From: Ron Lee Date: Thu, 21 May 2009 19:28:22 +0000 (+0930) Subject: slab: fix generic PAGE_POISONING conflict with SLAB_RED_ZONE X-Git-Url: http://drtracing.org/?a=commitdiff_plain;h=6746136520cd0827320a83e62d0a023a5a433650;p=deliverable%2Flinux.git slab: fix generic PAGE_POISONING conflict with SLAB_RED_ZONE A generic page poisoning mechanism was added with commit: 6a11f75b6a17b5d9ac5025f8d048382fd1f47377 which destructively poisons full pages with a bitpattern. On arches where PAGE_POISONING is used, this conflicts with the slab redzone checking enabled by DEBUG_SLAB, scribbling bits all over its magic words and making it complain about that quite emphatically. On x86 (and I presume at present all the other arches which set ARCH_SUPPORTS_DEBUG_PAGEALLOC too), the kernel_map_pages() operation is non destructive so it can coexist with the other DEBUG_SLAB mechanisms just fine. This patch favours the expensive full page destruction test for cases where there is a collision and it is explicitly selected. Signed-off-by: Ron Lee Signed-off-by: Pekka Enberg --- diff --git a/mm/slab.c b/mm/slab.c index 9a90b00d2f91..1a6040d0f41d 100644 --- a/mm/slab.c +++ b/mm/slab.c @@ -2353,6 +2353,15 @@ kmem_cache_create (const char *name, size_t size, size_t align, /* really off slab. No need for manual alignment */ slab_size = cachep->num * sizeof(kmem_bufctl_t) + sizeof(struct slab); + +#ifdef CONFIG_PAGE_POISONING + /* If we're going to use the generic kernel_map_pages() + * poisoning, then it's going to smash the contents of + * the redzone and userword anyhow, so switch them off. + */ + if (size % PAGE_SIZE == 0 && flags & SLAB_POISON) + flags &= ~(SLAB_RED_ZONE | SLAB_STORE_USER); +#endif } cachep->colour_off = cache_line_size();