[PATCH v2 2/4] block: Add the QUEUE_PREEMPT_ONLY request queue flag

Bart Van Assche
2017-09-21T21:22:53Z

This flag will be used in the next patch to let the block layer
core know whether or not a SCSI request queue has been quiesced.
A quiesced SCSI queue namely only processes RQF_PREEMPT requests.

Signed-off-by: Bart Van Assche <bart.vanassche@wdc.com>
Cc: Ming Lei <ming.lei@redhat.com>
Cc: Christoph Hellwig <hch@lst.de>
Cc: Hannes Reinecke <hare@suse.com>
Cc: Johannes Thumshirn <jthumshirn@suse.de>
---
block/blk-core.c | 13 +++++++++++++
include/linux/blkdev.h | 5 +++++
2 files changed, 18 insertions(+)

diff --git a/block/blk-core.c b/block/blk-core.c
index d709c0e3a2ac..1ac337712bbd 100644
--- a/block/blk-core.c
+++ b/block/blk-core.c
@@ -346,6 +346,19 @@ void blk_sync_queue(struct request_queue *q)
}
EXPORT_SYMBOL(blk_sync_queue);

+void blk_set_preempt_only(struct request_queue *q, bool preempt_only)
+{
+ unsigned long flags;
+
+ spin_lock_irqsave(q->queue_lock, flags);
+ if (preempt_only)
+ queue_flag_set(QUEUE_FLAG_PREEMPT_ONLY, q);
+ else
+ queue_flag_clear(QUEUE_FLAG_PREEMPT_ONLY, q);
+ spin_unlock_irqrestore(q->queue_lock, flags);
+}
+EXPORT_SYMBOL(blk_set_preempt_only);
+
/**
* __blk_run_queue_uncond - run a queue whether or not it has been stopped
* @q: The queue to run
diff --git a/include/linux/blkdev.h b/include/linux/blkdev.h
index cd26901a6e25..5bd87599eed0 100644
--- a/include/linux/blkdev.h
+++ b/include/linux/blkdev.h
@@ -627,6 +627,7 @@ 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_STACKABLE) | \
@@ -731,6 +732,10 @@ static inline void queue_flag_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)
+
+extern void blk_set_preempt_only(struct request_queue *q, bool preempt_only);

static inline bool blk_account_rq(struct request *rq)
{
--
2.14.1