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[192.55.52.120]) by mx.google.com with ESMTPS id n5si578050plp.260.2019.03.28.17.58.16 for (version=TLS1_2 cipher=ECDHE-RSA-AES128-GCM-SHA256 bits=128/128); Thu, 28 Mar 2019 17:58:16 -0700 (PDT) Received-SPF: pass (google.com: domain of ira.weiny@intel.com designates 192.55.52.120 as permitted sender) client-ip=192.55.52.120; Authentication-Results: mx.google.com; spf=pass (google.com: domain of ira.weiny@intel.com designates 192.55.52.120 as permitted sender) smtp.mailfrom=ira.weiny@intel.com; dmarc=pass (p=NONE sp=NONE dis=NONE) header.from=intel.com X-Amp-Result: UNKNOWN X-Amp-Original-Verdict: FILE UNKNOWN X-Amp-File-Uploaded: False Received: from fmsmga008.fm.intel.com ([10.253.24.58]) by fmsmga104.fm.intel.com with ESMTP/TLS/DHE-RSA-AES256-GCM-SHA384; 28 Mar 2019 17:58:16 -0700 X-ExtLoop1: 1 X-IronPort-AV: E=Sophos;i="5.60,282,1549958400"; d="scan'208";a="135750908" Received: from iweiny-desk2.sc.intel.com ([10.3.52.157]) by fmsmga008.fm.intel.com with ESMTP; 28 Mar 2019 17:58:16 -0700 Date: Thu, 28 Mar 2019 09:57:09 -0700 From: Ira Weiny To: John Hubbard Cc: Jerome Glisse , linux-mm@kvack.org, linux-kernel@vger.kernel.org, Andrew Morton , Dan Williams Subject: Re: [PATCH v2 02/11] mm/hmm: use reference counting for HMM struct v2 Message-ID: <20190328165708.GH31324@iweiny-DESK2.sc.intel.com> References: <20190325144011.10560-1-jglisse@redhat.com> <20190325144011.10560-3-jglisse@redhat.com> <20190328110719.GA31324@iweiny-DESK2.sc.intel.com> <20190328191122.GA5740@redhat.com> <20190328212145.GA13560@redhat.com> MIME-Version: 1.0 Content-Type: text/plain; charset=iso-8859-1 Content-Disposition: inline Content-Transfer-Encoding: 8bit In-Reply-To: User-Agent: Mutt/1.11.1 (2018-12-01) X-Bogosity: Ham, tests=bogofilter, spamicity=0.000000, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: On Thu, Mar 28, 2019 at 05:39:26PM -0700, John Hubbard wrote: > On 3/28/19 2:21 PM, Jerome Glisse wrote: > > On Thu, Mar 28, 2019 at 01:43:13PM -0700, John Hubbard wrote: > >> On 3/28/19 12:11 PM, Jerome Glisse wrote: > >>> On Thu, Mar 28, 2019 at 04:07:20AM -0700, Ira Weiny wrote: > >>>> On Mon, Mar 25, 2019 at 10:40:02AM -0400, Jerome Glisse wrote: > >>>>> From: Jérôme Glisse > [...] > >>>>> @@ -67,14 +78,9 @@ struct hmm { > >>>>> */ > >>>>> static struct hmm *hmm_register(struct mm_struct *mm) > >>>>> { > >>>>> - struct hmm *hmm = READ_ONCE(mm->hmm); > >>>>> + struct hmm *hmm = mm_get_hmm(mm); > >>>> > >>>> FWIW: having hmm_register == "hmm get" is a bit confusing... > >>> > >>> The thing is that you want only one hmm struct per process and thus > >>> if there is already one and it is not being destroy then you want to > >>> reuse it. > >>> > >>> Also this is all internal to HMM code and so it should not confuse > >>> anyone. > >>> > >> > >> Well, it has repeatedly come up, and I'd claim that it is quite > >> counter-intuitive. So if there is an easy way to make this internal > >> HMM code clearer or better named, I would really love that to happen. > >> > >> And we shouldn't ever dismiss feedback based on "this is just internal > >> xxx subsystem code, no need for it to be as clear as other parts of the > >> kernel", right? > > > > Yes but i have not seen any better alternative that present code. If > > there is please submit patch. > > > > Ira, do you have any patch you're working on, or a more detailed suggestion there? > If not, then I might (later, as it's not urgent) propose a small cleanup patch > I had in mind for the hmm_register code. But I don't want to duplicate effort > if you're already thinking about it. No I don't have anything. I was just really digging into these this time around and I was about to comment on the lack of "get's" for some "puts" when I realized that "hmm_register" _was_ the get... :-( Ira > > > thanks, > -- > John Hubbard > NVIDIA > >