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=-21.0 required=3.0 tests=BAYES_00,DKIMWL_WL_HIGH, DKIM_SIGNED,DKIM_VALID,DKIM_VALID_AU,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 EFAC2C43462 for ; Thu, 8 Apr 2021 15:41:00 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id B59A0610A3 for ; Thu, 8 Apr 2021 15:41:00 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S232058AbhDHPlK (ORCPT ); Thu, 8 Apr 2021 11:41:10 -0400 Received: from mail.kernel.org ([198.145.29.99]:50090 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S231480AbhDHPlJ (ORCPT ); Thu, 8 Apr 2021 11:41:09 -0400 Received: by mail.kernel.org (Postfix) with ESMTPSA id 9115361107; Thu, 8 Apr 2021 15:40:56 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1617896458; bh=AJAhG9HtEG365Wu9Zim+Won8T5Q6ni5Sm8/8FSGl46M=; h=Subject:From:To:Cc:Date:In-Reply-To:References:From; b=mCnWfyO7IND/OHZmnxZl2VF0iLoxxJ1lS9+aewL/NgkKc+N3YJQCWUgrS6zi2bzrz zgxG2ec2VtC+Gj7HR5UsL7Oj78cjLaBOcr0uEPeTUTrY3+BY4y5IWBKM/yTX6bDkCS nkL0uGHBdGs1bJ/GpHhZc9ptsUcCa7Ld7Ic861XFupstYuYExF5k854PlZ8hzFKRlk rfEGKJ8xWhU8qUTgL1SS+0WRFt0WZcm9/a1gAaG0EpzqQvqGODNzeyE0UzhPFTnG7u IeK0OY5rLK4bxKle50GQu0BMcxJr5qk7Q2EDlEcf4Ly0Eiz3YVYVinfafVtHEtwpwm oo3zW8WpCSLiA== Message-ID: Subject: Re: [PATCH v6 00/30] Network fs helper library & fscache kiocb API From: Jeff Layton To: David Howells , linux-fsdevel@vger.kernel.org Cc: Matthew Wilcox , linux-mm@kvack.org, linux-cifs@vger.kernel.org, Alexander Viro , Mike Marshall , linux-afs@lists.infradead.org, v9fs-developer@lists.sourceforge.net, Linus Torvalds , Christoph Hellwig , linux-nfs@vger.kernel.org, linux-cachefs@redhat.com, ceph-devel@vger.kernel.org, Trond Myklebust , Anna Schumaker , Steve French , Dominique Martinet , David Wysochanski , linux-kernel@vger.kernel.org Date: Thu, 08 Apr 2021 11:40:55 -0400 In-Reply-To: <161789062190.6155.12711584466338493050.stgit@warthog.procyon.org.uk> References: <161789062190.6155.12711584466338493050.stgit@warthog.procyon.org.uk> Content-Type: text/plain; charset="ISO-8859-15" User-Agent: Evolution 3.38.4 (3.38.4-1.fc33) MIME-Version: 1.0 Content-Transfer-Encoding: 7bit Precedence: bulk List-ID: X-Mailing-List: ceph-devel@vger.kernel.org On Thu, 2021-04-08 at 15:03 +0100, David Howells wrote: > Here's a set of patches to do two things: > > (1) Add a helper library to handle the new VM readahead interface. This > is intended to be used unconditionally by the filesystem (whether or > not caching is enabled) and provides a common framework for doing > caching, transparent huge pages and, in the future, possibly fscrypt > and read bandwidth maximisation. It also allows the netfs and the > cache to align, expand and slice up a read request from the VM in > various ways; the netfs need only provide a function to read a stretch > of data to the pagecache and the helper takes care of the rest. > > (2) Add an alternative fscache/cachfiles I/O API that uses the kiocb > facility to do async DIO to transfer data to/from the netfs's pages, > rather than using readpage with wait queue snooping on one side and > vfs_write() on the other. It also uses less memory, since it doesn't > do buffered I/O on the backing file. > > Note that this uses SEEK_HOLE/SEEK_DATA to locate the data available > to be read from the cache. Whilst this is an improvement from the > bmap interface, it still has a problem with regard to a modern > extent-based filesystem inserting or removing bridging