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From: Christoph Hellwig <hch@lst.de>
To: Keith Busch <kbusch@kernel.org>
Cc: Sagi Grimberg <sagi@grimberg.me>, Chao Leng <lengchao@huawei.com>,
	Christoph Hellwig <hch@lst.de>,
	linux-nvme@lists.infradead.org,
	Chaitanya Kulkarni <Chaitanya.Kulkarni@wdc.com>
Subject: Re: [PATCH 0/3 rfc] Fix nvme-tcp and nvme-rdma controller reset hangs
Date: Fri, 19 Mar 2021 15:05:32 +0100	[thread overview]
Message-ID: <20210319140532.GA7019@lst.de> (raw)
In-Reply-To: <20210318215256.GC31675@redsun51.ssa.fujisawa.hgst.com>

On Fri, Mar 19, 2021 at 06:52:56AM +0900, Keith Busch wrote:
> Having submit_bio() return the enter status was where I was going with
> this, but the recursive handling makes this more complicated than I
> initially thought.

Note that the recursion handling is not really required for
nvme-multipath.  I have some plans to actually kill it off entirely
for blk-mq submissions, which needs work on the bounce buffering
and bio splitting code, but should not be too hard.

> If you use the NOWAIT flag today with a freezing queue, the IO will end
> with BLK_STS_AGAIN and punt retry handling to the application. I'm
> guessing you don't want that to happen, so a little more is required for
> this idea.

We really should not use NOWAIT but a flag that only escapes the
freeze protection.  I think REQ_FAILFAST_DRIVER should probably be changed
to trigger that, but even if not we could add a new flag.

> Since it's an error path, perhaps a block operations callback is okay?
> Something like this compile tested patch?

We really should not need an indirection.  And more importantly I don't
think the consuming driver cares, it really is the submitting one.

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  parent reply	other threads:[~2021-03-19 14:06 UTC|newest]

Thread overview: 30+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2021-03-15 22:27 [PATCH 0/3 rfc] Fix nvme-tcp and nvme-rdma controller reset hangs Sagi Grimberg
2021-03-15 22:27 ` [PATCH 1/3] nvme: introduce nvme_ctrl_is_mpath helper Sagi Grimberg
2021-03-15 22:27 ` [PATCH 2/3] nvme-tcp: fix possible hang when trying to set a live path during I/O Sagi Grimberg
2021-03-15 22:27 ` [PATCH 3/3] nvme-rdma: " Sagi Grimberg
2021-03-16  3:24 ` [PATCH 0/3 rfc] Fix nvme-tcp and nvme-rdma controller reset hangs Chao Leng
2021-03-16  5:04   ` Sagi Grimberg
2021-03-16  6:18     ` Chao Leng
2021-03-16  6:25       ` Sagi Grimberg
2021-03-16 20:07 ` Sagi Grimberg
2021-03-16 20:42   ` Keith Busch
2021-03-16 23:51     ` Sagi Grimberg
2021-03-17  2:55       ` Chao Leng
2021-03-17  6:59         ` Christoph Hellwig
2021-03-17  7:59           ` Chao Leng
2021-03-17 18:43             ` Sagi Grimberg
2021-03-18  1:51               ` Chao Leng
2021-03-18  4:45                 ` Christoph Hellwig
2021-03-18 18:46                 ` Sagi Grimberg
2021-03-18 19:16                   ` Keith Busch
2021-03-18 19:31                     ` Sagi Grimberg
2021-03-18 21:52                       ` Keith Busch
2021-03-18 22:45                         ` Sagi Grimberg
2021-03-19 14:05                         ` Christoph Hellwig [this message]
2021-03-19 17:28                           ` Christoph Hellwig
2021-03-19 19:07                             ` Keith Busch
2021-03-19 19:34                             ` Sagi Grimberg
2021-03-20  6:11                               ` Christoph Hellwig
2021-03-21  6:49                                 ` Sagi Grimberg
2021-03-22  6:34                                   ` Christoph Hellwig
2021-03-17  8:16           ` Sagi Grimberg

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