linux-kernel - [PATCH 2/8] blk-mq: protect completion path with RCU

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Message-Id: <20180109162953.1211451-3-tj@kernel.org>
Date:   Tue,  9 Jan 2018 08:29:47 -0800
From:   Tejun Heo <tj@...nel.org>
To:     jack@...e.cz, axboe@...nel.dk, clm@...com, jbacik@...com
Cc:     kernel-team@...com, linux-kernel@...r.kernel.org,
        linux-btrfs@...r.kernel.org, peterz@...radead.org,
        jianchao.w.wang@...cle.com, Bart.VanAssche@....com,
        linux-block@...r.kernel.org, Tejun Heo <tj@...nel.org>
Subject: [PATCH 2/8] blk-mq: protect completion path with RCU

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@...nel.org>
---
 block/blk-mq.c | 5 +++++
 1 file changed, 5 insertions(+)

diff --git a/block/blk-mq.c b/block/blk-mq.c
index ddc9261..6741c3e 100644
--- a/block/blk-mq.c
+++ b/block/blk-mq.c
@@ -584,11 +584,16 @@ static void hctx_lock(struct blk_mq_hw_ctx *hctx, int *srcu_idx)
 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;
+
+	hctx_lock(hctx, &srcu_idx);
 	if (!blk_mark_rq_complete(rq))
 		__blk_mq_complete_request(rq);
+	hctx_unlock(hctx, srcu_idx);
 }
 EXPORT_SYMBOL(blk_mq_complete_request);
 
-- 
2.9.5