dm: optimize dm_mq_queue_rq to _not_ use kthread if using pure blk-mq
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>
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bfebd1cdb4
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022333427a
@ -428,7 +428,7 @@ static int __multipath_map(struct dm_target *ti, struct request *clone,
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} else {
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/* blk-mq request-based interface */
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*__clone = blk_get_request(bdev_get_queue(bdev),
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rq_data_dir(rq), GFP_KERNEL);
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rq_data_dir(rq), GFP_ATOMIC);
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if (IS_ERR(*__clone))
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/* ENOMEM, requeue */
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return r;
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@ -1077,9 +1077,10 @@ static void free_rq_clone(struct request *clone)
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blk_rq_unprep_clone(clone);
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if (clone->q && clone->q->mq_ops)
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if (clone->q->mq_ops)
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tio->ti->type->release_clone_rq(clone);
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else
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else if (!md->queue->mq_ops)
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/* request_fn queue stacked on request_fn queue(s) */
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free_clone_request(md, clone);
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if (!md->queue->mq_ops)
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@ -1838,14 +1839,24 @@ static int setup_clone(struct request *clone, struct request *rq,
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static struct request *clone_rq(struct request *rq, struct mapped_device *md,
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struct dm_rq_target_io *tio, gfp_t gfp_mask)
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{
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struct request *clone = alloc_clone_request(md, gfp_mask);
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/*
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* Do not allocate a clone if tio->clone was already set
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* (see: dm_mq_queue_rq).
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*/
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bool alloc_clone = !tio->clone;
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struct request *clone;
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if (alloc_clone) {
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clone = alloc_clone_request(md, gfp_mask);
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if (!clone)
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return NULL;
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} else
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clone = tio->clone;
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blk_rq_init(NULL, clone);
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if (setup_clone(clone, rq, tio, gfp_mask)) {
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/* -ENOMEM */
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if (alloc_clone)
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free_clone_request(md, clone);
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return NULL;
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}
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@ -1864,6 +1875,7 @@ static void init_tio(struct dm_rq_target_io *tio, struct request *rq,
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tio->orig = rq;
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tio->error = 0;
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memset(&tio->info, 0, sizeof(tio->info));
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if (md->kworker_task)
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init_kthread_work(&tio->work, map_tio_request);
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}
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@ -1941,7 +1953,7 @@ static int map_request(struct dm_rq_target_io *tio, struct request *rq,
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}
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if (IS_ERR(clone))
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return DM_MAPIO_REQUEUE;
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if (setup_clone(clone, rq, tio, GFP_NOIO)) {
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if (setup_clone(clone, rq, tio, GFP_ATOMIC)) {
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/* -ENOMEM */
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ti->type->release_clone_rq(clone);
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return DM_MAPIO_REQUEUE;
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@ -2408,7 +2420,7 @@ static void __bind_mempools(struct mapped_device *md, struct dm_table *t)
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p->bs = NULL;
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out:
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/* mempool bind completed, now no need any mempools in the table */
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/* mempool bind completed, no longer need any mempools in the table */
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dm_table_free_md_mempools(t);
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}
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@ -2713,9 +2725,24 @@ static int dm_mq_queue_rq(struct blk_mq_hw_ctx *hctx,
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/* Init tio using md established in .init_request */
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init_tio(tio, rq, md);
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/* Establish tio->ti before queuing work (map_tio_request) */
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/*
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* Establish tio->ti before queuing work (map_tio_request)
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* or making direct call to map_request().
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*/
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tio->ti = ti;
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/* Clone the request if underlying devices aren't blk-mq */
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if (dm_table_get_type(map) == DM_TYPE_REQUEST_BASED) {
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/* clone request is allocated at the end of the pdu */
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tio->clone = (void *)blk_mq_rq_to_pdu(rq) + sizeof(struct dm_rq_target_io);
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if (!clone_rq(rq, md, tio, GFP_ATOMIC))
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return BLK_MQ_RQ_QUEUE_BUSY;
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queue_kthread_work(&md->kworker, &tio->work);
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} else {
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/* Direct call is fine since .queue_rq allows allocations */
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if (map_request(tio, rq, md) == DM_MAPIO_REQUEUE)
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dm_requeue_unmapped_original_request(md, rq);
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}
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return BLK_MQ_RQ_QUEUE_OK;
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}
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@ -2729,6 +2756,7 @@ static struct blk_mq_ops dm_mq_ops = {
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static int dm_init_request_based_blk_mq_queue(struct mapped_device *md)
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{
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unsigned md_type = dm_get_md_type(md);
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struct request_queue *q;
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int err;
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@ -2738,6 +2766,10 @@ static int dm_init_request_based_blk_mq_queue(struct mapped_device *md)
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md->tag_set.numa_node = NUMA_NO_NODE;
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md->tag_set.flags = BLK_MQ_F_SHOULD_MERGE | BLK_MQ_F_SG_MERGE;
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md->tag_set.nr_hw_queues = 1;
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if (md_type == DM_TYPE_REQUEST_BASED) {
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/* make the memory for non-blk-mq clone part of the pdu */
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md->tag_set.cmd_size = sizeof(struct dm_rq_target_io) + sizeof(struct request);
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} else
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md->tag_set.cmd_size = sizeof(struct dm_rq_target_io);
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md->tag_set.driver_data = md;
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@ -2756,6 +2788,7 @@ static int dm_init_request_based_blk_mq_queue(struct mapped_device *md)
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/* backfill 'mq' sysfs registration normally done in blk_register_queue */
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blk_mq_register_disk(md->disk);
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if (md_type == DM_TYPE_REQUEST_BASED)
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init_rq_based_worker_thread(md);
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return 0;
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@ -2876,7 +2909,7 @@ static void __dm_destroy(struct mapped_device *md, bool wait)
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set_bit(DMF_FREEING, &md->flags);
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spin_unlock(&_minor_lock);
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if (dm_request_based(md))
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if (dm_request_based(md) && md->kworker_task)
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flush_kthread_worker(&md->kworker);
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/*
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@ -3130,6 +3163,7 @@ static int __dm_suspend(struct mapped_device *md, struct dm_table *map,
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*/
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if (dm_request_based(md)) {
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stop_queue(md->queue);
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if (md->kworker_task)
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flush_kthread_worker(&md->kworker);
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}
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