Some devices (most notably SMR drives) support only
one I/O stream eg for ensuring ordered I/O submission.
This patch adds a new block queue flag
'BLK_QUEUE_SINGLE' to support these devices.
Signed-off-by: Hannes Reinecke <hare@xxxxxxx>
---
block/blk-core.c | 2 ++
include/linux/blkdev.h | 2 ++
2 files changed, 4 insertions(+)
diff --git a/block/blk-core.c b/block/blk-core.c
index 4bcf30a..ff08d77 100644
--- a/block/blk-core.c
+++ b/block/blk-core.c
@@ -320,6 +320,8 @@ inline void __blk_run_queue_uncond(struct request_queue *q)
* number of active request_fn invocations such that blk_drain_queue()
* can wait until all these request_fn calls have finished.
*/
+ if (blk_queue_single(q) && q->request_fn_active)
+ return;
q->request_fn_active++;
q->request_fn(q);
q->request_fn_active--;
diff --git a/include/linux/blkdev.h b/include/linux/blkdev.h
index c351444..2f7775a 100644
--- a/include/linux/blkdev.h
+++ b/include/linux/blkdev.h
@@ -539,6 +539,7 @@ struct request_queue {
#define QUEUE_FLAG_WC 23 /* Write back caching */
#define QUEUE_FLAG_FUA 24 /* device supports FUA writes */
#define QUEUE_FLAG_FLUSH_NQ 25 /* flush not queueuable */
+#define QUEUE_FLAG_SINGLE 26 /* single-threaded submission only */
#define QUEUE_FLAG_DEFAULT ((1 << QUEUE_FLAG_IO_STAT) | \
(1 << QUEUE_FLAG_STACKABLE) | \
@@ -628,6 +629,7 @@ static inline void queue_flag_clear(unsigned int flag, struct request_queue *q)
#define blk_queue_discard(q) test_bit(QUEUE_FLAG_DISCARD, &(q)->queue_flags)
#define blk_queue_secdiscard(q) (blk_queue_discard(q) && \
test_bit(QUEUE_FLAG_SECDISCARD, &(q)->queue_flags))
+#define blk_queue_single(q) test_bit(QUEUE_FLAG_SINGLE, &(q)->queue_flags)
#define blk_noretry_request(rq) \
((rq)->cmd_flags & (REQ_FAILFAST_DEV|REQ_FAILFAST_TRANSPORT| \
--
1.8.5.6
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