Re: [PATCH v2] loop: add some basic read-only sysfs attributes

[Karel Zak <kzak@redhat.com>]

On Fri, Jul 30, 2010 at 04:34:43PM +0200, Kay Sievers wrote:
> On Fri, Jul 30, 2010 at 16:22, Milan Broz <mbroz@redhat.com> wrote:
> > On 07/30/2010 06:36 AM, Kay Sievers wrote:
> >
> >> Alternatively, these attributes could be created and removed/created
> >> with the ioctl, and before the 'change' event, only if there is an
> >> active backing file, but I would expect the attribute group at the
> >> device to work just fine.
> > I have no idea how you can add attribute group before add_disk() which
> > initializes kobj (it ends with BUG_ON in internal_create_group
> > - because !kobj->sd). Perhaps I missed something?
> 
> Attribute groups handle the creation of a kobject (subdir) for you,
> you only supply a name to the group. Without a name, they will put all
> the attributes in the root of the device.
> 
> The 'struct device' has a member **groups, and that can have a list of
> attribute groups assigned. You assign them before you register the
> device, and the core will take care of everything.
> 
> > Anyway, second approach works - now is loop attributes available only
> > when loop is configured and before CHANGE uevent is sent.
> >
> > Ok with that?
> 
> Sounds good, nothing to complain from a sysfs timing perspective.

Jens, ping... it would be really really nice to have this feature in 
kernel. 

The ioctls are useless and I'd like to minimize number of situations
where mount(8) behaviour depends on /etc/mtab.

Thanks.

    Karel

-- 
 Karel Zak  <kzak@redhat.com>
 http://karelzak.blogspot.com