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blk-mq-sched: add new parameter nr_requests in blk_mq_alloc_sched_tags()

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This helper only support to allocate the default number of requests,
add a new parameter to support specific number of requests.

Prepare to fix potential deadlock in the case nr_requests grow.

Signed-off-by: Yu Kuai <yukuai3@huawei.com>
Reviewed-by: Nilay Shroff <nilay@linux.ibm.com>
Signed-off-by: Jens Axboe <axboe@kernel.dk>
This commit is contained in:
Yu Kuai
2025-09-10 16:04:42 +08:00
committed by Jens Axboe
parent e632004044
commit 6293e336f6
4 changed files with 19 additions and 11 deletions
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14
block/blk-mq-sched.c
View File

@@ -454,7 +454,7 @@ void blk_mq_free_sched_tags_batch(struct xarray *et_table,
} }
struct elevator_tags *blk_mq_alloc_sched_tags(struct blk_mq_tag_set *set, struct elevator_tags *blk_mq_alloc_sched_tags(struct blk_mq_tag_set *set,
unsigned int nr_hw_queues) unsigned int nr_hw_queues, unsigned int nr_requests)
{ {
unsigned int nr_tags; unsigned int nr_tags;
int i; int i;
@@ -470,13 +470,8 @@ struct elevator_tags *blk_mq_alloc_sched_tags(struct blk_mq_tag_set *set,
nr_tags * sizeof(struct blk_mq_tags *), gfp); nr_tags * sizeof(struct blk_mq_tags *), gfp);
if (!et) if (!et)
return NULL; return NULL;
/*
* Default to double of smaller one between hw queue_depth and et->nr_requests = nr_requests;
* 128, since we don't split into sync/async like the old code
* did. Additionally, this is a per-hw queue depth.
*/
et->nr_requests = 2 * min_t(unsigned int, set->queue_depth,
BLKDEV_DEFAULT_RQ);
et->nr_hw_queues = nr_hw_queues; et->nr_hw_queues = nr_hw_queues;
if (blk_mq_is_shared_tags(set->flags)) { if (blk_mq_is_shared_tags(set->flags)) {
@@ -521,7 +516,8 @@ int blk_mq_alloc_sched_tags_batch(struct xarray *et_table,
* concurrently. * concurrently.
*/ */
if (q->elevator) { if (q->elevator) {
et = blk_mq_alloc_sched_tags(set, nr_hw_queues); et = blk_mq_alloc_sched_tags(set, nr_hw_queues,
blk_mq_default_nr_requests(set));
if (!et) if (!et)
goto out_unwind; goto out_unwind;
if (xa_insert(et_table, q->id, et, gfp)) if (xa_insert(et_table, q->id, et, gfp))

2
block/blk-mq-sched.h
View File

@@ -24,7 +24,7 @@ void blk_mq_exit_sched(struct request_queue *q, struct elevator_queue *e);
void blk_mq_sched_free_rqs(struct request_queue *q); void blk_mq_sched_free_rqs(struct request_queue *q);
struct elevator_tags *blk_mq_alloc_sched_tags(struct blk_mq_tag_set *set, struct elevator_tags *blk_mq_alloc_sched_tags(struct blk_mq_tag_set *set,
unsigned int nr_hw_queues); unsigned int nr_hw_queues, unsigned int nr_requests);
int blk_mq_alloc_sched_tags_batch(struct xarray *et_table, int blk_mq_alloc_sched_tags_batch(struct xarray *et_table,
struct blk_mq_tag_set *set, unsigned int nr_hw_queues); struct blk_mq_tag_set *set, unsigned int nr_hw_queues);
void blk_mq_free_sched_tags(struct elevator_tags *et, void blk_mq_free_sched_tags(struct elevator_tags *et,

11
block/blk-mq.h
View File

@@ -109,6 +109,17 @@ static inline struct blk_mq_hw_ctx *blk_mq_map_queue(blk_opf_t opf,
return ctx->hctxs[blk_mq_get_hctx_type(opf)]; return ctx->hctxs[blk_mq_get_hctx_type(opf)];
} }
/*
* Default to double of smaller one between hw queue_depth and
* 128, since we don't split into sync/async like the old code
* did. Additionally, this is a per-hw queue depth.
*/
static inline unsigned int blk_mq_default_nr_requests(
struct blk_mq_tag_set *set)
{
return 2 * min_t(unsigned int, set->queue_depth, BLKDEV_DEFAULT_RQ);
}
/* /*
* sysfs helpers * sysfs helpers
*/ */

3
block/elevator.c
View File

@@ -669,7 +669,8 @@ static int elevator_change(struct request_queue *q, struct elv_change_ctx *ctx)
lockdep_assert_held(&set->update_nr_hwq_lock); lockdep_assert_held(&set->update_nr_hwq_lock);
if (strncmp(ctx->name, "none", 4)) { if (strncmp(ctx->name, "none", 4)) {
ctx->et = blk_mq_alloc_sched_tags(set, set->nr_hw_queues); ctx->et = blk_mq_alloc_sched_tags(set, set->nr_hw_queues,
blk_mq_default_nr_requests(set));
if (!ctx->et) if (!ctx->et)
return -ENOMEM; return -ENOMEM;
} }