From: "Javier González" <javier@javigon.com> To: Christoph Hellwig <hch@lst.de> Cc: 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: Wed, 3 Mar 2021 11:02:12 +0100 [thread overview] Message-ID: <20210303100212.e43jgjvuomgybmy2@mpHalley.localdomain> (raw) In-Reply-To: <20210303091022.GA12784@lst.de> On 03.03.2021 10:10, Christoph Hellwig wrote: >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. I maintained the message to follow the original commit. In this patchset multipath is implemented. I maintains the same naming scheme. We can remove this comment as multipath is supported in the existing series. > >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?
WARNING: multiple messages have this Message-ID (diff)
From: "Javier González" <javier@javigon.com> To: Christoph Hellwig <hch@lst.de> Cc: 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: Wed, 3 Mar 2021 11:02:12 +0100 [thread overview] Message-ID: <20210303100212.e43jgjvuomgybmy2@mpHalley.localdomain> (raw) In-Reply-To: <20210303091022.GA12784@lst.de> On 03.03.2021 10:10, Christoph Hellwig wrote: >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. I maintained the message to follow the original commit. In this patchset multipath is implemented. I maintains the same naming scheme. We can remove this comment as multipath is supported in the existing series. > >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? _______________________________________________ Linux-nvme mailing list Linux-nvme@lists.infradead.org http://lists.infradead.org/mailman/listinfo/linux-nvme
next prev parent 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 2021-03-03 9:10 ` Christoph Hellwig 2021-03-03 10:02 ` Javier González [this message] 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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