block: use kmalloc alignment for bio slab

Various subsystems can ask the bio subsystem to create a bio slab cache
with some free space before the bio.  This free space can be used for any
purpose.  Device mapper uses this per-bio-data feature to place some
target-specific and device-mapper specific data before the bio, so that
the target-specific data doesn't have to be allocated separately.

This per-bio-data mechanism is used in place of kmalloc, so we need the
allocated slab to have the same memory alignment as memory allocated
with kmalloc.

Change bio_find_or_create_slab() so that it uses ARCH_KMALLOC_MINALIGN
alignment when creating the slab cache.  This is needed so that dm-crypt
can use per-bio-data for encryption - the crypto subsystem assumes this
data will have the same alignment as kmalloc'ed memory.

Signed-off-by: Mikulas Patocka <mpatocka@redhat.com>
Signed-off-by: Mike Snitzer <snitzer@redhat.com>
Acked-by: Jens Axboe <axboe@fb.com>

diff --git a/block/bio.c b/block/bio.c
index 0ec61c9..3e6331d 100644 (file)
--- a/block/bio.c
+++ b/block/bio.c
@@ -112,7 +112,8 @@ static struct kmem_cache *bio_find_or_create_slab(unsigned int extra_size)
        bslab = &bio_slabs[entry];
 
        snprintf(bslab->name, sizeof(bslab->name), "bio-%d", entry);
-       slab = kmem_cache_create(bslab->name, sz, 0, SLAB_HWCACHE_ALIGN, NULL);
+       slab = kmem_cache_create(bslab->name, sz, ARCH_KMALLOC_MINALIGN,
+                                SLAB_HWCACHE_ALIGN, NULL);
        if (!slab)
                goto out_unlock;