Re: [PATCH v2 1/2] blk-mq: add tagset quiesce interface

[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index]

 





On 10/13/22 12:44, Chao Leng wrote:
Drivers that have shared tagsets may need to quiesce potentially a lot
of request queues that all share a single tagset (e.g. nvme). Add an interface
to quiesce all the queues on a given tagset. This interface is useful because
it can speedup the quiesce by doing it in parallel.

For tagsets that have BLK_MQ_F_BLOCKING set, we use call_srcu to all hctxs
in parallel such that all of them wait for the same rcu elapsed period with
a per-hctx heap allocated rcu_synchronize. for tagsets that don't have
BLK_MQ_F_BLOCKING set, we simply call a single synchronize_rcu as this is
sufficient.

Because some queues never need to be quiesced(e.g. nvme connect_q).
So introduce QUEUE_FLAG_NOQUIESCED to tagset quiesce interface to
skip the queue.

I wouldn't say it never nor will ever quiesce, we just don't happen to
quiesce it today...


Signed-off-by: Sagi Grimberg <sagi@xxxxxxxxxxx>
Signed-off-by: Chao Leng <lengchao@xxxxxxxxxx>
---
  block/blk-mq.c         | 75 ++++++++++++++++++++++++++++++++++++++++++++++++++
  include/linux/blk-mq.h |  2 ++
  include/linux/blkdev.h |  2 ++
  3 files changed, 79 insertions(+)

diff --git a/block/blk-mq.c b/block/blk-mq.c
index 8070b6c10e8d..ebe25da08156 100644
--- a/block/blk-mq.c
+++ b/block/blk-mq.c
@@ -29,6 +29,7 @@
  #include <linux/prefetch.h>
  #include <linux/blk-crypto.h>
  #include <linux/part_stat.h>
+#include <linux/rcupdate_wait.h>
#include <trace/events/block.h> @@ -311,6 +312,80 @@ void blk_mq_unquiesce_queue(struct request_queue *q)
  }
  EXPORT_SYMBOL_GPL(blk_mq_unquiesce_queue);
+static void blk_mq_quiesce_blocking_tagset(struct blk_mq_tag_set *set)
+{
+	int i = 0;
+	int count = 0;
+	struct request_queue *q;
+	struct rcu_synchronize *rcu;
+
+	list_for_each_entry(q, &set->tag_list, tag_set_list) {
+		if (blk_queue_noquiesced(q))
+			continue;
+
+		blk_mq_quiesce_queue_nowait(q);
+		count++;
+	}
+
+	rcu = kvmalloc(count * sizeof(*rcu), GFP_KERNEL);
+	if (rcu) {
+		list_for_each_entry(q, &set->tag_list, tag_set_list) {
+			if (blk_queue_noquiesced(q))
+				continue;
+
+			init_rcu_head(&rcu[i].head);
+			init_completion(&rcu[i].completion);
+			call_srcu(q->srcu, &rcu[i].head, wakeme_after_rcu);
+			i++;
+		}
+
+		for (i = 0; i < count; i++) {
+			wait_for_completion(&rcu[i].completion);
+			destroy_rcu_head(&rcu[i].head);
+		}
+		kvfree(rcu);
+	} else {
+		list_for_each_entry(q, &set->tag_list, tag_set_list)
+			synchronize_srcu(q->srcu);
+	}
+}
+
+static void blk_mq_quiesce_nonblocking_tagset(struct blk_mq_tag_set *set)
+{
+	struct request_queue *q;
+
+	list_for_each_entry(q, &set->tag_list, tag_set_list) {
+		if (blk_queue_noquiesced(q))
+			continue;
+
+		blk_mq_quiesce_queue_nowait(q);
+	}
+	synchronize_rcu();
+}
+
+void blk_mq_quiesce_tagset(struct blk_mq_tag_set *set)
+{
+	mutex_lock(&set->tag_list_lock);
+	if (set->flags & BLK_MQ_F_BLOCKING)
+		blk_mq_quiesce_blocking_tagset(set);
+	else
+		blk_mq_quiesce_nonblocking_tagset(set);
+
+	mutex_unlock(&set->tag_list_lock);
+}
+EXPORT_SYMBOL_GPL(blk_mq_quiesce_tagset);
+
+void blk_mq_unquiesce_tagset(struct blk_mq_tag_set *set)
+{
+	struct request_queue *q;
+
+	mutex_lock(&set->tag_list_lock);
+	list_for_each_entry(q, &set->tag_list, tag_set_list)
+		blk_mq_unquiesce_queue(q);
+	mutex_unlock(&set->tag_list_lock);
+}
+EXPORT_SYMBOL_GPL(blk_mq_unquiesce_tagset);
+
  void blk_mq_wake_waiters(struct request_queue *q)
  {
  	struct blk_mq_hw_ctx *hctx;
diff --git a/include/linux/blk-mq.h b/include/linux/blk-mq.h
index ba18e9bdb799..1df47606d0a7 100644
--- a/include/linux/blk-mq.h
+++ b/include/linux/blk-mq.h
@@ -877,6 +877,8 @@ void blk_mq_start_hw_queues(struct request_queue *q);
  void blk_mq_start_stopped_hw_queue(struct blk_mq_hw_ctx *hctx, bool async);
  void blk_mq_start_stopped_hw_queues(struct request_queue *q, bool async);
  void blk_mq_quiesce_queue(struct request_queue *q);
+void blk_mq_quiesce_tagset(struct blk_mq_tag_set *set);
+void blk_mq_unquiesce_tagset(struct blk_mq_tag_set *set);
  void blk_mq_wait_quiesce_done(struct request_queue *q);
  void blk_mq_unquiesce_queue(struct request_queue *q);
  void blk_mq_delay_run_hw_queue(struct blk_mq_hw_ctx *hctx, unsigned long msecs);
diff --git a/include/linux/blkdev.h b/include/linux/blkdev.h
index 50e358a19d98..f15544299a67 100644
--- a/include/linux/blkdev.h
+++ b/include/linux/blkdev.h
@@ -579,6 +579,7 @@ struct request_queue {
  #define QUEUE_FLAG_HCTX_ACTIVE	28	/* at least one blk-mq hctx is active */
  #define QUEUE_FLAG_NOWAIT       29	/* device supports NOWAIT */
  #define QUEUE_FLAG_SQ_SCHED     30	/* single queue style io dispatch */
+#define QUEUE_FLAG_NOQUIESCED	31	/* queue is never quiesced */

the comment is misleading. If this is truely queue that is never
quiescing then blk_mq_quiesce_queue() and friends need to skip it.

I'd call it self_quiesce or something that would reflect that it is
black-listed from tagset-wide quiesce.



[Index of Archives]     [Linux RAID]     [Linux SCSI]     [Linux ATA RAID]     [IDE]     [Linux Wireless]     [Linux Kernel]     [ATH6KL]     [Linux Bluetooth]     [Linux Netdev]     [Kernel Newbies]     [Security]     [Git]     [Netfilter]     [Bugtraq]     [Yosemite News]     [MIPS Linux]     [ARM Linux]     [Linux Security]     [Device Mapper]

  Powered by Linux