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.
