ext4: ->tmpfile() support

very similar to ext3 counterpart...
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>

fs/ext4/namei.c

@@ -2299,6 +2299,45 @@ static int ext4_mknod(struct inode *dir, struct dentry *dentry,
 	return err;
 }
 
+static int ext4_tmpfile(struct inode *dir, struct dentry *dentry, umode_t mode)
+{
+	handle_t *handle;
+	struct inode *inode;
+	int err, retries = 0;
+
+	dquot_initialize(dir);
+
+retry:
+	inode = ext4_new_inode_start_handle(dir, mode,
+					    NULL, 0, NULL,
+					    EXT4_HT_DIR,
+			EXT4_MAXQUOTAS_INIT_BLOCKS(dir->i_sb) +
+			  4 + EXT4_XATTR_TRANS_BLOCKS);
+	handle = ext4_journal_current_handle();
+	err = PTR_ERR(inode);
+	if (!IS_ERR(inode)) {
+		inode->i_op = &ext4_file_inode_operations;
+		inode->i_fop = &ext4_file_operations;
+		ext4_set_aops(inode);
+		err = ext4_orphan_add(handle, inode);
+		if (err)
+			goto err_drop_inode;
+		mark_inode_dirty(inode);
+		d_tmpfile(dentry, inode);
+		unlock_new_inode(inode);
+	}
+	if (handle)
+		ext4_journal_stop(handle);
+	if (err == -ENOSPC && ext4_should_retry_alloc(dir->i_sb, &retries))
+		goto retry;
+	return err;
+err_drop_inode:
+	ext4_journal_stop(handle);
+	unlock_new_inode(inode);
+	iput(inode);
+	return err;
+}
+
 struct ext4_dir_entry_2 *ext4_init_dot_dotdot(struct inode *inode,
 			  struct ext4_dir_entry_2 *de,
 			  int blocksize, int csum_size,
@@ -2906,7 +2945,7 @@ static int ext4_link(struct dentry *old_dentry,
 retry:
 	handle = ext4_journal_start(dir, EXT4_HT_DIR,
 		(EXT4_DATA_TRANS_BLOCKS(dir->i_sb) +
-		 EXT4_INDEX_EXTRA_TRANS_BLOCKS));
+		 EXT4_INDEX_EXTRA_TRANS_BLOCKS) + 1);
 	if (IS_ERR(handle))
 		return PTR_ERR(handle);
 
@@ -2920,6 +2959,11 @@ static int ext4_link(struct dentry *old_dentry,
 	err = ext4_add_entry(handle, dentry, inode);
 	if (!err) {
 		ext4_mark_inode_dirty(handle, inode);
+		/* this can happen only for tmpfile being
+		 * linked the first time
+		 */
+		if (inode->i_nlink == 1)
+			ext4_orphan_del(handle, inode);
 		d_instantiate(dentry, inode);
 	} else {
 		drop_nlink(inode);
@@ -3172,6 +3216,7 @@ const struct inode_operations ext4_dir_inode_operations = {
 	.mkdir		= ext4_mkdir,
 	.rmdir		= ext4_rmdir,
 	.mknod		= ext4_mknod,
+	.tmpfile	= ext4_tmpfile,
 	.rename		= ext4_rename,
 	.setattr	= ext4_setattr,
 	.setxattr	= generic_setxattr,