From: Yuri Tikhonov Date: Mon, 13 Apr 2009 21:40:11 +0000 (-0700) Subject: shmem: fix division by zero X-Git-Tag: MMI-PSA29.97-13-9~28476 X-Git-Url: https://git.stricted.de/?a=commitdiff_plain;h=61609d01cbb3ab865c8cccaf85e6837c47096480;p=GitHub%2FMotorolaMobilityLLC%2Fkernel-slsi.git shmem: fix division by zero Fix a division by zero which we have in shmem_truncate_range() and shmem_unuse_inode() when using big PAGE_SIZE values (e.g. 256kB on ppc44x). With 256kB PAGE_SIZE, the ENTRIES_PER_PAGEPAGE constant becomes too large (0x1.0000.0000) on a 32-bit kernel, so this patch just changes its type from 'unsigned long' to 'unsigned long long'. Hugh: reverted its unsigned long longs in shmem_truncate_range() and shmem_getpage(): the pagecache index cannot be more than an unsigned long, so the divisions by zero occurred in unreached code. It's a pity we need any ULL arithmetic here, but I found no pretty way to avoid it. Signed-off-by: Yuri Tikhonov Signed-off-by: Hugh Dickins Cc: Paul Mackerras Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds --- diff --git a/mm/shmem.c b/mm/shmem.c index d94d2e9146bc..28024ce8b8fd 100644 --- a/mm/shmem.c +++ b/mm/shmem.c @@ -66,7 +66,7 @@ static struct vfsmount *shm_mnt; #include #define ENTRIES_PER_PAGE (PAGE_CACHE_SIZE/sizeof(unsigned long)) -#define ENTRIES_PER_PAGEPAGE (ENTRIES_PER_PAGE*ENTRIES_PER_PAGE) +#define ENTRIES_PER_PAGEPAGE ((unsigned long long)ENTRIES_PER_PAGE*ENTRIES_PER_PAGE) #define BLOCKS_PER_PAGE (PAGE_CACHE_SIZE/512) #define SHMEM_MAX_INDEX (SHMEM_NR_DIRECT + (ENTRIES_PER_PAGEPAGE/2) * (ENTRIES_PER_PAGE+1))