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[68.20.15.154]) by smtp.gmail.com with ESMTPSA id t129sm3626939qkh.33.2021.02.15.10.05.09 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Mon, 15 Feb 2021 10:05:10 -0800 (PST) Message-ID: <9e49f96cd80eaf9c8ed267a7fbbcb4c6467ee790.camel@redhat.com> Subject: Re: [PATCH 00/33] Network fs helper library & fscache kiocb API [ver #3] From: Jeff Layton To: David Howells , Trond Myklebust , Anna Schumaker , Steve French , Dominique Martinet Cc: linux-cifs@vger.kernel.org, ceph-devel@vger.kernel.org, Matthew Wilcox , linux-cachefs@redhat.com, Alexander Viro , linux-mm@kvack.org, linux-afs@lists.infradead.org, v9fs-developer@lists.sourceforge.net, Christoph Hellwig , linux-fsdevel@vger.kernel.org, linux-nfs@vger.kernel.org, Linus Torvalds , David Wysochanski , linux-kernel@vger.kernel.org Date: Mon, 15 Feb 2021 13:05:09 -0500 In-Reply-To: <161340385320.1303470.2392622971006879777.stgit@warthog.procyon.org.uk> References: <161340385320.1303470.2392622971006879777.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: 8bit Precedence: bulk List-ID: X-Mailing-List: ceph-devel@vger.kernel.org On Mon, 2021-02-15 at 15:44 +0000, 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 five 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. > >  (5) Patches from Jeff Layton to add support in Ceph for this. > > Dave Wysochanski also has patches for NFS for this, though they're not > included on this branch as there's an issue with PNFS. > > 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 and NFS also pass > the expected tests. > > These patches can be found also on: > > https://git.kernel.org/pub/scm/linux/kernel/git/dhowells/linux-fs.git/log/?h=fscache-netfs-lib > > For diffing reference, the tag for the 9th Feb pull request is > fscache-ioapi-20210203 and can be found in the same repository. > > > > Changes > ======= > >  (v3) Rolled in the bug fixes. > >       Adjusted the functions that unlock and wait for PG_fscache according >       to Linus's suggestion. > >       Hold a ref on a page when PG_fscache is set as per Linus's >       suggestion. > >       Dropped NFS support and added Ceph support. > >  (v2) Fixed some bugs and added NFS support. > > > References > ========== > > These patches have been published for review before, firstly as part of a > larger set: > > Link: https://lore.kernel.org/linux-fsdevel/158861203563.340223.7585359869938129395.stgit@warthog.procyon.org.uk/ > > Link: https://lore.kernel.org/linux-fsdevel/159465766378.1376105.11619976251039287525.stgit@warthog.procyon.org.uk/ > Link: https://lore.kernel.org/linux-fsdevel/159465784033.1376674.18106463693989811037.stgit@warthog.procyon.org.uk/ > Link: https://lore.kernel.org/linux-fsdevel/159465821598.1377938.2046362270225008168.stgit@warthog.procyon.org.uk/ > > Link: https://lore.kernel.org/linux-fsdevel/160588455242.3465195.3214733858273019178.stgit@warthog.procyon.org.uk/ > > Then as a cut-down set: > > Link: https://lore.kernel.org/linux-fsdevel/161118128472.1232039.11746799833066425131.stgit@warthog.procyon.org.uk/ > > Link: https://lore.kernel.org/linux-fsdevel/161161025063.2537118.2009249444682241405.stgit@warthog.procyon.org.uk/ > > > Proposals/information about the design has been published here: > > Link: https://lore.kernel.org/lkml/24942.1573667720@warthog.procyon.org.uk/ > Link: https://lore.kernel.org/linux-fsdevel/2758811.1610621106@warthog.procyon.org.uk/ > Link: https://lore.kernel.org/linux-fsdevel/1441311.1598547738@warthog.procyon.org.uk/ > Link: https://lore.kernel.org/linux-fsdevel/160655.1611012999@warthog.procyon.org.uk/ > > And requests for information: > > Link: https://lore.kernel.org/linux-fsdevel/3326.1579019665@warthog.procyon.org.uk/ > Link: https://lore.kernel.org/linux-fsdevel/4467.1579020509@warthog.procyon.org.uk/ > Link: https://lore.kernel.org/linux-fsdevel/3577430.1579705075@warthog.procyon.org.uk/ > > The NFS parts, though not included here, have been tested by someone who's > using fscache in production: > > Link: https://listman.redhat.com/archives/linux-cachefs/2020-December/msg00000.html > > I've posted partial patches to try and help 9p and cifs along: > > Link: https://lore.kernel.org/linux-fsdevel/1514086.1605697347@warthog.procyon.org.uk/ > Link: https://lore.kernel.org/linux-cifs/1794123.1605713481@warthog.procyon.org.uk/ > Link: https://lore.kernel.org/linux-fsdevel/241017.1612263863@warthog.procyon.org.uk/ > Link: https://lore.kernel.org/linux-cifs/270998.1612265397@warthog.procyon.org.uk/ > > David > --- > David Howells (27): >       iov_iter: Add ITER_XARRAY >       mm: Add an unlock function for PG_private_2/PG_fscache >       mm: Implement readahead_control pageset expansion >       vfs: Export rw_verify_area() for use by cachefiles >       netfs: Make a netfs helper module >       netfs, mm: Move PG_fscache helper funcs to linux/netfs.h >       netfs, mm: Add unlock_page_fscache() and wait_on_page_fscache() >       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: Hold a ref on a page when PG_private_2 is set >       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 fscache read helper API > > Jeff Layton (6): >       ceph: disable old fscache readpage handling >       ceph: rework PageFsCache handling >       ceph: fix fscache invalidation >       ceph: convert readpage to fscache read helper >       ceph: plug write_begin into read helper >       ceph: convert ceph_readpages to ceph_readahead > > >  fs/Kconfig | 1 + >  fs/Makefile | 1 + >  fs/afs/Kconfig | 1 + >  fs/afs/dir.c | 225 ++++--- >  fs/afs/file.c | 470 ++++--------- >  fs/afs/fs_operation.c | 4 +- >  fs/afs/fsclient.c | 108 +-- >  fs/afs/inode.c | 7 +- >  fs/afs/internal.h | 58 +- >  fs/afs/rxrpc.c | 150 ++--- >  fs/afs/write.c | 610 +++++++++-------- >  fs/afs/yfsclient.c | 82 +-- >  fs/cachefiles/Makefile | 1 + >  fs/cachefiles/interface.c | 5 +- >  fs/cachefiles/internal.h | 9 + >  fs/cachefiles/rdwr2.c | 412 ++++++++++++ >  fs/ceph/Kconfig | 1 + >  fs/ceph/addr.c | 535 ++++++--------- >  fs/ceph/cache.c | 125 ---- >  fs/ceph/cache.h | 101 +-- >  fs/ceph/caps.c | 10 +- >  fs/ceph/inode.c | 1 + >  fs/ceph/super.h | 1 + >  fs/fscache/Kconfig | 1 + >  fs/fscache/Makefile | 3 +- >  fs/fscache/internal.h | 3 + >  fs/fscache/page.c | 2 +- >  fs/fscache/page2.c | 117 ++++ >  fs/fscache/stats.c | 1 + >  fs/internal.h | 5 - >  fs/netfs/Kconfig | 23 + >  fs/netfs/Makefile | 5 + >  fs/netfs/internal.h | 97 +++ >  fs/netfs/read_helper.c | 1169 +++++++++++++++++++++++++++++++++ >  fs/netfs/stats.c | 59 ++ >  fs/read_write.c | 1 + >  include/linux/fs.h | 1 + >  include/linux/fscache-cache.h | 4 + >  include/linux/fscache.h | 40 +- >  include/linux/netfs.h | 195 ++++++ >  include/linux/pagemap.h | 3 + >  include/net/af_rxrpc.h | 2 +- >  include/trace/events/afs.h | 74 +-- >  include/trace/events/netfs.h | 201 ++++++ >  mm/filemap.c | 20 + >  mm/readahead.c | 70 ++ >  net/rxrpc/recvmsg.c | 9 +- >  47 files changed, 3473 insertions(+), 1550 deletions(-) >  create mode 100644 fs/cachefiles/rdwr2.c >  create mode 100644 fs/fscache/page2.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 > > Thanks David, I did an xfstests run on ceph with a kernel based on this and it seemed to do fine. I'll plan to pull this into the ceph-client/testing branch and run it through the ceph kclient test harness. There are only a few differences from the last run we did, so I'm not expecting big changes, but I'll keep you posted. -- Jeff Layton