Message-ID: <9412e93e-1e55-474d-ae8f-0ca25ce827b5@linux.alibaba.com>
Date: Mon, 30 Dec 2024 16:00:01 +0800
From: Joseph Qi <joseph.qi@...ux.alibaba.com>
To: Ferry Meng <mengferry@...ux.alibaba.com>,
 "Michael S . Tsirkin" <mst@...hat.com>, Jason Wang <jasowang@...hat.com>,
 linux-block@...r.kernel.org, Jens Axboe <axboe@...nel.dk>,
 virtualization@...ts.linux.dev
Cc: linux-kernel@...r.kernel.org, io-uring@...r.kernel.org,
 Stefan Hajnoczi <stefanha@...hat.com>, Christoph Hellwig
 <hch@...radead.org>, Jeffle Xu <jefflexu@...ux.alibaba.com>
Subject: Re: [PATCH v1 2/3] virtio-blk: add uring_cmd support for I/O passthru
 on chardev.



On 2024/12/18 17:24, Ferry Meng wrote:
> Add ->uring_cmd() support for virtio-blk chardev (/dev/vdXc0).
> According to virtio spec, in addition to passing 'hdr' info into kernel,
> we also need to pass vaddr & data length of the 'iov' requeired for the
> writev/readv op.
> 
> Signed-off-by: Ferry Meng <mengferry@...ux.alibaba.com>
> ---
>  drivers/block/virtio_blk.c      | 223 +++++++++++++++++++++++++++++++-
>  include/uapi/linux/virtio_blk.h |  16 +++
>  2 files changed, 235 insertions(+), 4 deletions(-)
> 
> diff --git a/drivers/block/virtio_blk.c b/drivers/block/virtio_blk.c
> index 3487aaa67514..cd88cf939144 100644
> --- a/drivers/block/virtio_blk.c
> +++ b/drivers/block/virtio_blk.c
> @@ -18,6 +18,9 @@
>  #include <linux/vmalloc.h>
>  #include <uapi/linux/virtio_ring.h>
>  #include <linux/cdev.h>
> +#include <linux/io_uring/cmd.h>
> +#include <linux/types.h>
> +#include <linux/uio.h>
>  
>  #define PART_BITS 4
>  #define VQ_NAME_LEN 16
> @@ -54,6 +57,20 @@ static struct class *vd_chr_class;
>  
>  static struct workqueue_struct *virtblk_wq;
>  
> +struct virtblk_uring_cmd_pdu {
> +	struct request *req;
> +	struct bio *bio;
> +	int status;
> +};
> +
> +struct virtblk_command {
> +	struct virtio_blk_outhdr out_hdr;
> +
> +	__u64	data;
> +	__u32	data_len;
> +	__u32	flag;
> +};
> +
>  struct virtio_blk_vq {
>  	struct virtqueue *vq;
>  	spinlock_t lock;
> @@ -122,6 +139,11 @@ struct virtblk_req {
>  	struct scatterlist sg[];
>  };
>  
> +static void __user *virtblk_to_user_ptr(uintptr_t ptrval)
> +{

Refer to nvme_to_user_ptr(), the logic for compat syscall is missing.

