Re: [PATCH v1 2/3] virtio-blk: add uring_cmd support for I/O passthru on chardev.

[Ferry Meng <mengferry@linux.alibaba.com>]

On 1/7/25 9:14 PM, lizetao wrote:
> Hi,
>
>> -----Original Message-----
>> From: Ferry Meng <mengferry@linux.alibaba.com>
>> Sent: Wednesday, December 18, 2024 5:25 PM
>> To: Michael S . Tsirkin <mst@redhat.com>; Jason Wang
>> <jasowang@redhat.com>; linux-block@vger.kernel.org; Jens Axboe
>> <axboe@kernel.dk>; virtualization@lists.linux.dev
>> Cc: linux-kernel@vger.kernel.org; io-uring@vger.kernel.org; Stefan Hajnoczi
>> <stefanha@redhat.com>; Christoph Hellwig <hch@infradead.org>; Joseph Qi
>> <joseph.qi@linux.alibaba.com>; Jeffle Xu <jefflexu@linux.alibaba.com>; Ferry
>> Meng <mengferry@linux.alibaba.com>
>> Subject: [PATCH v1 2/3] virtio-blk: add uring_cmd support for I/O passthru on
>> chardev.
>>
>> 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@linux.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) {
>> +	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);
>> +}
>> +
>> +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;
>> +	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;
> Shoule be goto out here? Or req will not be free. And I suggest to
> free request in virtblk_uring_cmd_io().
Thx, u are right. This will be fixed in v2 series.
I will send out v2 in next week.
>> +		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;
>> +	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));
>> +
>> +	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
>> --
>> 2.43.5
>>
>>