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=-16.1 required=3.0 tests=BAYES_00,DKIMWL_WL_HIGH, DKIM_SIGNED,DKIM_VALID,DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS, INCLUDES_PATCH,MAILING_LIST_MULTI,MENTIONS_GIT_HOSTING,SPF_HELO_NONE,SPF_PASS autolearn=ham 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 D60DBC433F5 for ; Tue, 14 Sep 2021 15:31:13 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id BA0CB6113B for ; Tue, 14 Sep 2021 15:31:13 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S234787AbhINPca (ORCPT ); Tue, 14 Sep 2021 11:32:30 -0400 Received: from us-smtp-delivery-124.mimecast.com ([216.205.24.124]:44116 "EHLO us-smtp-delivery-124.mimecast.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S233202AbhINPc3 (ORCPT ); Tue, 14 Sep 2021 11:32:29 -0400 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1631633471; 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=28uHVFlIgd259Tk0Onl6nVW85p5Wip9eeWyZFWWQ7Gw=; b=fXdfn+1Ig+uiow4UK7egCbAw5sZTWu84CebYaYGAbDa08Vh81kzvO+rIa2Q5wcU+j0GI+M +iwz15VgoaLQclb8nhMoJazn7UzXZ0CvzH05pARoddn1vZPv3sbeQIaNUgni3H/yK8rQqa U+jlRm8+dXTSxJtbVS52xQTCLEF5zJM= Received: from mail-ej1-f71.google.com (mail-ej1-f71.google.com [209.85.218.71]) (Using TLS) by relay.mimecast.com with ESMTP id us-mta-515-ENofWGy0MA-EhahBr_lliw-1; Tue, 14 Sep 2021 11:31:10 -0400 X-MC-Unique: ENofWGy0MA-EhahBr_lliw-1 Received: by mail-ej1-f71.google.com with SMTP id n18-20020a170906089200b005dc91303dfeso5559159eje.15 for ; Tue, 14 Sep 2021 08:31:10 -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=28uHVFlIgd259Tk0Onl6nVW85p5Wip9eeWyZFWWQ7Gw=; b=Nr8pBivzxynYMNm+ZbRjNR2+AYM+i3Pr70pOMuPCxK51wE/e4tmuQcuAV80jQ91I2Q pNwQxqiQrFsCJ2dG0O3N1BwYnbrbH0bLHzw0yzDmg65TSdvI58Se2bYpC/Y2AeMyUfwG wYSuIUN/u0si9zizh3oOkdiBm7JQ5wrR3YYFSTr/QR+skBnLddGEkKecx2W+B33LWxde 9lK1QoGTgYdgjOlru1Ct83E2Q3Sv6zqe2fkXmXm+0m45+dnZQhlmJFrQHt9AaDESS+kw 0Rqph7i8gE1mbL6TKEQAEueBDi7tGiJDtElFnFJVGZN8cVLX+F7pDap8miP0LzfaY7ok swlQ== X-Gm-Message-State: AOAM532aX/0vllAydWtO+LM6E+NsNHDwz307l5s7haIJQ/6RjEzN+Rtv wONeU5unvAArZ+XH1GuF6lAxMt+pGp5YiJI1013JxSLw1m2pzQur4AmHqgohjCVjbU6cThIgfdl PFG7d48BA0DXIHlZJU0rJp3Vy60v7PvatWvmXZA== X-Received: by 2002:a17:907:9602:: with SMTP id gb2mr19741329ejc.119.1631633467706; Tue, 14 Sep 2021 08:31:07 -0700 (PDT) X-Google-Smtp-Source: ABdhPJwBCsPMH/stPuTNHWIjWdIDFCeRDqb2JZpOnn0wdJ4EAfdOma5ARu4H6YXdUtlU3P33pyF7rZaoQLtYtlKQ92E= X-Received: by 2002:a17:907:9602:: with SMTP id gb2mr19741147ejc.119.1631633465397; Tue, 14 Sep 2021 08:31:05 -0700 (PDT) MIME-Version: 1.0 References: <163162767601.438332.9017034724960075707.stgit@warthog.procyon.org.uk> In-Reply-To: <163162767601.438332.9017034724960075707.stgit@warthog.procyon.org.uk> From: David Wysochanski Date: Tue, 14 Sep 2021 11:30:29 -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 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.