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block: don't acquire ->elevator_lock in blk_mq_map_swqueue and blk_mq_realloc_hw_ctxs 

Both blk_mq_map_swqueue() and blk_mq_realloc_hw_ctxs() are called before
the request queue is added to tagset list, so the two won't run concurrently
with blk_mq_update_nr_hw_queues().

When the two functions are only called from queue initialization or
blk_mq_update_nr_hw_queues(), elevator switch can't happen.

So remove ->elevator_lock uses from the two functions.

Reviewed-by: Hannes Reinecke <hare@suse.de>
Reviewed-by: Nilay Shroff <nilay@linux.ibm.com>
Signed-off-by: Ming Lei <ming.lei@redhat.com>
Reviewed-by: Christoph Hellwig <hch@lst.de>
Link: https://lore.kernel.org/r/20250505141805.2751237-24-ming.lei@redhat.com
Signed-off-by: Jens Axboe <axboe@kernel.dk>
This commit is contained in:
Ming Lei 2025-05-05 22:18:01 +08:00 committed by Jens Axboe
parent 9dc7a882ce
commit 0a47d2b433
1 changed files with 4 additions and 15 deletions
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19
block/blk-mq.c
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@ -4156,8 +4156,6 @@ static void blk_mq_map_swqueue(struct request_queue *q)
struct blk_mq_ctx *ctx; struct blk_mq_ctx *ctx;
struct blk_mq_tag_set *set = q->tag_set; struct blk_mq_tag_set *set = q->tag_set;
mutex_lock(&q->elevator_lock);
queue_for_each_hw_ctx(q, hctx, i) { queue_for_each_hw_ctx(q, hctx, i) {
cpumask_clear(hctx->cpumask); cpumask_clear(hctx->cpumask);
hctx->nr_ctx = 0; hctx->nr_ctx = 0;
@ -4262,8 +4260,6 @@ static void blk_mq_map_swqueue(struct request_queue *q)
hctx->next_cpu = blk_mq_first_mapped_cpu(hctx); hctx->next_cpu = blk_mq_first_mapped_cpu(hctx);
hctx->next_cpu_batch = BLK_MQ_CPU_WORK_BATCH; hctx->next_cpu_batch = BLK_MQ_CPU_WORK_BATCH;
} }
mutex_unlock(&q->elevator_lock);
} }
/* /*
@ -4567,16 +4563,9 @@ static void __blk_mq_realloc_hw_ctxs(struct blk_mq_tag_set *set,
} }
static void blk_mq_realloc_hw_ctxs(struct blk_mq_tag_set *set, static void blk_mq_realloc_hw_ctxs(struct blk_mq_tag_set *set,
struct request_queue *q, bool lock) struct request_queue *q)
{ {
if (lock) { __blk_mq_realloc_hw_ctxs(set, q);
/* protect against switching io scheduler */
mutex_lock(&q->elevator_lock);
__blk_mq_realloc_hw_ctxs(set, q);
mutex_unlock(&q->elevator_lock);
} else {
__blk_mq_realloc_hw_ctxs(set, q);
}
/* unregister cpuhp callbacks for exited hctxs */ /* unregister cpuhp callbacks for exited hctxs */
blk_mq_remove_hw_queues_cpuhp(q); blk_mq_remove_hw_queues_cpuhp(q);
@ -4608,7 +4597,7 @@ int blk_mq_init_allocated_queue(struct blk_mq_tag_set *set,
xa_init(&q->hctx_table); xa_init(&q->hctx_table);
blk_mq_realloc_hw_ctxs(set, q, false); blk_mq_realloc_hw_ctxs(set, q);
if (!q->nr_hw_queues) if (!q->nr_hw_queues)
goto err_hctxs; goto err_hctxs;
@ -5019,7 +5008,7 @@ static void __blk_mq_update_nr_hw_queues(struct blk_mq_tag_set *set,
fallback: fallback:
blk_mq_update_queue_map(set); blk_mq_update_queue_map(set);
list_for_each_entry(q, &set->tag_list, tag_set_list) { list_for_each_entry(q, &set->tag_list, tag_set_list) {
blk_mq_realloc_hw_ctxs(set, q, true); blk_mq_realloc_hw_ctxs(set, q);
if (q->nr_hw_queues != set->nr_hw_queues) { if (q->nr_hw_queues != set->nr_hw_queues) {
int i = prev_nr_hw_queues; int i = prev_nr_hw_queues;