ext4: code cleanup in mb_find_buddy()

Current code calculate max no matter whether order is zero, it's
unnecessary. This cleanup patch sets max to "1 << (e4b->bd_blkbits
+ 3)" only when order == 0.
Signed-off-by: Coly Li <bosong.ly@taobao.com>
Cc: Alex Tomas <alex@clusterfs.com>
Cc: Theodore Tso <tytso@google.com>

fs/ext4/mballoc.c

@@ -432,9 +432,10 @@ static void *mb_find_buddy(struct ext4_buddy *e4b, int order, int *max)
 	}
 
 	/* at order 0 we see each particular block */
-	*max = 1 << (e4b->bd_blkbits + 3);
-	if (order == 0)
+	if (order == 0) {
+		*max = 1 << (e4b->bd_blkbits + 3);
 		return EXT4_MB_BITMAP(e4b);
+	}
 
 	bb = EXT4_MB_BUDDY(e4b) + EXT4_SB(e4b->bd_sb)->s_mb_offsets[order];
 	*max = EXT4_SB(e4b->bd_sb)->s_mb_maxs[order];