ext4: start handle at the last possible moment in ext4_rmdir()

Don't start the jbd2 transaction handle until after the directory
entry has been found, to minimize the amount of time that a handle is
held active.
Signed-off-by: "Theodore Ts'o" <tytso@mit.edu>
Reviewed-by: Jan Kara <jack@suse.cz>

fs/ext4/namei.c

@@ -2725,26 +2725,18 @@ static int ext4_rmdir(struct inode *dir, struct dentry *dentry)
 	struct inode *inode;
 	struct buffer_head *bh;
 	struct ext4_dir_entry_2 *de;
-	handle_t *handle;
+	handle_t *handle = NULL;
 
 	/* Initialize quotas before so that eventual writes go in
 	 * separate transaction */
 	dquot_initialize(dir);
 	dquot_initialize(dentry->d_inode);
 
-	handle = ext4_journal_start(dir, EXT4_HT_DIR,
-				    EXT4_DELETE_TRANS_BLOCKS(dir->i_sb));
-	if (IS_ERR(handle))
-		return PTR_ERR(handle);
-
 	retval = -ENOENT;
 	bh = ext4_find_entry(dir, &dentry->d_name, &de, NULL);
 	if (!bh)
 		goto end_rmdir;
 
-	if (IS_DIRSYNC(dir))
-		ext4_handle_sync(handle);
-
 	inode = dentry->d_inode;
 
 	retval = -EIO;
@@ -2755,6 +2747,17 @@ static int ext4_rmdir(struct inode *dir, struct dentry *dentry)
 	if (!empty_dir(inode))
 		goto end_rmdir;
 
+	handle = ext4_journal_start(dir, EXT4_HT_DIR,
+				    EXT4_DELETE_TRANS_BLOCKS(dir->i_sb));
+	if (IS_ERR(handle)) {
+		retval = PTR_ERR(handle);
+		handle = NULL;
+		goto end_rmdir;
+	}
+
+	if (IS_DIRSYNC(dir))
+		ext4_handle_sync(handle);
+
 	retval = ext4_delete_entry(handle, dir, de, bh);
 	if (retval)
 		goto end_rmdir;
@@ -2776,8 +2779,9 @@ static int ext4_rmdir(struct inode *dir, struct dentry *dentry)
 	ext4_mark_inode_dirty(handle, dir);
 
 end_rmdir:
-	ext4_journal_stop(handle);
 	brelse(bh);
+	if (handle)
+		ext4_journal_stop(handle);
 	return retval;
 }