[PATCH 4/4] block: expose devt for GENHD_FL_HIDDEN disks

Thadeu Lima de Souza Cascardo
2018-12-14T08:56:07Z

On Fri, Dec 14, 2018@08:47:20AM +0100, Hannes Reinecke wrote:
> On 12/13/18 4:25 PM, Thadeu Lima de Souza Cascardo wrote:
> > On Thu, Dec 13, 2018@03:32:18PM +0100, Christoph Hellwig wrote:
> > > On Thu, Dec 13, 2018@10:18:40AM +0100, Hannes Reinecke wrote:
> > > > Welll ... this is not just 'lsblk', but more importantly this will force
> > > > udev to create _block_ device nodes for the hidden devices, essentially
> > > > 'unhide' them.
> > > >
> > > > Is this what we want?
> > > > Christoph?
> > > > I thought the entire _point_ of having hidden devices is that the are ...
> > > > well ... hidden ...
> > >
> > > Yes, that is why I really don't like the last two patches.
> > >
> > > And I've checked back - lsblk actually works just fine at the moment.
> > > But it turns out once we create the slave links it stops working,
> > > which is a really good argument against the first two patches, which
> > > would otherwise seem nice..
> >
> > Which is why I have sent the "paths/" patchset in the first place. Because I
> > did some homework and read the previous discussion about this, and how lsblk
> > failure to behave with slave links led to the revert of the slaves/holders
> > patch by Dr. Hannes.
> >
> But you haven't answered my question:
>
> Why can't we patch 'lsblk' to provide the required information even with the
> current sysfs layout?
>

I think we could, but with my Ubuntu hat on, after the kernel fix for
initramfs-tools, that is, slaves/holders links, the user will get an updated
kernel that breaks the current lsblk on Bionic (Ubuntu 18.04). That will
require that we backport the lsblk fix, which is not only more work, but there
may be users who only update from -security, which is where kernel updates end
regularly, but not this lsblk fix.

And that kernel update is a regression against that old lsblk version.

Cascardo.

> Cheers,
>
> Hannes
> --
> Dr. Hannes Reinecke Teamlead Storage & Networking
> hare at suse.de +49 911 74053 688
> SUSE LINUX GmbH, Maxfeldstr. 5, 90409 N?rnberg
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