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From: Kanchan Joshi <[email protected]>
To: Christoph Hellwig <[email protected]>
Cc: "Kanchan Joshi" <[email protected]>,
	"Jens Axboe" <[email protected]>,
	[email protected], [email protected],
	"Pavel Begunkov" <[email protected]>,
	"Ming Lei" <[email protected]>,
	"Luis Chamberlain" <[email protected]>,
	"Pankaj Raghav" <[email protected]>,
	"Javier González" <[email protected]>,
	"Anuj Gupta" <[email protected]>
Subject: Re: [RFC 5/5] nvme: wire-up support for async-passthru on char-device.
Date: Fri, 29 Apr 2022 18:46:47 +0530	[thread overview]
Message-ID: <20220429131647.GA10057@test-zns> (raw)
In-Reply-To: <20220425173803.GA2454@test-zns>

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On Mon, Apr 25, 2022 at 11:08:03PM +0530, Kanchan Joshi wrote:
>On Sat, Apr 23, 2022 at 07:53:09PM +0200, Christoph Hellwig wrote:
>>On Wed, Apr 06, 2022 at 10:50:14AM +0530, Kanchan Joshi wrote:
>>>> In that case we will base the newer version on its top.
>>>But if it saves some cycles for you, and also the travel from nvme to
>>>linux-block tree - I can carry that refactoring as a prep patch in
>>>this series. Your call.
>>
>>FYI, this is what I have so far:
>>
>>http://git.infradead.org/users/hch/misc.git/shortlog/refs/heads/nvme-passthrough-refactor
>>
>>the idea would be to use these lower level helpers for uring, and
>>not really share the higher level function at all.  This does create
>>a little extra code, but I think it'll be more modular and better
>>maintainable.  Feel free to pull this in if it helps you, otherwise
>>I'll try to find some time to do more than just light testing and
>>will post it.
>
>Thanks for sharing.
>So I had picked your previous version, and this one streamlines meta
>handling further. But the problem is bip gets freed before we reach to
>this point -
>
>+static int nvme_free_user_metadata(struct bio *bio, void __user *ubuf, int ret)
>+{
>+       struct bio_integrity_payload *bip = bio_integrity(bio);
>+       void *buf = bvec_virt(bip->bip_vec);
>+
>+       if (!ret && bio_op(bio) == REQ_OP_DRV_IN &&
>+           copy_to_user(ubuf, buf, bip->bip_vec->bv_len))
>
>Without bip, we cannot kill current meta/meta_len fields.

And by this I mean we cannot keep io_uring_cmd this way -

+struct io_uring_cmd {
+       struct file     *file;
+       void            *cmd;
+       /* for irq-completion - if driver requires doing stuff in task-context*/
+       void (*driver_cb)(struct io_uring_cmd *cmd);
+       u32             flags;
+       u32             cmd_op;
+
+       void            *private;
+
+       /*
+        * Out of band data can be used for data that is not the main data.
+        * E.g. block device PI/metadata or additional information.
+        */
+       void __user     *oob_user;
+};

Rather we need to backtrack to pdu[28], since nvme would need all that
space.

+struct io_uring_cmd {
+       struct file     *file;
+       void            *cmd;
+       /* for irq-completion - if driver requires doing stuff in task-context*/
+       void (*driver_cb)(struct io_uring_cmd *cmd);
+       u32             flags;
+       u32             cmd_op;
+       u32             unused;
+       u8              pdu[28]; /* available inline for free use */
+};

+struct nvme_uring_cmd_pdu {
+       union {
+               struct bio *bio;
+               struct request *req;
+       };
+       void *meta; /* kernel-resident buffer */
+       void __user *meta_buffer;
+       u32 meta_len;
+} __packed;


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  reply	other threads:[~2022-04-30  5:58 UTC|newest]

Thread overview: 28+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
     [not found] <CGME20220401110829epcas5p39f3cf4d3f6eb8a5c59794787a2b72b15@epcas5p3.samsung.com>
2022-04-01 11:03 ` [RFC 0/5] big-cqe based uring-passthru Kanchan Joshi
     [not found]   ` <CGME20220401110831epcas5p403bacabe8f7e5262356fdc1a2e66df90@epcas5p4.samsung.com>
2022-04-01 11:03     ` [RFC 1/5] io_uring: add support for 128-byte SQEs Kanchan Joshi
     [not found]   ` <CGME20220401110833epcas5p18e828a307a646cef5b7aa429be4396e0@epcas5p1.samsung.com>
2022-04-01 11:03     ` [RFC 2/5] fs: add file_operations->async_cmd() Kanchan Joshi
2022-04-04  7:09       ` Christoph Hellwig
     [not found]   ` <CGME20220401110834epcas5p4d1e5e8d1beb1a6205d670bbcb932bf77@epcas5p4.samsung.com>
2022-04-01 11:03     ` [RFC 3/5] io_uring: add infra and support for IORING_OP_URING_CMD Kanchan Joshi
2022-04-04  7:16       ` Christoph Hellwig
2022-04-04  8:20         ` Pavel Begunkov
2022-04-05  5:58           ` Christoph Hellwig
2022-04-06  6:37             ` Kanchan Joshi
2022-04-04 15:14         ` Kanchan Joshi
2022-04-05  6:00           ` Christoph Hellwig
2022-04-05 16:27             ` Kanchan Joshi
     [not found]   ` <CGME20220401110836epcas5p37bd59ab5a48cf77ca3ac05052a164b0b@epcas5p3.samsung.com>
2022-04-01 11:03     ` [RFC 4/5] io_uring: add support for big-cqe Kanchan Joshi
2022-04-04  7:07       ` Christoph Hellwig
2022-04-04 14:04         ` Kanchan Joshi
     [not found]   ` <CGME20220401110838epcas5p2c1a2e776923dfe5bf65a3e7946820150@epcas5p2.samsung.com>
2022-04-01 11:03     ` [RFC 5/5] nvme: wire-up support for async-passthru on char-device Kanchan Joshi
2022-04-04  7:20       ` Christoph Hellwig
2022-04-04 14:25         ` Kanchan Joshi
2022-04-05  6:02           ` Christoph Hellwig
2022-04-05 15:40             ` Jens Axboe
2022-04-05 15:49             ` Kanchan Joshi
2022-04-06  5:20               ` Kanchan Joshi
2022-04-06  5:23                 ` Christoph Hellwig
2022-04-23 17:53                 ` Christoph Hellwig
2022-04-25 17:38                   ` Kanchan Joshi
2022-04-29 13:16                     ` Kanchan Joshi [this message]
2022-04-04  7:21   ` [RFC 0/5] big-cqe based uring-passthru Christoph Hellwig
2022-04-05 15:37     ` Kanchan Joshi

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