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[216.228.121.64]) by mx.google.com with ESMTPS id t206si5637247ywt.415.2019.06.04.13.17.44 for (version=TLS1_2 cipher=ECDHE-RSA-AES128-GCM-SHA256 bits=128/128); Tue, 04 Jun 2019 13:17:44 -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=gx4TZAEO; 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 ; Tue, 04 Jun 2019 13:17:30 -0700 Received: from hqmail.nvidia.com ([172.20.161.6]) by hqpgpgate101.nvidia.com (PGP Universal service); Tue, 04 Jun 2019 13:17:43 -0700 X-PGP-Universal: processed; by hqpgpgate101.nvidia.com on Tue, 04 Jun 2019 13:17:43 -0700 Received: from [10.110.48.28] (172.20.13.39) by HQMAIL107.nvidia.com (172.20.187.13) with Microsoft SMTP Server (TLS) id 15.0.1473.3; Tue, 4 Jun 2019 20:17:43 +0000 Subject: Re: [PATCH v3] mm/swap: Fix release_pages() when releasing devmap pages To: Dan Williams CC: "Weiny, Ira" , Andrew Morton , Michal Hocko , Linux MM , Linux Kernel Mailing List , =?UTF-8?B?SsOpcsO0bWUgR2xpc3Nl?= References: <20190604164813.31514-1-ira.weiny@intel.com> From: John Hubbard X-Nvconfidentiality: public Message-ID: <4d97645c-0e55-37c0-1a16-8649706b9e78@nvidia.com> Date: Tue, 4 Jun 2019 13:17:42 -0700 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:60.0) Gecko/20100101 Thunderbird/60.7.0 MIME-Version: 1.0 In-Reply-To: X-Originating-IP: [172.20.13.39] X-ClientProxiedBy: HQMAIL106.nvidia.com (172.18.146.12) To HQMAIL107.nvidia.com (172.20.187.13) Content-Type: text/plain; charset="utf-8" Content-Language: en-US Content-Transfer-Encoding: 7bit DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=nvidia.com; s=n1; t=1559679450; bh=Ys4ew+Gn4nTU0UcGzoVS+OBJ0Amfu2GbT4HCKGZeoDg=; 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=gx4TZAEOnnJoMkQENcIFwkJRTeWMbOPM7mRcK+8rjXNzVqKtDzpAdmm7NnBAGtfQI A0eEnruDTcpmH8hKXEjNLMNckgvcHOStNiReVkWzaHHb1Q/iPZFkiDxQkhArWOMGC+ D7lv9c504aqW9XuEkLGvK+i/G2TqEq/rWS6bvB2zbHv4LjdpyUKlZvZLDo0wVQHUj8 Hdn4Q+2ZbnsI9Qk+d4lDU2LEf+nvS5D3BIYxFpgLmNtc9ORa9cEkMonoegxqbxAV/7 idTsoGv3ZZffMTpLFTJ6pWH+DvyHDvUPnGlSckAa0dLGLYzt1h97UYOsLMnyRPfttx Fsju2MaD0zNcQ== 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 6/4/19 1:11 PM, Dan Williams wrote: > On Tue, Jun 4, 2019 at 12:48 PM John Hubbard wrote: >> >> On 6/4/19 9:48 AM, ira.weiny@intel.com wrote: >>> From: Ira Weiny >>> ... >>> diff --git a/mm/swap.c b/mm/swap.c >>> index 7ede3eddc12a..6d153ce4cb8c 100644 >>> --- a/mm/swap.c >>> +++ b/mm/swap.c >>> @@ -740,15 +740,20 @@ void release_pages(struct page **pages, int nr) >>> if (is_huge_zero_page(page)) >>> continue; >>> >>> - /* Device public page can not be huge page */ >>> - if (is_device_public_page(page)) { >>> + if (is_zone_device_page(page)) { >>> if (locked_pgdat) { >>> spin_unlock_irqrestore(&locked_pgdat->lru_lock, >>> flags); >>> locked_pgdat = NULL; >>> } >>> - put_devmap_managed_page(page); >>> - continue; >>> + /* >>> + * Not all zone-device-pages require special >>> + * processing. Those pages return 'false' from >>> + * put_devmap_managed_page() expecting a call to >>> + * put_page_testzero() >>> + */ >> >> Just a documentation tweak: how about: >> >> /* >> * ZONE_DEVICE pages that return 'false' from >> * put_devmap_managed_page() do not require special >> * processing, and instead, expect a call to >> * put_page_testzero(). >> */ > > Looks better to me, but maybe just go ahead and list those > expectations explicitly. Something like: > > /* > * put_devmap_managed_page() only handles > * ZONE_DEVICE (struct dev_pagemap managed) > * pages when the hosting dev_pagemap has the > * ->free() or ->fault() callback handlers > * implemented as indicated by > * dev_pagemap.type. Otherwise the expectation > * is to fall back to a plain decrement / > * put_page_testzero(). > */ I like it--but not here, because it's too much internal detail in a call site that doesn't use that level of detail. The call site looks at the return value, only. Let's instead put that blurb above (or in) the put_devmap_managed_page() routine itself. And leave the blurb that I wrote where it is. And then I think everything will have an appropriate level of detail in the right places. thanks, -- John Hubbard NVIDIA