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From: Christoph Hellwig <[email protected]>
To: Kanchan Joshi <[email protected]>
Cc: [email protected], [email protected], [email protected],
	[email protected], [email protected],
	[email protected], [email protected],
	[email protected], [email protected], [email protected],
	[email protected], [email protected], [email protected],
	[email protected], [email protected]
Subject: Re: [PATCH 05/17] nvme: wire-up support for async-passthru on char-device.
Date: Fri, 11 Mar 2022 08:01:48 +0100	[thread overview]
Message-ID: <[email protected]> (raw)
In-Reply-To: <[email protected]>

On Tue, Mar 08, 2022 at 08:50:53PM +0530, Kanchan Joshi wrote:
> +/*
> + * This overlays struct io_uring_cmd pdu.
> + * Expect build errors if this grows larger than that.
> + */
> +struct nvme_uring_cmd_pdu {
> +	u32 meta_len;
> +	union {
> +		struct bio *bio;
> +		struct request *req;
> +	};
> +	void *meta; /* kernel-resident buffer */
> +	void __user *meta_buffer;
> +} __packed;

Why is this marked __packed?

In general I'd be much more happy if the meta elelements were a
io_uring-level feature handled outside the driver and typesafe in
struct io_uring_cmd, with just a normal private data pointer for the
actual user, which would remove all the crazy casting.

> +static void nvme_end_async_pt(struct request *req, blk_status_t err)
> +{
> +	struct io_uring_cmd *ioucmd = req->end_io_data;
> +	struct nvme_uring_cmd_pdu *pdu = nvme_uring_cmd_pdu(ioucmd);
> +	/* extract bio before reusing the same field for request */
> +	struct bio *bio = pdu->bio;
> +
> +	pdu->req = req;
> +	req->bio = bio;
> +	/* this takes care of setting up task-work */
> +	io_uring_cmd_complete_in_task(ioucmd, nvme_pt_task_cb);

This is a bit silly.  First we defer the actual request I/O completion
from the block layer to a different CPU or softirq and then we have
another callback here.  I think it would be much more useful if we
could find a way to enhance blk_mq_complete_request so that it could
directly complet in a given task.  That would also be really nice for
say normal synchronous direct I/O.

> +	if (ioucmd) { /* async dispatch */
> +		if (cmd->common.opcode == nvme_cmd_write ||
> +				cmd->common.opcode == nvme_cmd_read) {

No we can't just check for specific commands in the passthrough handler.

> +			nvme_setup_uring_cmd_data(req, ioucmd, meta, meta_buffer,
> +					meta_len);
> +			blk_execute_rq_nowait(req, 0, nvme_end_async_pt);
> +			return 0;
> +		} else {
> +			/* support only read and write for now. */
> +			ret = -EINVAL;
> +			goto out_meta;
> +		}

Pleae always handle error in the first branch and don't bother with an
else after a goto or return.

> +static int nvme_ns_async_ioctl(struct nvme_ns *ns, struct io_uring_cmd *ioucmd)
> +{
> +	int ret;
> +
> +	BUILD_BUG_ON(sizeof(struct nvme_uring_cmd_pdu) > sizeof(ioucmd->pdu));
> +
> +	switch (ioucmd->cmd_op) {
> +	case NVME_IOCTL_IO64_CMD:
> +		ret = nvme_user_cmd64(ns->ctrl, ns, NULL, ioucmd);
> +		break;
> +	default:
> +		ret = -ENOTTY;
> +	}
> +
> +	if (ret >= 0)
> +		ret = -EIOCBQUEUED;

That's a weird way to handle the returns.  Just return -EIOCBQUEUED
directly from the handler (which as said before should be split from
the ioctl handler anyway).

  parent reply	other threads:[~2022-03-11  7:01 UTC|newest]

