shmem: fix division by zero
authorYuri Tikhonov <yur@emcraft.com>
Mon, 13 Apr 2009 21:40:11 +0000 (14:40 -0700)
committerLinus Torvalds <torvalds@linux-foundation.org>
Mon, 13 Apr 2009 22:04:32 +0000 (15:04 -0700)
commit61609d01cbb3ab865c8cccaf85e6837c47096480
tree144e176568328a6fcd9c01853c3f88fd6bc1a08e
parent347486bb108fa6e0fd2753c1be3519d6be2516ed
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 <yur@emcraft.com>
Signed-off-by: Hugh Dickins <hugh@veritas.com>
Cc: Paul Mackerras <paulus@samba.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
mm/shmem.c