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[209.132.183.28]) by mx.google.com with ESMTPS id a5si1989299qva.8.2019.06.14.10.09.04 for (version=TLS1_2 cipher=ECDHE-RSA-AES128-GCM-SHA256 bits=128/128); Fri, 14 Jun 2019 10:09:04 -0700 (PDT) Received-SPF: pass (google.com: domain of jmoyer@redhat.com designates 209.132.183.28 as permitted sender) client-ip=209.132.183.28; Authentication-Results: mx.google.com; spf=pass (google.com: domain of jmoyer@redhat.com designates 209.132.183.28 as permitted sender) smtp.mailfrom=jmoyer@redhat.com; dmarc=pass (p=NONE sp=NONE dis=NONE) header.from=redhat.com Received: from smtp.corp.redhat.com (int-mx05.intmail.prod.int.phx2.redhat.com [10.5.11.15]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by mx1.redhat.com (Postfix) with ESMTPS id 8CEA5C18B2D6; Fri, 14 Jun 2019 17:08:51 +0000 (UTC) Received: from segfault.boston.devel.redhat.com (segfault.boston.devel.redhat.com [10.19.60.26]) by smtp.corp.redhat.com (Postfix) with ESMTPS id 973FC54382; Fri, 14 Jun 2019 17:08:49 +0000 (UTC) From: Jeff Moyer To: "Aneesh Kumar K.V" Cc: Dan Williams , Oscar Salvador , Qian Cai , Andrew Morton , Linux MM , Linux Kernel Mailing List , linux-nvdimm Subject: Re: [PATCH -next] mm/hotplug: skip bad PFNs from pfn_to_online_page() References: <1560366952-10660-1-git-send-email-cai@lca.pw> <1560376072.5154.6.camel@lca.pw> <87lfy4ilvj.fsf@linux.ibm.com> <20190614153535.GA9900@linux> <24fcb721-5d50-2c34-f44b-69281c8dd760@linux.ibm.com> <16108dac-a4ca-aa87-e3b0-a79aebdcfafd@linux.ibm.com> X-PGP-KeyID: 1F78E1B4 X-PGP-CertKey: F6FE 280D 8293 F72C 65FD 5A58 1FF8 A7CA 1F78 E1B4 Date: Fri, 14 Jun 2019 13:08:48 -0400 In-Reply-To: <16108dac-a4ca-aa87-e3b0-a79aebdcfafd@linux.ibm.com> (Aneesh Kumar K. V.'s message of "Fri, 14 Jun 2019 22:25:18 +0530") Message-ID: User-Agent: Gnus/5.13 (Gnus v5.13) Emacs/26.1 (gnu/linux) MIME-Version: 1.0 Content-Type: text/plain X-Scanned-By: MIMEDefang 2.79 on 10.5.11.15 X-Greylist: Sender IP whitelisted, not delayed by milter-greylist-4.5.16 (mx1.redhat.com [10.5.110.31]); Fri, 14 Jun 2019 17:08:56 +0000 (UTC) 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: "Aneesh Kumar K.V" writes: > On 6/14/19 10:06 PM, Dan Williams wrote: >> On Fri, Jun 14, 2019 at 9:26 AM Aneesh Kumar K.V >> wrote: > >>> Why not let the arch >>> arch decide the SUBSECTION_SHIFT and default to one subsection per >>> section if arch is not enabled to work with subsection. >> >> Because that keeps the implementation from ever reaching a point where >> a namespace might be able to be moved from one arch to another. If we >> can squash these arch differences then we can have a common tool to >> initialize namespaces outside of the kernel. The one wrinkle is >> device-dax that wants to enforce the mapping size, > > The fsdax have a much bigger issue right? The file system block size > is the same as PAGE_SIZE and we can't make it portable across archs > that support different PAGE_SIZE? File system blocks are not tied to page size. They can't be *bigger* than the page size currently, but they can be smaller. Still, I don't see that as an arugment against trying to make the namespaces work across architectures. Consider a user who only has sector mode namespaces. We'd like that to work if at all possible. -Jeff