blocks of > zeros. Fixing that requires a much greater overhaul. > > This is a step towards overhauling the fscache API. The change is opt-in > on the part of the network filesystem. A netfs should not try to mix the > old and the new API because of conflicting ways of handling pages and the > PG_fscache page flag and because it would be mixing DIO with buffered I/O. > Further, the helper library can't be used with the old API. > > This does not change any of the fscache cookie handling APIs or the way > invalidation is done. > > In the near term, I intend to deprecate and remove the old I/O API > (fscache_allocate_page{,s}(), fscache_read_or_alloc_page{,s}(), > fscache_write_page() and fscache_uncache_page()) and eventually replace > most of fscache/cachefiles with something simpler and easier to follow. > > The patchset contains the following parts: > > (1) Some helper patches, including provision of an ITER_XARRAY iov > iterator and a function to do readahead expansion. > > (2) Patches to add the netfs helper library. > > (3) A patch to add the fscache/cachefiles kiocb API. > > (4) Patches to add support in AFS for this. > > Jeff Layton has patches to add support in Ceph for this. > > With this, AFS without a cache passes all expected xfstests; with a cache, > there's an extra failure, but that's also there before these patches. > Fixing that probably requires a greater overhaul. Ceph also passes the > expected tests. > > The netfs lib and fscache/cachefiles patches can be found also on: > > https://git.kernel.org/pub/scm/linux/kernel/git/dhowells/linux-fs.git/log/?h=netfs-lib > > The afs patches can be found on: > > https://git.kernel.org/pub/scm/linux/kernel/git/dhowells/linux-fs.git/log/?h=afs-netfs-lib > > > Changes > ======= > > ver #6: > Merged in some fixes and added an additional tracepoint[8], including > fixing the amalgamation of contiguous subrequests that are to be > written to the cache. > > Added/merged some patches from Matthew Wilcox to make > readahead_expand() appropriately adjust the trigger for the next > readahead[9]. Also included is a patch to kerneldocify the > file_ra_state struct. > > Altered netfs_write_begin() to use DEFINE_READAHEAD()[10]. > > Split the afs patches out into their own branch. > > ver #5: > Fixed some review comments from Matthew Wilcox: > > - Put a comment into netfs_readahead() to indicate why there's a loop > that puts, but doesn't unlock, "unconsumed" pages at the end when > it could just return said pages to the caller to dispose of[6]. > (This is because where those pages are marked consumed). > > - Use the page_file_mapping() and page_index() helper functions > rather than accessing the page struct directly[6]. > > - Better names for wrangling functions for PG_private_2 and > PG_fscache wrangling functions[7]. Came up with > {set,end,wait_for}_page_private_2() and aliased these for fscache. > > Moved the taking of/dropping a page ref for the PG_private_2 flag > into the set and end functions. > > ver #4: > Fixed some review comments from Christoph Hellwig, including dropping > the export of rw_verify_area()[3] and some minor stuff[4]. > > Moved the declaration of readahead_expand() to a better location[5]. > > Rebased to v5.12-rc2 and added a bunch of references into individual > commits. > > Dropped Ceph support - that will go through the maintainer's tree. > > Added interface documentation for the netfs helper library. > > ver #3: > Rolled in the bug fixes. > > Adjusted the functions that unlock and wait for PG_fscache according > to Linus's suggestion[1]. > > Hold a ref on a page when PG_fscache is set as per Linus's > suggestion[2]. > > Dropped NFS support and added Ceph support. > > ver #2: > Fixed some bugs and added NFS support. > > Link: https://lore.kernel.org/r/CAHk-=wh+2gbF7XEjYc=HV9w_2uVzVf7vs60BPz0gFA=+pUm3ww@mail.gmail.com/ [1] > Link: https://lore.kernel.org/r/CAHk-=wjgA-74ddehziVk=XAEMTKswPu1Yw4uaro1R3ibs27ztw@mail.gmail.com/ [2] > Link: https://lore.kernel.org/r/20210216102614.GA27555@lst.de/ [3] > Link: https://lore.kernel.org/r/20210216084230.GA23669@lst.de/ [4] > Link: https://lore.kernel.org/r/20210217161358.GM2858050@casper.infradead.org/ [5] > Link: https://lore.kernel.org/r/20210321014202.GF3420@casper.infradead.org/ [6] > Link: https://lore.kernel.org/r/20210321105309.GG3420@casper.infradead.org/ [7] > Link: https://lore.kernel.org/r/161781041339.463527.18139104281901492882.stgit@warthog.procyon.org.uk/ [8] > Link: https://lore.kernel.org/r/20210407201857.3582797-1-willy@infradead.org/ [9] > Link: https://lore.kernel.org/r/1234933.1617886271@warthog.procyon.org.uk/ [10] > > References > ========== > > These patches have been published for review before, firstly as part of a > larger set: > > Link: https://lore.kernel.org/r/158861203563.340223.7585359869938129395.stgit@warthog.procyon.org.uk/ > > Link: https://lore.kernel.org/r/159465766378.1376105.11619976251039287525.stgit@warthog.procyon.org.uk/ > Link: https://lore.kernel.org/r/159465784033.1376674.18106463693989811037.stgit@warthog.procyon.org.uk/ > Link: https://lore.kernel.org/r/159465821598.1377938.2046362270225008168.stgit@warthog.procyon.org.uk/ > > Link: https://lore.kernel.org/r/160588455242.3465195.3214733858273019178.stgit@warthog.procyon.org.uk/ > > Then as a cut-down set: > > Link: https://lore.kernel.org/r/161118128472.1232039.11746799833066425131.stgit@warthog.procyon.org.uk/ # v1 > > Link: https://lore.kernel.org/r/161161025063.2537118.2009249444682241405.stgit@warthog.procyon.org.uk/ # v2 > > Link: https://lore.kernel.org/r/161340385320.1303470.2392622971006879777.stgit@warthog.procyon.org.uk/ # v3 > > Link: https://lore.kernel.org/r/161539526152.286939.8589700175877370401.stgit@warthog.procyon.org.uk/ # v4 > > Link: https://lore.kernel.org/r/161653784755.2770958.11820491619308713741.stgit@warthog.procyon.org.uk/ # v5 > > Proposals/information about the design has been published here: > > Link: https://lore.kernel.org/r/24942.1573667720@warthog.procyon.org.uk/ > Link: https://lore.kernel.org/r/2758811.1610621106@warthog.procyon.org.uk/ > Link: https://lore.kernel.org/r/1441311.1598547738@warthog.procyon.org.uk/ > Link: https://lore.kernel.org/r/160655.1611012999@warthog.procyon.org.uk/ > > And requests for information: > > Link: https://lore.kernel.org/r/3326.1579019665@warthog.procyon.org.uk/ > Link: https://lore.kernel.org/r/4467.1579020509@warthog.procyon.org.uk/ > Link: https://lore.kernel.org/r/3577430.1579705075@warthog.procyon.org.uk/ > > I've posted partial patches to try and help 9p and cifs along: > > Link: https://lore.kernel.org/r/1514086.1605697347@warthog.procyon.org.uk/ > Link: https://lore.kernel.org/r/1794123.1605713481@warthog.procyon.org.uk/ > Link: https://lore.kernel.org/r/241017.1612263863@warthog.procyon.org.uk/ > Link: https://lore.kernel.org/r/270998.1612265397@warthog.procyon.org.uk/ > > David > --- > David Howells (28): > iov_iter: Add ITER_XARRAY > mm: Add set/end/wait functions for PG_private_2 > mm: Implement readahead_control pageset expansion > netfs: Make a netfs helper module > netfs: Documentation for helper library > netfs, mm: Move PG_fscache helper funcs to linux/netfs.h > netfs, mm: Add set/end/wait_on_page_fscache() aliases > netfs: Provide readahead and readpage netfs helpers > netfs: Add tracepoints > netfs: Gather stats > netfs: Add write_begin helper > netfs: Define an interface to talk to a cache > netfs: Add a tracepoint to log failures that would be otherwise unseen > fscache, cachefiles: Add alternate API to use kiocb for read/write to cache > afs: Disable use of the fscache I/O routines > afs: Pass page into dirty region helpers to provide THP size > afs: Print the operation debug_id when logging an unexpected data version > afs: Move key to afs_read struct > afs: Don't truncate iter during data fetch > afs: Log remote unmarshalling errors > afs: Set up the iov_iter before calling afs_extract_data() > afs: Use ITER_XARRAY for writing > afs: Wait on PG_fscache before modifying/releasing a page > afs: Extract writeback extension into its own function > afs: Prepare for use of THPs > afs: Use the fs operation ops to handle FetchData completion > afs: Use new netfs lib read helper API > afs: Use the netfs_write_begin() helper > > Matthew Wilcox (Oracle) (2): > mm/filemap: Pass the file_ra_state in the ractl > fs: Document file_ra_state > > > Documentation/filesystems/index.rst | 1 + > Documentation/filesystems/netfs_library.rst | 526 ++++++++ > fs/Kconfig | 1 + > fs/Makefile | 1 + > fs/afs/Kconfig | 1 + > fs/afs/dir.c | 225 ++-- > fs/afs/file.c | 483 ++------ > fs/afs/fs_operation.c | 4 +- > fs/afs/fsclient.c | 108 +- > fs/afs/inode.c | 7 +- > fs/afs/internal.h | 59 +- > fs/afs/rxrpc.c | 150 +-- > fs/afs/write.c | 657 +++++----- > fs/afs/yfsclient.c | 82 +- > fs/cachefiles/Makefile | 1 + > fs/cachefiles/interface.c | 5 +- > fs/cachefiles/internal.h | 9 + > fs/cachefiles/io.c | 420 +++++++ > fs/ext4/verity.c | 2 +- > fs/f2fs/file.c | 2 +- > fs/f2fs/verity.c | 2 +- > fs/fscache/Kconfig | 1 + > fs/fscache/Makefile | 1 + > fs/fscache/internal.h | 4 + > fs/fscache/io.c | 116 ++ > fs/fscache/page.c | 2 +- > fs/fscache/stats.c | 1 + > fs/netfs/Kconfig | 23 + > fs/netfs/Makefile | 5 + > fs/netfs/internal.h | 97 ++ > fs/netfs/read_helper.c | 1185 +++++++++++++++++++ > fs/netfs/stats.c | 59 + > include/linux/fs.h | 24 +- > include/linux/fscache-cache.h | 4 + > include/linux/fscache.h | 50 +- > include/linux/netfs.h | 234 ++++ > include/linux/pagemap.h | 41 +- > include/net/af_rxrpc.h | 2 +- > include/trace/events/afs.h | 74 +- > include/trace/events/netfs.h | 261 ++++ > mm/filemap.c | 63 +- > mm/internal.h | 7 +- > mm/readahead.c | 97 +- > net/rxrpc/recvmsg.c | 9 +- > 44 files changed, 3998 insertions(+), 1108 deletions(-) > create mode 100644 Documentation/filesystems/netfs_library.rst > create mode 100644 fs/cachefiles/io.c > create mode 100644 fs/fscache/io.c > create mode 100644 fs/netfs/Kconfig > create mode 100644 fs/netfs/Makefile > create mode 100644 fs/netfs/internal.h > create mode 100644 fs/netfs/read_helper.c > create mode 100644 fs/netfs/stats.c > create mode 100644 include/linux/netfs.h > create mode 100644 include/trace/events/netfs.h > > You can add this to 1-16: Tested-by: Jeff Layton Tested with xfstests with fscache enabled on my local machine.