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[PATCH] slab: respect architecture and caller mandated alignment 

As explained by Heiko, on s390 (32-bit) ARCH_KMALLOC_MINALIGN is set to
eight because their common I/O layer allocates data structures that need to
have an eight byte alignment.  This does not work when CONFIG_SLAB_DEBUG is
enabled because kmem_cache_create will override alignment to BYTES_PER_WORD
which is four.

So change kmem_cache_create to ensure cache alignment is always at minimum
what the architecture or caller mandates even if slab debugging is enabled.

Cc: Heiko Carstens <heiko.carstens@de.ibm.com>
Cc: Christoph Lameter <clameter@sgi.com>
Signed-off-by: Manfred Spraul <manfred@colorfullife.com>
Signed-off-by: Pekka Enberg <penberg@cs.helsinki.fi>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>
This commit is contained in:
Pekka Enberg 2006-09-25 23:31:25 -07:00 committed by Linus Torvalds
parent db37648cd6
commit ca5f9703df
1 changed files with 16 additions and 9 deletions
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25
mm/slab.c
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@ -2096,6 +2096,15 @@ kmem_cache_create (const char *name, size_t size, size_t align,
} else { } else {
ralign = BYTES_PER_WORD; ralign = BYTES_PER_WORD;
} }
/*
* Redzoning and user store require word alignment. Note this will be
* overridden by architecture or caller mandated alignment if either
* is greater than BYTES_PER_WORD.
*/
if (flags & SLAB_RED_ZONE || flags & SLAB_STORE_USER)
ralign = BYTES_PER_WORD;
/* 2) arch mandated alignment: disables debug if necessary */ /* 2) arch mandated alignment: disables debug if necessary */
if (ralign < ARCH_SLAB_MINALIGN) { if (ralign < ARCH_SLAB_MINALIGN) {
ralign = ARCH_SLAB_MINALIGN; ralign = ARCH_SLAB_MINALIGN;
@ -2109,8 +2118,7 @@ kmem_cache_create (const char *name, size_t size, size_t align,
flags &= ~(SLAB_RED_ZONE | SLAB_STORE_USER); flags &= ~(SLAB_RED_ZONE | SLAB_STORE_USER);
} }
/* /*
* 4) Store it. Note that the debug code below can reduce * 4) Store it.
* the alignment to BYTES_PER_WORD.
*/ */
align = ralign; align = ralign;
@ -2122,20 +2130,19 @@ kmem_cache_create (const char *name, size_t size, size_t align,
#if DEBUG #if DEBUG
cachep->obj_size = size; cachep->obj_size = size;
/*
* Both debugging options require word-alignment which is calculated
* into align above.
*/
if (flags & SLAB_RED_ZONE) { if (flags & SLAB_RED_ZONE) {
/* redzoning only works with word aligned caches */
align = BYTES_PER_WORD;
/* add space for red zone words */ /* add space for red zone words */
cachep->obj_offset += BYTES_PER_WORD; cachep->obj_offset += BYTES_PER_WORD;
size += 2 * BYTES_PER_WORD; size += 2 * BYTES_PER_WORD;
} }
if (flags & SLAB_STORE_USER) { if (flags & SLAB_STORE_USER) {
/* user store requires word alignment and /* user store requires one word storage behind the end of
* one word storage behind the end of the real * the real object.
* object.
*/ */
align = BYTES_PER_WORD;
size += BYTES_PER_WORD; size += BYTES_PER_WORD;
} }
#if FORCED_DEBUG && defined(CONFIG_DEBUG_PAGEALLOC) #if FORCED_DEBUG && defined(CONFIG_DEBUG_PAGEALLOC)