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[216.228.121.64]) by mx.google.com with ESMTPS id f65si474254pff.195.2019.03.28.17.39.27 for (version=TLS1_2 cipher=ECDHE-RSA-AES128-GCM-SHA256 bits=128/128); Thu, 28 Mar 2019 17:39:27 -0700 (PDT) Received-SPF: pass (google.com: domain of jhubbard@nvidia.com designates 216.228.121.64 as permitted sender) client-ip=216.228.121.64; Authentication-Results: mx.google.com; dkim=pass header.i=@nvidia.com header.s=n1 header.b=Q0KbVjt4; spf=pass (google.com: domain of jhubbard@nvidia.com designates 216.228.121.64 as permitted sender) smtp.mailfrom=jhubbard@nvidia.com; dmarc=pass (p=NONE sp=NONE dis=NONE) header.from=nvidia.com Received: from hqpgpgate101.nvidia.com (Not Verified[216.228.121.13]) by hqemgate15.nvidia.com (using TLS: TLSv1.2, DES-CBC3-SHA) id ; Thu, 28 Mar 2019 17:39:20 -0700 Received: from hqmail.nvidia.com ([172.20.161.6]) by hqpgpgate101.nvidia.com (PGP Universal service); Thu, 28 Mar 2019 17:39:27 -0700 X-PGP-Universal: processed; by hqpgpgate101.nvidia.com on Thu, 28 Mar 2019 17:39:27 -0700 Received: from [10.110.48.28] (10.124.1.5) by HQMAIL101.nvidia.com (172.20.187.10) with Microsoft SMTP Server (TLS) id 15.0.1473.3; Fri, 29 Mar 2019 00:39:26 +0000 Subject: Re: [PATCH v2 02/11] mm/hmm: use reference counting for HMM struct v2 To: Jerome Glisse CC: Ira Weiny , , , Andrew Morton , Dan Williams 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> From: John Hubbard X-Nvconfidentiality: public Message-ID: Date: Thu, 28 Mar 2019 17:39:26 -0700 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:60.0) Gecko/20100101 Thunderbird/60.5.3 MIME-Version: 1.0 In-Reply-To: <20190328212145.GA13560@redhat.com> X-Originating-IP: [10.124.1.5] X-ClientProxiedBy: HQMAIL101.nvidia.com (172.20.187.10) To HQMAIL101.nvidia.com (172.20.187.10) Content-Type: text/plain; charset="utf-8" Content-Language: en-US-large Content-Transfer-Encoding: quoted-printable DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=nvidia.com; s=n1; t=1553819960; bh=tD7OqDvEuxyFdGL//3cLnWvjKrhcIjz2aOlgPkqRx0M=; h=X-PGP-Universal:Subject:To:CC:References:From:X-Nvconfidentiality: Message-ID:Date:User-Agent:MIME-Version:In-Reply-To: X-Originating-IP:X-ClientProxiedBy:Content-Type:Content-Language: Content-Transfer-Encoding; b=Q0KbVjt4rsznaiVDmvDr6VuTjjWZ2rlv20UdubVR77Kk269lggejhWVS3cKh7MYkY w9593VJNWmESvoEmlkOW846WaJIbzc6nUiJMLCzFkZb7GGGhQ7SGaDH2SsaebT7TNu /LRNYJXErEJG+9i26NOGwgXAKU9h54GkWxEIdwAtiG3dMRVYjwLtrfjVy/hCCHKS6m MWm6e+PEQx5rt+xGQzNBueRM6zrDM1MnYEp8fHDA4uoYvMTPww2Lgdk7TykKEp/Q36 385PMGmrePqwnlUTkvmAJjZF1+3tUhXtfanKcV5TzHTYLAvslJjSuaAhkk4O7yjm/H GHjFIj7XgIAoA== 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 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: J=C3=A9r=C3=B4me Glisse [...] >>>>> @@ -67,14 +78,9 @@ struct hmm { >>>>> */ >>>>> static struct hmm *hmm_register(struct mm_struct *mm) >>>>> { >>>>> - struct hmm *hmm =3D READ_ONCE(mm->hmm); >>>>> + struct hmm *hmm =3D mm_get_hmm(mm); >>>> >>>> FWIW: having hmm_register =3D=3D "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=20 >> counter-intuitive. So if there is an easy way to make this internal=20 >> 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? >=20 > Yes but i have not seen any better alternative that present code. If > there is please submit patch. >=20 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 pa= tch=20 I had in mind for the hmm_register code. But I don't want to duplicate effo= rt=20 if you're already thinking about it. thanks, --=20 John Hubbard NVIDIA