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 X-Spam-Level: X-Spam-Status: No, score=-3.8 required=3.0 tests=BAYES_00,FAKE_REPLY_C, HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS, USER_AGENT_SANE_1 autolearn=no autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id 7BB85C636CB for ; Mon, 19 Jul 2021 05:39:57 +0000 (UTC) Received: from kanga.kvack.org (kanga.kvack.org [205.233.56.17]) by mail.kernel.org (Postfix) with ESMTP id 9BA2A610A5 for ; Mon, 19 Jul 2021 05:39:56 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 9BA2A610A5 Authentication-Results: mail.kernel.org; dmarc=none (p=none dis=none) header.from=gondor.apana.org.au Authentication-Results: mail.kernel.org; spf=pass smtp.mailfrom=owner-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix) id 3FE398D00F5; Mon, 19 Jul 2021 01:39:57 -0400 (EDT) Received: by kanga.kvack.org (Postfix, from userid 40) id 3D54F8D00EC; Mon, 19 Jul 2021 01:39:57 -0400 (EDT) X-Delivered-To: int-list-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix, from userid 63042) id 29D838D00F5; Mon, 19 Jul 2021 01:39:57 -0400 (EDT) X-Delivered-To: linux-mm@kvack.org Received: from forelay.hostedemail.com (smtprelay0026.hostedemail.com [216.40.44.26]) by kanga.kvack.org (Postfix) with ESMTP id F15978D00EC for ; Mon, 19 Jul 2021 01:39:56 -0400 (EDT) Received: from smtpin37.hostedemail.com (10.5.19.251.rfc1918.com [10.5.19.251]) by forelay04.hostedemail.com (Postfix) with ESMTP id 90CB523E46 for ; Mon, 19 Jul 2021 05:39:55 +0000 (UTC) X-FDA: 78378235950.37.F3A197A Received: from deadmen.hmeau.com (helcar.hmeau.com [216.24.177.18]) by imf09.hostedemail.com (Postfix) with ESMTP id 9D7E03000101 for ; Mon, 19 Jul 2021 05:39:54 +0000 (UTC) Received: from gondobar.mordor.me.apana.org.au ([192.168.128.4] helo=gondobar) by deadmen.hmeau.com with esmtp (Exim 4.92 #5 (Debian)) id 1m5Lzk-0004RI-3h; Mon, 19 Jul 2021 13:39:12 +0800 Received: from herbert by gondobar with local (Exim 4.92) (envelope-from ) id 1m5LzP-0004N7-JA; Mon, 19 Jul 2021 13:38:51 +0800 Date: Mon, 19 Jul 2021 13:38:51 +0800 From: Herbert Xu To: Russell King Oracle Cc: hch@lst.de, torvalds@linux-foundation.org, akpm@linux-foundation.org, James.Bottomley@hansenpartnership.com, guoren@kernel.org, tsbogend@alpha.franken.de, nickhu@andestech.com, green.hu@gmail.com, deanbo422@gmail.com, deller@gmx.de, ysato@users.sourceforge.jp, dalias@libc.org, geoff@infradead.org, paul@crapouillou.net, ulf.hansson@linaro.org, alexs@kernel.org, linux-kernel@vger.kernel.org, linux-arm-kernel@lists.infradead.org, linux-csky@vger.kernel.org, linux-mips@vger.kernel.org, linux-parisc@vger.kernel.org, linux-sh@vger.kernel.org, linux-mmc@vger.kernel.org, linux-scsi@vger.kernel.org, linux-mm@kvack.org, linux-doc@vger.kernel.org Subject: Re: flush_kernel_dcache_page fixes and removal Message-ID: <20210719053851.GA16780@gondor.apana.org.au> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20210713084648.GF22278@shell.armlinux.org.uk> X-Newsgroups: apana.lists.os.linux.doc,apana.lists.os.linux.kernel,apana.lists.os.linux.scsi Organization: Core User-Agent: Mutt/1.10.1 (2018-07-13) X-Rspamd-Server: rspam06 X-Rspamd-Queue-Id: 9D7E03000101 X-Stat-Signature: sm77gspgfqxwod9xijeo7h37fgn5asyg Authentication-Results: imf09.hostedemail.com; dkim=none; spf=pass (imf09.hostedemail.com: domain of herbert@gondor.apana.org.au designates 216.24.177.18 as permitted sender) smtp.mailfrom=herbert@gondor.apana.org.au; dmarc=none X-HE-Tag: 1626673194-776292 X-Bogosity: Ham, tests=bogofilter, spamicity=0.000037, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: Russell King Oracle wrote: > > I think you need to be careful - I seem to have a recollection that the > reason we ended up with flush_kernel_dcache_page() was the need to avoid > the taking of the mmap lock for 32-bit ARM VIVT based CPUs in > flush_dcache_page(). 32-bit ARM flush_dcache_page() can block. > > If you're sure that all these changes you're making do not end up > calling flush_dcache_page() from a path where we are atomic, then fine. The Crypto API has been calling flush_dcache_page from softirq context since before the advent of git (see crypto/scatterwalk.c from the initial import). So if 32-bit ARM blocks on it then this has been broken for almost 20 years. Cheers, -- Email: Herbert Xu Home Page: http://gondor.apana.org.au/~herbert/ PGP Key: http://gondor.apana.org.au/~herbert/pubkey.txt