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04225d13ae
Move scheduler tags (sched_tags) allocation and deallocation outside both the ->elevator_lock and ->freeze_lock when updating nr_hw_queues. This change breaks the dependency chain from the percpu allocator lock to the elevator lock, helping to prevent potential deadlocks, as observed in the reported lockdep splat[1]. This commit introduces batch allocation and deallocation helpers for sched_tags, which are now used from within __blk_mq_update_nr_hw_queues routine while iterating through the tagset. With this change, all sched_tags memory management is handled entirely outside the ->elevator_lock and the ->freeze_lock context, thereby eliminating the lock dependency that could otherwise manifest during nr_hw_queues updates. [1] https://lore.kernel.org/all/0659ea8d-a463-47c8-9180-43c719e106eb@linux.ibm.com/ Reported-by: Stefan Haberland <sth@linux.ibm.com> Closes: https://lore.kernel.org/all/0659ea8d-a463-47c8-9180-43c719e106eb@linux.ibm.com/ Reviewed-by: Ming Lei <ming.lei@redhat.com> Reviewed-by: Christoph Hellwig <hch@lst.de> Reviewed-by: Hannes Reinecke <hare@suse.de> Signed-off-by: Nilay Shroff <nilay@linux.ibm.com> Link: https://lore.kernel.org/r/20250730074614.2537382-4-nilay@linux.ibm.com Signed-off-by: Jens Axboe <axboe@kernel.dk>
95 lines
2.7 KiB
C
95 lines
2.7 KiB
C
/* SPDX-License-Identifier: GPL-2.0 */
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#ifndef BLK_MQ_SCHED_H
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#define BLK_MQ_SCHED_H
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#include "elevator.h"
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#include "blk-mq.h"
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#define MAX_SCHED_RQ (16 * BLKDEV_DEFAULT_RQ)
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bool blk_mq_sched_try_merge(struct request_queue *q, struct bio *bio,
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unsigned int nr_segs, struct request **merged_request);
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bool blk_mq_sched_bio_merge(struct request_queue *q, struct bio *bio,
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unsigned int nr_segs);
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bool blk_mq_sched_try_insert_merge(struct request_queue *q, struct request *rq,
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struct list_head *free);
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void blk_mq_sched_mark_restart_hctx(struct blk_mq_hw_ctx *hctx);
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void __blk_mq_sched_restart(struct blk_mq_hw_ctx *hctx);
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void blk_mq_sched_dispatch_requests(struct blk_mq_hw_ctx *hctx);
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int blk_mq_init_sched(struct request_queue *q, struct elevator_type *e,
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struct elevator_tags *et);
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void blk_mq_exit_sched(struct request_queue *q, struct elevator_queue *e);
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void blk_mq_sched_free_rqs(struct request_queue *q);
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struct elevator_tags *blk_mq_alloc_sched_tags(struct blk_mq_tag_set *set,
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unsigned int nr_hw_queues);
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int blk_mq_alloc_sched_tags_batch(struct xarray *et_table,
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struct blk_mq_tag_set *set, unsigned int nr_hw_queues);
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void blk_mq_free_sched_tags(struct elevator_tags *et,
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struct blk_mq_tag_set *set);
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void blk_mq_free_sched_tags_batch(struct xarray *et_table,
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struct blk_mq_tag_set *set);
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static inline void blk_mq_sched_restart(struct blk_mq_hw_ctx *hctx)
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{
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if (test_bit(BLK_MQ_S_SCHED_RESTART, &hctx->state))
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__blk_mq_sched_restart(hctx);
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}
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static inline bool bio_mergeable(struct bio *bio)
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{
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return !(bio->bi_opf & REQ_NOMERGE_FLAGS);
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}
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static inline bool
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blk_mq_sched_allow_merge(struct request_queue *q, struct request *rq,
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struct bio *bio)
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{
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if (rq->rq_flags & RQF_USE_SCHED) {
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struct elevator_queue *e = q->elevator;
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if (e->type->ops.allow_merge)
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return e->type->ops.allow_merge(q, rq, bio);
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}
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return true;
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}
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static inline void blk_mq_sched_completed_request(struct request *rq, u64 now)
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{
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if (rq->rq_flags & RQF_USE_SCHED) {
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struct elevator_queue *e = rq->q->elevator;
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if (e->type->ops.completed_request)
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e->type->ops.completed_request(rq, now);
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}
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}
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static inline void blk_mq_sched_requeue_request(struct request *rq)
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{
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if (rq->rq_flags & RQF_USE_SCHED) {
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struct request_queue *q = rq->q;
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struct elevator_queue *e = q->elevator;
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if (e->type->ops.requeue_request)
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e->type->ops.requeue_request(rq);
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}
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}
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static inline bool blk_mq_sched_has_work(struct blk_mq_hw_ctx *hctx)
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{
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struct elevator_queue *e = hctx->queue->elevator;
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if (e && e->type->ops.has_work)
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return e->type->ops.has_work(hctx);
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return false;
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}
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static inline bool blk_mq_sched_needs_restart(struct blk_mq_hw_ctx *hctx)
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{
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return test_bit(BLK_MQ_S_SCHED_RESTART, &hctx->state);
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}
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#endif
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