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 lists.ozlabs.org (lists.ozlabs.org [112.213.38.117]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.lore.kernel.org (Postfix) with ESMTPS id C34F3C7EE22 for ; Wed, 10 May 2023 06:09:33 +0000 (UTC) Received: from boromir.ozlabs.org (localhost [IPv6:::1]) by lists.ozlabs.org (Postfix) with ESMTP id 4QGPkM70Snz3fKp for ; Wed, 10 May 2023 16:09:31 +1000 (AEST) Authentication-Results: lists.ozlabs.org; dkim=fail reason="signature verification failed" (2048-bit key; secure) header.d=infradead.org header.i=@infradead.org header.a=rsa-sha256 header.s=casper.20170209 header.b=GqtBVAri; dkim-atps=neutral Authentication-Results: lists.ozlabs.org; spf=none (no SPF record) smtp.mailfrom=infradead.org (client-ip=2001:8b0:10b:1236::1; helo=casper.infradead.org; envelope-from=willy@infradead.org; receiver=) Authentication-Results: lists.ozlabs.org; dkim=pass (2048-bit key; secure) header.d=infradead.org header.i=@infradead.org header.a=rsa-sha256 header.s=casper.20170209 header.b=GqtBVAri; dkim-atps=neutral Received: from casper.infradead.org (casper.infradead.org [IPv6:2001:8b0:10b:1236::1]) (using TLSv1.3 with cipher TLS_AES_256_GCM_SHA384 (256/256 bits) key-exchange X25519 server-signature RSA-PSS (2048 bits) server-digest SHA256) (No client certificate requested) by lists.ozlabs.org (Postfix) with ESMTPS id 4QGPjM2LGpz3cjD for ; Wed, 10 May 2023 16:08:36 +1000 (AEST) 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=/B3tOo2DcdV+TWomt1rdQnWS8nj/GpV0fFl476JBaqo=; b=GqtBVAriUhmAJ9gyQunowN/4FI IKPnDz7LbDDzd0Fgb9Z22xH9B0GothgTazfupCK9odsy8jdQ7d5rjIU0buEMmJgHPsqbRmD3rjRlS pe9WkgZOQJjVVUr2Nn9sQ+jGwW9hZdqgIKJXJ8Sf5r1YY8KiJJck+y51d1I4lWN/uji1Mhux3PR9z 4FQGYDQlCPyDgWt1HB2pIN4QBP8zK1HHd8c8SPjYOnj4IT/rnTHO2Gch9hA825q32K7voVZkZwShj 4YKfoYDVbZy6WQjNBqGFIRoL8UF3dgWpYlgtRh3uLSK2Af3sbYZbz1g5vy/PAMZKbCX9yrTkl5Mjy NzylU7Eg==; Received: from willy by casper.infradead.org with local (Exim 4.94.2 #2 (Red Hat Linux)) id 1pwcyp-00FzBu-D0; Wed, 10 May 2023 06:07:15 +0000 Date: Wed, 10 May 2023 07:07:15 +0100 From: Matthew Wilcox To: Hugh Dickins Subject: Re: [PATCH 00/23] arch: allow pte_offset_map[_lock]() to fail Message-ID: References: <77a5d8c-406b-7068-4f17-23b7ac53bc83@google.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <77a5d8c-406b-7068-4f17-23b7ac53bc83@google.com> X-BeenThere: linuxppc-dev@lists.ozlabs.org X-Mailman-Version: 2.1.29 Precedence: list List-Id: Linux on PowerPC Developers Mail List List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Cc: linux-ia64@vger.kernel.org, David Hildenbrand , Catalin Marinas , Qi Zheng , linux-kernel@vger.kernel.org, Max Filippov , sparclinux@vger.kernel.org, linux-riscv@lists.infradead.org, Claudio Imbrenda , Will Deacon , Greg Ungerer , linux-s390@vger.kernel.org, linux-sh@vger.kernel.org, Helge Deller , x86@kernel.org, Russell King , Geert Uytterhoeven , Christian Borntraeger , Alexandre Ghiti , Heiko Carstens , linux-m68k@lists.linux-m68k.org, John Paul Adrian Glaubitz , John David Anglin , Suren Baghdasaryan , linux-arm-kernel@lists.infradead.org, Chris Zankel , Michal Simek , Thomas Bogendoerfer , linux-parisc@vger.kernel.org, linux-mm@kvack.org, linux-mips@vger.kernel.org, Palmer Dabbelt , "Kirill A. Shutemov" , "Aneesh Kumar K.V" , Andrew Morton , linuxppc-dev@lists.ozlabs.org, "David S. Miller" , Mike Rapoport , Mike Kravetz Errors-To: linuxppc-dev-bounces+linuxppc-dev=archiver.kernel.org@lists.ozlabs.org Sender: "Linuxppc-dev" On Tue, May 09, 2023 at 09:39:13PM -0700, Hugh Dickins wrote: > Two: pte_offset_map() will need to do an rcu_read_lock(), with the > corresponding rcu_read_unlock() in pte_unmap(). But most architectures > never supported CONFIG_HIGHPTE, so some don't always call pte_unmap() > after pte_offset_map(), or have used userspace pte_offset_map() where > pte_offset_kernel() is more correct. No problem in the current tree, > but a problem once an rcu_read_unlock() will be needed to keep balance. Hi Hugh, I shall have to spend some time looking at these patches, but at LSFMM just a few hours ago, I proposed and nobody objected to removing CONFIG_HIGHPTE. I don't intend to take action on that consensus immediately, so I can certainly wait until your patches are applied, but if this information simplifies what you're doing, feel free to act on it.