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slab: fix generic PAGE_POISONING conflict with SLAB_RED_ZONE

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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 <ron@debian.org>
Signed-off-by: Pekka Enberg <penberg@cs.helsinki.fi>
This commit is contained in:
Ron Lee 2009-05-22 04:58:22 +09:30 committed by Pekka Enberg
parent 45d447406a
commit 6746136520
1 changed files with 9 additions and 0 deletions
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9
mm/slab.c
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@ -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();