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[209.85.220.65]) by mx.google.com with SMTPS id s15sor1393871otq.5.2019.05.24.10.02.16 for (Google Transport Security); Fri, 24 May 2019 10:02:16 -0700 (PDT) Received-SPF: pass (google.com: domain of dan.j.williams@intel.com designates 209.85.220.65 as permitted sender) client-ip=209.85.220.65; Authentication-Results: mx.google.com; dkim=pass header.i=@intel-com.20150623.gappssmtp.com header.s=20150623 header.b=J6E7gPFq; spf=pass (google.com: domain of dan.j.williams@intel.com designates 209.85.220.65 as permitted sender) smtp.mailfrom=dan.j.williams@intel.com; dmarc=pass (p=NONE sp=NONE dis=NONE) header.from=intel.com DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=intel-com.20150623.gappssmtp.com; s=20150623; h=mime-version:references:in-reply-to:from:date:message-id:subject:to :cc; bh=uxIEMvL9NPIZt76HNNKGot2fHQFb8ScQQVFnfVEGVdE=; b=J6E7gPFqhGjQkK6F3GbGp2bqy4JZqM2JGDp4Q4363sxZZKkY1eebXwTOzadjVyNxa/ AwEmFnD2OnTGLyCOsb4EVByimH7YKeH+ofbH0xOkO83ECfI0kA1wzco1g7dCyhxMmqn1 lAjQLIEU87kbYcXgUjMEft09EG/s78/uSMvtXR561r30xuSwzTQgeEs/f23iRNxDK0Oq iv1DfXdnUJiXSNllUJOnrj1nEQzbEEh613meCgyIzDBkPavcXHBSW8mDbIRUarQv5EPB dh51oEmUu1WNnPiJZf+vDq4g8Yp9QXZQJUaZzJ7lJ/aNehbHAk4st7jpd1AxQslcrFO3 kCKg== X-Google-Smtp-Source: APXvYqxVRQpBpCep9TCI1kPQh1cOH82JFn3Gk+gMokzzTN7nj9KB6DFm/LKWbO3WZKAfI141c5e4MkYQ3VfCFR+tiNo= X-Received: by 2002:a9d:2963:: with SMTP id d90mr14793834otb.126.1558717336323; Fri, 24 May 2019 10:02:16 -0700 (PDT) MIME-Version: 1.0 References: <1557417933-15701-1-git-send-email-larry.bassel@oracle.com> <1557417933-15701-3-git-send-email-larry.bassel@oracle.com> <20190514130147.2pk2xx32aiomm57b@box> <20190524160711.GF19025@ubuette> In-Reply-To: <20190524160711.GF19025@ubuette> From: Dan Williams Date: Fri, 24 May 2019 10:02:04 -0700 Message-ID: Subject: Re: [PATCH, RFC 2/2] Implement sharing/unsharing of PMDs for FS/DAX To: Larry Bassel Cc: "Kirill A. Shutemov" , Mike Kravetz , Matthew Wilcox , Linux MM , Linux Kernel Mailing List , linux-nvdimm Content-Type: text/plain; charset="UTF-8" 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 Fri, May 24, 2019 at 9:07 AM Larry Bassel wrote: > On 14 May 19 16:01, Kirill A. Shutemov wrote: > > On Thu, May 09, 2019 at 09:05:33AM -0700, Larry Bassel wrote: [..] > > > diff --git a/mm/memory.c b/mm/memory.c > > > index f7d962d..4c1814c 100644 > > > --- a/mm/memory.c > > > +++ b/mm/memory.c > > > @@ -3845,6 +3845,109 @@ static vm_fault_t handle_pte_fault(struct vm_fault *vmf) > > > return 0; > > > } > > > > > > +#ifdef CONFIG_MAY_SHARE_FSDAX_PMD > > > +static pmd_t *huge_pmd_offset(struct mm_struct *mm, > > > + unsigned long addr, unsigned long sz) > > > > Could you explain what this function suppose to do? > > > > As far as I can see vma_mmu_pagesize() is always PAGE_SIZE of DAX > > filesystem. So we have 'sz' == PAGE_SIZE here. > > I thought so too, but in my testing I found that vma_mmu_pagesize() returns > 4KiB, which differs from the DAX filesystem's 2MiB pagesize. A given filesystem-dax vma is allowed to support both 4K and 2M mappings, so the vma_mmu_pagesize() is not granular enough to describe the capabilities of a filesystem-dax vma. In the device-dax case, where there are mapping guarantees, the implementation does arrange for vma_mmu_pagesize() to reflect the right page size.