Re: [PATCH RFC 12/12] vdpa_sim_blk: implement ramdisk behaviour

Stefan Hajnoczi
2020-11-17T11:36:54Z

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On Fri, Nov 13, 2020 at 02:47:12PM +0100, Stefano Garzarella wrote:
> diff --git a/drivers/vdpa/vdpa_sim/vdpa_sim_blk.c b/drivers/vdpa/vdpa_sim/vdpa_sim_blk.c
> index 8e41b3ab98d5..68e74383322f 100644
> --- a/drivers/vdpa/vdpa_sim/vdpa_sim_blk.c
> +++ b/drivers/vdpa/vdpa_sim/vdpa_sim_blk.c
> @@ -7,6 +7,7 @@
> */
>
> #include <linux/module.h>
> +#include <linux/blkdev.h>
> #include <uapi/linux/virtio_blk.h>
>
> #include "vdpa_sim.h"
> @@ -24,10 +25,137 @@
>
> static struct vdpasim *vdpasim_blk_dev;
>
> +static int vdpasim_blk_handle_req(struct vdpasim *vdpasim,
> + struct vdpasim_virtqueue *vq)

This function has a non-standard int return value. Please document it.

> +{
> + size_t wrote = 0, to_read = 0, to_write = 0;
> + struct virtio_blk_outhdr hdr;
> + uint8_t status;
> + uint32_t type;
> + ssize_t bytes;
> + loff_t offset;
> + int i, ret;
> +
> + vringh_kiov_cleanup(&vq->riov);
> + vringh_kiov_cleanup(&vq->wiov);
> +
> + ret = vringh_getdesc_iotlb(&vq->vring, &vq->riov, &vq->wiov,
> + &vq->head, GFP_ATOMIC);
> + if (ret != 1)
> + return ret;
> +
> + for (i = 0; i < vq->wiov.used; i++)
> + to_write += vq->wiov.iov[i].iov_len;
> + to_write -= 1; /* last byte is the status */

What if vq->wiov.used == 0?

> +
> + for (i = 0; i < vq->riov.used; i++)
> + to_read += vq->riov.iov[i].iov_len;
> +
> + bytes = vringh_iov_pull_iotlb(&vq->vring, &vq->riov, &hdr, sizeof(hdr));
> + if (bytes != sizeof(hdr))
> + return 0;
> +
> + to_read -= bytes;
> +
> + type = le32_to_cpu(hdr.type);
> + offset = le64_to_cpu(hdr.sector) << SECTOR_SHIFT;
> + status = VIRTIO_BLK_S_OK;
> +
> + switch (type) {
> + case VIRTIO_BLK_T_IN:
> + if (offset + to_write > VDPASIM_BLK_CAPACITY << SECTOR_SHIFT) {

Integer overflow is not handled.

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