ocfs2: optimize ocfs2_check_dir_entry() with unlikely() annotations

In cad3f00, ext4_check_dir_entry was modified by adding some unlikely.
Ted described it as "This function gets called a lot for large
directories, and the answer is almost always 'no, no, there's no problem'.
This means using unlikely() is a good thing."
ext3 added the similar change in commit a4ae309.

So change it accordingly in ocfs2.

Cc: Joel Becker <jlbec@evilplan.org>
Signed-off-by: Tao Ma <boyu.mt@taobao.com>
Signed-off-by: Joel Becker <jlbec@evilplan.org>

fs/ocfs2/dir.c

@@ -322,21 +322,23 @@ static int ocfs2_check_dir_entry(struct inode * dir,
 	const char *error_msg = NULL;
 	const int rlen = le16_to_cpu(de->rec_len);
 
-	if (rlen < OCFS2_DIR_REC_LEN(1))
+	if (unlikely(rlen < OCFS2_DIR_REC_LEN(1)))
 		error_msg = "rec_len is smaller than minimal";
-	else if (rlen % 4 != 0)
+	else if (unlikely(rlen % 4 != 0))
 		error_msg = "rec_len % 4 != 0";
-	else if (rlen < OCFS2_DIR_REC_LEN(de->name_len))
+	else if (unlikely(rlen < OCFS2_DIR_REC_LEN(de->name_len)))
 		error_msg = "rec_len is too small for name_len";
-	else if (((char *) de - bh->b_data) + rlen > dir->i_sb->s_blocksize)
+	else if (unlikely(
+		 ((char *) de - bh->b_data) + rlen > dir->i_sb->s_blocksize))
 		error_msg = "directory entry across blocks";
 
-	if (error_msg != NULL)
+	if (unlikely(error_msg != NULL))
 		mlog(ML_ERROR, "bad entry in directory #%llu: %s - "
 		     "offset=%lu, inode=%llu, rec_len=%d, name_len=%d\n",
 		     (unsigned long long)OCFS2_I(dir)->ip_blkno, error_msg,
 		     offset, (unsigned long long)le64_to_cpu(de->inode), rlen,
 		     de->name_len);
+
 	return error_msg == NULL ? 1 : 0;
 }