Thread overview: 122+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
     [not found] <CGME20220308152651epcas5p1ebd2dc7fa01db43dd587c228a3695696@epcas5p1.samsung.com>
2022-03-08 15:20 ` [PATCH 00/17] io_uring passthru over nvme Kanchan Joshi
     [not found]   ` <CGME20220308152653epcas5p10c31f58cf6bff125cc0baa176b4d4fac@epcas5p1.samsung.com>
2022-03-08 15:20     ` [PATCH 01/17] io_uring: add support for 128-byte SQEs Kanchan Joshi
     [not found]   ` <CGME20220308152655epcas5p4ae47d715e1c15069e97152dcd283fd40@epcas5p4.samsung.com>
2022-03-08 15:20     ` [PATCH 02/17] fs: add file_operations->async_cmd() Kanchan Joshi
     [not found]   ` <CGME20220308152658epcas5p3929bd1fcf75edc505fec71901158d1b5@epcas5p3.samsung.com>
2022-03-08 15:20     ` [PATCH 03/17] io_uring: add infra and support for IORING_OP_URING_CMD Kanchan Joshi
2022-03-11  1:51       ` Luis Chamberlain
2022-03-11  2:43         ` Jens Axboe
2022-03-11 17:11           ` Luis Chamberlain
2022-03-11 18:47             ` Paul Moore
2022-03-11 20:57               ` Luis Chamberlain
2022-03-11 21:03                 ` Paul Moore
2022-03-14 16:25             ` Casey Schaufler
2022-03-14 16:32               ` Luis Chamberlain
2022-03-14 18:05                 ` Casey Schaufler
2022-03-14 19:40                   ` Luis Chamberlain
     [not found]   ` <CGME20220308152700epcas5p4130d20119a3a250a2515217d6552f668@epcas5p4.samsung.com>
2022-03-08 15:20     ` [PATCH 04/17] nvme: modify nvme_alloc_request to take an additional parameter Kanchan Joshi
2022-03-11  6:38       ` Christoph Hellwig
     [not found]   ` <CGME20220308152702epcas5p1eb1880e024ac8b9531c85a82f31a4e78@epcas5p1.samsung.com>
2022-03-08 15:20     ` [PATCH 05/17] nvme: wire-up support for async-passthru on char-device Kanchan Joshi
2022-03-10  0:02       ` Clay Mayers
2022-03-10  8:32         ` Kanchan Joshi
2022-03-11  7:01       ` Christoph Hellwig [this message]
2022-03-14 16:23         ` Kanchan Joshi
2022-03-15  8:54           ` Christoph Hellwig
2022-03-16  7:27             ` Kanchan Joshi
2022-03-24  6:22               ` Christoph Hellwig
2022-03-24 17:45                 ` Kanchan Joshi
2022-03-11 17:56       ` Luis Chamberlain
2022-03-11 18:53         ` Paul Moore
2022-03-11 21:02           ` Luis Chamberlain
2022-03-13 21:53       ` Sagi Grimberg
2022-03-14 17:54         ` Kanchan Joshi
2022-03-15  9:02           ` Sagi Grimberg
2022-03-16  9:21             ` Kanchan Joshi
2022-03-16 10:56               ` Sagi Grimberg
2022-03-16 11:51                 ` Kanchan Joshi
2022-03-16 13:52                   ` Sagi Grimberg
2022-03-16 14:35                     ` Jens Axboe
2022-03-16 14:50                       ` Sagi Grimberg
2022-03-24  6:20                         ` Christoph Hellwig
2022-03-24 10:42                           ` Sagi Grimberg
2022-03-22 15:18       ` Clay Mayers
2022-03-22 16:57         ` Kanchan Joshi
     [not found]   ` <CGME20220308152704epcas5p16610e1f50672b25fa1df5f7c5c261bb5@epcas5p1.samsung.com>
2022-03-08 15:20     ` [PATCH 06/17] io_uring: prep for fixed-buffer enabled uring-cmd Kanchan Joshi
     [not found]   ` <CGME20220308152707epcas5p430127761a7fd4bf90c2501eabe9ee96e@epcas5p4.samsung.com>
2022-03-08 15:20     ` [PATCH 07/17] io_uring: add support for uring_cmd with fixed-buffer Kanchan Joshi
     [not found]   ` <CGME20220308152709epcas5p1f9d274a0214dc462c22c278a72d8697c@epcas5p1.samsung.com>
2022-03-08 15:20     ` [PATCH 08/17] nvme: enable passthrough " Kanchan Joshi
2022-03-10  8:32       ` Christoph Hellwig
2022-03-11  6:43       ` Christoph Hellwig
2022-03-14 13:06         ` Kanchan Joshi
2022-03-15  8:55           ` Christoph Hellwig
2022-03-14 12:18       ` Ming Lei
2022-03-14 13:09         ` Kanchan Joshi
     [not found]   ` <CGME20220308152711epcas5p31de5d63f5de91fae94e61e5c857c0f13@epcas5p3.samsung.com>
2022-03-08 15:20     ` [PATCH 09/17] io_uring: plug for async bypass Kanchan Joshi
2022-03-10  8:33       ` Christoph Hellwig
2022-03-14 14:33         ` Ming Lei
2022-03-15  8:56           ` Christoph Hellwig
2022-03-11 17:15       ` Luis Chamberlain
     [not found]   ` <CGME20220308152714epcas5p4c5a0d16512fd7054c9a713ee28ede492@epcas5p4.samsung.com>
2022-03-08 15:20     ` [PATCH 10/17] block: wire-up support for plugging Kanchan Joshi
2022-03-10  8:34       ` Christoph Hellwig
2022-03-10 12:40         ` Kanchan Joshi
2022-03-14 14:40           ` Ming Lei
