Commit ca5f9703 authored by Pekka Enberg's avatar Pekka Enberg Committed by Linus Torvalds
Browse files

[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: default avatarManfred Spraul <manfred@colorfullife.com>
Signed-off-by: default avatarPekka Enberg <penberg@cs.helsinki.fi>
Signed-off-by: default avatarAndrew Morton <akpm@osdl.org>
Signed-off-by: default avatarLinus Torvalds <torvalds@osdl.org>
parent db37648c
......@@ -2096,6 +2096,15 @@ kmem_cache_create (const char *name, size_t size, size_t align,
} else {
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 */
if (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);
}
/*
* 4) Store it. Note that the debug code below can reduce
* the alignment to BYTES_PER_WORD.
* 4) Store it.
*/
align = ralign;
......@@ -2122,20 +2130,19 @@ kmem_cache_create (const char *name, size_t size, size_t align,
#if DEBUG
cachep->obj_size = size;
/*
* Both debugging options require word-alignment which is calculated
* into align above.
*/
if (flags & SLAB_RED_ZONE) {
/* redzoning only works with word aligned caches */
align = BYTES_PER_WORD;
/* add space for red zone words */
cachep->obj_offset += BYTES_PER_WORD;
size += 2 * BYTES_PER_WORD;
}
if (flags & SLAB_STORE_USER) {
/* user store requires word alignment and
* one word storage behind the end of the real
* object.
/* user store requires one word storage behind the end of
* the real object.
*/
align = BYTES_PER_WORD;
size += BYTES_PER_WORD;
}
#if FORCED_DEBUG && defined(CONFIG_DEBUG_PAGEALLOC)
......
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