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[216.228.121.65]) by mx.google.com with ESMTPS id x71si569846ywx.166.2019.06.13.18.46.33 for (version=TLS1_2 cipher=ECDHE-RSA-AES128-GCM-SHA256 bits=128/128); Thu, 13 Jun 2019 18:46:34 -0700 (PDT) Received-SPF: pass (google.com: domain of jhubbard@nvidia.com designates 216.228.121.65 as permitted sender) client-ip=216.228.121.65; Authentication-Results: mx.google.com; dkim=pass header.i=@nvidia.com header.s=n1 header.b="hZ/DTJ5k"; spf=pass (google.com: domain of jhubbard@nvidia.com designates 216.228.121.65 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 hqemgate16.nvidia.com (using TLS: TLSv1.2, DES-CBC3-SHA) id ; Thu, 13 Jun 2019 18:46:33 -0700 Received: from hqmail.nvidia.com ([172.20.161.6]) by hqpgpgate101.nvidia.com (PGP Universal service); Thu, 13 Jun 2019 18:46:33 -0700 X-PGP-Universal: processed; by hqpgpgate101.nvidia.com on Thu, 13 Jun 2019 18:46:33 -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; Fri, 14 Jun 2019 01:46:30 +0000 Subject: Re: [PATCH 04/22] mm: don't clear ->mapping in hmm_devmem_free To: Christoph Hellwig , Dan Williams , =?UTF-8?B?SsOpcsO0bWUgR2xpc3Nl?= , Jason Gunthorpe , Ben Skeggs CC: , , , , , References: <20190613094326.24093-1-hch@lst.de> <20190613094326.24093-5-hch@lst.de> X-Nvconfidentiality: public From: John Hubbard Message-ID: Date: Thu, 13 Jun 2019 18:46:29 -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: <20190613094326.24093-5-hch@lst.de> X-Originating-IP: [172.20.13.39] X-ClientProxiedBy: HQMAIL107.nvidia.com (172.20.187.13) 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=1560476793; bh=aWY+o31YpTUXYNCWR/tUiybGk+oQfQT9Eqi8enXkBOQ=; h=X-PGP-Universal:Subject:To:CC:References:X-Nvconfidentiality:From: Message-ID:Date:User-Agent:MIME-Version:In-Reply-To: X-Originating-IP:X-ClientProxiedBy:Content-Type:Content-Language: Content-Transfer-Encoding; b=hZ/DTJ5kKqWdpCL12ZwwtnQNfLWFCFSPcl2k46LOsH4pNokmtsOInOl9+GJ8FKmKO hXZGdDzxG+P+INltKZYs7MH3/UvgeCnHg5hunwwq2bHUiutlLY5os0Z0ZWt+qrOuk9 K1Cep9JhG5g0OourqoO6QLKWzZukRM6NdlGEbmjrnoEWvH3YVwufa/VDbhQJ2OHW1T paLBoqcpz6yETgLWr50DBrY8lfihmvAJXfVj+3zCeNHjlAyMFyqJD9rLf7d5TUXr4L SqhY59v6TJmTfzJl0WQ5JTwHaXZZRXMzmrFJGWFYPUDt0cJm6MdR4wx/+QlT3y9K7k 1VdCdX4iXd9+w== 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 6/13/19 2:43 AM, Christoph Hellwig wrote: > ->mapping isn't even used by HMM users, and the field at the same offset > in the zone_device part of the union is declared as pad. (Which btw is > rather confusing, as DAX uses ->pgmap and ->mapping from two different > sides of the union, but DAX doesn't use hmm_devmem_free). > > Signed-off-by: Christoph Hellwig > --- > mm/hmm.c | 2 -- > 1 file changed, 2 deletions(-) > > diff --git a/mm/hmm.c b/mm/hmm.c > index 0c62426d1257..e1dc98407e7b 100644 > --- a/mm/hmm.c > +++ b/mm/hmm.c > @@ -1347,8 +1347,6 @@ static void hmm_devmem_free(struct page *page, void *data) > { > struct hmm_devmem *devmem = data; > > - page->mapping = NULL; > - > devmem->ops->free(devmem, page); > } > > Yes, I think that line was unnecessary. I see from git history that it was originally being set to NULL from within __put_devmap_managed_page(), and then in commit 2fa147bdbf672c53386a8f5f2c7fe358004c3ef8, Dan moved it out of there, and stashed in specifically here. But it appears to have been unnecessary from the beginning. Reviewed-by: John Hubbard thanks, -- John Hubbard NVIDIA