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Date: Sun, 4 May 2014 19:51:40 +0800
From: Fam Zheng <famz@redhat.com>
Message-ID: <20140504115140.GI1124@T430.nay.redhat.com>
References: <1398956086-20171-1-git-send-email-stefanha@redhat.com>
	<1398956086-20171-20-git-send-email-stefanha@redhat.com>
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Subject: Re: [Qemu-devel] [PATCH 19/22] dataplane: use the QEMU block layer
 for I/O
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To: Stefan Hajnoczi <stefanha@redhat.com>
Cc: Kevin Wolf <kwolf@redhat.com>, Paolo Bonzini <pbonzini@redhat.com>, "Shergill, Gurinder" <gurinder.shergill@hp.com>, "Vinod,
	Chegu" <chegu_vinod@hp.com>, qemu-devel@nongnu.org

On Thu, 05/01 16:54, Stefan Hajnoczi wrote:
> @@ -152,51 +132,53 @@ static void do_get_id_cmd(VirtIOBlockDataPlane *s,
>      complete_request_early(s, elem, inhdr, VIRTIO_BLK_S_OK);
>  }
>  
> -static int do_rdwr_cmd(VirtIOBlockDataPlane *s, bool read,
> -                       struct iovec *iov, unsigned iov_cnt,
> -                       long long offset, VirtQueueElement *elem,
> -                       QEMUIOVector *inhdr)
> +static void do_rdwr_cmd(VirtIOBlockDataPlane *s, bool read,
> +                        struct iovec *iov, unsigned iov_cnt,
> +                        int64_t sector_num, VirtQueueElement *elem,
> +                        QEMUIOVector *inhdr)
>  {
> -    struct iocb *iocb;
> -    QEMUIOVector qiov;
> -    struct iovec *bounce_iov = NULL;
> -    QEMUIOVector *read_qiov = NULL;
> -
> -    qemu_iovec_init_external(&qiov, iov, iov_cnt);
> -    if (!bdrv_qiov_is_aligned(s->blk->conf.bs, &qiov)) {
> -        void *bounce_buffer = qemu_blockalign(s->blk->conf.bs, qiov.size);
> -
> -        if (read) {
> -            /* Need to copy back from bounce buffer on completion */
> -            read_qiov = g_slice_new(QEMUIOVector);
> -            qemu_iovec_init(read_qiov, iov_cnt);
> -            qemu_iovec_concat_iov(read_qiov, iov, iov_cnt, 0, qiov.size);
> -        } else {
> -            qemu_iovec_to_buf(&qiov, 0, bounce_buffer, qiov.size);
> +    VirtIOBlockRequest *req = g_slice_new(VirtIOBlockRequest);

Could be g_slice_new0,

> +    QEMUIOVector *qiov;
> +    int nb_sectors;
> +
> +    /* Fill in virtio block metadata needed for completion */
> +    memset(req, 0, sizeof(*req));

so this memset is not needed.

> +    req->s = s;
> +    req->elem = elem;
> +    req->inhdr = inhdr;
> +    req->read = read;
> +    qemu_iovec_init_external(&req->qiov, iov, iov_cnt);
> +
> +    qiov = &req->qiov;
> +
> +    if (!bdrv_qiov_is_aligned(s->blk->conf.bs, qiov)) {
> +        void *bounce_buffer = qemu_blockalign(s->blk->conf.bs, qiov->size);
> +
> +        /* Populate bounce buffer with data for writes */
> +        if (!read) {
> +            qemu_iovec_to_buf(qiov, 0, bounce_buffer, qiov->size);
>          }
>  

Fam