From cd84a62e0078dce09f4ed349bec84f86c9d54b30 Mon Sep 17 00:00:00 2001 From: Bart Van Assche Date: Wed, 26 Sep 2018 14:01:04 -0700 Subject: block, scsi: Change the preempt-only flag into a counter The RQF_PREEMPT flag is used for three purposes: - In the SCSI core, for making sure that power management requests are executed even if a device is in the "quiesced" state. - For domain validation by SCSI drivers that use the parallel port. - In the IDE driver, for IDE preempt requests. Rename "preempt-only" into "pm-only" because the primary purpose of this mode is power management. Since the power management core may but does not have to resume a runtime suspended device before performing system-wide suspend and since a later patch will set "pm-only" mode as long as a block device is runtime suspended, make it possible to set "pm-only" mode from more than one context. Since with this change scsi_device_quiesce() is no longer idempotent, make that function return early if it is called for a quiesced queue. Signed-off-by: Bart Van Assche Acked-by: Martin K. Petersen Reviewed-by: Hannes Reinecke Reviewed-by: Christoph Hellwig Reviewed-by: Ming Lei Cc: Jianchao Wang Cc: Johannes Thumshirn Cc: Alan Stern Signed-off-by: Jens Axboe --- block/blk-core.c | 35 ++++++++++++++++++----------------- 1 file changed, 18 insertions(+), 17 deletions(-) (limited to 'block/blk-core.c') diff --git a/block/blk-core.c b/block/blk-core.c index 6d4dd176bd9d..1a691f5269bb 100644 --- a/block/blk-core.c +++ b/block/blk-core.c @@ -422,24 +422,25 @@ void blk_sync_queue(struct request_queue *q) EXPORT_SYMBOL(blk_sync_queue); /** - * blk_set_preempt_only - set QUEUE_FLAG_PREEMPT_ONLY + * blk_set_pm_only - increment pm_only counter * @q: request queue pointer - * - * Returns the previous value of the PREEMPT_ONLY flag - 0 if the flag was not - * set and 1 if the flag was already set. */ -int blk_set_preempt_only(struct request_queue *q) +void blk_set_pm_only(struct request_queue *q) { - return blk_queue_flag_test_and_set(QUEUE_FLAG_PREEMPT_ONLY, q); + atomic_inc(&q->pm_only); } -EXPORT_SYMBOL_GPL(blk_set_preempt_only); +EXPORT_SYMBOL_GPL(blk_set_pm_only); -void blk_clear_preempt_only(struct request_queue *q) +void blk_clear_pm_only(struct request_queue *q) { - blk_queue_flag_clear(QUEUE_FLAG_PREEMPT_ONLY, q); - wake_up_all(&q->mq_freeze_wq); + int pm_only; + + pm_only = atomic_dec_return(&q->pm_only); + WARN_ON_ONCE(pm_only < 0); + if (pm_only == 0) + wake_up_all(&q->mq_freeze_wq); } -EXPORT_SYMBOL_GPL(blk_clear_preempt_only); +EXPORT_SYMBOL_GPL(blk_clear_pm_only); /** * __blk_run_queue_uncond - run a queue whether or not it has been stopped @@ -918,7 +919,7 @@ EXPORT_SYMBOL(blk_alloc_queue); */ int blk_queue_enter(struct request_queue *q, blk_mq_req_flags_t flags) { - const bool preempt = flags & BLK_MQ_REQ_PREEMPT; + const bool pm = flags & BLK_MQ_REQ_PREEMPT; while (true) { bool success = false; @@ -926,11 +927,11 @@ int blk_queue_enter(struct request_queue *q, blk_mq_req_flags_t flags) rcu_read_lock(); if (percpu_ref_tryget_live(&q->q_usage_counter)) { /* - * The code that sets the PREEMPT_ONLY flag is - * responsible for ensuring that that flag is globally - * visible before the queue is unfrozen. + * The code that increments the pm_only counter is + * responsible for ensuring that that counter is + * globally visible before the queue is unfrozen. */ - if (preempt || !blk_queue_preempt_only(q)) { + if (pm || !blk_queue_pm_only(q)) { success = true; } else { percpu_ref_put(&q->q_usage_counter); @@ -955,7 +956,7 @@ int blk_queue_enter(struct request_queue *q, blk_mq_req_flags_t flags) wait_event(q->mq_freeze_wq, (atomic_read(&q->mq_freeze_depth) == 0 && - (preempt || !blk_queue_preempt_only(q))) || + (pm || !blk_queue_pm_only(q))) || blk_queue_dying(q)); if (blk_queue_dying(q)) return -ENODEV; -- cgit v1.2.3-55-g7522