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=-22.2 required=3.0 tests=BAYES_00,DKIMWL_WL_HIGH, DKIM_SIGNED,DKIM_VALID,DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS, INCLUDES_CR_TRAILER,INCLUDES_PATCH,MAILING_LIST_MULTI,MENTIONS_GIT_HOSTING, SPF_HELO_NONE,SPF_PASS autolearn=unavailable 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 11384C433FE for ; Mon, 20 Sep 2021 12:55:41 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id E248B60F6B for ; Mon, 20 Sep 2021 12:55:40 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S236800AbhITM5G (ORCPT ); Mon, 20 Sep 2021 08:57:06 -0400 Received: from us-smtp-delivery-124.mimecast.com ([170.10.133.124]:30450 "EHLO us-smtp-delivery-124.mimecast.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S238755AbhITM5F (ORCPT ); Mon, 20 Sep 2021 08:57:05 -0400 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1632142534; h=from:from:reply-to:subject:subject:date:date:message-id:message-id: to:to:cc:cc:mime-version:mime-version:content-type:content-type: in-reply-to:in-reply-to:references:references; bh=2pfCQSUTEHtxvGUE7L+msEadtTL5UoS3j8kSdpaAr2M=; b=O2B5G1kr+d860mSLzxlNOSKoR6jyNQwdJRl4aMKW3seW+CN08TJdpib03rF3qSSiPYQqxr KtAIwlwSaxSwHHmpY5EAeyCAwlxAtt02GesSdf3p370vNuhqiUJNPn+rArczHsifOEbWZa Gr0idIlv78hX4CqOTlIqBUZEqR31qZo= Received: from mail-ed1-f71.google.com (mail-ed1-f71.google.com [209.85.208.71]) (Using TLS) by relay.mimecast.com with ESMTP id us-mta-46--vHR_4xmOOiC_Nt3vFpMqQ-1; Mon, 20 Sep 2021 08:55:33 -0400 X-MC-Unique: -vHR_4xmOOiC_Nt3vFpMqQ-1 Received: by mail-ed1-f71.google.com with SMTP id h24-20020a50cdd8000000b003d8005fe2f8so11451408edj.6 for ; Mon, 20 Sep 2021 05:55:33 -0700 (PDT) X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20210112; h=x-gm-message-state:mime-version:references:in-reply-to:from:date :message-id:subject:to:cc; bh=2pfCQSUTEHtxvGUE7L+msEadtTL5UoS3j8kSdpaAr2M=; b=yUqZELOMARyjl/d36tC51WID0swlHfDCeGThrgT7IEMoD1w8DZWclDbOYy7Ox3gsSL c+W52EtY164MbU/2r/Z0kMmpZhpGSSvaP3oUsvU+KGtHhHE14eUJ6FqQnHJNY0FGims5 7Bkb1bzjvlSFddTbPxfSlX55ff+lJmhHQvInjuEyw3CKuf1Ncj6CXqN0CcLnOKhOxu4j wCufVtSh9Z0IZPwuxgR7fuVxEGZ9bVpABcvGgnCBIkVpN4mgU6u9+m/35AdJVJ4knzrQ CxPVRyoaIMdLZDRy0Q/sO+rgmhVfliCUd5cVA+YhKzL0zbkDVeTAqt4OYmR7rMOSwHsR a82A== X-Gm-Message-State: AOAM531uiLlQh0GzWSL2i+HE0sqLCRSy5ldDc/L622CGYyCKGHlbkh87 IJiYFQjtGm8C+G618rJQyWMMYpNggIzAyubcv3pj5xgu7Mvj5ItBTVrly1DrxPKRbJPvxacLxK0 oq9zs9Glm/AKagciDyS3gQyhxyrfK2xxi46vVDQ== X-Received: by 2002:a05:6402:897:: with SMTP id e23mr29275320edy.366.1632142532341; Mon, 20 Sep 2021 05:55:32 -0700 (PDT) X-Google-Smtp-Source: ABdhPJzlDFvRn78rkRZA594LdXUAWQmcz2jxyF/fehBHkaHwnv53x2WQ0in/WyUSP9JJllei7jnYtq334xLMF93TdIE= X-Received: by 2002:a05:6402:897:: with SMTP id e23mr29275298edy.366.1632142532147; Mon, 20 Sep 2021 05:55:32 -0700 (PDT) MIME-Version: 1.0 References: <163162767601.438332.9017034724960075707.stgit@warthog.procyon.org.uk> In-Reply-To: From: David Wysochanski Date: Mon, 20 Sep 2021 08:54:56 -0400 Message-ID: Subject: Re: [RFC PATCH 0/8] fscache: Replace and remove old I/O API To: David Howells Cc: Trond Myklebust , Anna Schumaker , Steve French , Dominique Martinet , linux-nfs , v9fs-developer@lists.sourceforge.net, Trond Myklebust , linux-cachefs , linux-cifs , Shyam Prasad N , Jeff Layton , Matthew Wilcox , Alexander Viro , Linus Torvalds , linux-afs@lists.infradead.org, ceph-devel@vger.kernel.org, linux-fsdevel , Linux Kernel Mailing List Content-Type: text/plain; charset="UTF-8" Precedence: bulk List-ID: X-Mailing-List: ceph-devel@vger.kernel.org On Tue, Sep 14, 2021 at 11:30 AM David Wysochanski wrote: > > On Tue, Sep 14, 2021 at 9:55 AM David Howells wrote: > > > > > > Here's a set of patches that removes the old fscache I/O API by the following > > means: > > > > (1) A simple fallback API is added that can read or write a single page > > synchronously. The functions for this have "deprecated" in their names > > as they have to be removed at some point. > > > > (2) An implementation of this is provided in cachefiles. It creates a kiocb > > to use DIO to the backing file rather than calling readpage on the > > backing filesystem page and then snooping the page wait queue. > > > > (3) NFS is switched to use the fallback API. > > > > (4) CIFS is switched to use the fallback API also for the moment. > > > > (5) 9P is switched to using netfslib. > > > > (6) The old I/O API is removed from fscache and the