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=-5.2 required=3.0 tests=BAYES_00, HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI,NICE_REPLY_A,SPF_HELO_NONE, SPF_PASS,URIBL_BLOCKED,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 A03DCC43467 for ; Mon, 12 Oct 2020 07:41:38 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 6B52A2080D for ; Mon, 12 Oct 2020 07:41:38 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1728202AbgJLHlP (ORCPT ); Mon, 12 Oct 2020 03:41:15 -0400 Received: from mx2.suse.de ([195.135.220.15]:44468 "EHLO mx2.suse.de" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1727722AbgJLHk4 (ORCPT ); Mon, 12 Oct 2020 03:40:56 -0400 X-Virus-Scanned: by amavisd-new at test-mx.suse.de Received: from relay2.suse.de (unknown [195.135.221.27]) by mx2.suse.de (Postfix) with ESMTP id 3DEE1AC1D; Mon, 12 Oct 2020 07:40:52 +0000 (UTC) Subject: Re: [PATCH RFC PKS/PMEM 48/58] drivers/md: Utilize new kmap_thread() To: Ira Weiny Cc: Andrew Morton , Thomas Gleixner , Ingo Molnar , Borislav Petkov , Andy Lutomirski , Peter Zijlstra , Kent Overstreet , x86@kernel.org, Dave Hansen , Dan Williams , Fenghua Yu , linux-doc@vger.kernel.org, linux-kernel@vger.kernel.org, linux-nvdimm@lists.01.org, linux-fsdevel@vger.kernel.org, linux-mm@kvack.org, linux-kselftest@vger.kernel.org, linuxppc-dev@lists.ozlabs.org, kvm@vger.kernel.org, netdev@vger.kernel.org, bpf@vger.kernel.org, kexec@lists.infradead.org, linux-bcache@vger.kernel.org, linux-mtd@lists.infradead.org, devel@driverdev.osuosl.org, linux-efi@vger.kernel.org, linux-mmc@vger.kernel.org, linux-scsi@vger.kernel.org, target-devel@vger.kernel.org, linux-nfs@vger.kernel.org, ceph-devel@vger.kernel.org, linux-ext4@vger.kernel.org, linux-aio@kvack.org, io-uring@vger.kernel.org, linux-erofs@lists.ozlabs.org, linux-um@lists.infradead.org, linux-ntfs-dev@lists.sourceforge.net, reiserfs-devel@vger.kernel.org, linux-f2fs-devel@lists.sourceforge.net, linux-nilfs@vger.kernel.org, cluster-devel@redhat.com, ecryptfs@vger.kernel.org, linux-cifs@vger.kernel.org, linux-btrfs@vger.kernel.org, linux-afs@lists.infradead.org, linux-rdma@vger.kernel.org, amd-gfx@lists.freedesktop.org, dri-devel@lists.freedesktop.org, intel-gfx@lists.freedesktop.org, drbd-dev@lists.linbit.com, linux-block@vger.kernel.org, xen-devel@lists.xenproject.org, linux-cachefs@redhat.com, samba-technical@lists.samba.org, intel-wired-lan@lists.osuosl.org References: <20201009195033.3208459-1-ira.weiny@intel.com> <20201009195033.3208459-49-ira.weiny@intel.com> <20201012052817.GZ2046448@iweiny-DESK2.sc.intel.com> From: Coly Li Autocrypt: addr=colyli@suse.de; 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Intel Mac OS X 10.15; rv:68.0) Gecko/20100101 Thunderbird/68.12.1 MIME-Version: 1.0 In-Reply-To: <20201012052817.GZ2046448@iweiny-DESK2.sc.intel.com> Content-Type: text/plain; charset=utf-8 Content-Language: en-US Content-Transfer-Encoding: 7bit Precedence: bulk List-ID: X-Mailing-List: bpf@vger.kernel.org On 2020/10/12 13:28, Ira Weiny wrote: > On Sat, Oct 10, 2020 at 10:20:34AM +0800, Coly Li wrote: >> On 2020/10/10 03:50, ira.weiny@intel.com wrote: >>> From: Ira Weiny >>> >>> These kmap() calls are localized to a single thread. To avoid the over >>> head of global PKRS updates use the new kmap_thread() call. >>> >> >> Hi Ira, >> >> There were a number of options considered. >> >> 1) Attempt to change all the thread local kmap() calls to kmap_atomic() >> 2) Introduce a flags parameter to kmap() to indicate if the mapping >> should be global or not >> 3) Change ~20-30 call sites to 'kmap_global()' to indicate that they >> require a global mapping of the pages >> 4) Change ~209 call sites to 'kmap_thread()' to indicate that the >> mapping is to be used within that thread of execution only >> >> >> I copied the above information from patch 00/58 to this message. The >> idea behind kmap_thread() is fine to me, but as you said the new api is >> very easy to be missed in new code (even for me). I would like to be >> supportive to option 2) introduce a flag to kmap(), then we won't forget >> the new thread-localized kmap method, and people won't ask why a >> _thread() function is called but no kthread created. > > Thanks for the feedback. > > I'm going to hold off making any changes until others weigh in. FWIW, I kind > of like option 2 as well. But there is already kmap_atomic() so it seemed like > kmap_XXXX() was more in line with the current API. I understand it now, the idea is fine to me. Acked-by: Coly Li Thanks. Coly Li