before we unlock the inode */
-	inode->i_op = &btrfs_dir_inode_operations;
-	inode->i_fop = &btrfs_dir_file_operations;
-
 	err = btrfs_init_inode_security(trans, inode, dir, &dentry->d_name);
 	if (err)
 		goto out_fail;
@@ -8747,25 +8738,39 @@  static int btrfs_truncate(struct inode *inode, bool skip_writeback)
 	return ret;
 }
 
+struct inode *btrfs_new_subvol_inode(struct user_namespace *mnt_userns,
+				     struct inode *dir)
+{
+	struct inode *inode;
+
+	inode = new_inode(dir->i_sb);
+	if (inode) {
+		/*
+		 * Subvolumes don't inherit the sgid bit or the parent's gid if
+		 * the parent's sgid bit is set. This is probably a bug.
+		 */
+		inode_init_owner(mnt_userns, inode, NULL,
+				 S_IFDIR | (~current_umask() & S_IRWXUGO));
+		inode->i_op = &btrfs_dir_inode_operations;
+		inode->i_fop = &btrfs_dir_file_operations;
+	}
+	return inode;
+}
+
 /*
  * create a new subvolume directory/inode (helper for the ioctl).
  */
 int btrfs_create_subvol_root(struct btrfs_trans_handle *trans,
-			     struct btrfs_root *new_root,
 			     struct btrfs_root *parent_root,
-			     struct user_namespace *mnt_userns)
+			     struct inode *inode)
 {
-	struct inode *inode;
+	struct btrfs_root *new_root = BTRFS_I(inode)->root;
 	int err;
 	u64 index = 0;
 
-	inode = btrfs_new_inode(trans, new_root, mnt_userns, NULL, "..", 2,
-				S_IFDIR | (~current_umask() & S_IRWXUGO),
-				&index);
-	if (IS_ERR(inode))
-		return PTR_ERR(inode);
-	inode->i_op = &btrfs_dir_inode_operations;
-	inode->i_fop = &btrfs_dir_file_operations;
+	err = btrfs_new_inode(trans, new_root, inode, NULL, "..", 2, &index);
+	if (err)
+		return err;
 
 	unlock_new_inode(inode);
 
@@ -8776,8 +8781,6 @@  int btrfs_create_subvol_root(struct btrfs_trans_handle *trans,
 			  new_root->root_key.objectid, err);
 
 	err = btrfs_update_inode(trans, new_root, BTRFS_I(inode));
-
-	iput(inode);
 	return err;
 }
 
@@ -9254,31 +9257,36 @@  static int btrfs_rename_exchange(struct inode *old_dir,
 	return ret;
 }
 
+static struct inode *new_whiteout_inode(struct user_namespace *mnt_userns,
+					struct inode *dir)
+{
+	struct inode *inode;
+
+	inode = new_inode(dir->i_sb);
+	if (inode) {
+		inode_init_owner(mnt_userns, inode, dir,
+				 S_IFCHR | WHITEOUT_MODE);
+		inode->i_op = &btrfs_special_inode_operations;
+		init_special_inode(inode, inode->i_mode, WHITEOUT_DEV);
+	}
+	return inode;
+}
+
 static int btrfs_whiteout_for_rename(struct btrfs_trans_handle *trans,
 				     struct btrfs_root *root,
-				     struct user_namespace *mnt_userns,
-				     struct inode *dir,
+				     struct inode *inode, struct inode *dir,
 				     struct dentry *dentry)
 {
 	int ret;
-	struct inode *inode;
 	u64 index;
 
-	inode = btrfs_new_inode(trans, root, mnt_userns, dir,
-				dentry->d_name.name,
-				dentry->d_name.len,
-				S_IFCHR | WHITEOUT_MODE,
-				&index);
-
-	if (IS_ERR(inode)) {
-		ret = PTR_ERR(inode);
+	ret = btrfs_new_inode(trans, root, inode, dir, dentry->d_name.name,
+			      dentry->d_name.len, &index);
+	if (ret) {
+		iput(inode);
 		return ret;
 	}
 
-	inode->i_op = &btrfs_special_inode_operations;
-	init_special_inode(inode, inode->i_mode,
-		WHITEOUT_DEV);
-
 	ret = btrfs_init_inode_security(trans, inode, dir,
 				&dentry->d_name);
 	if (ret)
@@ -9305,6 +9313,7 @@  static int btrfs_rename(struct user_namespace *mnt_userns,
 			unsigned int flags)
 {
 	struct btrfs_fs_info *fs_info = btrfs_sb(old_dir->i_sb);
+	struct inode *whiteout_inode;
 	struct btrfs_trans_handle *trans;
 	unsigned int trans_num_items;
 	struct btrfs_root *root = BTRFS_I(old_dir)->root;
@@ -9359,6 +9368,12 @@  static int btrfs_rename(struct user_namespace *mnt_userns,
 	if (new_inode && S_ISREG(old_inode->i_mode) && new_inode->i_size)
 		filemap_flush(old_inode->i_mapping);
 
