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=-5.3 required=3.0 tests=BAYES_00, HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI,NICE_REPLY_A,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 D4AB7C352BC for ; Mon, 12 Oct 2020 16:29:08 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id A91CF2087D for ; Mon, 12 Oct 2020 16:29:08 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S2390636AbgJLQ3G (ORCPT ); Mon, 12 Oct 2020 12:29:06 -0400 Received: from mga05.intel.com ([192.55.52.43]:7333 "EHLO mga05.intel.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S2403778AbgJLQ2k (ORCPT ); Mon, 12 Oct 2020 12:28:40 -0400 IronPort-SDR: oKfo37Fz351a3BR2Kz24NLdo8V0LNzfiRTEDwG3dAnum11rVSc8LByfTgerpBbE8JoydgYl+0f TJ4UnHwnbotA== X-IronPort-AV: E=McAfee;i="6000,8403,9772"; a="250460933" X-IronPort-AV: E=Sophos;i="5.77,367,1596524400"; d="scan'208";a="250460933" X-Amp-Result: SKIPPED(no attachment in message) X-Amp-File-Uploaded: False Received: from fmsmga003.fm.intel.com ([10.253.24.29]) by fmsmga105.fm.intel.com with ESMTP/TLS/ECDHE-RSA-AES256-GCM-SHA384; 12 Oct 2020 09:28:33 -0700 IronPort-SDR: lpVqfUJ9kdOGINFzSz3Rb/+voVruUqKl5QXBieW8JLewmkz3mmd/w7cERQhz4kzL6b3gTh7T5C 5oHwexl8ugkg== X-IronPort-AV: E=Sophos;i="5.77,367,1596524400"; d="scan'208";a="355847059" Received: from soumyaka-mobl.amr.corp.intel.com (HELO [10.212.101.39]) ([10.212.101.39]) by fmsmga003-auth.fm.intel.com with ESMTP/TLS/ECDHE-RSA-AES256-GCM-SHA384; 12 Oct 2020 09:28:30 -0700 Subject: Re: [PATCH RFC PKS/PMEM 22/58] fs/f2fs: Utilize new kmap_thread() To: Eric Biggers , Ira Weiny Cc: Matthew Wilcox , Andrew Morton , Thomas Gleixner , Ingo Molnar , Borislav Petkov , Andy Lutomirski , Peter Zijlstra , linux-aio@kvack.org, linux-efi@vger.kernel.org, kvm@vger.kernel.org, linux-doc@vger.kernel.org, linux-mmc@vger.kernel.org, Dave Hansen , dri-devel@lists.freedesktop.org, linux-mm@kvack.org, target-devel@vger.kernel.org, linux-mtd@lists.infradead.org, linux-kselftest@vger.kernel.org, samba-technical@lists.samba.org, ceph-devel@vger.kernel.org, drbd-dev@lists.linbit.com, devel@driverdev.osuosl.org, linux-cifs@vger.kernel.org, linux-nilfs@vger.kernel.org, linux-scsi@vger.kernel.org, linux-nvdimm@lists.01.org, linux-rdma@vger.kernel.org, x86@kernel.org, amd-gfx@lists.freedesktop.org, linux-afs@lists.infradead.org, cluster-devel@redhat.com, linux-cachefs@redhat.com, intel-wired-lan@lists.osuosl.org, xen-devel@lists.xenproject.org, linux-ext4@vger.kernel.org, Fenghua Yu , ecryptfs@vger.kernel.org, linux-um@lists.infradead.org, intel-gfx@lists.freedesktop.org, linux-erofs@lists.ozlabs.org, reiserfs-devel@vger.kernel.org, linux-block@vger.kernel.org, linux-bcache@vger.kernel.org, Jaegeuk Kim , Dan Williams , io-uring@vger.kernel.org, linux-nfs@vger.kernel.org, linux-ntfs-dev@lists.sourceforge.net, netdev@vger.kernel.org, kexec@lists.infradead.org, linux-kernel@vger.kernel.org, linux-f2fs-devel@lists.sourceforge.net, linux-fsdevel@vger.kernel.org, bpf@vger.kernel.org, linuxppc-dev@lists.ozlabs.org, linux-btrfs@vger.kernel.org References: <20201009195033.3208459-1-ira.weiny@intel.com> <20201009195033.3208459-23-ira.weiny@intel.com> <20201009213434.GA839@sol.localdomain> <20201010003954.GW20115@casper.infradead.org> <20201010013036.GD1122@sol.localdomain> <20201012065635.GB2046448@iweiny-DESK2.sc.intel.com> <20201012161946.GA858@sol.localdomain> From: Dave Hansen Autocrypt: addr=dave.hansen@intel.com; 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Linux x86_64; rv:68.0) Gecko/20100101 Thunderbird/68.10.0 MIME-Version: 1.0 In-Reply-To: <20201012161946.GA858@sol.localdomain> Content-Type: text/plain; charset=utf-8 Content-Language: en-US Content-Transfer-Encoding: 8bit Precedence: bulk List-ID: X-Mailing-List: io-uring@vger.kernel.org On 10/12/20 9:19 AM, Eric Biggers wrote: > On Sun, Oct 11, 2020 at 11:56:35PM -0700, Ira Weiny wrote: >>> And I still don't really understand. After this patchset, there is still code >>> nearly identical to the above (doing a temporary mapping just for a memcpy) that >>> would still be using kmap_atomic(). >> I don't understand. You mean there would be other call sites calling: >> >> kmap_atomic() >> memcpy() >> kunmap_atomic() > Yes, there are tons of places that do this. Try 'git grep -A6 kmap_atomic' > and look for memcpy(). > > Hence why I'm asking what will be the "recommended" way to do this... > kunmap_thread() or kmap_atomic()? kmap_atomic() is always preferred over kmap()/kmap_thread(). kmap_atomic() is _much_ more lightweight since its TLB invalidation is always CPU-local and never broadcast. So, basically, unless you *must* sleep while the mapping is in place, kmap_atomic() is preferred.