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dm: optimize dm_mq_queue_rq to _not_ use kthread if using pure blk-mq

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dm_mq_queue_rq() is in atomic context so care must be taken to not
sleep -- as such GFP_ATOMIC is used for the md->bs bioset allocations
and dm-mpath's call to blk_get_request().  In the future the bioset
allocations will hopefully go away (by removing support for partial
completions of bios in a cloned request).

Also prepare for supporting DM blk-mq ontop of old-style request_fn
device(s) if a new dm-mod 'use_blk_mq' parameter is set.  The kthread
will still be used to queue work if blk-mq is used ontop of old-style
request_fn device(s).

Signed-off-by: Mike Snitzer <snitzer@redhat.com>
This commit is contained in:
Mike Snitzer 2015-03-10 23:49:26 -04:00
commit 022333427a
2 changed files with 50 additions and 16 deletions
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2
drivers/md/dm-mpath.c
View file

@ -428,7 +428,7 @@ static int __multipath_map(struct dm_target *ti, struct request *clone,
} else {
/* blk-mq request-based interface */
*__clone = blk_get_request(bdev_get_queue(bdev),
rq_data_dir(rq), GFP_KERNEL);
rq_data_dir(rq), GFP_ATOMIC);
if (IS_ERR(*__clone))
/* ENOMEM, requeue */
return r;

64
drivers/md/dm.c
View file

@ -1077,9 +1077,10 @@ static void free_rq_clone(struct request *clone)
blk_rq_unprep_clone(clone);
if (clone->q && clone->q->mq_ops)
if (clone->q->mq_ops)
tio->ti->type->release_clone_rq(clone);
else
else if (!md->queue->mq_ops)
/* request_fn queue stacked on request_fn queue(s) */
free_clone_request(md, clone);
if (!md->queue->mq_ops)
@ -1838,15 +1839,25 @@ static int setup_clone(struct request *clone, struct request *rq,
static struct request *clone_rq(struct request *rq, struct mapped_device *md,
struct dm_rq_target_io *tio, gfp_t gfp_mask)
{
struct request *clone = alloc_clone_request(md, gfp_mask);
/*
* Do not allocate a clone if tio->clone was already set
* (see: dm_mq_queue_rq).
*/
bool alloc_clone = !tio->clone;
struct request *clone;
if (!clone)
return NULL;
if (alloc_clone) {
clone = alloc_clone_request(md, gfp_mask);
if (!clone)
return NULL;
} else
clone = tio->clone;
blk_rq_init(NULL, clone);
if (setup_clone(clone, rq, tio, gfp_mask)) {
/* -ENOMEM */
free_clone_request(md, clone);
if (alloc_clone)
free_clone_request(md, clone);
return NULL;
}
@ -1864,7 +1875,8 @@ static void init_tio(struct dm_rq_target_io *tio, struct request *rq,
tio->orig = rq;
tio->error = 0;
memset(&tio->info, 0, sizeof(tio->info));
init_kthread_work(&tio->work, map_tio_request);
if (md->kworker_task)
init_kthread_work(&tio->work, map_tio_request);
}
static struct dm_rq_target_io *prep_tio(struct request *rq,
@ -1941,7 +1953,7 @@ static int map_request(struct dm_rq_target_io *tio, struct request *rq,
}
if (IS_ERR(clone))
return DM_MAPIO_REQUEUE;
if (setup_clone(clone, rq, tio, GFP_NOIO)) {
if (setup_clone(clone, rq, tio, GFP_ATOMIC)) {
/* -ENOMEM */
ti->type->release_clone_rq(clone);
return DM_MAPIO_REQUEUE;
@ -2408,7 +2420,7 @@ static void __bind_mempools(struct mapped_device *md, struct dm_table *t)
p->bs = NULL;
out:
/* mempool bind completed, now no need any mempools in the table */
/* mempool bind completed, no longer need any mempools in the table */
dm_table_free_md_mempools(t);
}
@ -2713,9 +2725,24 @@ static int dm_mq_queue_rq(struct blk_mq_hw_ctx *hctx,
/* Init tio using md established in .init_request */
init_tio(tio, rq, md);
/* Establish tio->ti before queuing work (map_tio_request) */
/*
* Establish tio->ti before queuing work (map_tio_request)
* or making direct call to map_request().
*/
tio->ti = ti;
queue_kthread_work(&md->kworker, &tio->work);
/* Clone the request if underlying devices aren't blk-mq */
if (dm_table_get_type(map) == DM_TYPE_REQUEST_BASED) {
/* clone request is allocated at the end of the pdu */
tio->clone = (void *)blk_mq_rq_to_pdu(rq) + sizeof(struct dm_rq_target_io);
if (!clone_rq(rq, md, tio, GFP_ATOMIC))
return BLK_MQ_RQ_QUEUE_BUSY;
queue_kthread_work(&md->kworker, &tio->work);
} else {
/* Direct call is fine since .queue_rq allows allocations */
if (map_request(tio, rq, md) == DM_MAPIO_REQUEUE)
dm_requeue_unmapped_original_request(md, rq);
}
return BLK_MQ_RQ_QUEUE_OK;
}
@ -2729,6 +2756,7 @@ static struct blk_mq_ops dm_mq_ops = {
static int dm_init_request_based_blk_mq_queue(struct mapped_device *md)
{
unsigned md_type = dm_get_md_type(md);
struct request_queue *q;
int err;
@ -2738,7 +2766,11 @@ static int dm_init_request_based_blk_mq_queue(struct mapped_device *md)
md->tag_set.numa_node = NUMA_NO_NODE;
md->tag_set.flags = BLK_MQ_F_SHOULD_MERGE | BLK_MQ_F_SG_MERGE;
md->tag_set.nr_hw_queues = 1;
md->tag_set.cmd_size = sizeof(struct dm_rq_target_io);
if (md_type == DM_TYPE_REQUEST_BASED) {
/* make the memory for non-blk-mq clone part of the pdu */
md->tag_set.cmd_size = sizeof(struct dm_rq_target_io) + sizeof(struct request);
} else
md->tag_set.cmd_size = sizeof(struct dm_rq_target_io);
md->tag_set.driver_data = md;
err = blk_mq_alloc_tag_set(&md->tag_set);
@ -2756,7 +2788,8 @@ static int dm_init_request_based_blk_mq_queue(struct mapped_device *md)
/* backfill 'mq' sysfs registration normally done in blk_register_queue */
blk_mq_register_disk(md->disk);
init_rq_based_worker_thread(md);
if (md_type == DM_TYPE_REQUEST_BASED)
init_rq_based_worker_thread(md);
return 0;
@ -2876,7 +2909,7 @@ static void __dm_destroy(struct mapped_device *md, bool wait)
set_bit(DMF_FREEING, &md->flags);
spin_unlock(&_minor_lock);
if (dm_request_based(md))
if (dm_request_based(md) && md->kworker_task)
flush_kthread_worker(&md->kworker);
/*
@ -3130,7 +3163,8 @@ static int __dm_suspend(struct mapped_device *md, struct dm_table *map,
*/
if (dm_request_based(md)) {
stop_queue(md->queue);
flush_kthread_worker(&md->kworker);
if (md->kworker_task)
flush_kthread_worker(&md->kworker);
}
flush_workqueue(md->wq);