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Date: Thu, 05 Jun 2014 04:54:19 +0200
From: Paolo Bonzini <pbonzini@redhat.com>
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Subject: Re: [Qemu-devel] [PATCH v2 7/8] virtio-blk: Convert
	VirtIOBlockReq.out to structrue
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To: Fam Zheng <famz@redhat.com>, qemu-devel@nongnu.org
Cc: Kevin Wolf <kwolf@redhat.com>, Stefan Hajnoczi <stefanha@redhat.com>

Il 05/06/2014 03:58, Fam Zheng ha scritto:
>
> -    if (req->elem->out_sg[0].iov_len < sizeof(*req->out) ||
> +    if (req->elem->out_sg[0].iov_len < sizeof(req->out) ||

This is not needed anymore.

>          req->elem->in_sg[req->elem->in_num - 1].iov_len < sizeof(*req->in)) {
>          error_report("virtio-blk header not in correct element");
>          exit(1);
>      }
>
> -    req->out = (void *)req->elem->out_sg[0].iov_base;
> +    if (unlikely(iov_to_buf(iov, out_num, 0, &req->out,
> +                            sizeof(req->out)) != sizeof(req->out))) {
> +        error_report("virtio-blk request outhdr too short");
> +        exit(1);
> +    }
> +    iov_discard_front(&iov, &out_num, sizeof(req->out));
>      req->in = (void *)req->elem->in_sg[req->elem->in_num - 1].iov_base;

Here, in a separate patch, you can add iov_len-1 as suggested in the 
previous review, and then use iov_discard_back on in_num.  You can then 
drop the other part of the "virtio-blk header not in correct element" check.

Paolo