> +	return (void __user *)ptrval;
> +}
> +
>  static inline blk_status_t virtblk_result(u8 status)
>  {
>  	switch (status) {
> @@ -259,9 +281,6 @@ static blk_status_t virtblk_setup_cmd(struct virtio_device *vdev,
>  	if (!IS_ENABLED(CONFIG_BLK_DEV_ZONED) && op_is_zone_mgmt(req_op(req)))
>  		return BLK_STS_NOTSUPP;
>  
> -	/* Set fields for all request types */
> -	vbr->out_hdr.ioprio = cpu_to_virtio32(vdev, req_get_ioprio(req));
> -
>  	switch (req_op(req)) {
>  	case REQ_OP_READ:
>  		type = VIRTIO_BLK_T_IN;
> @@ -309,9 +328,11 @@ static blk_status_t virtblk_setup_cmd(struct virtio_device *vdev,
>  		type = VIRTIO_BLK_T_ZONE_RESET_ALL;
>  		break;
>  	case REQ_OP_DRV_IN:
> +	case REQ_OP_DRV_OUT:
>  		/*
>  		 * Out header has already been prepared by the caller (virtblk_get_id()
> -		 * or virtblk_submit_zone_report()), nothing to do here.
> +		 * virtblk_submit_zone_report() or io_uring passthrough cmd), nothing
> +		 * to do here.
>  		 */
>  		return 0;
>  	default:
> @@ -323,6 +344,7 @@ static blk_status_t virtblk_setup_cmd(struct virtio_device *vdev,
>  	vbr->in_hdr_len = in_hdr_len;
>  	vbr->out_hdr.type = cpu_to_virtio32(vdev, type);
>  	vbr->out_hdr.sector = cpu_to_virtio64(vdev, sector);
> +	vbr->out_hdr.ioprio = cpu_to_virtio32(vdev, req_get_ioprio(req));
>  
>  	if (type == VIRTIO_BLK_T_DISCARD || type == VIRTIO_BLK_T_WRITE_ZEROES ||
>  	    type == VIRTIO_BLK_T_SECURE_ERASE) {
> @@ -832,6 +854,7 @@ static int virtblk_get_id(struct gendisk *disk, char *id_str)
>  	vbr = blk_mq_rq_to_pdu(req);
>  	vbr->in_hdr_len = sizeof(vbr->in_hdr.status);
>  	vbr->out_hdr.type = cpu_to_virtio32(vblk->vdev, VIRTIO_BLK_T_GET_ID);
> +	vbr->out_hdr.ioprio = cpu_to_virtio32(vblk->vdev, req_get_ioprio(req));
>  	vbr->out_hdr.sector = 0;
>  
>  	err = blk_rq_map_kern(q, req, id_str, VIRTIO_BLK_ID_BYTES, GFP_KERNEL);
> @@ -1250,6 +1273,197 @@ static const struct blk_mq_ops virtio_mq_ops = {
>  	.poll		= virtblk_poll,
>  };
>  
> +static inline struct virtblk_uring_cmd_pdu *virtblk_get_uring_cmd_pdu(
> +		struct io_uring_cmd *ioucmd)
> +{
> +	return (struct virtblk_uring_cmd_pdu *)&ioucmd->pdu;
> +}
> +
> +static void virtblk_uring_task_cb(struct io_uring_cmd *ioucmd,
> +		unsigned int issue_flags)
> +{
> +	struct virtblk_uring_cmd_pdu *pdu = virtblk_get_uring_cmd_pdu(ioucmd);
> +	struct virtblk_req *vbr = blk_mq_rq_to_pdu(pdu->req);
> +	u64 result = 0;
> +
> +	if (pdu->bio)
> +		blk_rq_unmap_user(pdu->bio);
> +
> +	/* currently result has no use, it should be zero as cqe->res */
> +	io_uring_cmd_done(ioucmd, vbr->in_hdr.status, result, issue_flags);
> +}
> +
> +static enum rq_end_io_ret virtblk_uring_cmd_end_io(struct request *req,
> +						   blk_status_t err)
> +{
> +	struct io_uring_cmd *ioucmd = req->end_io_data;
> +	struct virtblk_uring_cmd_pdu *pdu = virtblk_get_uring_cmd_pdu(ioucmd);
> +
> +	/*
> +	 * For iopoll, complete it directly. Note that using the uring_cmd
> +	 * helper for this is safe only because we check blk_rq_is_poll().
> +	 * As that returns false if we're NOT on a polled queue, then it's
> +	 * safe to use the polled completion helper.
> +	 *
> +	 * Otherwise, move the completion to task work.
> +	 */
> +	if (blk_rq_is_poll(req)) {
> +		if (pdu->bio)
> +			blk_rq_unmap_user(pdu->bio);
> +		io_uring_cmd_iopoll_done(ioucmd, 0, pdu->status);
> +	} else {
> +		io_uring_cmd_do_in_task_lazy(ioucmd, virtblk_uring_task_cb);
> +	}
> +
> +	return RQ_END_IO_FREE;
> +}
> +
> +static struct virtblk_req *virtblk_req(struct request *req)
> +{
> +	return blk_mq_rq_to_pdu(req);
> +}

Don't think this helper is necessary.
You've already open-coded in other places.

