btrfs: factor out common part of btrfs_{mknod,create,mkdir}()

btrfs_{mknod,create,mkdir}() are now identical other than the inode
initialization and some inconsequential function call order differences.
Factor out the common code to reduce code duplication.
Reviewed-by: Sweet Tea Dorminy <sweettea-kernel@dorminy.me>
Signed-off-by: Omar Sandoval <osandov@fb.com>
Signed-off-by: David Sterba <dsterba@suse.com>

fs/btrfs/inode.c

@@ -6326,23 +6326,15 @@ int btrfs_add_link(struct btrfs_trans_handle *trans,
 	return ret;
 }
 
-static int btrfs_mknod(struct user_namespace *mnt_userns, struct inode *dir,
-		       struct dentry *dentry, umode_t mode, dev_t rdev)
+static int btrfs_create_common(struct inode *dir, struct dentry *dentry,
+			       struct inode *inode)
 {
 	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;
+	struct btrfs_trans_handle *trans;
 	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
@@ -6366,33 +6358,45 @@ static int btrfs_mknod(struct user_namespace *mnt_userns, struct inode *dir,
 	if (err)
 		goto out_unlock;
 
+	err = btrfs_update_inode(trans, root, BTRFS_I(inode));
+	if (err)
+		goto out_unlock;
+
 	err = btrfs_add_link(trans, BTRFS_I(dir), BTRFS_I(inode),
 			     dentry->d_name.name, dentry->d_name.len, 0, index);
 	if (err)
 		goto out_unlock;
 
-	btrfs_update_inode(trans, root, BTRFS_I(inode));
 	d_instantiate_new(dentry, inode);
 
 out_unlock:
 	btrfs_end_transaction(trans);
-	btrfs_btree_balance_dirty(fs_info);
 	if (err && inode) {
 		inode_dec_link_count(inode);
 		discard_new_inode(inode);
 	}
+	btrfs_btree_balance_dirty(fs_info);
 	return err;
 }
 
+static int btrfs_mknod(struct user_namespace *mnt_userns, struct inode *dir,
+		       struct dentry *dentry, umode_t mode, dev_t rdev)
+{
+	struct inode *inode;
+
+	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);
+	return btrfs_create_common(dir, dentry, inode);
+}
+
 static int btrfs_create(struct user_namespace *mnt_userns, struct inode *dir,
 			struct dentry *dentry, umode_t mode, bool excl)
 {
-	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;
-	int err;
-	u64 index = 0;
 
 	inode = new_inode(dir->i_sb);
 	if (!inode)
@@ -6401,49 +6405,7 @@ static int btrfs_create(struct user_namespace *mnt_userns, struct inode *dir,
 	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)) {
-		iput(inode);
-		return PTR_ERR(trans);
-	}
-
-	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;
-	}
-
-	err = btrfs_init_inode_security(trans, inode, dir, &dentry->d_name);
-	if (err)
-		goto out_unlock;
-
-	err = btrfs_update_inode(trans, root, BTRFS_I(inode));
-	if (err)
-		goto out_unlock;
-
-	err = btrfs_add_link(trans, BTRFS_I(dir), BTRFS_I(inode),
-			     dentry->d_name.name, dentry->d_name.len, 0, index);
-	if (err)
-		goto out_unlock;
-
-	d_instantiate_new(dentry, inode);
-
-out_unlock:
-	btrfs_end_transaction(trans);
-	if (err && inode) {
-		inode_dec_link_count(inode);
-		discard_new_inode(inode);
-	}
-	btrfs_btree_balance_dirty(fs_info);
-	return err;
+	return btrfs_create_common(dir, dentry, inode);
 }
 
 static int btrfs_link(struct dentry *old_dentry, struct inode *dir,
@@ -6527,12 +6489,7 @@ static int btrfs_link(struct dentry *old_dentry, struct inode *dir,
 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;
-	struct btrfs_trans_handle *trans;
-	struct btrfs_root *root = BTRFS_I(dir)->root;
-	int err;
-	u64 index = 0;
 
 	inode = new_inode(dir->i_sb);
 	if (!inode)
@@ -6540,50 +6497,7 @@ static int btrfs_mkdir(struct user_namespace *mnt_userns, struct inode *dir,
 	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)) {
-		iput(inode);
-		return PTR_ERR(trans);
-	}
-
-	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;
-	}
-
-	err = btrfs_init_inode_security(trans, inode, dir, &dentry->d_name);
-	if (err)
-		goto out_fail;
-
-	err = btrfs_update_inode(trans, root, BTRFS_I(inode));
-	if (err)
-		goto out_fail;
-
-	err = btrfs_add_link(trans, BTRFS_I(dir), BTRFS_I(inode),
-			dentry->d_name.name,
-			dentry->d_name.len, 0, index);
-	if (err)
-		goto out_fail;
-
-	d_instantiate_new(dentry, inode);
-
-out_fail:
-	btrfs_end_transaction(trans);
-	if (err && inode) {
-		inode_dec_link_count(inode);
-		discard_new_inode(inode);
-	}
-	btrfs_btree_balance_dirty(fs_info);
-	return err;
+	return btrfs_create_common(dir, dentry, inode);
 }
 
 static noinline int uncompress_inline(struct btrfs_path *path,