From abca7c4965845924f65d40e0aa1092bdd895e314 Mon Sep 17 00:00:00 2001 From: Pravin B Shelar Date: Wed, 20 Jun 2012 12:52:56 -0700 Subject: [PATCH] mm: fix slab->page _count corruption when using slub On arches that do not support this_cpu_cmpxchg_double() slab_lock is used to do atomic cmpxchg() on double word which contains page->_count. The page count can be changed from get_page() or put_page() without taking slab_lock. That corrupts page counter. Fix it by moving page->_count out of cmpxchg_double data. So that slub does no change it while updating slub meta-data in struct page. [akpm@linux-foundation.org: use standard comment layout, tweak comment text] Reported-by: Amey Bhide Signed-off-by: Pravin B Shelar Acked-by: Christoph Lameter Cc: Pekka Enberg Cc: Andrea Arcangeli Cc: Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds --- include/linux/mm_types.h | 10 ++++++++++ 1 file changed, 10 insertions(+) diff --git a/include/linux/mm_types.h b/include/linux/mm_types.h index dad95bdd06d7..704a626d94a0 100644 --- a/include/linux/mm_types.h +++ b/include/linux/mm_types.h @@ -57,8 +57,18 @@ struct page { }; union { +#if defined(CONFIG_HAVE_CMPXCHG_DOUBLE) && \ + defined(CONFIG_HAVE_ALIGNED_STRUCT_PAGE) /* Used for cmpxchg_double in slub */ unsigned long counters; +#else + /* + * Keep _count separate from slub cmpxchg_double data. + * As the rest of the double word is protected by + * slab_lock but _count is not. + */ + unsigned counters; +#endif struct {