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.
Signed-off-by: Sagi Grimberg <sagi@xxxxxxxxxxx>
---
block/blk-mq.c | 66 ++++++++++++++++++++++++++++++++++++++++++
include/linux/blk-mq.h | 4 +++
2 files changed, 70 insertions(+)
diff --git a/block/blk-mq.c b/block/blk-mq.c
index abcf590f6238..c37e37354330 100644
--- a/block/blk-mq.c
+++ b/block/blk-mq.c
@@ -209,6 +209,42 @@ void blk_mq_quiesce_queue_nowait(struct request_queue *q)
}
EXPORT_SYMBOL_GPL(blk_mq_quiesce_queue_nowait);
+static void blk_mq_quiesce_blocking_queue_async(struct request_queue *q)
+{
+ struct blk_mq_hw_ctx *hctx;
+ unsigned int i;
+
+ blk_mq_quiesce_queue_nowait(q);
+
+ queue_for_each_hw_ctx(q, hctx, i) {
+ WARN_ON_ONCE(!(hctx->flags & BLK_MQ_F_BLOCKING));
+ hctx->rcu_sync = kmalloc(sizeof(*hctx->rcu_sync), GFP_KERNEL);
+ if (!hctx->rcu_sync)
+ continue;
This approach of quiesce/unquiesce tagset is good abstraction.
I'm thinking I don't want to use this interface, it quiesce the
connect_q hctxs as well and then I need to unquiesce them which is
awkward...
Just one more thing, please allocate a rcu_sync array because hctx is supposed
to not store scratch stuff.
Sorry, I object to any interface that returns back the rcu_sync
allocation. Its just awkward. really..