+	if (flags & RENAME_WHITEOUT) {
+		whiteout_inode = new_whiteout_inode(mnt_userns, old_dir);
+		if (!whiteout_inode)
+			return -ENOMEM;
+	}
+
 	if (old_ino == BTRFS_FIRST_FREE_OBJECTID) {
 		/* close the racy window with snapshot create/destroy ioctl */
 		down_read(&fs_info->subvol_sem);
@@ -9495,9 +9510,9 @@  static int btrfs_rename(struct user_namespace *mnt_userns,
 				   rename_ctx.index, new_dentry->d_parent);
 
 	if (flags & RENAME_WHITEOUT) {
-		ret = btrfs_whiteout_for_rename(trans, root, mnt_userns,
+		ret = btrfs_whiteout_for_rename(trans, root, whiteout_inode,
 						old_dir, old_dentry);
-
+		whiteout_inode = NULL;
 		if (ret) {
 			btrfs_abort_transaction(trans, ret);
 			goto out_fail;
@@ -9509,7 +9524,8 @@  static int btrfs_rename(struct user_namespace *mnt_userns,
 out_notrans:
 	if (old_ino == BTRFS_FIRST_FREE_OBJECTID)
 		up_read(&fs_info->subvol_sem);
-
+	if (flags & RENAME_WHITEOUT)
+		iput(whiteout_inode);
 	return ret;
 }
 
@@ -9728,7 +9744,7 @@  static int btrfs_symlink(struct user_namespace *mnt_userns, struct inode *dir,
 	struct btrfs_root *root = BTRFS_I(dir)->root;
 	struct btrfs_path *path;
 	struct btrfs_key key;
-	struct inode *inode = NULL;
+	struct inode *inode;
 	int err;
 	u64 index = 0;
 	int name_len;
@@ -9741,6 +9757,14 @@  static int btrfs_symlink(struct user_namespace *mnt_userns, struct inode *dir,
 	if (name_len > BTRFS_MAX_INLINE_DATA_SIZE(fs_info))
 		return -ENAMETOOLONG;
 
+	inode = new_inode(dir->i_sb);
+	if (!inode)
+		return -ENOMEM;
+	inode_init_owner(mnt_userns, inode, dir, S_IFLNK | S_IRWXUGO);
+	inode->i_op = &btrfs_symlink_inode_operations;
+	inode_nohighmem(inode);
+	inode->i_mapping->a_ops = &btrfs_aops;
+
 	/*
 	 * 2 items for inode item and ref
 	 * 2 items for dir items
@@ -9749,28 +9773,19 @@  static int btrfs_symlink(struct user_namespace *mnt_userns, struct inode *dir,
 	 * 1 item for xattr if selinux is on
 	 */
 	trans = btrfs_start_transaction(root, 7);
-	if (IS_ERR(trans))
+	if (IS_ERR(trans)) {
+		iput(inode);
 		return PTR_ERR(trans);
+	}
 
-	inode = btrfs_new_inode(trans, root, mnt_userns, dir,
-				dentry->d_name.name, dentry->d_name.len,
-				S_IFLNK | S_IRWXUGO, &index);
-	if (IS_ERR(inode)) {
-		err = PTR_ERR(inode);
+	err = btrfs_new_inode(trans, root, inode, dir, dentry->d_name.name,
+			      dentry->d_name.len, &index);
+	if (err) {
+		iput(inode);
 		inode = NULL;
 		goto out_unlock;
 	}
 
-	/*
-	* If the active LSM wants to access the inode during
-	* d_instantiate it needs these. Smack checks to see
-	* if the filesystem supports xattrs by looking at the
-	* ops vector.
-	*/
-	inode->i_fop = &btrfs_file_operations;
-	inode->i_op = &btrfs_file_inode_operations;
-	inode->i_mapping->a_ops = &btrfs_aops;
-
 	err = btrfs_init_inode_security(trans, inode, dir, &dentry->d_name);
 	if (err)
 		goto out_unlock;
@@ -9806,8 +9821,6 @@  static int btrfs_symlink(struct user_namespace *mnt_userns, struct inode *dir,
 	btrfs_mark_buffer_dirty(leaf);
 	btrfs_free_path(path);
 
