From ab6c756f28c741d704a7c3e04814bfc3adf6f818 Mon Sep 17 00:00:00 2001 From: Keith Busch Date: Tue, 22 Sep 2026 10:27:10 -0700 Subject: [PATCH] blk-mq: set RQF_USE_SCHED when the operation is known The cached requests are allocated for one operation but can be handed out for another. A passthrough command has RQF_USE_SCHED cleared, so using those flags for a subsequent read/write bio will insert it into the scheduler without ->prepare_request() and frees it without ->finish_request(). For kyber, this leaks the domain token acquired at dispatch and stalls the queue. Don't set RQF_USE_SCHED based on the first operation the batch happened to be allocated for. Instead, set it after the request is claimed by an operation. Introduce a helper function, blk_mq_rq_late_init() for this, and absorb blk_mq_rq_time_init() since the two run together. Fixes: 4b6a5d9cea91 ("block: enable batched allocation for blk_mq_alloc_request()") Link: https://lore.kernel.org/linux-block/20260916151655.2588-1-15815827059@163.com/ Reported-by: Henry Hu Signed-off-by: Keith Busch Reviewed-by: Christoph Hellwig Link: https://patch.msgid.link/20260922172711.1573186-1-kbusch@meta.com Signed-off-by: Jens Axboe --- block/blk-mq.c | 59 ++++++++++++++++++++++++++++----------------- block/mq-deadline.c | 2 +- 2 files changed, 38 insertions(+), 23 deletions(-) diff --git a/block/blk-mq.c b/block/blk-mq.c index a26a11c73ee3..5df6d2244db8 100644 --- a/block/blk-mq.c +++ b/block/blk-mq.c @@ -447,16 +447,6 @@ static struct request *blk_mq_rq_ctx_init(struct blk_mq_alloc_data *data, WRITE_ONCE(rq->deadline, 0); req_ref_set(rq, 1); - if (rq->rq_flags & RQF_USE_SCHED) { - struct elevator_queue *e = data->q->elevator; - - INIT_HLIST_NODE(&rq->hash); - RB_CLEAR_NODE(&rq->rb_node); - - if (e->type->ops.prepare_request) - e->type->ops.prepare_request(rq); - } - return rq; } @@ -498,6 +488,12 @@ __blk_mq_alloc_requests_batch(struct blk_mq_alloc_data *data) return rq_list_pop(data->cached_rqs); } +static bool blk_op_bypass_sched(blk_opf_t opf) +{ + return (opf & REQ_OP_MASK) == REQ_OP_FLUSH || + blk_op_is_passthrough(opf); +} + static void blk_mq_limit_depth(struct blk_mq_alloc_data *data) { struct elevator_mq_ops *ops; @@ -518,12 +514,10 @@ static void blk_mq_limit_depth(struct blk_mq_alloc_data *data) * Flush/passthrough requests are special and go directly to the * dispatch list, they are not subject to the async_depth limit. */ - if ((data->cmd_flags & REQ_OP_MASK) == REQ_OP_FLUSH || - blk_op_is_passthrough(data->cmd_flags)) + if (blk_op_bypass_sched(data->cmd_flags)) return; WARN_ON_ONCE(data->flags & BLK_MQ_REQ_RESERVED); - data->rq_flags |= RQF_USE_SCHED; /* * By default, sync requests have no limit, and async requests are @@ -534,6 +528,29 @@ static void blk_mq_limit_depth(struct blk_mq_alloc_data *data) ops->limit_depth(data->cmd_flags, data); } +/* + * Finish initializing a request once it has been claimed for an operation. + * Cached requests are allocated before that operation is known. + */ +static void blk_mq_rq_late_init(struct request *rq, u64 alloc_time_ns) +{ + struct elevator_queue *e; + + blk_mq_rq_time_init(rq, alloc_time_ns); + + if (!(rq->rq_flags & RQF_SCHED_TAGS) || (rq->rq_flags & RQF_RESV) || + blk_op_bypass_sched(rq->cmd_flags)) + return; + + rq->rq_flags |= RQF_USE_SCHED; + INIT_HLIST_NODE(&rq->hash); + RB_CLEAR_NODE(&rq->rb_node); + + e = rq->q->elevator; + if (e->type->ops.prepare_request) + e->type->ops.prepare_request(rq); +} + static struct request *__blk_mq_alloc_requests(struct blk_mq_alloc_data *data) { struct request_queue *q = data->q; @@ -562,7 +579,7 @@ retry: if (data->nr_tags > 1) { rq = __blk_mq_alloc_requests_batch(data); if (rq) { - blk_mq_rq_time_init(rq, alloc_time_ns); + blk_mq_rq_late_init(rq, alloc_time_ns); return rq; } data->nr_tags = 1; @@ -590,7 +607,7 @@ retry: if (!(data->rq_flags & RQF_SCHED_TAGS)) blk_mq_inc_active_requests(data->hctx); rq = blk_mq_rq_ctx_init(data, blk_mq_tags_from_data(data), tag); - blk_mq_rq_time_init(rq, alloc_time_ns); + blk_mq_rq_late_init(rq, alloc_time_ns); return rq; } @@ -637,8 +654,6 @@ static struct request *blk_mq_alloc_cached_request(struct request_queue *q, if (plug->nr_ios == 1) return NULL; rq = blk_mq_rq_cache_fill(q, plug, opf, flags); - if (!rq) - return NULL; } else { rq = rq_list_peek(&plug->cached_rqs); if (!rq || rq->q != q) @@ -650,11 +665,11 @@ static struct request *blk_mq_alloc_cached_request(struct request_queue *q, return NULL; rq_list_pop(&plug->cached_rqs); - blk_mq_rq_time_init(rq, blk_time_get_ns()); + rq->cmd_flags = opf; + INIT_LIST_HEAD(&rq->queuelist); + blk_mq_rq_late_init(rq, blk_time_get_ns()); } - rq->cmd_flags = opf; - INIT_LIST_HEAD(&rq->queuelist); return rq; } @@ -766,7 +781,7 @@ struct request *blk_mq_alloc_request_hctx(struct request_queue *q, if (!(data.rq_flags & RQF_SCHED_TAGS)) blk_mq_inc_active_requests(data.hctx); rq = blk_mq_rq_ctx_init(&data, blk_mq_tags_from_data(&data), tag); - blk_mq_rq_time_init(rq, alloc_time_ns); + blk_mq_rq_late_init(rq, alloc_time_ns); rq->__data_len = 0; rq->phys_gap_bit = 0; rq->__sector = (sector_t) -1; @@ -3163,9 +3178,9 @@ void blk_mq_submit_bio(struct bio *bio) new_request: if (rq) { rq_qos_throttle(rq->q, bio); - blk_mq_rq_time_init(rq, blk_time_get_ns()); rq->cmd_flags = bio->bi_opf; INIT_LIST_HEAD(&rq->queuelist); + blk_mq_rq_late_init(rq, blk_time_get_ns()); } else { rq = blk_mq_get_new_requests(q, plug, bio); if (unlikely(!rq)) { diff --git a/block/mq-deadline.c b/block/mq-deadline.c index 5f643c0ce2a8..e5db1ee097c3 100644 --- a/block/mq-deadline.c +++ b/block/mq-deadline.c @@ -685,7 +685,7 @@ static void dd_insert_requests(struct blk_mq_hw_ctx *hctx, blk_mq_free_requests(&free); } -/* Callback from inside blk_mq_rq_ctx_init(). */ +/* Callback from inside blk_mq_rq_late_init(). */ static void dd_prepare_request(struct request *rq) { rq->elv.priv[0] = NULL;