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dm bufio: fix buffer alignment

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Commit 6b5e718cc1 ("dm bufio: relax alignment constraint on slab
cache") relaxed alignment on dm-bufio cache, however it may break
dm-crypt or dm-integrity.

dm-crypt and dm-integrity require that the size of bio vector entries
(bv_len) is aligned on its sector size. bv_offset doesn't have to be
aligned, but bv_len must be. XFS sends unaligned bios, but they do not
cross page boundary, so the requirement for aligned bv_len is met.

Commit 6b5e718cc1 made dm-bufio send unaligned bios that cross page
boundary, this could break dm-crypt and dm-integrity.

Reinstates the alignment. Note that misaligned entries only happen when
we use slab/slub debugging. Without debugging, the entries are always
aligned.

Fixes: 6b5e718cc1 ("dm bufio: relax alignment constraint on slab cache")
Signed-off-by: Mikulas Patocka <mpatocka@redhat.com>
Signed-off-by: Mike Snitzer <snitzer@redhat.com>
This commit is contained in:
Mikulas Patocka 2018-04-19 08:33:00 -04:00 committed by Mike Snitzer
parent fc8cec1139
commit f7879b4cea
1 changed files with 3 additions and 2 deletions
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5
drivers/md/dm-bufio.c
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@ -1681,8 +1681,9 @@ struct dm_bufio_client *dm_bufio_client_create(struct block_device *bdev, unsign
if (block_size <= KMALLOC_MAX_SIZE &&
(block_size < PAGE_SIZE || !is_power_of_2(block_size))) {
snprintf(slab_name, sizeof slab_name, "dm_bufio_cache-%u", c->block_size);
c->slab_cache = kmem_cache_create(slab_name, c->block_size, ARCH_KMALLOC_MINALIGN,
unsigned align = min(1U << __ffs(block_size), (unsigned)PAGE_SIZE);
snprintf(slab_name, sizeof slab_name, "dm_bufio_cache-%u", block_size);
c->slab_cache = kmem_cache_create(slab_name, block_size, align,
SLAB_RECLAIM_ACCOUNT, NULL);
if (!c->slab_cache) {
r = -ENOMEM;