On 04/28/2016 07:16 AM, Kevin Wolf wrote:
> Signed-off-by: Kevin Wolf <kwolf@redhat.com>
> ---
>  block/bochs.c | 51 +++++++++++++++++++++++++++++++++------------------
>  1 file changed, 33 insertions(+), 18 deletions(-)
> 

> +    uint64_t sector_num = offset >> BDRV_SECTOR_BITS;
> +    int nb_sectors = bytes >> BDRV_SECTOR_BITS;

Since we're using the named constant here (instead of /512 or >>9),...

> +    uint64_t bytes_done = 0;
> +    QEMUIOVector local_qiov;
>      int ret;
>  
> +    assert((offset & (BDRV_SECTOR_SIZE - 1)) == 0);
> +    assert((bytes & (BDRV_SECTOR_SIZE - 1)) == 0);
> +
> +    qemu_iovec_init(&local_qiov, qiov->niov);
> +    qemu_co_mutex_lock(&s->lock);
> +
>      while (nb_sectors > 0) {
>          int64_t block_offset = seek_to_sector(bs, sector_num);
>          if (block_offset < 0) {
> -            return block_offset;
> -        } else if (block_offset > 0) {
> -            ret = bdrv_pread(bs->file->bs, block_offset, buf, 512);
> +            ret = block_offset;
> +            goto fail;
> +        }
> +
> +        qemu_iovec_reset(&local_qiov);
> +        qemu_iovec_concat(&local_qiov, qiov, bytes_done, 512);

should we also use the named constant BDRV_SECTOR_SIZE here instead of 512?

I don't care strongly enough for a respin, though, particularly since it
would affect line wrapping.

Reviewed-by: Eric Blake <eblake@redhat.com>

> +
> +        if (block_offset > 0) {
> +            ret = bdrv_co_preadv(bs->file->bs, block_offset, 512,
> +                                 &local_qiov, 0);
>              if (ret < 0) {
> -                return ret;
> +                goto fail;
>              }
>          } else {
> -            memset(buf, 0, 512);
> +            qemu_iovec_memset(&local_qiov, 0, 0, 512);
>          }
>          nb_sectors--;
>          sector_num++;
> -        buf += 512;
> +        bytes_done += 512;

More of the magic 512, if you care.

-- 
Eric Blake   eblake redhat com    +1-919-301-3266
Libvirt virtualization library http://libvirt.org