[PATCH 1/6] blk-mq: protect completion path with RCU

Tejun Heo
2017-12-09T19:25:42Z

Currently, blk-mq protects only the issue path with RCU. This patch
puts the completion path under the same RCU protection. This will be
used to synchronize issue/completion against timeout by later patches,
which will also add the comments.

Signed-off-by: Tejun Heo <tj@kernel.org>
---
block/blk-mq.c | 16 ++++++++++++++--
1 file changed, 14 insertions(+), 2 deletions(-)

diff --git a/block/blk-mq.c b/block/blk-mq.c
index 1109747..acf4fbb 100644
--- a/block/blk-mq.c
+++ b/block/blk-mq.c
@@ -568,11 +568,23 @@ static void __blk_mq_complete_request(struct request *rq)
void blk_mq_complete_request(struct request *rq)
{
struct request_queue *q = rq->q;
+ struct blk_mq_hw_ctx *hctx = blk_mq_map_queue(q, rq->mq_ctx->cpu);
+ int srcu_idx;

if (unlikely(blk_should_fake_timeout(q)))
return;
- if (!blk_mark_rq_complete(rq))
- __blk_mq_complete_request(rq);
+
+ if (!(hctx->flags & BLK_MQ_F_BLOCKING)) {
+ rcu_read_lock();
+ if (!blk_mark_rq_complete(rq))
+ __blk_mq_complete_request(rq);
+ rcu_read_unlock();
+ } else {
+ srcu_idx = srcu_read_lock(hctx->queue_rq_srcu);
+ if (!blk_mark_rq_complete(rq))
+ __blk_mq_complete_request(rq);
+ srcu_read_unlock(hctx->queue_rq_srcu, srcu_idx);
+ }
}
EXPORT_SYMBOL(blk_mq_complete_request);

--
2.9.5