From ca522482e3eafd005b8d4e8b1331c911505a58d5 Mon Sep 17 00:00:00 2001 From: Mike Snitzer Date: Wed, 11 May 2022 09:38:38 -0400 Subject: [PATCH] dm: pass NULL bdev to bio_alloc_clone 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: 7ecc56c62b27 ("block: allow passing a NULL bdev to bio_alloc_clone/bio_init_clone") Signed-off-by: Mike Snitzer --- drivers/md/dm.c | 40 ++++++++++++++++++++++++---------------- 1 file changed, 24 insertions(+), 16 deletions(-) diff --git a/drivers/md/dm.c b/drivers/md/dm.c index 9650ba2..d62f135 100644 --- a/drivers/md/dm.c +++ b/drivers/md/dm.c @@ -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); -- 2.7.4