[PATCH] md: fix calculation for size of filemap_attr array in md/bitmap

If 'num_pages' were ever 1 more than a multiple of 8 (32bit platforms)
or of 16 (64 bit platforms).  filemap_attr would be allocated one
'unsigned long' shorter than required.  We need a round-up in there.

Signed-off-by: Neil Brown <neilb@suse.de>
Cc: <stable@kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

1 files changed, 1 insertions, 3 deletions

diff --git a/drivers/md/bitmap.c b/drivers/md/bitmap.c
index 5554adaa58f9..e61e0efe9ec7 100644
--- a/drivers/md/bitmap.c
+++ b/drivers/md/bitmap.c
@@ -863,9 +863,7 @@ static int bitmap_init_from_disk(struct bitmap *bitmap, sector_t start)
 
         /* We need 4 bits per page, rounded up to a multiple of sizeof(unsigned long) */
         bitmap->filemap_attr = kzalloc(
-                (((num_pages*4/8)+sizeof(unsigned long)-1)
-                 /sizeof(unsigned long))
-                *sizeof(unsigned long),
+                roundup( DIV_ROUND_UP(num_pages*4, 8), sizeof(unsigned long)),
                 GFP_KERNEL);
         if (!bitmap->filemap_attr)
                 goto out;