>From 25f02ed7ab7b2308fd18b89d180c0c613e55d416 Mon Sep 17 00:00:00 2001 From: Bart Van Assche Date: Tue, 27 Sep 2016 10:52:36 -0700 Subject: [PATCH] blk-mq: Introduce blk_mq_quiesce_queue() blk_mq_quiesce_queue() waits until ongoing .queue_rq() invocations have finished. This function does *not* wait until all outstanding requests have finished (this means invocation of request.end_io()). Signed-off-by: Bart Van Assche Cc: Ming Lei Cc: Hannes Reinecke Cc: Johannes Thumshirn --- block/blk-mq.c | 40 ++++++++++++++++++++++++++++++++++------ include/linux/blk-mq.h | 3 +++ include/linux/blkdev.h | 1 + 3 files changed, 38 insertions(+), 6 deletions(-) diff --git a/block/blk-mq.c b/block/blk-mq.c index d8c45de..38ae685 100644 --- a/block/blk-mq.c +++ b/block/blk-mq.c @@ -115,6 +115,23 @@ void blk_mq_unfreeze_queue(struct request_queue *q) } EXPORT_SYMBOL_GPL(blk_mq_unfreeze_queue); +/** + * blk_mq_quiesce_queue() - wait until all ongoing queue_rq calls have finished + * + * Note: this function does not prevent that the struct request end_io() + * callback function is invoked. Additionally, it is not prevented that + * new queue_rq() calls occur unless the queue has been stopped first. + */ +void blk_mq_quiesce_queue(struct request_queue *q) +{ + struct blk_mq_hw_ctx *hctx; + unsigned int i; + + queue_for_each_hw_ctx(q, hctx, i) + synchronize_srcu(&hctx->queue_rq_srcu); +} +EXPORT_SYMBOL_GPL(blk_mq_quiesce_queue); + void blk_mq_wake_waiters(struct request_queue *q) { struct blk_mq_hw_ctx *hctx; @@ -789,11 +806,13 @@ static void __blk_mq_run_hw_queue(struct blk_mq_hw_ctx *hctx) LIST_HEAD(rq_list); LIST_HEAD(driver_list); struct list_head *dptr; - int queued; + int queued, srcu_idx; if (unlikely(test_bit(BLK_MQ_S_STOPPED, &hctx->state))) return; + srcu_idx = srcu_read_lock(&hctx->queue_rq_srcu); + WARN_ON(!cpumask_test_cpu(raw_smp_processor_id(), hctx->cpumask) && cpu_online(hctx->next_cpu)); @@ -885,6 +904,8 @@ static void __blk_mq_run_hw_queue(struct blk_mq_hw_ctx *hctx) **/ blk_mq_run_hw_queue(hctx, true); } + + srcu_read_unlock(&hctx->queue_rq_srcu, srcu_idx); } /* @@ -1298,7 +1319,7 @@ static blk_qc_t blk_mq_make_request(struct request_queue *q, struct bio *bio) const int is_flush_fua = bio->bi_opf & (REQ_PREFLUSH | REQ_FUA); struct blk_map_ctx data; struct request *rq; - unsigned int request_count = 0; + unsigned int request_count = 0, srcu_idx; struct blk_plug *plug; struct request *same_queue_rq = NULL; blk_qc_t cookie; @@ -1341,7 +1362,7 @@ static blk_qc_t blk_mq_make_request(struct request_queue *q, struct bio *bio) blk_mq_bio_to_request(rq, bio); /* - * We do limited pluging. If the bio can be merged, do that. + * We do limited plugging. If the bio can be merged, do that. * Otherwise the existing request in the plug list will be * issued. So the plug list will have one request at most */ @@ -1361,9 +1382,12 @@ static blk_qc_t blk_mq_make_request(struct request_queue *q, struct bio *bio) blk_mq_put_ctx(data.ctx); if (!old_rq) goto done; - if (!blk_mq_direct_issue_request(old_rq, &cookie)) - goto done; - blk_mq_insert_request(old_rq, false, true, true); + + srcu_idx = srcu_read_lock(&data.hctx->queue_rq_srcu); + if (blk_mq_direct_issue_request(old_rq, &cookie) != 0) + blk_mq_insert_request(old_rq, false, true, true); + srcu_read_unlock(&data.hctx->queue_rq_srcu, srcu_idx); + goto done; } @@ -1659,6 +1683,8 @@ static void blk_mq_exit_hctx(struct request_queue *q, if (set->ops->exit_hctx) set->ops->exit_hctx(hctx, hctx_idx); + cleanup_srcu_struct(&hctx->queue_rq_srcu); + blk_mq_unregister_cpu_notifier(&hctx->cpu_notifier); blk_free_flush_queue(hctx->fq); sbitmap_free(&hctx->ctx_map); @@ -1741,6 +1767,8 @@ static int blk_mq_init_hctx(struct request_queue *q, flush_start_tag + hctx_idx, node)) goto free_fq; + init_srcu_struct(&hctx->queue_rq_srcu); + return 0; free_fq: diff --git a/include/linux/blk-mq.h b/include/linux/blk-mq.h index 368c460d..b2ccd3c 100644 --- a/include/linux/blk-mq.h +++ b/include/linux/blk-mq.h @@ -3,6 +3,7 @@ #include #include +#include struct blk_mq_tags; struct blk_flush_queue; @@ -41,6 +42,8 @@ struct blk_mq_hw_ctx { struct blk_mq_tags *tags; + struct srcu_struct queue_rq_srcu; + unsigned long queued; unsigned long run; #define BLK_MQ_MAX_DISPATCH_ORDER 7 diff --git a/include/linux/blkdev.h b/include/linux/blkdev.h index c47c358..8259d87 100644 --- a/include/linux/blkdev.h +++ b/include/linux/blkdev.h @@ -824,6 +824,7 @@ extern void __blk_run_queue(struct request_queue *q); extern void __blk_run_queue_uncond(struct request_queue *q); extern void blk_run_queue(struct request_queue *); extern void blk_run_queue_async(struct request_queue *q); +extern void blk_mq_quiesce_queue(struct request_queue *q); extern int blk_rq_map_user(struct request_queue *, struct request *, struct rq_map_data *, void __user *, unsigned long, gfp_t); -- 2.9.3