From: Keith Busch <kbusch@kernel.org>
To: Minwoo Im <minwoo.im.dev@gmail.com>
Cc: Jens Axboe <axboe@fb.com>, Christoph Hellwig <hch@lst.de>,
linux-nvme@lists.infradead.org, Sagi Grimberg <sagi@grimberg.me>
Subject: Re: [PATCH] nvme: introduce passthrough ioctl for multipath
Date: Mon, 15 Feb 2021 09:02:33 -0800 [thread overview]
Message-ID: <20210215170233.GA2707454@dhcp-10-100-145-180.wdc.com> (raw)
In-Reply-To: <20210214110126.24023-2-minwoo.im.dev@gmail.com>
On Sun, Feb 14, 2021 at 08:01:25PM +0900, Minwoo Im wrote:
> We don't allow NVME_IOCTL_IO_CMD ioctl in case that a controller has
> multiple namespaces attached. Also, I/O request to the controller
> character device has not been recommended and deprecated because we have
> block device to I/O with where the multipath consideration is taken.
>
> Once kernel decided a path to I/O for a namespace based on the I/O
> policy of a NVMe subsystem, userspace is not allowed to choose a path to
> I/O. If a path is broken(inaccessible state in ANA), then it will not
> try to I/O to that path.
>
> This patch introduced NVME_IOCTL_MPATH_IO command for controller
> device(e.g., /dev/nvme0) to support multipath I/O passthrough for
> userspace. Regardless driver's path decision, userspace can target a
> namespace to I/O. In this case, `cmd.nsid` will be used to find out the
> namespace instance target which is hidden(e.g., nvmeXcYnZ).
IO commands are not allowed through the character handle with the
existing ioctls. A new ioctl doesn't make it okay. If it was okay, then
we could just remove the limitation in the current ones.
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next prev parent reply other threads:[~2021-02-15 17:02 UTC|newest]
Thread overview: 11+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-02-14 11:01 [PATCH 0/2] nvme: support I/O passthrough for multipath Minwoo Im
2021-02-14 11:01 ` [PATCH] nvme: introduce passthrough ioctl " Minwoo Im
2021-02-15 17:02 ` Keith Busch [this message]
2021-02-16 9:51 ` Minwoo Im
2021-02-16 17:57 ` Keith Busch
2021-02-17 2:14 ` Minwoo Im
2021-02-18 8:40 ` Christoph Hellwig
2021-02-18 8:48 ` Javier González
2021-02-19 21:27 ` Minwoo Im
2021-02-19 21:26 ` Minwoo Im
2021-02-14 11:01 ` [nvme-cli PATCH] nvme: add [--mpath|-M] option to io-passthru Minwoo Im
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