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From: Christoph Hellwig <hch@lst.de>
To: "Javier González" <javier@javigon.com>
Cc: Christoph Hellwig <hch@lst.de>,
	linux-nvme@lists.infradead.org, linux-block@vger.kernel.org,
	kbusch@kernel.org, sagi@grimberg.me, minwoo.im.dev@gmail.com
Subject: Re: [PATCH V6 1/2] nvme: enable char device per namespace
Date: Tue, 9 Mar 2021 12:31:03 +0100	[thread overview]
Message-ID: <20210309113103.GA9233@lst.de> (raw)
In-Reply-To: <20210303100212.e43jgjvuomgybmy2@mpHalley.localdomain>

On Wed, Mar 03, 2021 at 11:02:12AM +0100, Javier González wrote:
>> 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
>
> Sounds good.
>
> The current implementation re-routes IOCTLs to the char device through
> the existing bdev IOCTLs, so I believe we follow this policy already. We
> basically default to current behavior.
>
> And I assume that for legacy, namespace IOCTLs to the controller will
> still be routed to the namespace (assuming a single namespace).
>
>> Which also makes me wonder about patch 2 in the series that seems
>> somewhat dangerous.   Can we clearly state the policy implemented?
>
> Patch 2 is the one that exposes the existing logic for multipath. How do
> you think we should do it instead?

So trying to follow the code:

 - nvme_cdev_fops implements file operations that directly on a nvme_ns,
   so they are path specific
 - we allow opening them even for a hidden controller
 - there does not seem to be a char device node for ns_head at all.

WARNING: multiple messages have this Message-ID (diff)
From: Christoph Hellwig <hch@lst.de>
To: "Javier González" <javier@javigon.com>
Cc: Christoph Hellwig <hch@lst.de>,
	linux-nvme@lists.infradead.org, linux-block@vger.kernel.org,
	kbusch@kernel.org, sagi@grimberg.me, minwoo.im.dev@gmail.com
Subject: Re: [PATCH V6 1/2] nvme: enable char device per namespace
Date: Tue, 9 Mar 2021 12:31:03 +0100	[thread overview]
Message-ID: <20210309113103.GA9233@lst.de> (raw)
In-Reply-To: <20210303100212.e43jgjvuomgybmy2@mpHalley.localdomain>

On Wed, Mar 03, 2021 at 11:02:12AM +0100, Javier González wrote:
>> 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
>
> Sounds good.
>
> The current implementation re-routes IOCTLs to the char device through
> the existing bdev IOCTLs, so I believe we follow this policy already. We
> basically default to current behavior.
>
> And I assume that for legacy, namespace IOCTLs to the controller will
> still be routed to the namespace (assuming a single namespace).
>
>> Which also makes me wonder about patch 2 in the series that seems
>> somewhat dangerous.   Can we clearly state the policy implemented?
>
> Patch 2 is the one that exposes the existing logic for multipath. How do
> you think we should do it instead?

So trying to follow the code:

 - nvme_cdev_fops implements file operations that directly on a nvme_ns,
   so they are path specific
 - we allow opening them even for a hidden controller
 - there does not seem to be a char device node for ns_head at all.

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

  reply	other threads:[~2021-03-09 11:32 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
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 [this message]
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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