ext2: Remove i_mutex use from ext2_quota_write()

We don't need i_mutex in ext2_quota_write() because writes to quota file
are serialized by dqio_mutex anyway. Changes to quota files outside of quota
code are forbidded and enforced by NOATIME and IMMUTABLE bits.
Signed-off-by: NJan Kara <jack@suse.cz>

fs/ext2/super.c

@@ -1434,7 +1434,6 @@ static ssize_t ext2_quota_write(struct super_block *sb, int type,
 	struct buffer_head tmp_bh;
 	struct buffer_head *bh;
 
-	mutex_lock_nested(&inode->i_mutex, I_MUTEX_QUOTA);
 	while (towrite > 0) {
 		tocopy = sb->s_blocksize - offset < towrite ?
 				sb->s_blocksize - offset : towrite;
@@ -1464,16 +1463,13 @@ static ssize_t ext2_quota_write(struct super_block *sb, int type,
 		blk++;
 	}
 out:
-	if (len == towrite) {
-		mutex_unlock(&inode->i_mutex);
+	if (len == towrite)
 		return err;
-	}
 	if (inode->i_size < off+len-towrite)
 		i_size_write(inode, off+len-towrite);
 	inode->i_version++;
 	inode->i_mtime = inode->i_ctime = CURRENT_TIME;
 	mark_inode_dirty(inode);
-	mutex_unlock(&inode->i_mutex);
 	return len - towrite;
 }