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| author | Pekka Enberg <penberg@cs.helsinki.fi> | 2006-09-25 23:31:25 -0700 |
|---|---|---|
| committer | Linus Torvalds <torvalds@g5.osdl.org> | 2006-09-26 08:48:48 -0700 |
| commit | ca5f9703dffa012cc46166e6206c5a992910e041 (patch) | |
| tree | d1fb19019db14465eb8674aa1b13c6506a569705 /mm | |
| parent | db37648cd6ce9b828abd6d49aa3d269926ee7b7d (diff) | |
| download | lwn-ca5f9703dffa012cc46166e6206c5a992910e041.tar.gz lwn-ca5f9703dffa012cc46166e6206c5a992910e041.zip | |
[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>
Diffstat (limited to 'mm')
| -rw-r--r-- | mm/slab.c | 25 |
1 files changed, 16 insertions, 9 deletions
diff --git a/mm/slab.c b/mm/slab.c index 00584dbbec03..d47d0e186973 100644 --- a/mm/slab.c +++ b/mm/slab.c @@ -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) |