> +
> +static inline enum req_op virtblk_req_op(const struct virtblk_uring_cmd *cmd)
> +{
> +	return (cmd->type & VIRTIO_BLK_T_OUT) ? REQ_OP_DRV_OUT : REQ_OP_DRV_IN;
> +}
> +
> +static struct request *virtblk_alloc_user_request(
> +		struct request_queue *q, struct virtblk_command *cmd,
> +		blk_opf_t rq_flags, blk_mq_req_flags_t blk_flags)
> +{
> +	struct request *req;
> +
> +	req = blk_mq_alloc_request(q, rq_flags, blk_flags);
> +	if (IS_ERR(req))
> +		return req;
> +
> +	req->rq_flags |= RQF_DONTPREP;

Do we have to do some other initialization? e.g. REQ_POLLED.

> +	memcpy(&virtblk_req(req)->out_hdr, &cmd->out_hdr, sizeof(struct virtio_blk_outhdr));
> +	return req;
> +}
> +
> +static int virtblk_map_user_request(struct request *req, u64 ubuffer,
> +		unsigned int bufflen, struct io_uring_cmd *ioucmd,
> +		bool vec)
> +{
> +	struct request_queue *q = req->q;
> +	struct virtio_blk *vblk = q->queuedata;
> +	struct block_device *bdev = vblk ? vblk->disk->part0 : NULL;
> +	struct bio *bio = NULL;
> +	int ret;
> +
> +	if (ioucmd && (ioucmd->flags & IORING_URING_CMD_FIXED)) {
> +		struct iov_iter iter;
> +
> +		/* fixedbufs is only for non-vectored io */
> +		if (WARN_ON_ONCE(vec))
> +			return -EINVAL;
> +		ret = io_uring_cmd_import_fixed(ubuffer, bufflen,
> +				rq_data_dir(req), &iter, ioucmd);
> +		if (ret < 0)
> +			goto out;
> +		ret = blk_rq_map_user_iov(q, req, NULL,
> +			&iter, GFP_KERNEL);
> +	} else {
> +		ret = blk_rq_map_user_io(req, NULL,
> +				virtblk_to_user_ptr(ubuffer),
> +				bufflen, GFP_KERNEL, vec, 0,
> +				0, rq_data_dir(req));
> +	}
> +	if (ret)
> +		goto out;
> +
> +	bio = req->bio;
> +	if (bdev)
> +		bio_set_dev(bio, bdev);
> +	return 0;
> +
> +out:
> +	blk_mq_free_request(req);
> +	return ret;
> +}
> +
> +static int virtblk_uring_cmd_io(struct virtio_blk *vblk,
> +		struct io_uring_cmd *ioucmd, unsigned int issue_flags, bool vec)
> +{
> +	struct virtblk_uring_cmd_pdu *pdu = virtblk_get_uring_cmd_pdu(ioucmd);
> +	const struct virtblk_uring_cmd *cmd = io_uring_sqe_cmd(ioucmd->sqe);
> +	struct request_queue *q = vblk->disk->queue;
> +	struct virtblk_req *vbr;
> +	struct virtblk_command d;

Or use 'c' for command?

