introduce SIZE_MAX

ULONG_MAX is often used to check for integer overflow when calculating
allocation size.  While ULONG_MAX happens to work on most systems, there
is no guarantee that `size_t' must be the same size as `long'.

This patch introduces SIZE_MAX, the maximum value of `size_t', to improve
portability and readability for allocation size validation.

Signed-off-by: Xi Wang <xi.wang@gmail.com>
Acked-by: Alex Elder <elder@dreamhost.com>
Cc: David Airlie <airlied@linux.ie>
Cc: Pekka Enberg <penberg@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, 1 deletions

diff --git a/fs/ceph/snap.c b/fs/ceph/snap.c
index f04c0961f993..e5206fc76562 100644
--- a/fs/ceph/snap.c
+++ b/fs/ceph/snap.c
@@ -331,7 +331,7 @@ static int build_snap_context(struct ceph_snap_realm *realm)
 
         /* alloc new snap context */
         err = -ENOMEM;
-        if (num > (ULONG_MAX - sizeof(*snapc)) / sizeof(u64))
+        if (num > (SIZE_MAX - sizeof(*snapc)) / sizeof(u64))
                 goto fail;
         snapc = kzalloc(sizeof(*snapc) + num*sizeof(u64), GFP_NOFS);
         if (!snapc)