Re: dm sysfs: use default_groups in kobj_type

[Mike Snitzer <snitzer@redhat.com>]

On Thu, Jan 06 2022 at 10:04P -0500,
Greg Kroah-Hartman <gregkh@linuxfoundation.org> wrote:

> On Thu, Jan 06, 2022 at 09:25:11AM -0500, Mike Snitzer wrote:
> > On Thu, Jan 06 2022 at  5:02P -0500,
> > Greg Kroah-Hartman <gregkh@linuxfoundation.org> wrote:
> > 
> > > There are currently 2 ways to create a set of sysfs files for a
> > > kobj_type, through the default_attrs field, and the default_groups
> > > field.  Move the dm sysfs code to use default_groups field which has
> > > been the preferred way since aa30f47cf666 ("kobject: Add support for
> > > default attribute groups to kobj_type") so that we can soon get rid of
> > > the obsolete default_attrs field.
> > > 
> > > Cc: Alasdair Kergon <agk@redhat.com>
> > > Cc: Mike Snitzer <snitzer@redhat.com>
> > > Cc: dm-devel@redhat.com
> > > Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
> > > ---
> > >  drivers/md/dm-sysfs.c | 3 ++-
> > >  1 file changed, 2 insertions(+), 1 deletion(-)
> > > 
> > > diff --git a/drivers/md/dm-sysfs.c b/drivers/md/dm-sysfs.c
> > > index a05fcd50e1b9..e28c92478536 100644
> > > --- a/drivers/md/dm-sysfs.c
> > > +++ b/drivers/md/dm-sysfs.c
> > > @@ -112,6 +112,7 @@ static struct attribute *dm_attrs[] = {
> > >  	&dm_attr_rq_based_seq_io_merge_deadline.attr,
> > >  	NULL,
> > >  };
> > > +ATTRIBUTE_GROUPS(dm);
> > 
> > Bit strange to pass "dm" but then have ATTRIBUTE_GROUPS assume dm_attrs defined.
> > Feels like it'll invite janitors sending patches, that they never
> > compile, to remove dm_attrs.
> 
> 0-day would instantly catch that :)
> 
> That's the way the ATTRIBUTE_GROUPS() macro works.  It's tricky, yes,
> and I don't like it all that much, but couldn't come up with a better
> way at the time.  It saves lots and lots of boiler-plate code from
> having to be typed all the time.

OK, thanks for the insight.

Mike