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From: Christoph Hellwig <hch@lst.de>
To: Sagi Grimberg <sagi@grimberg.me>
Cc: Keith Busch <kbusch@kernel.org>, Christoph Hellwig <hch@lst.de>,
	linux-nvme@lists.infradead.org,
	James Smart <james.smart@broadcom.com>
Subject: Re: [PATCH v3 2/9] nvme-fabrics: allow to queue requests for live queues
Date: Tue, 25 Aug 2020 09:13:45 +0200	[thread overview]
Message-ID: <20200825071345.GF29268@lst.de> (raw)
In-Reply-To: <77e27c4e-f939-2c14-8e63-209197f1133c@grimberg.me>

On Mon, Aug 24, 2020 at 01:02:40AM -0700, Sagi Grimberg wrote:
> I checked again, and regarding the comment:
>
> "I'm still rather bothered with the admin queue exception.  And given that
> the q_usage_counter problem should only really be an issue for file system
> requests, as passthrough requests do not automatically get retried why
> can't we just reject all user command to be symetric and straight forward?
> The callers in userspace need to be able to cope with retryable errors
> anyway."
>
> blk_mq_alloc_request calls blk_queue_enter, which means that if we don't
> let them in, controller reset can hang, just like in normal fs I/O.

Yes.  But the difference is that they don't get retrieѕ, but instead just
fail.

> So we either keep this exception for admin commands, or we also let
> them through as it seems to be safe with the current code (from the
> reset forward-progress perspective).
>
> I vote to remove this exception altogether...

To me the right answer would be to reject user commands on the admin
or I/O queue for the not live controller as the callers need to handle
it.  That seems to make more sense to me than a special admin queue
exception.

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  reply	other threads:[~2020-08-25  7:13 UTC|newest]

Thread overview: 44+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2020-08-20  5:36 [PATCH v3 0/9] fix possible controller reset hangs in nvme-tcp/nvme-rdma Sagi Grimberg
2020-08-20  5:36 ` [PATCH v3 1/9] nvme-fabrics: don't check state NVME_CTRL_NEW for request acceptance Sagi Grimberg
2020-08-20  6:02   ` Christoph Hellwig
2020-08-20 20:49   ` James Smart
2020-08-20  5:36 ` [PATCH v3 2/9] nvme-fabrics: allow to queue requests for live queues Sagi Grimberg
2020-08-20  6:09   ` Christoph Hellwig
2020-08-20 16:58     ` Sagi Grimberg
2020-08-20 20:45       ` James Smart
2020-08-20 22:13         ` Sagi Grimberg
2020-08-20 22:17           ` James Smart
2020-08-21  6:22         ` Christoph Hellwig
2020-08-21 15:22           ` James Smart
2020-08-21 19:44           ` Sagi Grimberg
2020-08-23 15:19             ` James Smart
2020-08-24  8:06               ` Sagi Grimberg
2020-08-24  8:02           ` Sagi Grimberg
2020-08-25  7:13             ` Christoph Hellwig [this message]
2020-08-25 15:00               ` Sagi Grimberg
2020-08-25 15:41                 ` James Smart
2020-08-25 17:35                   ` Sagi Grimberg
2020-09-04 20:26                     ` Sagi Grimberg
2020-09-08  9:05                       ` Christoph Hellwig
2020-09-08 16:47                         ` Sagi Grimberg
2020-09-08 16:48                           ` Christoph Hellwig
2020-09-08 19:56                             ` Sagi Grimberg
2020-08-20 20:54   ` James Smart
2020-08-20 20:56   ` James Smart
2020-08-20  5:36 ` [PATCH v3 3/9] nvme: have nvme_wait_freeze_timeout return if it timed out Sagi Grimberg
2020-08-20  6:09   ` Christoph Hellwig
2020-08-20  5:36 ` [PATCH v3 4/9] nvme-tcp: serialize controller teardown sequences Sagi Grimberg
2020-08-20  5:36 ` [PATCH v3 5/9] nvme-tcp: fix timeout handler Sagi Grimberg
2020-08-20  5:36 ` [PATCH v3 6/9] nvme-tcp: fix reset hang if controller died in the middle of a reset Sagi Grimberg
2020-08-20  5:36 ` [PATCH v3 7/9] nvme-rdma: serialize controller teardown sequences Sagi Grimberg
2020-08-20 21:04   ` James Smart
2020-08-20 22:16     ` Sagi Grimberg
2020-08-21 21:08   ` James Smart
2020-08-20  5:36 ` [PATCH v3 8/9] nvme-rdma: fix timeout handler Sagi Grimberg
2020-08-20  6:10   ` Christoph Hellwig
2020-08-20 21:37   ` James Smart
2020-08-20  5:36 ` [PATCH v3 9/9] nvme-rdma: fix reset hang if controller died in the middle of a reset Sagi Grimberg
2020-08-20  6:10   ` Christoph Hellwig
2020-08-24 18:29 ` [PATCH v3 0/9] fix possible controller reset hangs in nvme-tcp/nvme-rdma Sagi Grimberg
2020-08-25  7:16   ` Christoph Hellwig
2020-08-25 15:35     ` James Smart

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