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Sun, 28 Aug 2022 10:44:36 -0400 X-MC-Unique: _VW9_-tSOkiUcRiPCEVYfA-1 Received: from smtp.corp.redhat.com (int-mx05.intmail.prod.int.rdu2.redhat.com [10.11.54.5]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by mimecast-mx02.redhat.com (Postfix) with ESMTPS id 8858F1C051AF; Sun, 28 Aug 2022 14:44:35 +0000 (UTC) Received: from localhost (ovpn-12-25.pek2.redhat.com [10.72.12.25]) by smtp.corp.redhat.com (Postfix) with ESMTPS id DD2B94C816; Sun, 28 Aug 2022 14:44:32 +0000 (UTC) Date: Sun, 28 Aug 2022 22:44:28 +0800 From: Baoquan He To: David Laight Cc: 'Christophe Leroy' , "linux-kernel@vger.kernel.org" , "linux-mm@kvack.org" , "akpm@linux-foundation.org" , "hch@infradead.org" , "agordeev@linux.ibm.com" , "wangkefeng.wang@huawei.com" , "linux-arm-kernel@lists.infradead.org" Subject: Re: [PATCH v2 01/11] mm/ioremap: change the return value of io[re|un]map_allowed and rename Message-ID: References: <20220820003125.353570-1-bhe@redhat.com> <20220820003125.353570-2-bhe@redhat.com> <429cb367-923f-bb3d-ccf0-57dce0c7f35b@csgroup.eu> MIME-Version: 1.0 Content-Type: text/plain; charset=iso-8859-1 Content-Disposition: inline Content-Transfer-Encoding: 8bit In-Reply-To: X-Scanned-By: MIMEDefang 2.79 on 10.11.54.5 ARC-Seal: i=1; s=arc-20220608; d=hostedemail.com; t=1661697884; a=rsa-sha256; cv=none; b=DX7tDmAU9DBMc3ojZLjq1qNnduzN1R+tJksw1D7H6kiiffneEGgzjlJZsvC9gT3eN4OBrk lV+jqwUvKhCgCaDIa9bulI/xHtR6OFxbVi+tXFq/9s4hIo3mlSgXTan2pVVm5O9sX4pOwP mHr7F/KnYGMGr5u+cd00i69Ts5RAxOs= ARC-Authentication-Results: i=1; imf19.hostedemail.com; dkim=pass header.d=redhat.com header.s=mimecast20190719 header.b=LyWYiENi; spf=pass (imf19.hostedemail.com: domain of bhe@redhat.com designates 170.10.133.124 as permitted sender) smtp.mailfrom=bhe@redhat.com; dmarc=pass (policy=none) header.from=redhat.com ARC-Message-Signature: i=1; a=rsa-sha256; c=relaxed/relaxed; d=hostedemail.com; s=arc-20220608; t=1661697884; h=from:from:sender:reply-to:subject:subject:date:date: message-id:message-id:to:to:cc:cc:mime-version:mime-version: content-type:content-type: content-transfer-encoding:content-transfer-encoding: in-reply-to:in-reply-to:references:references:dkim-signature; bh=hTdmiB22wnq3dmvK7RjNhZhCqkVHrOk+1i/pQcMS7HE=; b=588fX4hblIF1Nmo/usXniEE6MGtXot+HElAp9W9Iflo2fNs/OUN2BYkOzrIXIZ73XehZNR sC92GSOGQenz9nnRRdshgry6GgV73lFvM0iTjy9Y8K6U2Al7rcs5cBiJXHnjCk+n0flmvg HogmSN2CUhIz7DFKsYctYTCUH8iFSKI= X-Rspam-User: Authentication-Results: imf19.hostedemail.com; dkim=pass header.d=redhat.com header.s=mimecast20190719 header.b=LyWYiENi; spf=pass (imf19.hostedemail.com: domain of bhe@redhat.com designates 170.10.133.124 as permitted sender) smtp.mailfrom=bhe@redhat.com; dmarc=pass (policy=none) header.from=redhat.com X-Rspamd-Server: rspam10 X-Stat-Signature: uk8ucqdnmsgmkwu4qtyd8jfjmsk1epkf X-Rspamd-Queue-Id: 124561A0027 X-HE-Tag: 1661697882-180976 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: Hi David, On 08/24/22 at 08:16am, David Laight wrote: ...... > > >>>> Le 20/08/2022 à 02:31, Baoquan He a écrit : > > >>>>> In some architectures, there are ARCH specifici io address mapping > > >>>>> handling when calling ioremap() or ioremap_prot(), e.g, arc, ia64, > > >>>>> openrisc, s390, sh. > > >>>>> > > >>>>> In oder to convert them to take GENERIC_IOREMAP method, we need change > > >>>>> the return value of hook ioremap_allowed() and iounmap_allowed(). > > >>>>> Meanwhile, rename them to arch_ioremap() and arch_iounmap() to reflect > > >>>>> their current behaviour. > > >>> > > >>> Thanks for reviewing. > > >>> > > >>>> > > >>>> Please don't just say you need to change the return value. Explain why. > > >>> > > >>> The 1st paragraph and the sentence 'In oder to convert them to take > > >>> GENERIC_IOREMAP method' tell the reason, no? > > >> > > >> What I would like to read is _why_ you need to change the return value > > >> in order to convert to GENERIC_IOREMAP > > > > > > I rephrase the log as below, it's OK to you? Or please help check and > > > tell what I need to improve to better explain the reason. > > > > > > ==== > > > The current io[re|un]map_allowed() hooks are used to check if the > > > io[re|un]map() actions are qualified to proceed when taking > > > GENERIC_IOREMAP way to do ioremap()/iounmap(). Otherwise io[re|un]map() > > > will return NULL. > > > > > > On some architectures like arc, ia64, openris, s390, sh, there are > > > ARCH specific io address mapping to translate the passed in physical > > > address to io address when calling ioremap(). In order to convert > > > these architectures to take GENERIC_IOREMAP way to ioremap(), we need > > > change the return value of hook ioremap_allowed() and iounmap_allowed(). > > > With the change, we can move the architecture specific io address > > > mapping into ioremap_allowed() hook, and give the mapped io address > > > out to let ioremap_prot() return it. While at it, rename the hooks to > > > arch_ioremap() and arch_iounmap() to reflect their new behaviour. > > > ==== > > > > > > > That looks more in line with the type of explanation I foresee in the > > commit message, thanks. > > I think you also need to summarise the change itself. > If the success/fail return actually changes then you really > need to change something so the compiler errors unchanged code. > Otherwise it is a complete recipe for disaster. Thanks for looking into this and sorry for late response. I am not sure if I follow you. In this patch, I just rename the old ioremap_allowed() to arch_ioremap(), and change its return value. Except of arm64 which has taken GENERIC_IOREMAP way to provide ioremap_allowed(), no other ARCHes are affected yet. This is what have been changed. Could you be more specific what I should add? Or are you suggesting words like below sentences need be added to patch log? If the success/fail return actually changes then you really need to change something so the compiler errors unchanged code. Otherwise it is a complete recipe for disaster. Thanks Baoquan