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block, scsi: Change the preempt-only flag into a counter

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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 <bvanassche@acm.org>
Acked-by: Martin K. Petersen <martin.petersen@oracle.com>
Reviewed-by: Hannes Reinecke <hare@suse.com>
Reviewed-by: Christoph Hellwig <hch@lst.de>
Reviewed-by: Ming 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: Jens Axboe <axboe@kernel.dk>
This commit is contained in:
Bart Van Assche 2018-09-26 14:01:04 -07:00 committed by Jens Axboe
parent bca6b067b0
commit cd84a62e00
4 changed files with 43 additions and 27 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

35
block/blk-core.c
View File

@ -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;

10
block/blk-mq-debugfs.c
View File

@ -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 },

11
drivers/scsi/scsi_lib.c
View File

@ -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);

14
include/linux/blkdev.h
View File

@ -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)
{