-	inode->i_op = &btrfs_symlink_inode_operations;
-	inode_nohighmem(inode);
 	inode_set_bytes(inode, name_len);
 	btrfs_i_size_write(BTRFS_I(inode), name_len);
 	err = btrfs_update_inode(trans, root, BTRFS_I(inode));
@@ -10087,30 +10100,34 @@  static int btrfs_tmpfile(struct user_namespace *mnt_userns, struct inode *dir,
 	struct btrfs_fs_info *fs_info = btrfs_sb(dir->i_sb);
 	struct btrfs_trans_handle *trans;
 	struct btrfs_root *root = BTRFS_I(dir)->root;
-	struct inode *inode = NULL;
+	struct inode *inode;
 	u64 index;
-	int ret = 0;
+	int ret;
+
+	inode = new_inode(dir->i_sb);
+	if (!inode)
+		return -ENOMEM;
+	inode_init_owner(mnt_userns, inode, dir, mode);
+	inode->i_fop = &btrfs_file_operations;
+	inode->i_op = &btrfs_file_inode_operations;
+	inode->i_mapping->a_ops = &btrfs_aops;
 
 	/*
 	 * 5 units required for adding orphan entry
 	 */
 	trans = btrfs_start_transaction(root, 5);
-	if (IS_ERR(trans))
+	if (IS_ERR(trans)) {
+		iput(inode);
 		return PTR_ERR(trans);
+	}
 
-	inode = btrfs_new_inode(trans, root, mnt_userns, dir, NULL, 0,
-			mode, &index);
-	if (IS_ERR(inode)) {
-		ret = PTR_ERR(inode);
+	ret = btrfs_new_inode(trans, root, inode, dir, NULL, 0, &index);
+	if (ret) {
+		iput(inode);
 		inode = NULL;
 		goto out;
 	}
 
-	inode->i_fop = &btrfs_file_operations;
-	inode->i_op = &btrfs_file_inode_operations;
-
-	inode->i_mapping->a_ops = &btrfs_aops;
-
 	ret = btrfs_init_inode_security(trans, inode, dir, NULL);
 	if (ret)
 		goto out;
diff --git a/fs/btrfs/ioctl.c b/fs/btrfs/ioctl.c
index 891352fd6d0f..60c907b14547 100644
--- a/fs/btrfs/ioctl.c
+++ b/fs/btrfs/ioctl.c
@@ -587,6 +587,12 @@  static noinline int create_subvol(struct user_namespace *mnt_userns,
 	if (ret < 0)
 		goto out_root_item;
 
+	inode = btrfs_new_subvol_inode(mnt_userns, dir);
+	if (!inode) {
+		ret = -ENOMEM;
+		goto out_anon_dev;
+	}
+
 	btrfs_init_block_rsv(&block_rsv, BTRFS_BLOCK_RSV_TEMP);
 	/*
 	 * The same as the snapshot creation, please see the comment
@@ -594,13 +600,13 @@  static noinline int create_subvol(struct user_namespace *mnt_userns,
 	 */
 	ret = btrfs_subvolume_reserve_metadata(root, &block_rsv, 8, false);
 	if (ret)
-		goto out_anon_dev;
+		goto out_inode;
 
 	trans = btrfs_start_transaction(root, 0);
 	if (IS_ERR(trans)) {
 		ret = PTR_ERR(trans);
 		btrfs_subvolume_release_metadata(root, &block_rsv);
-		goto out_anon_dev;
+		goto out_inode;
 	}
 	trans->block_rsv = &block_rsv;
 	trans->bytes_reserved = block_rsv.size;
@@ -683,16 +689,16 @@  static noinline int create_subvol(struct user_namespace *mnt_userns,
 	}
 	/* anon_dev is owned by new_root now. */
 	anon_dev = 0;
+	BTRFS_I(inode)->root = new_root;
+	/* ... and new_root is owned by inode now. */
 
 	ret = btrfs_record_root_in_trans(trans, new_root);
 	if (ret) {
-		btrfs_put_root(new_root);
 		btrfs_abort_transaction(trans, ret);
 		goto out;
 	}
 
-	ret = btrfs_create_subvol_root(trans, new_root, root, mnt_userns);
-	btrfs_put_root(new_root);
+	ret = btrfs_create_subvol_root(trans, root, inode);
 	if (ret) {
 		/* We potentially lose an unused inode item here */
 		btrfs_abort_transaction(trans, ret);
@@ -745,11 +751,11 @@  static noinline int create_subvol(struct user_namespace *mnt_userns,
 		ret = btrfs_commit_transaction(trans);
 
 	if (!ret) {
-		inode = btrfs_lookup_dentry(dir, dentry);
-		if (IS_ERR(inode))
-			return PTR_ERR(inode);
 		d_instantiate(dentry, inode);
+		inode = NULL;
 	}
+out_inode:
+	iput(inode);
 out_anon_dev:
 	if (anon_dev)
 		free_anon_bdev(anon_dev);