Commit cd84a62e authored by Bart Van Assche's avatar Bart Van Assche Committed by Jens Axboe
Browse files

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: default avatarBart Van Assche <bvanassche@acm.org>
Acked-by: default avatarMartin K. Petersen <martin.petersen@oracle.com>
Reviewed-by: default avatarHannes Reinecke <hare@suse.com>
Reviewed-by: default avatarChristoph Hellwig <hch@lst.de>
Reviewed-by: default avatarMing Lei <ming.lei@redhat.com>
Cc: Jianchao Wang <jianchao.w.wang@oracle.com>
Cc: Johannes Thumshirn <jthumshirn@suse.de>
Cc: Alan Stern <stern@rowland.harvard.edu>
Signed-off-by: default avatarJens Axboe <axboe@kernel.dk>
parent bca6b067

block/blk-core.c

+18 −17
Original line number Diff line number Diff line
@@ -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);

	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;

block/blk-mq-debugfs.c

+9 −1
Original line number Diff line number Diff line
@@ -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 },

drivers/scsi/scsi_lib.c

+7 −4
Original line number Diff line number Diff line
@@ -3046,11 +3046,14 @@ 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/.
@@ -3063,7 +3066,7 @@ 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;
@@ -3088,7 +3091,7 @@ void scsi_device_resume(struct scsi_device *sdev) 
	mutex_lock(&sdev->state_mutex);

	WARN_ON_ONCE(!sdev->quiesced_by);

	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);

include/linux/blkdev.h

+9 −5
Original line number Diff line number Diff line
@@ -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)

{

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