Received-SPF: pass (google.com: domain of linux-kernel-owner@vger.kernel.org designates 23.128.96.18 as permitted sender) client-ip=23.128.96.18;
MIME-Version: 1.0
References: <20210624102623.24563-1-sjpark@amazon.de> <20210624102623.24563-4-sjpark@amazon.de>
In-Reply-To: <20210624102623.24563-4-sjpark@amazon.de>
From:   Shakeel Butt <shakeelb@google.com>
Date:   Thu, 24 Jun 2021 07:52:59 -0700
Message-ID: <CALvZod7gLSCqqYVR50F9-8DxG=gRL4seiHAqvSsr3A6U6cvjig@mail.gmail.com>
Subject: Re: [PATCH v31 07/13] mm/damon: Implement a debugfs-based user space interface
To:     SeongJae Park <sj38.park@gmail.com>
Cc:     SeongJae Park <sjpark@amazon.de>, Jonathan.Cameron@huawei.com,
        acme@kernel.org, alexander.shishkin@linux.intel.com,
        amit@kernel.org, benh@kernel.crashing.org,
        Brendan Higgins <brendanhiggins@google.com>,
        Jonathan Corbet <corbet@lwn.net>,
        David Hildenbrand <david@redhat.com>, dwmw@amazon.com,
        Marco Elver <elver@google.com>, "Du, Fan" <fan.du@intel.com>,
        foersleo@amazon.de, greg@kroah.com,
        Greg Thelen <gthelen@google.com>, guoju.fgj@alibaba-inc.com,
        jgowans@amazon.com, Mel Gorman <mgorman@suse.de>, mheyne@amazon.de,
        Minchan Kim <minchan@kernel.org>,
        Ingo Molnar <mingo@redhat.com>, namhyung@kernel.org,
        "Peter Zijlstra (Intel)" <peterz@infradead.org>,
        Rik van Riel <riel@surriel.com>,
        David Rientjes <rientjes@google.com>,
        Steven Rostedt <rostedt@goodmis.org>,
        Mike Rapoport <rppt@kernel.org>, Shuah Khan <shuah@kernel.org>,
        sieberf@amazon.com, snu@zelle79.org,
        Vlastimil Babka <vbabka@suse.cz>,
        Vladimir Davydov <vdavydov.dev@gmail.com>,
        zgf574564920@gmail.com, linux-damon@amazon.com,
        Linux MM <linux-mm@kvack.org>, linux-doc@vger.kernel.org,
        LKML <linux-kernel@vger.kernel.org>
Content-Type: text/plain; charset="UTF-8"
Precedence: bulk

On Thu, Jun 24, 2021 at 3:26 AM SeongJae Park <sj38.park@gmail.com> wrote:
>
[...]
> >
> > The high level comment I have for this patch is the layering of pid
> > reference counting. The dbgfs should treat the targets as abstract
> > objects and vaddr should handle the reference counting of pids. More
> > specifically move find_get_pid from dbgfs to vaddr and to add an
> > interface to the primitive for set_targets.
> >
> > At the moment, the pid reference is taken in dbgfs and put in vaddr.
> > This will be the source of bugs in future.
>
> Good point, and agreed on the problem.  But, I'd like to move 'put_pid()' to
> dbgfs, because I think that would let extending the dbgfs user interface to
> pidfd a little bit simpler.  Also, I think that would be easier to use for
> in-kernel programming interface usages.  If you disagree, please feel free to
> let me know.
>

I was thinking of removing targetid_is_pid() checks. Anyways this is
not something we can not change later, so I will let you decide which
direction you want to take.