From: Tejun Heo <tj@kernel.org>
Date: Tue, 9 Jan 2018 08:29:47 -0800
Subject: [PATCH] blk-mq: protect completion path with RCU
Git-commit: 5197c05e16b49885cc9086f1676455371e821b0e
Patch-mainline: v4.16-rc1
References: bsc#1104967,FATE#325924

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>
Signed-off-by: Jens Axboe <axboe@kernel.dk>
Acked-by: Hannes Reinecke <hare@suse.com>
---
 block/blk-mq.c | 5 +++++
 1 file changed, 5 insertions(+)

diff --git a/block/blk-mq.c b/block/blk-mq.c
index bd7c47eb2923..f5e57c80a82b 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);
 
-- 
2.16.4