| Message ID | 161918446704.3145707.14418606303992174310.stgit@warthog.procyon.org.uk |
|---|---|
| Headers | show |
| Series | Network fs helper library & fscache kiocb API | expand |
Matthew Wilcox <willy@infradead.org> wrote: > On Fri, Apr 23, 2021 at 02:28:01PM +0100, David Howells wrote: > Now, is this important? There are no filesystems which do I/O to THPs > today. So it's not possible to pick up the fact that it doesn't work, > and I hope to have the page cache fixed soon. And fixing this now > will create more work later as part of fixing the page cache. But I > wouldn't feel right not mentioning this problem ... So I can leave the code as-is for the moment and it can be fixed with your patches? David
On Mon, Apr 26, 2021 at 10:06:24PM +0100, David Howells wrote: > @@ -968,7 +968,7 @@ int netfs_readpage(struct file *file, > return -ENOMEM; > } > rreq->mapping = page_file_mapping(page); > - rreq->start = page_index(page) * PAGE_SIZE; > + rreq->start = page_offset(page); This one needs to use page_file_offset() because swap-over-NFS. > @@ -1105,8 +1105,8 @@ int netfs_write_begin(struct file *file, struct address_space *mapping, > rreq = netfs_alloc_read_request(ops, netfs_priv, file); > if (!rreq) > goto error; > - rreq->mapping = page->mapping; > - rreq->start = page->index * PAGE_SIZE; > + rreq->mapping = page_file_mapping(page); There's nothing wrong with using page->mapping here. The swap-over-NFS path doesn't use write_begin, it uses O_DIRECT writes.
On Mon, Apr 26, 2021 at 10:20:03PM +0100, David Howells wrote:
> Okay, how about the attached, then?
LGTM! Thanks.
On Mon, 2021-04-26 at 22:20 +0100, David Howells wrote: > Okay, how about the attached, then? > > David > --- > netfs: Miscellaneous fixes > > > > > Fix some miscellaneous things in the new netfs lib[1]: > > (1) The kerneldoc for netfs_readpage() shouldn't say netfs_page(). > > (2) netfs_readpage() can get an integer overflow on 32-bit when it > multiplies page_index(page) by PAGE_SIZE. It should use > page_file_offset() instead. > > (3) netfs_write_begin() should use page_offset() to avoid the same > overflow. > > Note that netfs_readpage() needs to use page_file_offset() rather than > page_offset() as it may see swap-over-NFS. > > Reported-by: Matthew Wilcox <willy@infradead.org> > Signed-off-by: David Howells <dhowells@redhat.com> > Link: https://lore.kernel.org/r/161789062190.6155.12711584466338493050.stgit@warthog.procyon.org.uk/ [1] > --- > fs/netfs/read_helper.c | 6 +++--- > 1 file changed, 3 insertions(+), 3 deletions(-) > > diff --git a/fs/netfs/read_helper.c b/fs/netfs/read_helper.c > index 1d3b50c5db6d..193841d03de0 100644 > --- a/fs/netfs/read_helper.c > +++ b/fs/netfs/read_helper.c > @@ -933,7 +933,7 @@ void netfs_readahead(struct readahead_control *ractl, > EXPORT_SYMBOL(netfs_readahead); > > > > > /** > - * netfs_page - Helper to manage a readpage request > + * netfs_readpage - Helper to manage a readpage request > * @file: The file to read from > * @page: The page to read > * @ops: The network filesystem's operations for the helper to use > @@ -968,7 +968,7 @@ int netfs_readpage(struct file *file, > return -ENOMEM; > } > rreq->mapping = page_file_mapping(page); > - rreq->start = page_index(page) * PAGE_SIZE; > + rreq->start = page_file_offset(page); > rreq->len = thp_size(page); > > > > > if (ops->begin_cache_operation) { > @@ -1106,7 +1106,7 @@ int netfs_write_begin(struct file *file, struct address_space *mapping, > if (!rreq) > goto error; > rreq->mapping = page->mapping; > - rreq->start = page->index * PAGE_SIZE; > + rreq->start = page_offset(page); > rreq->len = thp_size(page); > rreq->no_unlock_page = page->index; > __set_bit(NETFS_RREQ_NO_UNLOCK_PAGE, &rreq->flags); > Reviewed-by: Jeff Layton <jlayton@kernel.org>
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 I also have some supplementary patches 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: https://git.kernel.org/pub/scm/linux/kernel/git/dhowells/linux-fs.git/log/?h=netfs-lib-mm Changes ======= 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] 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 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) (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/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 | 42 +- include/net/af_rxrpc.h | 2 +- include/trace/events/afs.h | 74 +- include/trace/events/netfs.h | 261 ++++ mm/filemap.c | 65 +- mm/internal.h | 7 +- mm/readahead.c | 101 +- net/rxrpc/recvmsg.c | 9 +- 44 files changed, 4003 insertions(+), 1110 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