linux-kernel - Re: [PATCH 03/12] mm/damon: Implement a minimal stub for sysfs-based DAMON interface

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Date:   Wed, 23 Feb 2022 19:03:37 +0000
From:   SeongJae Park <sj@...nel.org>
To:     Greg KH <gregkh@...uxfoundation.org>
Cc:     SeongJae Park <sj@...nel.org>, akpm@...ux-foundation.org,
        corbet@....net, skhan@...uxfoundation.org, rientjes@...gle.com,
        xhao@...ux.alibaba.com, linux-damon@...zon.com, linux-mm@...ck.org,
        linux-doc@...r.kernel.org, linux-kselftest@...r.kernel.org,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH 03/12] mm/damon: Implement a minimal stub for sysfs-based DAMON interface

On Wed, 23 Feb 2022 19:33:31 +0100 Greg KH <gregkh@...uxfoundation.org> wrote:

> On Wed, Feb 23, 2022 at 05:13:41PM +0000, SeongJae Park wrote:
> > On Wed, 23 Feb 2022 16:45:13 +0000 SeongJae Park <sj@...nel.org> wrote:
> > 
> > > On Wed, 23 Feb 2022 17:09:38 +0100 Greg KH <gregkh@...uxfoundation.org> wrote:
> > > 
> > > > On Wed, Feb 23, 2022 at 03:20:42PM +0000, SeongJae Park wrote:
> > > > > +static struct kobj_attribute damon_sysfs_ul_range_min_attr =
> > > > > +		__ATTR(min, 0600, damon_sysfs_ul_range_min_show,
> > > > > +				damon_sysfs_ul_range_min_store);
> > > > > +
> > > > > +static struct kobj_attribute damon_sysfs_ul_range_max_attr =
> > > > > +		__ATTR(max, 0600, damon_sysfs_ul_range_max_show,
> > > > > +				damon_sysfs_ul_range_max_store);
> > > > 
> > > > Can you use __ATTR_RW_MODE() instead here and elsewhere?
> > > 
> > > Sure, I will, in the next revision.
> > 
> > After thinking once more, I realized that it might not so simple.  First of
> > all, there are two files having same name in different directories
> > (kdamonds/<N>/pid and targets/<N>/pid).  The files work differently, so I need
> > to use different _show/_store callbacks for them but __ATTR_RW_MODE() wouldn't
> > support the case.
> 
> The reason I recommend using these macros is to prevent you from having
> sysfs files with the same name, yet doing different things in different
> places in the sysfs tree :)

Thank you for clarifying!  Maybe I was making the hierarchy unnecessarily deep
and thus naming files too short and/or common, which could confuses relative
paths users.

> 
> > Secondly, I'd like to keep the file names short because the meaning of the
> > files can easily inferred from the hierarchy, but want to keep the _show/_store
> > callback names to have prefixes that allows us easily know their meaning and
> > usage even though it makes the name a little bit longer because I don't want to
> > have too much source files for DAMON sysfs interface.
> > 
> > Am I missing some of your point?
> 
> How about renaming one of the files?

Thank you for the suggestion, will do so.


Thanks,
SJ