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

[Sarthak Kukreti]

On Thu, Sep 15, 2022 at 10:48 PM Stefan Hajnoczi <stefanha@xxxxxxxxxx> wrote:
>
> On Thu, Sep 15, 2022 at 09:48:21AM -0700, Sarthak Kukreti wrote:
> > From: Sarthak Kukreti <sarthakkukreti@xxxxxxxxxxxx>
> >
> > Adds support for provision requests. Provision requests act like
> > the inverse of discards.
> >
> > Signed-off-by: Sarthak Kukreti <sarthakkukreti@xxxxxxxxxxxx>
> > ---
> >  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
> >