[libvirt] [PATCH] Implement vol delete for disk pools

Cole Robinson crobinso at redhat.com
Wed Aug 13 03:58:07 UTC 2008


Daniel P. Berrange wrote:
> On Mon, Aug 11, 2008 at 03:58:41PM -0400, Cole Robinson wrote:
>   
>> The patch below implements virStorageVolDelete for volumes
>> on a disk pool.
>>
>> The only interesting thing here is that parted wants a
>> partition number to delete, so we need to peel off the
>> end of the volume's target path which will be of the form
>> '/dev/sda1' or similar (I assume. If not, it's still
>> better than having nothing implemented).
>>
>> Thanks,
>> Cole
>>     
>>  {
>> -    /* delete a partition */
>> -    virStorageReportError(conn, VIR_ERR_NO_SUPPORT,
>> -                          _("Disk pools are not yet supported"));
>> -    return -1;
>> +    char *part_num = NULL;
>> +    int i;
>> +
>> +    /* Strip target path (ex. '/dev/sda1') of its partition number */
>> +    for (i = (strlen(vol->target.path)-1); i >= 0; --i) {
>> +        if (!c_isdigit(vol->target.path[i]))
>> +            break;
>> +        part_num = &(vol->target.path[i]);
>> +    }
>> +
>> +    if (!part_num) {
>> +        virStorageReportError(conn, VIR_ERR_INTERNAL_ERROR,
>> +                              _("cannot parse partition number from target "
>> +                                "path '%s'"), vol->target.path);
>> +        return -1;
>> +    }
>>     
>
> This isn't correct because the target path is not guarenteed to point to
> the master device name /dev/sda1.  The user could have configured it to
> use a stable path such as /dev/disk/by-uuid/4cb23887-0d02-4e4c-bc95-7599c85afc1a
>
>   

Hmm, I couldn't actually get /dev/disk/by-uuid to work. Seems like the
vol populating code for disks doesn't take into account the the pools
target path, and just uses the real partition path.

> So, you need to first call 'readlink' on the vol->target.path, ignoring
> EINVAL which you'll get if it wasn't a symlink. Once you've done that
> you'll need to validate that it is sane by checking that vol->source.devices[0]
> is a prefix of the resolved pathname. Finally, you can extract the partition
> number. So something along the lines of
>
>        char devname[PATH_MAX];
>
>        if (readlink(vol->target.path, devname, sizeof(devname)) < 0 &&
>            errno != EINVAL)
>             virStorageReportError(...)
>
>        if (!STRPREFIX(devname, vol->source.devices[0].path))
>             virStorageReportError(....)
>
>        part_num = devname + strlen(vol->source.devices[0].path)
>   

The attached patch uses this approach. It works for the case with
vols of the form /dev/sdx123, but as mentioned above I couldn't
get by-uuid method to work, so can't be certain about that.

Thanks,
Cole
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