blk: make the bioset rescue_workqueue optional.
authorNeilBrown <neilb@suse.com>
Sun, 18 Jun 2017 04:38:57 +0000 (14:38 +1000)
committerJens Axboe <axboe@kernel.dk>
Sun, 18 Jun 2017 18:40:59 +0000 (12:40 -0600)
commit47e0fb461fca1a68a566c82fcc006cc787312d8c
tree5362bdaeb18fdbe069062d33cb27622088698374
parent011067b05668b05aae88e5a24cff0ca0a67ca0b0
blk: make the bioset rescue_workqueue optional.

This patch converts bioset_create() to not create a workqueue by
default, so alloctions will never trigger punt_bios_to_rescuer().  It
also introduces a new flag BIOSET_NEED_RESCUER which tells
bioset_create() to preserve the old behavior.

All callers of bioset_create() that are inside block device drivers,
are given the BIOSET_NEED_RESCUER flag.

biosets used by filesystems or other top-level users do not
need rescuing as the bio can never be queued behind other
bios.  This includes fs_bio_set, blkdev_dio_pool,
btrfs_bioset, xfs_ioend_bioset, and one allocated by
target_core_iblock.c.

biosets used by md/raid do not need rescuing as
their usage was recently audited and revised to never
risk deadlock.

It is hoped that most, if not all, of the remaining biosets
can end up being the non-rescued version.

Reviewed-by: Christoph Hellwig <hch@lst.de>
Credit-to: Ming Lei <ming.lei@redhat.com> (minor fixes)
Reviewed-by: Ming Lei <ming.lei@redhat.com>
Signed-off-by: NeilBrown <neilb@suse.com>
Signed-off-by: Jens Axboe <axboe@kernel.dk>
block/bio.c
block/blk-core.c
drivers/block/drbd/drbd_main.c
drivers/md/bcache/super.c
drivers/md/dm-crypt.c
drivers/md/dm-io.c
drivers/md/dm.c
include/linux/bio.h