From: Sagi Grimberg <sagi@grimberg.me>
To: Keith Busch <kbusch@kernel.org>
Cc: 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: Thu, 18 Mar 2021 12:31:35 -0700 [thread overview]
Message-ID: <be15cc68-2129-286e-55b3-a2c23f8c93fd@grimberg.me> (raw)
In-Reply-To: <20210318191613.GB31675@redsun51.ssa.fujisawa.hgst.com>
>> Placing the request on the requeue_list is fine, but the question is
>> when to kick the requeue_work, nothing guarantees that an alternate path
>> exist or will in a sane period. So constantly requeue+kick sounds like
>> a really bad practice to me.
>
> nvme_mpath_set_live(), where you reported the deadlock, kicks the
> requeue_list. The difference that NOWAIT provides is that
> nvme_mpath_set_live's schronize_srcu() is no longer blocked forever
> because the .submit_bio() isn't waiting for entery on a frozen queue, so
> now it's free to schedule the dispatch.
>
> There's probably an optimization to kick it sooner if there's a viable
> alternate path, but that could be a follow on.
That would be mandatory I think, otherwise this would introduce
a regression...
> If there's no immediate viable path, then the requests would remain on
> the requeue list. That currently happens as long as there's a potential
> controller in a reset or connecting state.
Well, also worth to keep in mind that now we'll need to clone the bio
because we need to override bi_end_io which adds us some overhead
in the data path. Unless we make submit_bio return a status which
is a much bigger scope of a change I would expect...
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next prev parent reply other threads:[~2021-03-18 19:31 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 [this message]
2021-03-18 21:52 ` Keith Busch
2021-03-18 22:45 ` Sagi Grimberg
2021-03-19 14:05 ` Christoph Hellwig
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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