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Registered in England and Wales under Company Registration No. 3798903 From: David Howells To: Linus Torvalds Cc: dhowells@redhat.com, Alexander Viro , "Matthew Wilcox (Oracle)" , Anna Schumaker , Christoph Hellwig , David Wysochanski , Dominique Martinet , Jeff Layton , Marc Dionne , Mike Marshall , Steve French , Trond Myklebust , ceph-devel@vger.kernel.org, linux-afs@lists.infradead.org, linux-cachefs@redhat.com, linux-cifs@vger.kernel.org, linux-fsdevel@vger.kernel.org, linux-kernel@vger.kernel.org, linux-mm@kvack.org, linux-nfs@vger.kernel.org, v9fs-developer@lists.sourceforge.net Subject: [GIT PULL] Network fs helper library & fscache kiocb API MIME-Version: 1.0 Content-ID: <3779936.1619478404.1@warthog.procyon.org.uk> Date: Tue, 27 Apr 2021 00:06:44 +0100 Message-ID: <3779937.1619478404@warthog.procyon.org.uk> X-Scanned-By: MIMEDefang 2.84 on 10.5.11.22 Precedence: bulk List-ID: X-Mailing-List: linux-fsdevel@vger.kernel.org Hi Linus, Here's a set of patches for 5.13 to begin the process of overhauling the local caching API for network filesystems. This set consists of two parts: (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 at this time. 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. This 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) A pair of patches to fix some review issues in the ITER_XARRAY and read helpers as spotted by Al and Willy. Jeff Layton has patches to add support in Ceph for this that he intends for this merge window. I have a set of patches to support AFS that I will post a separate pull request for. 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. I also have patches in a separate branch to tidy up the handling of PG_fscache/PG_private_2 and their contribution to page refcounting in the core kernel here, but I haven't included them in this set and will route them separately. Changes ======= Fixed some ITER_XARRAY issues spotted by Al Viro[14]. Fixed a kernel doc issue and a couple of potential integer overflows in the read helpers spotted by Matthew Wilcox[15]. ver #7: Put some missing compound_head() calls in the *_page_private_2() functions[11]. Included a patch from Matthew Wilcox to make it possible to modify the readahead_control descriptor in a filesystem without occasionally triggering a BUG in the VM core[12]. Renamed iter_xarray_copy_pages() to iter_xarray_populate_pages() as it doesn't copy the contents of the pages, but rather fills out a list of pages[13]. 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] Link: https://lore.kernel.org/r/20210408145057.GN2531743@casper.infradead.org/ [11] Link: https://lore.kernel.org/r/20210421170923.4005574-1-willy@infradead.org/ [12] Link: https://lore.kernel.org/r/27c369a8f42bb8a617672b2dc0126a5c6df5a050.camel@kernel.org [13] Link: https://lore.kernel.org/r/YIVrJT8GwLI0Wlgx@zeniv-ca.linux.org.uk [14] Link: https://lore.kernel.org/r/3726642.1619471184@warthog.procyon.org.uk [15] 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 Link: https://lore.kernel.org/r/161789062190.6155.12711584466338493050.stgit@warthog.procyon.org.uk/ # v6 Link: https://lore.kernel.org/r/161918446704.3145707.14418606303992174310.stgit@warthog.procyon.org.uk # v7 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 --- The following changes since commit 4ee998b0ef8b6d7b1267cd4d953182224929abba: Merge tag 'clk-fixes-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/clk/linux (2021-03-24 11:26:50 -0700) are available in the Git repository at: git://git.kernel.org/pub/scm/linux/kernel/git/dhowells/linux-fs.git tags/netfs-lib-20210426 for you to fetch changes up to 53b776c77aca99b663a5512a04abc27670d61058: netfs: Miscellaneous fixes (2021-04-26 23:23:41 +0100) ---------------------------------------------------------------- Network filesystem helper library ---------------------------------------------------------------- David Howells (16): 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 iov_iter: Four fixes for ITER_XARRAY netfs: Miscellaneous fixes Matthew Wilcox (Oracle) (3): mm/filemap: Pass the file_ra_state in the ractl fs: Document file_ra_state mm/readahead: Handle ractl nr_pages being modified Documentation/filesystems/index.rst | 1 + Documentation/filesystems/netfs_library.rst | 526 ++++++++++++ fs/Kconfig | 1 + fs/Makefile | 1 + 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 | 42 +- include/linux/uio.h | 10 + include/trace/events/netfs.h | 261 ++++++ lib/iov_iter.c | 318 ++++++- mm/filemap.c | 65 +- mm/internal.h | 7 +- mm/readahead.c | 101 ++- 33 files changed, 3503 insertions(+), 77 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