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,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 A4B20C43467 for ; Mon, 12 Oct 2020 06:56:44 +0000 (UTC) Received: from gabe.freedesktop.org (gabe.freedesktop.org [131.252.210.177]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by mail.kernel.org (Postfix) with ESMTPS id 57E8120735 for ; Mon, 12 Oct 2020 06:56:44 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 57E8120735 Authentication-Results: mail.kernel.org; dmarc=fail (p=none dis=none) header.from=intel.com Authentication-Results: mail.kernel.org; spf=none smtp.mailfrom=dri-devel-bounces@lists.freedesktop.org Received: from gabe.freedesktop.org (localhost [127.0.0.1]) by gabe.freedesktop.org (Postfix) with ESMTP id 9B9AF6E09E; Mon, 12 Oct 2020 06:56:41 +0000 (UTC) Received: from mga02.intel.com (mga02.intel.com [134.134.136.20]) by gabe.freedesktop.org (Postfix) with ESMTPS id A617D6E07B; Mon, 12 Oct 2020 06:56:39 +0000 (UTC) IronPort-SDR: J5pHIn7aSuQjCIKysETNS6iP1yBEj3+Qb7I1h5hvCZC6N0tzTyCu4Bee8UBMqvvJXx/AIcag8n gUpHs1fLOD6g== X-IronPort-AV: E=McAfee;i="6000,8403,9771"; a="152624631" X-IronPort-AV: E=Sophos;i="5.77,366,1596524400"; d="scan'208";a="152624631" X-Amp-Result: SKIPPED(no attachment in message) X-Amp-File-Uploaded: False Received: from orsmga005.jf.intel.com ([10.7.209.41]) by orsmga101.jf.intel.com with ESMTP/TLS/ECDHE-RSA-AES256-GCM-SHA384; 11 Oct 2020 23:56:37 -0700 IronPort-SDR: DSpSIoZKV7KPLq4zxFvBA+ZLKNkpgmuUQCwMmUi8wsqk6OFxxWBKXoVpyUUZRY9EN2DChpPczf 4EPhWIQlBVGQ== X-IronPort-AV: E=Sophos;i="5.77,366,1596524400"; d="scan'208";a="529842687" Received: from iweiny-desk2.sc.intel.com (HELO localhost) ([10.3.52.147]) by orsmga005-auth.jf.intel.com with ESMTP/TLS/ECDHE-RSA-AES256-GCM-SHA384; 11 Oct 2020 23:56:35 -0700 Date: Sun, 11 Oct 2020 23:56:35 -0700 From: Ira Weiny To: Eric Biggers Subject: Re: [PATCH RFC PKS/PMEM 22/58] fs/f2fs: Utilize new kmap_thread() Message-ID: <20201012065635.GB2046448@iweiny-DESK2.sc.intel.com> 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> MIME-Version: 1.0 Content-Disposition: inline In-Reply-To: <20201010013036.GD1122@sol.localdomain> User-Agent: Mutt/1.11.1 (2018-12-01) X-BeenThere: dri-devel@lists.freedesktop.org X-Mailman-Version: 2.1.29 Precedence: list List-Id: Direct Rendering Infrastructure - Development List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Cc: linux-aio@kvack.org, linux-efi@vger.kernel.org, kvm@vger.kernel.org, linux-doc@vger.kernel.org, Peter Zijlstra , 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, amd-gfx@lists.freedesktop.org, linux-kselftest@vger.kernel.org, Thomas Gleixner , 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, Matthew Wilcox , linux-afs@lists.infradead.org, cluster-devel@redhat.com, Ingo Molnar , intel-wired-lan@lists.osuosl.org, kexec@lists.infradead.org, xen-devel@lists.xenproject.org, linux-ext4@vger.kernel.org, bpf@vger.kernel.org, Dan Williams , Fenghua Yu , intel-gfx@lists.freedesktop.org, ecryptfs@vger.kernel.org, linux-um@lists.infradead.org, reiserfs-devel@vger.kernel.org, linux-block@vger.kernel.org, linux-bcache@vger.kernel.org, Borislav Petkov , Andy Lutomirski , Jaegeuk Kim , ceph-devel@vger.kernel.org, io-uring@vger.kernel.org, linux-cachefs@redhat.com, linux-nfs@vger.kernel.org, linux-ntfs-dev@lists.sourceforge.net, netdev@vger.kernel.org, linuxppc-dev@lists.ozlabs.org, samba-technical@lists.samba.org, linux-kernel@vger.kernel.org, linux-f2fs-devel@lists.sourceforge.net, linux-fsdevel@vger.kernel.org, Andrew