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authorBart Van Assche <bvanassche@acm.org>2018-09-26 14:01:04 -0700
committerJens Axboe <axboe@kernel.dk>2018-09-26 15:11:28 -0600
commitcd84a62e0078dce09f4ed349bec84f86c9d54b30 (patch)
tree2cdd58e3abebc23c86351ca12815b751a62bdc1a /block/blk-core.c
parentbca6b067b0b269a7b8ba129e2a918309ca8b4a55 (diff)
downloadlinux-cd84a62e0078dce09f4ed349bec84f86c9d54b30.tar.bz2
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 <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>
Diffstat (limited to 'block/blk-core.c')
-rw-r--r--block/blk-core.c35
1 files changed, 18 insertions, 17 deletions
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;