On Tue, May 02, 2017 at 01:42:24PM +1000, NeilBrown wrote: > This patch converts bioset_create() and > bioset_create_nobvec() to not create a workqueue so > alloctions will never trigger punt_bios_to_rescuer(). It > also introduces bioset_create_rescued() and > bioset_create_nobvec_rescued() which preserve the old > behaviour. > > All callers of bioset_create() and bioset_create_nobvec(), > that are inside block device drivers, are converted to the > _rescued() version. > > 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, drbd_md_io_bio_set, > and one allocated by target_core_iblock.c. > > biosets used by md/raid to not need rescuing as > their usage was recently audited to 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. > > Signed-off-by: NeilBrown <neilb@xxxxxxxx> > --- > block/bio.c | 12 ++++++++++-- > block/blk-core.c | 2 +- > drivers/md/bcache/super.c | 6 ++++-- > drivers/md/dm-crypt.c | 2 +- > drivers/md/dm-io.c | 2 +- > drivers/md/dm.c | 5 +++-- > include/linux/bio.h | 1 + > 7 files changed, 21 insertions(+), 9 deletions(-) > > diff --git a/block/bio.c b/block/bio.c > index 3f1286ed301e..257606e742e0 100644 > --- a/block/bio.c > +++ b/block/bio.c > @@ -363,6 +363,8 @@ static void punt_bios_to_rescuer(struct bio_set *bs) > struct bio_list punt, nopunt; > struct bio *bio; > > + if (!WARN_ON_ONCE(!bs->rescue_workqueue)) > + return; > /* > * In order to guarantee forward progress we must punt only bios that > * were allocated from this bio_set; otherwise, if there was a bio on > @@ -474,7 +476,8 @@ struct bio *bio_alloc_bioset(gfp_t gfp_mask, unsigned int nr_iovecs, > > if (current->bio_list && > (!bio_list_empty(¤t->bio_list[0]) || > - !bio_list_empty(¤t->bio_list[1]))) > + !bio_list_empty(¤t->bio_list[1])) && > + bs->rescue_workqueue) > gfp_mask &= ~__GFP_DIRECT_RECLAIM; > > p = mempool_alloc(bs->bio_pool, gfp_mask); > @@ -1925,7 +1928,7 @@ EXPORT_SYMBOL(bioset_free); > * bioset_create - Create a bio_set > * @pool_size: Number of bio and bio_vecs to cache in the mempool > * @front_pad: Number of bytes to allocate in front of the returned bio > - * @flags: Flags to modify behavior, currently only %BIOSET_NEED_BVECS > + * @flags: Flags to modify behavior, currently %BIOSET_NEED_BVECS and %BIOSET_NEED_RESCUER > * > * Description: > * Set up a bio_set to be used with @bio_alloc_bioset. Allows the caller > @@ -1936,6 +1939,8 @@ EXPORT_SYMBOL(bioset_free); > * or things will break badly. > * If %BIOSET_NEED_BVECS is set in @flags, a separate pool will be allocated > * for allocating iovecs. This pool is not needed e.g. for bio_clone_fast(). > + * If %BIOSET_NEED_RESCUER is set, workqueue is create which can be used to > + * dispatch queued requests when the mempool runs out of space. > * > */ > struct bio_set *bioset_create(unsigned int pool_size, > @@ -1971,6 +1976,9 @@ struct bio_set *bioset_create(unsigned int pool_size, > goto bad; > } > > + if (!(flags & BIOSET_NEED_RESCUER)) > + return bs; > + > bs->rescue_workqueue = alloc_workqueue("bioset", WQ_MEM_RECLAIM, 0); > if (!bs->rescue_workqueue) > goto bad; > diff --git a/block/blk-core.c b/block/blk-core.c > index 3797753f4085..ae51f159a2ca 100644 > --- a/block/blk-core.c > +++ b/block/blk-core.c > @@ -730,7 +730,7 @@ struct request_queue *blk_alloc_queue_node(gfp_t gfp_mask, int node_id) > if (q->id < 0) > goto fail_q; > > - q->bio_split = bioset_create(BIO_POOL_SIZE, 0, BIOSET_NEED_BVECS); > + q->bio_split = bioset_create(BIO_POOL_SIZE, 0, BIOSET_NEED_BVECS | BIOSET_NEED_RESCUER); Please avoid > 80 char lines. Otherwise looks fine, Reviewed-by: Christoph Hellwig <hch@xxxxxx>