Morton , linux-erofs@lists.ozlabs.org, linux-btrfs@vger.kernel.org Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Errors-To: dri-devel-bounces@lists.freedesktop.org Sender: "dri-devel" On Fri, Oct 09, 2020 at 06:30:36PM -0700, Eric Biggers wrote: > On Sat, Oct 10, 2020 at 01:39:54AM +0100, Matthew Wilcox wrote: > > On Fri, Oct 09, 2020 at 02:34:34PM -0700, Eric Biggers wrote: > > > On Fri, Oct 09, 2020 at 12:49:57PM -0700, ira.weiny@intel.com wrote: > > > > The kmap() calls in this FS are localized to a single thread. To avoid > > > > the over head of global PKRS updates use the new kmap_thread() call. > > > > > > > > @@ -2410,12 +2410,12 @@ static inline struct page *f2fs_pagecache_get_page( > > > > > > > > static inline void f2fs_copy_page(struct page *src, struct page *dst) > > > > { > > > > - char *src_kaddr = kmap(src); > > > > - char *dst_kaddr = kmap(dst); > > > > + char *src_kaddr = kmap_thread(src); > > > > + char *dst_kaddr = kmap_thread(dst); > > > > > > > > memcpy(dst_kaddr, src_kaddr, PAGE_SIZE); > > > > - kunmap(dst); > > > > - kunmap(src); > > > > + kunmap_thread(dst); > > > > + kunmap_thread(src); > > > > } > > > > > > Wouldn't it make more sense to switch cases like this to kmap_atomic()? > > > The pages are only mapped to do a memcpy(), then they're immediately unmapped. > > > > Maybe you missed the earlier thread from Thomas trying to do something > > similar for rather different reasons ... > > > > https://lore.kernel.org/lkml/20200919091751.011116649@linutronix.de/ > > I did miss it. I'm not subscribed to any of the mailing lists it was sent to. > > Anyway, it shouldn't matter. Patchsets should be standalone, and not require > reading random prior threads on linux-kernel to understand. Sorry, but I did not think that the discussion above was directly related. If I'm not mistaken, Thomas' work was directed at relaxing kmap_atomic() into kmap_thread() calls. While interesting, it is not the point of this series. I want to restrict kmap() callers into kmap_thread(). For this series it was considered to change the kmap_thread() call sites to kmap_atomic(). But like I said in the cover letter kmap_atomic() is not the same semantic. It is too strict. Perhaps I should have expanded that explanation. > > 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() ? > Is the idea that later, such code will be > converted to use kmap_thread() instead? If not, why use one over the other? The reason for the new call is that with PKS added behind kmap we have 3 levels of mapping we want. global kmap (can span threads and sleep) 'thread' kmap (can sleep but not span threads) 'atomic' kmap (can't sleep nor span threads [by definition]) As Matthew said perhaps 'global kmaps' may be best changed to vmaps? I just don't know the details of every call site. And since I don't know the call site details if there are kmap_thread() calls which are better off as kmap_atomic() calls I think it is worth converting them. But I made the assumption that kmap users would already be calling kmap_atomic() if they could (because it is more efficient). Ira _______________________________________________ dri-devel mailing list dri-devel@lists.freedesktop.org https://lists.freedesktop.org/mailman/listinfo/dri-devel