| Message ID | 20171216120726.517153-2-tj@kernel.org (mailing list archive) |
|---|---|
| State | New, archived |
| Headers | show |
Why do you need the srcu protection? The completion path can never sleep. If there is a good reason to keep it please add commment, and make the srcu variant a separate function only used by drivers that need it instead of adding the conditional. -- To unsubscribe from this list: send the line "unsubscribe linux-btrfs" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html
Hello, Christoph. On Fri, Dec 29, 2017 at 02:04:18AM -0800, Christoph Hellwig wrote: > Why do you need the srcu protection? The completion path can never > sleep. > > If there is a good reason to keep it please add commment, and > make the srcu variant a separate function only used by drivers that > need it instead of adding the conditional. It's either that or adding protection against both srcu and rcu in the counterpart. It's easier / cleaner to just use single rcu construct for a given queue. Will add a comment. Jens already has a patch which factors out the conditionals. Thanks.
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);
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(-)