Re: [PATCH RFC 3/8] virtio_blk: Add support for provision requests

Stefan Hajnoczi
2022-09-16T05:48:17Z

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On Thu, Sep 15, 2022 at 09:48:21AM -0700, Sarthak Kukreti wrote:
> From: Sarthak Kukreti <sarthakkukreti@chromium.org>
>
> Adds support for provision requests. Provision requests act like
> the inverse of discards.
>
> Signed-off-by: Sarthak Kukreti <sarthakkukreti@chromium.org>
> ---
> drivers/block/virtio_blk.c | 48 +++++++++++++++++++++++++++++++++
> include/uapi/linux/virtio_blk.h | 9 +++++++
> 2 files changed, 57 insertions(+)

Please send a VIRTIO spec patch too:
https://github.com/oasis-tcs/virtio-spec#providing-feedback

Stefan

>
> diff --git a/drivers/block/virtio_blk.c b/drivers/block/virtio_blk.c
> index 30255fcaf181..eacc2bffe1d1 100644
> --- a/drivers/block/virtio_blk.c
> +++ b/drivers/block/virtio_blk.c
> @@ -178,6 +178,39 @@ static int virtblk_setup_discard_write_zeroes(struct request *req, bool unmap)
> return 0;
> }
>
> +static int virtblk_setup_provision(struct request *req)
> +{
> + unsigned short segments = blk_rq_nr_discard_segments(req);
> + unsigned short n = 0;
> +
> + struct virtio_blk_discard_write_zeroes *range;
> + struct bio *bio;
> + u32 flags = 0;
> +
> + range = kmalloc_array(segments, sizeof(*range), GFP_ATOMIC);
> + if (!range)
> + return -ENOMEM;
> +
> + __rq_for_each_bio(bio, req) {
> + u64 sector = bio->bi_iter.bi_sector;
> + u32 num_sectors = bio->bi_iter.bi_size >> SECTOR_SHIFT;
> +
> + range[n].flags = cpu_to_le32(flags);
> + range[n].num_sectors = cpu_to_le32(num_sectors);
> + range[n].sector = cpu_to_le64(sector);
> + n++;
> + }
> +
> + WARN_ON_ONCE(n != segments);
> +
> + req->special_vec.bv_page = virt_to_page(range);
> + req->special_vec.bv_offset = offset_in_page(range);
> + req->special_vec.bv_len = sizeof(*range) * segments;
> + req->rq_flags |= RQF_SPECIAL_PAYLOAD;
> +
> + return 0;
> +}
> +
> static void virtblk_unmap_data(struct request *req, struct virtblk_req *vbr)
> {
> if (blk_rq_nr_phys_segments(req))
> @@ -243,6 +276,9 @@ static blk_status_t virtblk_setup_cmd(struct virtio_device *vdev,
> case REQ_OP_DRV_IN:
> type = VIRTIO_BLK_T_GET_ID;
> break;
> + case REQ_OP_PROVISION:
> + type = VIRTIO_BLK_T_PROVISION;
> + break;
> default:
> WARN_ON_ONCE(1);
> return BLK_STS_IOERR;
> @@ -256,6 +292,11 @@ static blk_status_t virtblk_setup_cmd(struct virtio_device *vdev,
> return BLK_STS_RESOURCE;
> }
>
> + if (type == VIRTIO_BLK_T_PROVISION) {
> + if (virtblk_setup_provision(req))
> + return BLK_STS_RESOURCE;
> + }
> +
> return 0;
> }
>
> @@ -1075,6 +1116,12 @@ static int virtblk_probe(struct virtio_device *vdev)
> blk_queue_max_write_zeroes_sectors(q, v ? v : UINT_MAX);
> }
>
> + if (virtio_has_feature(vdev, VIRTIO_BLK_F_PROVISION)) {
> + virtio_cread(vdev, struct virtio_blk_config,
> + max_provision_sectors, &v);
> + q->limits.max_provision_sectors = v ? v : UINT_MAX;
> + }
> +
> virtblk_update_capacity(vblk, false);
> virtio_device_ready(vdev);
>
> @@ -1177,6 +1224,7 @@ static unsigned int features[] = {
> VIRTIO_BLK_F_RO, VIRTIO_BLK_F_BLK_SIZE,
> VIRTIO_BLK_F_FLUSH, VIRTIO_BLK_F_TOPOLOGY, VIRTIO_BLK_F_CONFIG_WCE,
> VIRTIO_BLK_F_MQ, VIRTIO_BLK_F_DISCARD, VIRTIO_BLK_F_WRITE_ZEROES,
> + VIRTIO_BLK_F_PROVISION,
> };
>
> static struct virtio_driver virtio_blk = {
> diff --git a/include/uapi/linux/virtio_blk.h b/include/uapi/linux/virtio_blk.h
> index d888f013d9ff..184f8cf6d185 100644
> --- a/include/uapi/linux/virtio_blk.h
> +++ b/include/uapi/linux/virtio_blk.h
> @@ -40,6 +40,7 @@
> #define VIRTIO_BLK_F_MQ 12 /* support more than one vq */
> #define VIRTIO_BLK_F_DISCARD 13 /* DISCARD is supported */
> #define VIRTIO_BLK_F_WRITE_ZEROES 14 /* WRITE ZEROES is supported */
> +#define VIRTIO_BLK_F_PROVISION 15 /* provision is supported */
>
> /* Legacy feature bits */
> #ifndef VIRTIO_BLK_NO_LEGACY
> @@ -120,6 +121,11 @@ struct virtio_blk_config {
> */
> __u8 write_zeroes_may_unmap;
>
> + /*
> + * The maximum number of sectors in a provision request.
> + */
> + __virtio32 max_provision_sectors;
> +
> __u8 unused1[3];
> } __attribute__((packed));
>
> @@ -155,6 +161,9 @@ struct virtio_blk_config {
> /* Write zeroes command */
> #define VIRTIO_BLK_T_WRITE_ZEROES 13
>
> +/* Provision command */
> +#define VIRTIO_BLK_T_PROVISION 14
> +
> #ifndef VIRTIO_BLK_NO_LEGACY
> /* Barrier before this op. */
> #define VIRTIO_BLK_T_BARRIER 0x80000000
> --
> 2.31.0
>

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