[sheepdog] 答复: [PATCH] sheep: do COW at local node for just one time

[无觉]

-----邮件原件-----
发件人: Liu Yuan [mailto:namei.unix at gmail.com]
发送时间: 2012年6月25日 12:09
收件人: yaohaiting.wujue at gmail.com
抄送: sheepdog at lists.wpkg.org; 无觉
主题: Re: [sheepdog] [PATCH] sheep: do COW at local node for just one time

On 06/21/2012 11:09 AM, yaohaiting.wujue at gmail.com wrote:
>  int forward_write_obj_req(struct request *req)
>  {
>       int i, fd, ret, pollret;
> @@ -106,6 +144,14 @@ int forward_write_obj_req(struct request *req)
>       memcpy(&fwd_hdr, &req->rq, sizeof(fwd_hdr));
>       fwd_hdr.flags |= SD_FLAG_CMD_IO_LOCAL;
>
> +     if (fwd_hdr.flags & SD_FLAG_CMD_COW) {
> +             ret = do_cow_at_local(req, &fwd_hdr);
> +             if (!ret) {
> +                     fwd_hdr.flags &= ~SD_FLAG_CMD_COW;
> +                     req->rq.flags &= ~SD_FLAG_CMD_COW;
> +             }
> +     }
> +
>       wlen = fwd_hdr.data_length;

This optimization should be handled before forward_write_obj_req(),
which handles request forwarding only.

I have moved this to another place.

If we do an early COW object reading at gateway node, it seems we don't
need the COW code in store_create_and_write().

If we do COW at gateway failing, we then pass the COW to separate nodes. The separate nodes maybe have retry. We will not retry at gateway.

Thanks,
Yuan

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