Devices that can be used as raw kdump target

[Vivek Goyal]

On Mon, Sep 29, 2014 at 02:27:50PM +0200, Martin Milata wrote:
> On Mon, Sep 29, 2014 at 13:02:07 +0800, Dave Young wrote:
> > On 09/25/14 at 12:15pm, Martin Milata wrote:
> > > system-config-kdump has hardcoded whitelist of major numbers for block
> > > devices that can be used as raw kdump targets. With the current list it
> > > does not show virtio disks [1] as possible targets. The major device
> > > number for virtio is assigned dynamically, thus I cannot simply add a
> > > new number.
> > > 
> > > I have no idea how the major numbers in the list were chosen. I see
> > > these possibilities for fixing the bug:
> > > 
> > > * Do not try to outsmart the user, throw away the list, and offer all
> > >   devices that are listed in /proc/partitions.
> > > 
> > > * Add all the numbers that can be used for dynamic assignment to the
> > >   whitelist.
> > > 
> > > * Determine whether a device is suitable by some other means. For
> > >   example, /sys/dev/block/MAJOR:MINOR/ro should contain 1 if the device
> > >   is read-only. However it contains 0 for my optical drive, so using
> > >   this is probably not as useful.
> > 
> > For CDROM we can not check the /sys/dev/block/MAJOR:MINOR/ro because it
> > depends on the media type in the drive. Anyway we do not support writing
> > to cdrom so it's safe to skip any devices in /proc/sys/dev/cdrom/info 
> > The first line should list the cdrom device names.
> 
> Thanks for the suggestion. Looks like blacklisting devices instead of
> whitelisting makes more sense here.

I agree. Removing devices from list which are not writables makes
more sense.

> 
> > BTW, how about let user provide the device path name manually instead provide
> > a list in UI?
> 
> I don't know - I guess the point of s-c-kdump is configuring kdump
> without much typing?:) I don't see any advantage (except perhaps in the
> case when the list is very long).

If it is not too hard, I think it is not a bad idea to provide user
list of devices. To me it just makes configuration easier. Instead
of asking user to figure out the path.

Thanks
Vivek