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[2607:7c80:54:e::133]) by mx.google.com with ESMTPS id p9si23754172plo.49.2019.04.25.17.51.29 for (version=TLS1_2 cipher=ECDHE-RSA-CHACHA20-POLY1305 bits=256/256); Thu, 25 Apr 2019 17:51:29 -0700 (PDT) Received-SPF: pass (google.com: best guess record for domain of willy@infradead.org designates 2607:7c80:54:e::133 as permitted sender) client-ip=2607:7c80:54:e::133; Authentication-Results: mx.google.com; dkim=pass header.i=@infradead.org header.s=bombadil.20170209 header.b=E0F6hjuo; spf=pass (google.com: best guess record for domain of willy@infradead.org designates 2607:7c80:54:e::133 as permitted sender) smtp.mailfrom=willy@infradead.org DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=infradead.org; s=bombadil.20170209; h=In-Reply-To:Content-Type:MIME-Version :References:Message-ID:Subject:Cc:To:From:Date:Sender:Reply-To: Content-Transfer-Encoding:Content-ID:Content-Description:Resent-Date: Resent-From:Resent-Sender:Resent-To:Resent-Cc:Resent-Message-ID:List-Id: List-Help:List-Unsubscribe:List-Subscribe:List-Post:List-Owner:List-Archive; bh=ZPxMilL55F88OfnrEUq9EeEkyqqENOE39GSG+Um9TxI=; b=E0F6hjuoTiAbr23o8nn5Dpddz W2QnBTSDLijahKTNq51dB36Q26RPSHKGDMcbHl3mNZ7/2TB6PcDitNtwEsUH4qjhfqb8NruFV5Bdl Zjqr+j73L7y/6aiZCiWrVn1GhBSnczo24TZGBrkITbqsS8D63JOkFxwnhUIDhKlLMD9IVKKfSLHzx gFmt8CBd4G4CcrHR5wj3+QsIKwHD7Y49lwsayA6YTkmZ94uV8MHLFIN4ZBtC2M6EEyR2oQ7kcWoLf 3rayZelRy2skZeQ7D8uS7667hcWZ6TIALxdtMaZlyKVjJ6aAHyJVmXKT0ei21HN6FUBiVyhaDKMU9 hqLRXyD8A==; Received: from willy by bombadil.infradead.org with local (Exim 4.90_1 #2 (Red Hat Linux)) id 1hJp5J-0000Zp-2k; Fri, 26 Apr 2019 00:51:25 +0000 Date: Thu, 25 Apr 2019 17:51:24 -0700 From: Matthew Wilcox To: Dan Williams Cc: Jan Kara , "Aneesh Kumar K.V" , Andrew Morton , linux-nvdimm , Linux MM , linuxppc-dev , stable , Chandan Rajendra Subject: Re: [PATCH v2] mm: Fix modifying of page protection by insert_pfn_pmd() Message-ID: <20190426005124.GA25606@bombadil.infradead.org> References: <20190402115125.18803-1-aneesh.kumar@linux.ibm.com> <20190424173833.GE19031@bombadil.infradead.org> <20190425073149.GA21215@quack2.suse.cz> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: User-Agent: Mutt/1.9.2 (2017-12-15) 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, Apr 25, 2019 at 05:33:04PM -0700, Dan Williams wrote: > On Thu, Apr 25, 2019 at 12:32 AM Jan Kara wrote: > > > > We also call vmf_insert_pfn_pmd() in dax_insert_pfn_mkwrite() -- does > > > > that need to change too? > > > > > > It wasn't clear to me that it was a problem. I think that one already > > > happens to be pmd-aligned. > > > > Why would it need to be? The address is taken from vmf->address and that's > > set up in __handle_mm_fault() like .address = address & PAGE_MASK. So I > > don't see anything forcing PMD alignment of the virtual address... > > True. So now I'm wondering if the masking should be done internal to > the routine. Given it's prefixed vmf_ it seems to imply the api is > prepared to take raw 'struct vm_fault' parameters. I think I'll go > that route unless someone sees a reason to require the caller to > handle this responsibility. The vmf_ prefix was originally used to indicate 'returns a vm_fault_t' instead of 'returns an errno'. That said, I like the interpretation you're coming up with here, and it makes me wonder if we shouldn't change vmf_insert_pfn_pmd() to take (vmf, pfn, write) as arguments instead of separate vma, address & pmd arguments.