On Mon, Jul 02, 2012 at 08:56:32PM -0300, Herton Ronaldo Krzesinski wrote: > So, 3.2 didn't have the CONFIG_HAVE_CMPXCHG_DOUBLE and > CONFIG_HAVE_ALIGNED_STRUCT_PAGE defines, it had instead CMPXCHG_DOUBLE > and HAVE_ALIGNED_STRUCT_PAGE is a new logic. So the patch is broken for > 3.2 indeed.
So here is a proposed backport for 3.2, I tested it etc., but please someone review/ack it as well... From: Pravin B Shelar <[email protected]> Subject: mm: fix slab->page _count corruption when using slub commit abca7c4965845924f65d40e0aa1092bdd895e314 upstream. 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. [[email protected]: use standard comment layout, tweak comment text] Reported-by: Amey Bhide <[email protected]> Signed-off-by: Pravin B Shelar <[email protected]> Acked-by: Christoph Lameter <[email protected]> Cc: Pekka Enberg <[email protected]> Cc: Andrea Arcangeli <[email protected]> Signed-off-by: Andrew Morton <[email protected]> Signed-off-by: Linus Torvalds <[email protected]> Signed-off-by: Ben Hutchings <[email protected]> [herton: backport to 3.2, use CONFIG_CMPXCHG_DOUBLE] Signed-off-by: Herton R. Krzesinski <[email protected]> --- include/linux/mm_types.h | 9 +++++++++ 1 file changed, 9 insertions(+) diff --git a/include/linux/mm_types.h b/include/linux/mm_types.h index 5b42f1b..2153639 100644 --- a/include/linux/mm_types.h +++ b/include/linux/mm_types.h @@ -56,8 +56,17 @@ struct page { }; union { +#ifdef CONFIG_CMPXCHG_DOUBLE /* 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 { -- 1.7.9.5 -- []'s Herton -- To unsubscribe from this list: send the line "unsubscribe stable" in the body of a message to [email protected] More majordomo info at http://vger.kernel.org/majordomo-info.html
