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dm: pass NULL bdev to bio_alloc_clone

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Most DM targets will remap the clone bio passed to their ->map
function using bio_set_bdev(). So this change to pass NULL bdev to
bio_alloc_clone avoids clone-time work that sets up resources for a
bdev association that will not be used in practice (e.g. clone issued
to underlying device will not use DM device's blk-cgroups resources).

But clone->bi_bdev is still initialized following bio_alloc_clone to
preserve DM target expectations that clone->bi_bdev will be set.
Follow-up work is needed to audit DM targets to remove accesses to a
clone->bi_bdev that the target didn't initialize with bio_set_dev().

Depends-on: 7ecc56c62b ("block: allow passing a NULL bdev to bio_alloc_clone/bio_init_clone")
Signed-off-by: Mike Snitzer <snitzer@kernel.org>
This commit is contained in:
Mike Snitzer 2022-05-11 09:38:38 -04:00
parent d254c3699f
commit ca522482e3
1 changed files with 24 additions and 16 deletions
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40
drivers/md/dm.c
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@ -581,7 +581,9 @@ static struct dm_io *alloc_io(struct mapped_device *md, struct bio *bio)
struct dm_target_io *tio;
struct bio *clone;
clone = bio_alloc_clone(bio->bi_bdev, bio, GFP_NOIO, &md->io_bs);
clone = bio_alloc_clone(NULL, bio, GFP_NOIO, &md->io_bs);
/* Set default bdev, but target must bio_set_dev() before issuing IO */
clone->bi_bdev = md->disk->part0;
tio = clone_to_tio(clone);
tio->flags = 0;
@ -613,7 +615,7 @@ static void free_io(struct dm_io *io)
}
static struct bio *alloc_tio(struct clone_info *ci, struct dm_target *ti,
unsigned target_bio_nr, unsigned *len, gfp_t gfp_mask)
unsigned target_bio_nr, unsigned *len, gfp_t gfp_mask)
{
struct dm_target_io *tio;
struct bio *clone;
@ -624,10 +626,13 @@ static struct bio *alloc_tio(struct clone_info *ci, struct dm_target *ti,
/* alloc_io() already initialized embedded clone */
clone = &tio->clone;
} else {
clone = bio_alloc_clone(ci->bio->bi_bdev, ci->bio,
gfp_mask, &ci->io->md->bs);
struct mapped_device *md = ci->io->md;
clone = bio_alloc_clone(NULL, ci->bio, gfp_mask, &md->bs);
if (!clone)
return NULL;
/* Set default bdev, but target must bio_set_dev() before issuing IO */
clone->bi_bdev = md->disk->part0;
/* REQ_DM_POLL_LIST shouldn't be inherited */
clone->bi_opf &= ~REQ_DM_POLL_LIST;
@ -1012,25 +1017,28 @@ static bool swap_bios_limit(struct dm_target *ti, struct bio *bio)
static void clone_endio(struct bio *bio)
{
blk_status_t error = bio->bi_status;
struct request_queue *q = bio->bi_bdev->bd_disk->queue;
struct dm_target_io *tio = clone_to_tio(bio);
struct dm_target *ti = tio->ti;
dm_endio_fn endio = ti->type->end_io;
struct dm_io *io = tio->io;
struct mapped_device *md = io->md;
if (unlikely(error == BLK_STS_TARGET)) {
if (bio_op(bio) == REQ_OP_DISCARD &&
!bdev_max_discard_sectors(bio->bi_bdev))
disable_discard(md);
else if (bio_op(bio) == REQ_OP_WRITE_ZEROES &&
!q->limits.max_write_zeroes_sectors)
disable_write_zeroes(md);
}
if (likely(bio->bi_bdev != md->disk->part0)) {
struct request_queue *q = bdev_get_queue(bio->bi_bdev);
if (static_branch_unlikely(&zoned_enabled) &&
unlikely(blk_queue_is_zoned(q)))
dm_zone_endio(io, bio);
if (unlikely(error == BLK_STS_TARGET)) {
if (bio_op(bio) == REQ_OP_DISCARD &&
!bdev_max_discard_sectors(bio->bi_bdev))
disable_discard(md);
else if (bio_op(bio) == REQ_OP_WRITE_ZEROES &&
!q->limits.max_write_zeroes_sectors)
disable_write_zeroes(md);
}
if (static_branch_unlikely(&zoned_enabled) &&
unlikely(blk_queue_is_zoned(q)))
dm_zone_endio(io, bio);
}
if (endio) {
int r = endio(ti, bio, &error);