blk-mq: use QUEUE_FLAG_QUIESCED to quiesce queue
It is required that no dispatch can happen any more once
blk_mq_quiesce_queue() returns, and we don't have such requirement
on APIs of stopping queue.
But blk_mq_quiesce_queue() still may not block/drain dispatch in the
the case of BLK_MQ_S_START_ON_RUN, so use the new introduced flag of
QUEUE_FLAG_QUIESCED and evaluate it inside RCU read-side critical
sections for fixing this issue.
Also blk_mq_quiesce_queue() is implemented via stopping queue, which
limits its uses, and easy to cause race, because any queue restart in
other paths may break blk_mq_quiesce_queue(). With the introduced
flag of QUEUE_FLAG_QUIESCED, we don't need to depend on stopping queue
for quiescing any more.
Signed-off-by: Ming Lei <ming.lei@redhat.com>
Reviewed-by: Bart Van Assche <Bart.VanAssche@sandisk.com>
Signed-off-by: Jens Axboe <axboe@kernel.dk>
diff --git a/include/linux/blkdev.h b/include/linux/blkdev.h
index 8423f6b..22cfba6 100644
--- a/include/linux/blkdev.h
+++ b/include/linux/blkdev.h
@@ -619,6 +619,7 @@
#define QUEUE_FLAG_POLL_STATS 28 /* collecting stats for hybrid polling */
#define QUEUE_FLAG_REGISTERED 29 /* queue has been registered to a disk */
#define QUEUE_FLAG_SCSI_PASSTHROUGH 30 /* queue supports SCSI commands */
+#define QUEUE_FLAG_QUIESCED 31 /* queue has been quiesced */
#define QUEUE_FLAG_DEFAULT ((1 << QUEUE_FLAG_IO_STAT) | \
(1 << QUEUE_FLAG_STACKABLE) | \
@@ -715,6 +716,7 @@
#define blk_noretry_request(rq) \
((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)
static inline bool blk_account_rq(struct request *rq)
{