[PATCH V8 1/4] block: use test_and_{clear|test}_bit to set/clear QUEUE_FLAG_QUIESCED

[Ming Lei]

Prepare for replacing srcu with percpu-refcount for implementing queue
quiesce.

The following patch needs to avoid duplicated quiesce action for
BLK_MQ_F_BLOCKING, so use test_and_{clear|test}_bit to set/clear
QUEUE_FLAG_QUIESCED.

Signed-off-by: Ming Lei <ming.lei at redhat.com>
Cc: Sagi Grimberg <sagi at grimberg.me>
Cc: Bart Van Assche <bvanassche at acm.org>
Cc: Johannes Thumshirn <Johannes.Thumshirn at wdc.com>
Cc: Chao Leng <lengchao at huawei.com>
Reviewed-by: Hannes Reinecke <hare at suse.de>
Tested-by: Sagi Grimberg <sagi at grimberg.me>
Reviewed-by: Keith Busch <kbusch at kernel.org>
---
 block/blk-core.c | 13 +++++++++++++
 block/blk-mq.c   | 11 ++++++++---
 block/blk.h      |  2 ++
 3 files changed, 23 insertions(+), 3 deletions(-)

diff --git a/block/blk-core.c b/block/blk-core.c
index ac00d2fa4eb4..abdcc0a57c75 100644
--- a/block/blk-core.c
+++ b/block/blk-core.c
@@ -107,6 +107,19 @@ bool blk_queue_flag_test_and_set(unsigned int flag, struct request_queue *q)
 }
 EXPORT_SYMBOL_GPL(blk_queue_flag_test_and_set);
 
+/**
+ * blk_queue_flag_test_and_clear - atomically test and clear a queue flag
+ * @flag: flag to be clear
+ * @q: request queue
+ *
+ * Returns the previous value of @flag - 0 if the flag was not set and 1 if
+ * the flag was set.
+ */
+bool blk_queue_flag_test_and_clear(unsigned int flag, struct request_queue *q)
+{
+	return test_and_clear_bit(flag, &q->queue_flags);
+}
+
 void blk_rq_init(struct request_queue *q, struct request *rq)
 {
 	memset(rq, 0, sizeof(*rq));
diff --git a/block/blk-mq.c b/block/blk-mq.c
index 696450257ac1..6ff538d74b62 100644
--- a/block/blk-mq.c
+++ b/block/blk-mq.c
@@ -199,13 +199,18 @@ void blk_mq_unfreeze_queue(struct request_queue *q)
 }
 EXPORT_SYMBOL_GPL(blk_mq_unfreeze_queue);
 
+static bool __blk_mq_quiesce_queue_nowait(struct request_queue *q)
+{
+	return blk_queue_flag_test_and_set(QUEUE_FLAG_QUIESCED, q);
+}
+
 /*
  * FIXME: replace the scsi_internal_device_*block_nowait() calls in the
  * mpt3sas driver such that this function can be removed.
  */
 void blk_mq_quiesce_queue_nowait(struct request_queue *q)
 {
-	blk_queue_flag_set(QUEUE_FLAG_QUIESCED, q);
+	__blk_mq_quiesce_queue_nowait(q);
 }
 EXPORT_SYMBOL_GPL(blk_mq_quiesce_queue_nowait);
 
@@ -224,7 +229,7 @@ void blk_mq_quiesce_queue(struct request_queue *q)
 	unsigned int i;
 	bool rcu = false;
 
-	blk_mq_quiesce_queue_nowait(q);
+	__blk_mq_quiesce_queue_nowait(q);
 
 	queue_for_each_hw_ctx(q, hctx, i) {
 		if (hctx->flags & BLK_MQ_F_BLOCKING)
@@ -246,7 +251,7 @@ EXPORT_SYMBOL_GPL(blk_mq_quiesce_queue);
  */
 void blk_mq_unquiesce_queue(struct request_queue *q)
 {
-	blk_queue_flag_clear(QUEUE_FLAG_QUIESCED, q);
+	blk_queue_flag_test_and_clear(QUEUE_FLAG_QUIESCED, q);
 
 	/* dispatch requests which are inserted during quiescing */
 	blk_mq_run_hw_queues(q, true);
diff --git a/block/blk.h b/block/blk.h
index dfab98465db9..f925268ce7fd 100644
--- a/block/blk.h
+++ b/block/blk.h
@@ -444,4 +444,6 @@ int bio_add_hw_page(struct request_queue *q, struct bio *bio,
 		struct page *page, unsigned int len, unsigned int offset,
 		unsigned int max_sectors, bool *same_page);
 
+bool blk_queue_flag_test_and_clear(unsigned int flag, struct request_queue *q);
+
 #endif /* BLK_INTERNAL_H */
-- 
2.25.2