2022-03-21  7:02             ` Kanchan Joshi
2022-03-23  1:27               ` Ming Lei
2022-03-23  1:41                 ` Jens Axboe
2022-03-23  1:58                   ` Jens Axboe
2022-03-23  2:10                     ` Ming Lei
2022-03-23  2:17                       ` Jens Axboe
     [not found]   ` <CGME20220308152716epcas5p3d38d2372c184259f1a10c969f7e4396f@epcas5p3.samsung.com>
2022-03-08 15:20     ` [PATCH 11/17] block: factor out helper for bio allocation from cache Kanchan Joshi
2022-03-10  8:35       ` Christoph Hellwig
2022-03-10 12:25         ` Kanchan Joshi
2022-03-24  6:30           ` Christoph Hellwig
2022-03-24 17:45             ` Kanchan Joshi
2022-03-25  5:38               ` Christoph Hellwig
     [not found]   ` <CGME20220308152718epcas5p3afd2c8a628f4e9733572cbb39270989d@epcas5p3.samsung.com>
2022-03-08 15:21     ` [PATCH 12/17] nvme: enable bio-cache for fixed-buffer passthru Kanchan Joshi
2022-03-11  6:48       ` Christoph Hellwig
2022-03-14 18:18         ` Kanchan Joshi
2022-03-15  8:57           ` Christoph Hellwig
     [not found]   ` <CGME20220308152720epcas5p19653942458e160714444942ddb8b8579@epcas5p1.samsung.com>
2022-03-08 15:21     ` [PATCH 13/17] nvme: allow user passthrough commands to poll Kanchan Joshi
2022-03-08 17:08       ` Keith Busch
2022-03-09  7:03         ` Kanchan Joshi
2022-03-11  6:49           ` Christoph Hellwig
     [not found]   ` <CGME20220308152723epcas5p34460b4af720e515317f88dbb78295f06@epcas5p3.samsung.com>
2022-03-08 15:21     ` [PATCH 14/17] io_uring: add polling support for uring-cmd Kanchan Joshi
2022-03-11  6:50       ` Christoph Hellwig
2022-03-14 10:16         ` Kanchan Joshi
2022-03-15  8:57           ` Christoph Hellwig
2022-03-16  5:09             ` Kanchan Joshi
2022-03-24  6:30               ` Christoph Hellwig
     [not found]   ` <CGME20220308152725epcas5p36d1ce3269a47c1c22cc0d66bdc2b9eb3@epcas5p3.samsung.com>
2022-03-08 15:21     ` [PATCH 15/17] nvme: wire-up polling for uring-passthru Kanchan Joshi
     [not found]   ` <CGME20220308152727epcas5p20e605718dd99e97c94f9232d40d04d95@epcas5p2.samsung.com>
2022-03-08 15:21     ` [PATCH 16/17] io_uring: add support for non-inline uring-cmd Kanchan Joshi
     [not found]   ` <CGME20220308152729epcas5p17e82d59c68076eb46b5ef658619d65e3@epcas5p1.samsung.com>
2022-03-08 15:21     ` [PATCH 17/17] nvme: enable non-inline passthru commands Kanchan Joshi
2022-03-10  8:36       ` Christoph Hellwig
2022-03-10 11:50         ` Kanchan Joshi
2022-03-10 14:19           ` Christoph Hellwig
2022-03-10 18:43             ` Kanchan Joshi
2022-03-11  6:27               ` Christoph Hellwig
2022-03-22 17:10                 ` Kanchan Joshi
2022-03-24  6:32                   ` Christoph Hellwig
2022-03-25 13:39                     ` Kanchan Joshi
2022-03-28  4:44                       ` Kanchan Joshi
2022-03-30 12:59                         ` Christoph Hellwig
2022-03-30 13:02                       ` Christoph Hellwig
2022-03-30 13:14                         ` Kanchan Joshi
2022-04-01  1:25                           ` Jens Axboe
2022-04-01  2:33                             ` Kanchan Joshi
2022-04-01  2:44                               ` Jens Axboe
2022-04-01  3:05                                 ` Jens Axboe
2022-04-01  6:32                                 ` Kanchan Joshi
2022-04-19 17:31                                 ` Kanchan Joshi
2022-04-19 18:19                                   ` Jens Axboe
     [not found]                                     ` <CGME20220420152003epcas5p3991e6941773690bcb425fd9d817105c3@epcas5p3.samsung.com>
2022-04-20 15:14                                       ` Kanchan Joshi
2022-04-20 15:28                                         ` Kanchan Joshi
2022-04-01  1:23                         ` Jens Axboe
2022-04-01  1:22                   ` Jens Axboe
2022-04-01  6:29                     ` Kanchan Joshi
2022-03-24 21:09       ` Clay Mayers
2022-03-24 23:36         ` Jens Axboe
2022-03-10  8:29   ` [PATCH 00/17] io_uring passthru over nvme Christoph Hellwig
2022-03-10 10:05     ` Kanchan Joshi
2022-03-11 16:43       ` Luis Chamberlain
2022-03-11 23:35         ` Adam Manzanares
2022-03-12  2:27           ` Adam Manzanares
2022-03-13  5:07             ` Kanchan Joshi
2022-03-14 20:30               ` Adam Manzanares
2022-03-13  5:10         ` Kanchan Joshi

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