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From: Christoph Hellwig <hch@lst.de>
To: javier@javigon.com
Cc: linux-nvme@lists.infradead.org, linux-block@vger.kernel.org,
	hch@lst.de, kbusch@kernel.org, sagi@grimberg.me,
	minwoo.im.dev@gmail.com,
	"Javier González" <javier.gonz@samsung.com>
Subject: Re: [PATCH V6 1/2] nvme: enable char device per namespace
Date: Wed, 3 Mar 2021 10:10:22 +0100	[thread overview]
Message-ID: <20210303091022.GA12784@lst.de> (raw)
In-Reply-To: <20210301192452.16770-2-javier.gonz@samsung.com>

On Mon, Mar 01, 2021 at 08:24:51PM +0100, javier@javigon.com wrote:
> From: Javier González <javier.gonz@samsung.com>
> 
> Create a char device per NVMe namespace. This char device is always
> initialized, independently of whether the features implemented by the
> device are supported by the kernel. User-space can therefore always
> issue IOCTLs to the NVMe driver using the char device.
> 
> The char device is presented as /dev/nvme-generic-XcYnZ. This naming
> scheme follows the convention of the hidden device (nvmeXcYnZ). Support
> for multipath will follow.

So I'm a little worried about the "support for multipath will follow" as
this has implications for the naming scheme, and our policy of how we
allow access to a namespace.

Ignoring some of the deprecated historic mistakes I think the policy
should be:

 - admin commands that often are controller specific should usually
   go to a controller-specific device, the existing /dev/nvmeX
   devices
 - I/O commands and admin command that do specific a nsid should go
   through a per-namespace node that is multipath aware and not
   controller specific

Which also makes me wonder about patch 2 in the series that seems
somewhat dangerous.   Can we clearly state the policy implemented?

WARNING: multiple messages have this Message-ID (diff)
From: Christoph Hellwig <hch@lst.de>
To: javier@javigon.com
Cc: linux-nvme@lists.infradead.org, linux-block@vger.kernel.org,
	hch@lst.de, kbusch@kernel.org, sagi@grimberg.me,
	minwoo.im.dev@gmail.com,
	"Javier González" <javier.gonz@samsung.com>
Subject: Re: [PATCH V6 1/2] nvme: enable char device per namespace
Date: Wed, 3 Mar 2021 10:10:22 +0100	[thread overview]
Message-ID: <20210303091022.GA12784@lst.de> (raw)
In-Reply-To: <20210301192452.16770-2-javier.gonz@samsung.com>

On Mon, Mar 01, 2021 at 08:24:51PM +0100, javier@javigon.com wrote:
> From: Javier González <javier.gonz@samsung.com>
> 
> Create a char device per NVMe namespace. This char device is always
> initialized, independently of whether the features implemented by the
> device are supported by the kernel. User-space can therefore always
> issue IOCTLs to the NVMe driver using the char device.
> 
> The char device is presented as /dev/nvme-generic-XcYnZ. This naming
> scheme follows the convention of the hidden device (nvmeXcYnZ). Support
> for multipath will follow.

So I'm a little worried about the "support for multipath will follow" as
this has implications for the naming scheme, and our policy of how we
allow access to a namespace.

Ignoring some of the deprecated historic mistakes I think the policy
should be:

 - admin commands that often are controller specific should usually
   go to a controller-specific device, the existing /dev/nvmeX
   devices
 - I/O commands and admin command that do specific a nsid should go
   through a per-namespace node that is multipath aware and not
   controller specific

Which also makes me wonder about patch 2 in the series that seems
somewhat dangerous.   Can we clearly state the policy implemented?

_______________________________________________
Linux-nvme mailing list
Linux-nvme@lists.infradead.org
http://lists.infradead.org/mailman/listinfo/linux-nvme

  reply	other threads:[~2021-03-03 16:41 UTC|newest]

Thread overview: 34+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2021-03-01 19:24 [PATCH V6 0/2] nvme: enable char device per namespace javier
2021-03-01 19:24 ` javier
2021-03-01 19:24 ` [PATCH V6 1/2] " javier
2021-03-01 19:24   ` javier
2021-03-03  9:10   ` Christoph Hellwig [this message]
2021-03-03  9:10     ` Christoph Hellwig
2021-03-03 10:02     ` Javier González
2021-03-03 10:02       ` Javier González
2021-03-09 11:31       ` Christoph Hellwig
2021-03-09 11:31         ` Christoph Hellwig
2021-03-09 12:42         ` Javier González
2021-03-09 12:42           ` Javier González
2021-03-09 15:05           ` Christoph Hellwig
2021-03-09 15:05             ` Christoph Hellwig
2021-03-09 21:18             ` Javier González
2021-03-09 21:18               ` Javier González
2021-03-24 12:29   ` Niklas Cassel
2021-03-24 12:29     ` Niklas Cassel
2021-03-25  2:09     ` Minwoo Im
2021-03-25  2:09       ` Minwoo Im
2021-03-25  8:26       ` hch
2021-03-25  8:26         ` hch
2021-03-25  8:39         ` Niklas Cassel
2021-03-25  8:39           ` Niklas Cassel
2021-03-25  9:34           ` Minwoo Im
2021-03-25  9:34             ` Minwoo Im
2021-03-25 12:25   ` Niklas Cassel
2021-03-25 12:25     ` Niklas Cassel
2021-03-25 12:33     ` Minwoo Im
2021-03-25 12:33       ` Minwoo Im
2021-03-25 15:14     ` Keith Busch
2021-03-25 15:14       ` Keith Busch
2021-03-01 19:24 ` [PATCH V6 2/2] nvme: allow open for nvme-generic char device javier
2021-03-01 19:24   ` javier

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