ext4: fixup 64-bit divides in 3.0-stable backport of upstream fix

Orabug: 17488415

Replace C division operators with div64_u64 for divides introduced in:
commit 503f4bdcc078e7abee273a85ce322de81b18a224
ext4: use atomic64_t for the per-flexbg free_clusters count

Specific to the 3.0-stable backport of the upstream patch.

Signed-off-by: Todd Poynor <toddpoynor@google.com>
Reviewed-by: "Theodore Ts'o" <tytso@mit.edu>
Cc: Christoph Biedl <linux-kernel.bfrz@manchmal.in-ulm.de>
Cc: Lukas Czerner <lczerner@redhat.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

(cherry picked from commit a58e3e13f5f8c03a88195c45771b2ef3a7a53f75)

Signed-off-by: Todd Vierling <todd.vierling@oracle.com>
Acked-by: John Haxby <john.haxby@oracle.com>
Signed-off-by: Brian Maly <brian.maly@oracle.com>

Author: toddpoynor

fs/ext4/ialloc.c

@@ -22,6 +22,7 @@
 #include <linux/random.h>
 #include <linux/bitops.h>
 #include <linux/blkdev.h>
+#include <linux/math64.h>
 #include <asm/byteorder.h>
 
 #include "ext4.h"
@@ -356,7 +357,7 @@ static int find_group_flex(struct super_block *sb, struct inode *parent,
 
 find_close_to_parent:
 	flexbg_free_blocks = atomic64_read(&flex_group[best_flex].free_blocks);
-	flex_freeb_ratio = flexbg_free_blocks * 100 / blocks_per_flex;
+	flex_freeb_ratio = div64_u64(flexbg_free_blocks * 100, blocks_per_flex);
 	if (atomic_read(&flex_group[best_flex].free_inodes) &&
 	    flex_freeb_ratio > free_block_ratio)
 		goto found_flexbg;
@@ -371,7 +372,7 @@ static int find_group_flex(struct super_block *sb, struct inode *parent,
 			continue;
 
 		flexbg_free_blocks = atomic64_read(&flex_group[i].free_blocks);
-		flex_freeb_ratio = flexbg_free_blocks * 100 / blocks_per_flex;
+		flex_freeb_ratio = div64_u64(flexbg_free_blocks * 100, blocks_per_flex);
 
 		if (flex_freeb_ratio > free_block_ratio &&
 		    (atomic_read(&flex_group[i].free_inodes))) {