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From: Logan Gunthorpe <logang@deltatee.com>
To: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Cc: linux-kernel@vger.kernel.org, linux-nvme@lists.infradead.org,
	linux-block@vger.kernel.org, linux-fsdevel@vger.kernel.org,
	Christoph Hellwig <hch@lst.de>, Sagi Grimberg <sagi@grimberg.me>,
	Keith Busch <kbusch@kernel.org>, Jens Axboe <axboe@fb.com>,
	Chaitanya Kulkarni <Chaitanya.Kulkarni@wdc.com>,
	Max Gurtovoy <maxg@mellanox.com>,
	Stephen Bates <sbates@raithlin.com>,
	Alexander Viro <viro@zeniv.linux.org.uk>
Subject: Re: [PATCH v6 02/16] chardev: introduce cdev_get_by_path()
Date: Thu, 25 Jul 2019 12:36:24 -0600	[thread overview]
Message-ID: <a3262a7f-b78e-05ba-cda3-a7587946bd91@deltatee.com> (raw)
In-Reply-To: <20190725182701.GA11547@kroah.com>



On 2019-07-25 12:27 p.m., Greg Kroah-Hartman wrote:
>>> Why do you have a "string" within the kernel and are not using the
>>> normal open() call from userspace on the character device node on the
>>> filesystem in your namespace/mount/whatever?
>>
>> NVMe-OF is configured using configfs. The target is specified by the
>> user writing a path to a configfs attribute. This is the way it works
>> today but with blkdev_get_by_path()[1]. For the passthru code, we need
>> to get a nvme_ctrl instead of a block_device, but the principal is the same.
> 
> Why isn't a fd being passed in there instead of a random string?

I wouldn't know the answer to this but I assume because once we decided
to use configfs, there was no way for the user to pass the kernel an fd.

> Seems odd, but oh well, that ship sailed a long time ago for block
> devices I guess.

Yup.

> So what do you actually _do_ with that char device once you have it?

We lookup the struct nvme_ctrl and use it to submit passed-through NVMe
commands directly to the controller.

Logan

  reply	other threads:[~2019-07-25 18:36 UTC|newest]

Thread overview: 61+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2019-07-25 17:23 [PATCH v6 00/16] nvmet: add target passthru commands support Logan Gunthorpe
2019-07-25 17:23 ` [PATCH v6 01/16] chardev: factor out cdev_lookup() helper Logan Gunthorpe
2019-07-25 17:23 ` [PATCH v6 02/16] chardev: introduce cdev_get_by_path() Logan Gunthorpe
2019-07-25 17:40   ` Greg Kroah-Hartman
2019-07-25 17:53     ` Logan Gunthorpe
2019-07-25 17:58       ` Matthew Wilcox
2019-07-25 18:08         ` Logan Gunthorpe
2019-07-25 18:08       ` Greg Kroah-Hartman
2019-07-25 18:14         ` Logan Gunthorpe
2019-07-25 18:27           ` Greg Kroah-Hartman
2019-07-25 18:36             ` Logan Gunthorpe [this message]
2019-07-25 19:02               ` Sagi Grimberg
2019-07-25 19:34                 ` Greg Kroah-Hartman
2019-07-25 19:37                   ` Sagi Grimberg
2019-07-25 19:43                     ` Greg Kroah-Hartman
2019-07-25 19:45                       ` Sagi Grimberg
2019-07-25 19:43                     ` Sagi Grimberg
2019-07-25 19:41                   ` Logan Gunthorpe
2019-07-25 19:00             ` Matthew Wilcox
2019-07-25 19:05               ` Sagi Grimberg
2019-07-25 19:11                 ` Matthew Wilcox
2019-07-25 19:24                   ` Logan Gunthorpe
2019-07-25 19:26                     ` Matthew Wilcox
2019-07-25 19:31                       ` Logan Gunthorpe
2019-07-25 23:55                     ` Al Viro
2019-07-26  4:29                       ` Sagi Grimberg
2019-07-26  7:13                         ` Greg Kroah-Hartman
2019-07-26 15:46                         ` Logan Gunthorpe
2019-07-25 19:31                   ` Sagi Grimberg
2019-07-25 18:10       ` Greg Kroah-Hartman
2019-07-25 18:16         ` Logan Gunthorpe
2019-07-25 17:23 ` [PATCH v6 03/16] chardev: export cdev_put() Logan Gunthorpe
2019-07-25 17:23 ` [PATCH v6 04/16] nvme-core: introduce nvme_get_by_path() Logan Gunthorpe
2019-07-25 17:50   ` Matthew Wilcox
2019-07-25 17:54     ` Logan Gunthorpe
2019-07-25 19:58       ` Keith Busch
2019-07-25 20:12         ` Sagi Grimberg
2019-07-25 20:28         ` Logan Gunthorpe
2019-07-25 20:31           ` Keith Busch
2019-07-25 20:37             ` Logan Gunthorpe
2019-07-25 17:23 ` [PATCH v6 05/16] nvme-core: export existing ctrl and ns interfaces Logan Gunthorpe
2019-07-25 17:23 ` [PATCH v6 06/16] nvmet: add return value to nvmet_add_async_event() Logan Gunthorpe
2019-07-25 17:23 ` [PATCH v6 07/16] nvmet: make nvmet_copy_ns_identifier() non-static Logan Gunthorpe
2019-07-25 17:23 ` [PATCH v6 08/16] nvmet-passthru: update KConfig with config passthru option Logan Gunthorpe
2019-07-25 17:23 ` [PATCH v6 09/16] nvmet-passthru: add passthru code to process commands Logan Gunthorpe
2019-07-25 17:23 ` [PATCH v6 10/16] nvmet-passthru: add enable/disable helpers Logan Gunthorpe
2019-07-25 17:23 ` [PATCH v6 11/16] nvmet-core: allow one host per passthru-ctrl Logan Gunthorpe
2019-07-25 17:23 ` [PATCH v6 12/16] nvmet-core: don't check the data len for pt-ctrl Logan Gunthorpe
2019-07-25 17:23 ` [PATCH v6 13/16] nvmet-configfs: introduce passthru configfs interface Logan Gunthorpe
2019-07-25 17:23 ` [PATCH v6 14/16] block: don't check blk_rq_is_passthrough() in blk_do_io_stat() Logan Gunthorpe
2019-07-25 17:23 ` [PATCH v6 15/16] block: call blk_account_io_start() in blk_execute_rq_nowait() Logan Gunthorpe
2019-07-25 17:23 ` [PATCH v6 16/16] nvmet-passthru: support block accounting Logan Gunthorpe
2019-07-26  6:23 ` [PATCH v6 00/16] nvmet: add target passthru commands support Hannes Reinecke
2019-07-26 17:07   ` Logan Gunthorpe
2019-07-26 22:21     ` Sagi Grimberg
2019-07-26 22:37       ` Logan Gunthorpe
2019-07-26 23:13         ` Sagi Grimberg
2019-07-27  0:09           ` Logan Gunthorpe
2019-07-27  0:50             ` Stephen  Bates
2019-07-29 16:15               ` Sagi Grimberg
2019-07-29 16:17                 ` Logan Gunthorpe

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