page snooping > > implementation is removed from cachefiles. > > > > The reasons for doing this are: > > > > (A) Using a kiocb to do asynchronous DIO from/to the pages of the backing > > file is now a possibility that didn't exist when cachefiles was created. > > This is much simpler than the snooping mechanism with a proper callback > > path and it also requires fewer copies and less memory. > > > > (B) We have to stop using bmap() or SEEK_DATA/SEEK_HOLE to work out what > > blocks are present in the backing file is dangerous and can lead to data > > corruption if the backing filesystem can insert or remove blocks of zeros > > arbitrarily in order to optimise its extent list[1]. > > > > Whilst this patchset doesn't fix that yet, it does simplify the code and > > the fix for that can be made in a subsequent patchset. > > > > (C) In order to fix (B), the cache will need to keep track itself of what > > data is present. To make this easier to manage, the intention is to > > increase the cache block granularity to, say, 256KiB - importantly, a > > size that will span multiple pages - which means the single-page > > interface will have to go away. netfslib is designed to deal with > > that on behalf of a filesystem, though a filesystem could use raw > > cache calls instead and manage things itself. > > > > These patches can be found also on: > > > > https://git.kernel.org/pub/scm/linux/kernel/git/dhowells/linux-fs.git/log/?h=fscache-iter-3 > > > > David > > > > Link: https://lore.kernel.org/r/YO17ZNOcq+9PajfQ@mit.edu [1] > > --- > > David Howells (8): > > fscache: Generalise the ->begin_read_operation method > > fscache: Implement an alternate I/O interface to replace the old API > > nfs: Move to using the alternate (deprecated) fscache I/O API > > 9p: (untested) Convert to using the netfs helper lib to do reads and caching > > cifs: (untested) Move to using the alternate (deprecated) fscache I/O API > > fscache: Remove the old I/O API > > fscache: Remove stats that are no longer used > > fscache: Update the documentation to reflect I/O API changes > > > > > > .../filesystems/caching/backend-api.rst | 138 +-- > > .../filesystems/caching/netfs-api.rst | 386 +----- > > fs/9p/Kconfig | 1 + > > fs/9p/cache.c | 137 --- > > fs/9p/cache.h | 98 +- > > fs/9p/v9fs.h | 9 + > > fs/9p/vfs_addr.c | 174 ++- > > fs/9p/vfs_file.c | 21 +- > > fs/cachefiles/Makefile | 1 - > > fs/cachefiles/interface.c | 15 - > > fs/cachefiles/internal.h | 38 - > > fs/cachefiles/io.c | 28 +- > > fs/cachefiles/main.c | 1 - > > fs/cachefiles/rdwr.c | 972 --------------- > > fs/cifs/file.c | 64 +- > > fs/cifs/fscache.c | 105 +- > > fs/cifs/fscache.h | 74 +- > > fs/fscache/cache.c | 6 - > > fs/fscache/cookie.c | 10 - > > fs/fscache/internal.h | 58 +- > > fs/fscache/io.c | 140 ++- > > fs/fscache/object.c | 2 - > > fs/fscache/page.c | 1066 ----------------- > > fs/fscache/stats.c | 73 +- > > fs/nfs/file.c | 14 +- > > fs/nfs/fscache-index.c | 26 - > > fs/nfs/fscache.c | 161 +-- > > fs/nfs/fscache.h | 84 +- > > fs/nfs/read.c | 25 +- > > fs/nfs/write.c | 7 +- > > include/linux/fscache-cache.h | 131 -- > > include/linux/fscache.h | 418 ++----- > > include/linux/netfs.h | 17 +- > > 33 files changed, 508 insertions(+), 3992 deletions(-) > > delete mode 100644 fs/cachefiles/rdwr.c > > > > > > I tested an earlier version of these with NFS, which identified a > couple issues which you fixed. Last I checked my unit tests and > xfstests were looking good. I'll do some testing on this latest branch > / patches and report back. For the series, you can add Tested-by: Dave Wysochanski Testing was limited to NFS enabled code paths. I ran custom unit tests, as well as a series of xfstest generic runs with various NFS versions, both fscache enabled and not enabled, as well as various NFS servers, comparing 5.15.0-rc1 runs vs runs with these patches. I did not see any failures with these new patches that were not already present with 5.15.0-rc1. Here are the list of xfstest generic runs: 1. Hammerspace (pNFS flexfiles) version 4.6.3-166: vers=4.1,fsc 2. Hammerspace (pNFS flexfiles) version 4.6.3-166: vers=4.2 3. Netapp (pNFS filelayout) version 9.5RC1: vers=4.1 4. Netapp (pNFS filelayout) version 9.5RC1: vers=4.1,fsc 5. Red Hat version 8.2 (kernel-4.18.0-193.el8): vers=4.2,fsc 6. Red Hat version 8.2 (kernel-4.18.0-193.el8): vers=4.0,fsc 7. Red Hat version 8.2 (kernel-4.18.0-193.el8): vers=3,fsc