Commit 67461365 authored May 22, 2009 by Ron Lee Committed by Pekka Enberg May 22, 2009

slab: fix generic PAGE_POISONING conflict with SLAB_RED_ZONE



A generic page poisoning mechanism was added with commit:
 6a11f75b
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>

parent 45d44740

mm/slab.c

+9 −0

Original line number	Diff line number	Diff line
		@@ -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();