> +	struct request *req;
> +	blk_opf_t rq_flags = REQ_ALLOC_CACHE | virtblk_req_op(cmd);
> +	blk_mq_req_flags_t blk_flags = 0;
> +	int ret;
> +
> +	if (!capable(CAP_SYS_ADMIN))
> +		return -EACCES;
> +
> +	d.out_hdr.ioprio = cpu_to_virtio32(vblk->vdev, READ_ONCE(cmd->ioprio));
> +	d.out_hdr.type = cpu_to_virtio32(vblk->vdev, READ_ONCE(cmd->type));
> +	d.out_hdr.sector = cpu_to_virtio64(vblk->vdev, READ_ONCE(cmd->sector));
> +	d.data = READ_ONCE(cmd->data);
> +	d.data_len = READ_ONCE(cmd->data_len);
> +
> +	if (issue_flags & IO_URING_F_NONBLOCK) {
> +		rq_flags |= REQ_NOWAIT;
> +		blk_flags = BLK_MQ_REQ_NOWAIT;
> +	}
> +	if (issue_flags & IO_URING_F_IOPOLL)
> +		rq_flags |= REQ_POLLED;
> +
> +	req = virtblk_alloc_user_request(q, &d, rq_flags, blk_flags);
> +	if (IS_ERR(req))
> +		return PTR_ERR(req);
> +
> +	vbr = virtblk_req(req);
> +	vbr->in_hdr_len = sizeof(vbr->in_hdr.status);
> +	if (d.data && d.data_len) {
> +		ret = virtblk_map_user_request(req, d.data, d.data_len, ioucmd, vec);
> +		if (ret)
> +			return ret;
> +	}
> +
> +	/* to free bio on completion, as req->bio will be null at that time */
> +	pdu->bio = req->bio;
> +	pdu->req = req;
> +	req->end_io_data = ioucmd;
> +	req->end_io = virtblk_uring_cmd_end_io;
> +	blk_execute_rq_nowait(req, false);
> +	return -EIOCBQUEUED;
> +}
> +
> +
> +static int virtblk_uring_cmd(struct virtio_blk *vblk, struct io_uring_cmd *ioucmd,
> +			     unsigned int issue_flags)
> +{
> +	int ret;
> +
> +	BUILD_BUG_ON(sizeof(struct virtblk_uring_cmd_pdu) > sizeof(ioucmd->pdu));

io_uring passthrough requires big sqe/cqe support.
So it is deserved a check here.

Thanks,
Joseph

> +
> +	switch (ioucmd->cmd_op) {
> +	case VIRTBLK_URING_CMD_IO:
> +		ret = virtblk_uring_cmd_io(vblk, ioucmd, issue_flags, false);
> +		break;
> +	case VIRTBLK_URING_CMD_IO_VEC:
> +		ret = virtblk_uring_cmd_io(vblk, ioucmd, issue_flags, true);
> +		break;
> +	default:
> +		ret = -ENOTTY;
> +	}
> +
> +	return ret;
> +}
> +
> +static int virtblk_chr_uring_cmd(struct io_uring_cmd *ioucmd, unsigned int issue_flags)
> +{
> +	struct virtio_blk *vblk = container_of(file_inode(ioucmd->file)->i_cdev,
> +			struct virtio_blk, cdev);
> +
> +	return virtblk_uring_cmd(vblk, ioucmd, issue_flags);
> +}
> +
>  static void virtblk_cdev_rel(struct device *dev)
>  {
>  	ida_free(&vd_chr_minor_ida, MINOR(dev->devt));
> @@ -1297,6 +1511,7 @@ static int virtblk_cdev_add(struct virtio_blk *vblk,
>  
>  static const struct file_operations virtblk_chr_fops = {
>  	.owner		= THIS_MODULE,
> +	.uring_cmd	= virtblk_chr_uring_cmd,
>  };
>  
>  static unsigned int virtblk_queue_depth;
> diff --git a/include/uapi/linux/virtio_blk.h b/include/uapi/linux/virtio_blk.h
> index 3744e4da1b2a..93b6e1b5b9a4 100644
> --- a/include/uapi/linux/virtio_blk.h
> +++ b/include/uapi/linux/virtio_blk.h
> @@ -313,6 +313,22 @@ struct virtio_scsi_inhdr {
>  };
>  #endif /* !VIRTIO_BLK_NO_LEGACY */
>  
> +struct virtblk_uring_cmd {
> +	/* VIRTIO_BLK_T* */
> +	__u32 type;
> +	/* io priority. */
> +	__u32 ioprio;
> +	/* Sector (ie. 512 byte offset) */
> +	__u64 sector;
> +
> +	__u64 data;
> +	__u32 data_len;
> +	__u32 flag;
> +};
> +
> +#define VIRTBLK_URING_CMD_IO		1
> +#define VIRTBLK_URING_CMD_IO_VEC	2
> +
>  /* And this is the final byte of the write scatter-gather list. */
>  #define VIRTIO_BLK_S_OK		0
>  #define VIRTIO_BLK_S_IOERR	1

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