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

Sarthak Kukreti
2022-09-20T02:33:55Z

On Thu, Sep 15, 2022 at 10:48 PM Stefan Hajnoczi <stefanha@redhat.com> wrote:
>
> 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
>
Thanks for the suggestion! Ref:
https://lists.oasis-open.org/archives/virtio-comment/202209/msg00025.html

The patch needs to be amended a bit to account for the diff. in the
spec and the original patch. Will update in the next patch iteration.

Best
Sarthak

> 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
> >