Re: [PATCH 1/6] blk-mq: protect completion path with RCU
From: jianchao.wang <hidden>
Date: 2017-12-13 03:31:21
Also in:
lkml
Hello tejun Sorry for missing the V2, same comment again. On 12/13/2017 03:01 AM, Tejun Heo wrote:
quoted hunk ↗ jump to hunk
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);
The __blk_mq_complete_request() could be executed in irq context. There should not be any sleeping operations in it. If just synchronize with the timeout path to ensure the aborted_gstate to be seen, only rcu is needed here ,as well as the blk_mq_timeout_work.
+ } } EXPORT_SYMBOL(blk_mq_complete_request);