From c58a6507363b7d9b5ac3aefeb4b54172eafa3bc6 Mon Sep 17 00:00:00 2001 From: Bart Van Assche Date: Wed, 26 Sep 2018 14:01:04 -0700 Subject: [PATCH] block, scsi: Change the preempt-only flag into a counter commit cd84a62e0078dce09f4ed349bec84f86c9d54b30 upstream. 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 Signed-off-by: Greg Kroah-Hartman --- block/blk-core.c | 35 ++++++++++++++++++----------------- block/blk-mq-debugfs.c | 10 +++++++++- drivers/scsi/scsi_lib.c | 11 +++++++---- include/linux/blkdev.h | 14 +++++++++----- 4 files changed, 43 insertions(+), 27 deletions(-) diff --git a/block/blk-core.c b/block/blk-core.c index 9ca703b..4a3e1f4 100644 --- a/block/blk-core.c +++ b/block/blk-core.c @@ -421,24 +421,25 @@ 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 @@ -916,7 +917,7 @@ 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; @@ -924,11 +925,11 @@ 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); @@ -953,7 +954,7 @@ 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; diff --git a/block/blk-mq-debugfs.c b/block/blk-mq-debugfs.c index cb1e6cf..a5ea868 100644 --- a/block/blk-mq-debugfs.c +++ b/block/blk-mq-debugfs.c @@ -102,6 +102,14 @@ static int blk_flags_show(struct seq_file *m, const unsigned long flags, return 0; } +static int queue_pm_only_show(void *data, struct seq_file *m) +{ + struct request_queue *q = data; + + seq_printf(m, "%d\n", atomic_read(&q->pm_only)); + return 0; +} + #define QUEUE_FLAG_NAME(name) [QUEUE_FLAG_##name] = #name static const char *const blk_queue_flag_name[] = { QUEUE_FLAG_NAME(QUEUED), @@ -132,7 +140,6 @@ static const char *const blk_queue_flag_name[] = { QUEUE_FLAG_NAME(REGISTERED), QUEUE_FLAG_NAME(SCSI_PASSTHROUGH), QUEUE_FLAG_NAME(QUIESCED), - QUEUE_FLAG_NAME(PREEMPT_ONLY), }; #undef QUEUE_FLAG_NAME @@ -209,6 +216,7 @@ static ssize_t queue_write_hint_store(void *data, const char __user *buf, static const struct blk_mq_debugfs_attr blk_mq_debugfs_queue_attrs[] = { { "poll_stat", 0400, queue_poll_stat_show }, { "requeue_list", 0400, .seq_ops = &queue_requeue_list_seq_ops }, + { "pm_only", 0600, queue_pm_only_show, NULL }, { "state", 0600, queue_state_show, queue_state_write }, { "write_hints", 0600, queue_write_hint_show, queue_write_hint_store }, { "zone_wlock", 0400, queue_zone_wlock_show, NULL }, diff --git a/drivers/scsi/scsi_lib.c b/drivers/scsi/scsi_lib.c index 32652b2..83bbcdb6 100644 --- a/drivers/scsi/scsi_lib.c +++ b/drivers/scsi/scsi_lib.c @@ -3059,11 +3059,14 @@ scsi_device_quiesce(struct scsi_device *sdev) */ WARN_ON_ONCE(sdev->quiesced_by && sdev->quiesced_by != current); - blk_set_preempt_only(q); + if (sdev->quiesced_by == current) + return 0; + + blk_set_pm_only(q); blk_mq_freeze_queue(q); /* - * Ensure that the effect of blk_set_preempt_only() will be visible + * Ensure that the effect of blk_set_pm_only() will be visible * for percpu_ref_tryget() callers that occur after the queue * unfreeze even if the queue was already frozen before this function * was called. See also https://lwn.net/Articles/573497/. @@ -3076,7 +3079,7 @@ scsi_device_quiesce(struct scsi_device *sdev) if (err == 0) sdev->quiesced_by = current; else - blk_clear_preempt_only(q); + blk_clear_pm_only(q); mutex_unlock(&sdev->state_mutex); return err; @@ -3100,7 +3103,7 @@ void scsi_device_resume(struct scsi_device *sdev) */ mutex_lock(&sdev->state_mutex); sdev->quiesced_by = NULL; - blk_clear_preempt_only(sdev->request_queue); + blk_clear_pm_only(sdev->request_queue); if (sdev->sdev_state == SDEV_QUIESCE) scsi_device_set_state(sdev, SDEV_RUNNING); mutex_unlock(&sdev->state_mutex); diff --git a/include/linux/blkdev.h b/include/linux/blkdev.h index 6980014..d51e10f 100644 --- a/include/linux/blkdev.h +++ b/include/linux/blkdev.h @@ -504,6 +504,12 @@ struct request_queue { * various queue flags, see QUEUE_* below */ unsigned long queue_flags; + /* + * Number of contexts that have called blk_set_pm_only(). If this + * counter is above zero then only RQF_PM and RQF_PREEMPT requests are + * processed. + */ + atomic_t pm_only; /* * ida allocated id for this queue. Used to index queues from @@ -698,7 +704,6 @@ struct request_queue { #define QUEUE_FLAG_REGISTERED 26 /* queue has been registered to a disk */ #define QUEUE_FLAG_SCSI_PASSTHROUGH 27 /* queue supports SCSI commands */ #define QUEUE_FLAG_QUIESCED 28 /* queue has been quiesced */ -#define QUEUE_FLAG_PREEMPT_ONLY 29 /* only process REQ_PREEMPT requests */ #define QUEUE_FLAG_DEFAULT ((1 << QUEUE_FLAG_IO_STAT) | \ (1 << QUEUE_FLAG_SAME_COMP) | \ @@ -736,12 +741,11 @@ bool blk_queue_flag_test_and_clear(unsigned int flag, struct request_queue *q); ((rq)->cmd_flags & (REQ_FAILFAST_DEV|REQ_FAILFAST_TRANSPORT| \ REQ_FAILFAST_DRIVER)) #define blk_queue_quiesced(q) test_bit(QUEUE_FLAG_QUIESCED, &(q)->queue_flags) -#define blk_queue_preempt_only(q) \ - test_bit(QUEUE_FLAG_PREEMPT_ONLY, &(q)->queue_flags) +#define blk_queue_pm_only(q) atomic_read(&(q)->pm_only) #define blk_queue_fua(q) test_bit(QUEUE_FLAG_FUA, &(q)->queue_flags) -extern int blk_set_preempt_only(struct request_queue *q); -extern void blk_clear_preempt_only(struct request_queue *q); +extern void blk_set_pm_only(struct request_queue *q); +extern void blk_clear_pm_only(struct request_queue *q); static inline int queue_in_flight(struct request_queue *q) { -- 2.7.4