From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org Received: from kanga.kvack.org (kanga.kvack.org [205.233.56.17]) by smtp.lore.kernel.org (Postfix) with ESMTP id CC2D7C5AC75 for ; Wed, 26 Jan 2022 02:51:12 +0000 (UTC) Received: by kanga.kvack.org (Postfix) id 3ED116B0071; Tue, 25 Jan 2022 21:51:12 -0500 (EST) Received: by kanga.kvack.org (Postfix, from userid 40) id 374816B0075; Tue, 25 Jan 2022 21:51:12 -0500 (EST) X-Delivered-To: int-list-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix, from userid 63042) id 1ED876B0078; Tue, 25 Jan 2022 21:51:12 -0500 (EST) X-Delivered-To: linux-mm@kvack.org Received: from forelay.hostedemail.com (smtprelay0012.hostedemail.com [216.40.44.12]) by kanga.kvack.org (Postfix) with ESMTP id 0B8976B0071 for ; Tue, 25 Jan 2022 21:51:12 -0500 (EST) Received: from smtpin07.hostedemail.com (10.5.19.251.rfc1918.com [10.5.19.251]) by forelay03.hostedemail.com (Postfix) with ESMTP id C5B168249980 for ; Wed, 26 Jan 2022 02:51:11 +0000 (UTC) X-FDA: 79070911542.07.2240418 Received: from casper.infradead.org (casper.infradead.org [90.155.50.34]) by imf23.hostedemail.com (Postfix) with ESMTP id E3F0E140017 for ; Wed, 26 Jan 2022 02:51:10 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=infradead.org; s=casper.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; bh=86XwsEqiHWcpAKS+1w66D4BvB/zNvs89vkaCBpH8v1A=; b=WVIaPz8PNke5qT2GHlggxTERIt 1gByfyYpDfCQf3V4cJwM8jJX1yZjxR7A5zbsBQgSgJA5GOtlRgQpLiqkAG87yRkPSdMt/Hb7X+biu 1CNLDxWXRd/rkXeiZrkTquDHB6Z7vn7QwjiQ8TVckrWw8oSvmtZ+P7f2pT+9il3b010BOL9pXMyGN cfsxfsq2hvoFGT2KOkRv4FYjhfEUHyyg5YX2WbTtVHY197jxgs77IvBxmpZds6dst8x7n+OEa6sG4 Leb1KP/pny3DOZid1GUF9FEp+yFHOcXK9hyuGMVBjp7dDDtC2QvNL3403LwMcbxSdBqhtIpvrukkd ocKpgIkA==; Received: from willy by casper.infradead.org with local (Exim 4.94.2 #2 (Red Hat Linux)) id 1nCYOZ-003di7-Ho; Wed, 26 Jan 2022 02:50:51 +0000 Date: Wed, 26 Jan 2022 02:50:51 +0000 From: Matthew Wilcox To: Robin Murphy Cc: Yury Norov , Catalin Marinas , Will Deacon , Andrew Morton , Nicholas Piggin , Ding Tianhong , Anshuman Khandual , Alexey Klimov , linux-arm-kernel@lists.infradead.org, linux-kernel@vger.kernel.org, linux-mm@kvack.org Subject: Re: [PATCH] vmap(): don't allow invalid pages Message-ID: References: <20220118235244.540103-1-yury.norov@gmail.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: X-Rspamd-Server: rspam07 X-Rspamd-Queue-Id: E3F0E140017 X-Stat-Signature: hqubhjbm77ohumrb3rqceugatc7eg9yj X-Rspam-User: nil Authentication-Results: imf23.hostedemail.com; dkim=pass header.d=infradead.org header.s=casper.20170209 header.b=WVIaPz8P; spf=none (imf23.hostedemail.com: domain of willy@infradead.org has no SPF policy when checking 90.155.50.34) smtp.mailfrom=willy@infradead.org; dmarc=none X-HE-Tag: 1643165470-909219 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 Wed, Jan 19, 2022 at 01:28:14PM +0000, Robin Murphy wrote: > Is it page_to_pfn() guaranteed to work without blowing up if page is invalid > in the first place? Looking at the CONFIG_SPARSEMEM case I'm not sure that's > true... Something that all the ARM people weighing in on this don't understand is that basically nobody uses SPARSEMEM without SPARSEMEM_VMEMMAP. So all this complicated code to do page_to_pfn() is never tested. Real users all do a simple subtraction and so the simple pfn_valid() works fine.