ext4: use unlikely to improve the efficiency of the kernel

Because the function 'sb_getblk' seldomly fails to return NULL
value,it will be better to use 'unlikely' to optimize it.

Signed-off-by: Wang Shilong <wangsl-fnst@cn.fujitsu.com>
Signed-off-by: "Theodore Ts'o" <tytso@mit.edu>
diff --git a/fs/ext4/inode.c b/fs/ext4/inode.c
index 9ccc140..93a7e84 100644
--- a/fs/ext4/inode.c
+++ b/fs/ext4/inode.c
@@ -713,7 +713,7 @@
 		return NULL;
 
 	bh = sb_getblk(inode->i_sb, map.m_pblk);
-	if (!bh) {
+	if (unlikely(!bh)) {
 		*errp = -ENOMEM;
 		return NULL;
 	}
@@ -3660,7 +3660,7 @@
 	iloc->offset = (inode_offset % inodes_per_block) * EXT4_INODE_SIZE(sb);
 
 	bh = sb_getblk(sb, block);
-	if (!bh)
+	if (unlikely(!bh))
 		return -ENOMEM;
 	if (!buffer_uptodate(bh)) {
 		lock_buffer(bh);
@@ -3693,7 +3693,7 @@
 
 			/* Is the inode bitmap in cache? */
 			bitmap_bh = sb_getblk(sb, ext4_inode_bitmap(sb, gdp));
-			if (!bitmap_bh)
+			if (unlikely(!bitmap_bh))
 				goto make_io;
 
 			/*