linux-kernel - Re: I/O hangs after resuming from suspend-to-ram

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Date:   Wed, 30 Aug 2017 16:06:29 +0800
From:   Ming Lei <ming.lei@...hat.com>
To:     oleksandr@...alenko.name
Cc:     Jens Axboe <axboe@...nel.dk>, Christoph Hellwig <hch@....de>,
        linux-block@...r.kernel.org, linux-raid@...r.kernel.org,
        linux-kernel@...r.kernel.org, Shaohua Li <shli@...nel.org>
Subject: Re: I/O hangs after resuming from suspend-to-ram

Hi,

On Wed, Aug 30, 2017 at 08:15:02AM +0200, oleksandr@...alenko.name wrote:
> Hello.
> 
> Addressing your questions below.
> 
> > Can't reproduce even with putting dmcypt on raid10 after applying my
> > patch.
> 
> Just a side note, that dm-crypt is not necessary here — I am able to trigger
> hang with RAID10 and LVM only.
> 
> > BTW, could you share us which blk-mq scheduler you are using on sata?
> 
> Okay, now it makes sense. Previously, without your patch I was able to
> reproduce the issue with "mq-deadline", "bfq" and "none". Now, I cannot
> trigger it with "none" set, but "mq-deadline" still hangs for me. Does this
> mean each scheduler should be modified separately?

No, it shouldn't.

> 
> > Could you apply the following debug patch and provide the dmesg log
> > after running the commands below?
> 
> Is it still relevant since I confirm issue to be fixed with "none"?

Please try the following patch and previous patch together and see
if they make a difference:


>From bc5626b4b65c7ff26567e75f42584c2c43ffe7c1 Mon Sep 17 00:00:00 2001
From: Ming Lei <ming.lei@...hat.com>
Date: Wed, 30 Aug 2017 15:53:01 +0800
Subject: [PATCH] blk-mq: add requests in the tail of hctx->dispatch

So that we can allow to insert request at the head
of hctx->dispatch.

Signed-off-by: Ming Lei <ming.lei@...hat.com>
---
 block/blk-mq-sched.c | 2 +-
 block/blk-mq.c       | 2 +-
 2 files changed, 2 insertions(+), 2 deletions(-)

diff --git a/block/blk-mq-sched.c b/block/blk-mq-sched.c
index eeeea026fb47..b40dd063d61f 100644
--- a/block/blk-mq-sched.c
+++ b/block/blk-mq-sched.c
@@ -272,7 +272,7 @@ static bool blk_mq_sched_bypass_insert(struct blk_mq_hw_ctx *hctx,
 	 * the dispatch list.
 	 */
 	spin_lock(&hctx->lock);
-	list_add(&rq->queuelist, &hctx->dispatch);
+	list_add_tail(&rq->queuelist, &hctx->dispatch);
 	spin_unlock(&hctx->lock);
 	return true;
 }
diff --git a/block/blk-mq.c b/block/blk-mq.c
index 4603b115e234..fed3d0c16266 100644
--- a/block/blk-mq.c
+++ b/block/blk-mq.c
@@ -1067,7 +1067,7 @@ bool blk_mq_dispatch_rq_list(struct request_queue *q, struct list_head *list)
 		blk_mq_put_driver_tag(rq);
 
 		spin_lock(&hctx->lock);
-		list_splice_init(list, &hctx->dispatch);
+		list_splice_tail_init(list, &hctx->dispatch);
 		spin_unlock(&hctx->lock);
 
 		/*
-- 
2.9.5


-- 
Ming