Re: [PATCH] make qemu handle drbd properly

[Shriram Rajagopalan <rshriram@gmail.com>]

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On Wed, Jan 26, 2011 at 11:43 PM, James Harper <
james.harper@bendigoit.com.au> wrote:

> This attached patch allows qemu to accept a drbd: prefix and interpret
> it as a drbd resource. It then searches for it in /dev/drbd/by-res/
> (which must be mapped via udev). It's against 4.0-testing.
>
> Also, the block scripts make the drbd resource primary but don't want
> for it to actually become available. A secondary drbd resource returns
> EMEDIUMTYPE so if we get that result, wait half a second and retry, up
> to a total of 5 retries. Fixing this in the block scripts might be
> better but I can't see how to do it cleanly.
>
> James
>
>
> diff --git a/xenstore.c b/xenstore.c
> index 13b8d57..f6e2170 100644
> --- a/xenstore.c
> +++ b/xenstore.c
> @@ -413,6 +413,9 @@ void xenstore_parse_domain_config(int hvm_domid)
>     char *danger_buf = NULL;
>     char *danger_type = NULL;
>
> +    int retries = 1; /* number of attempts to open the block device -
> drbd can take a second to become available */
> +    int status;
> +
>     for(i = 0; i < MAX_DRIVES + 1; i++)
>         media_filename[i] = NULL;
>
> @@ -519,6 +522,14 @@ void xenstore_parse_domain_config(int hvm_domid)
>            format = &bdrv_raw;
>         }
>
> +        if (!strcmp(drv, "drbd")) {
> +            char *newparams = malloc(17 + strlen(params) + 1);
> +            sprintf(newparams, "/dev/drbd/by-res/%s", params);
> +            free(params);
> +            params = newparams;
> +           format = &bdrv_raw;
> +            retries = 5;
> +        }
>  #if 0
>        /* Phantom VBDs are disabled because the use of paths
>         * from guest-controlled areas in xenstore is unsafe.
> @@ -617,7 +628,14 @@ void xenstore_parse_domain_config(int hvm_domid)
>
>             fprintf(stderr, "Using file %s in read-%s mode\n",
> bs->filename, is_readonly ? "only" : "write");
>
> -            if (bdrv_open2(bs, params, flags, format) < 0)
> +            do {
> +                int status = bdrv_open2(bs, params, flags, format);
> +                if (status != -EMEDIUMTYPE)
> +                    break;
> +                usleep(500000); /* 500ms */
> +                retries--;
> +            } while (retries);
> +            if (status < 0)
>                 fprintf(stderr, "qemu: could not open vbd '%s' or hard
> disk image '%s' (drv '%s' format '%s')\n", buf, params, drv ? drv : "?",
> format ? format->format_name : "
>         }
>
>
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> Xen-devel@lists.xensource.com
> http://lists.xensource.com/xen-devel
>

Sorry to dig up an old thread. This patch doesnt seem to be in any of the
qemu-xen-*, xen-*-testing or xen-unstable trees. Any reason why?

shriram

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