| Message ID | 20230214171330.2722188-1-dhowells@redhat.com (mailing list archive) |
|---|---|
| Headers | show |
| Series | iov_iter: Improve page extraction (pin or just list) | expand |
Hi Jens, If you decide not to take my patches in this merge window, would you have any objection to my patches 1-3 and 10-11 in this series going through Steve French's cifs tree so that he can take my cifs iteratorisation patches? Patches 1-3 would add filemap_splice_read() and direct_splice_read(), but not connect them up to anything and 10-11 would add iov_iter_extract_pages(). I can then give Steve a patch to make cifs use them as part of my patches for that. This would only affect cifs. See my iov-cifs branch: https://git.kernel.org/pub/scm/linux/kernel/git/dhowells/linux-fs.git/log/?h=iov-cifs for an example of how this would look. David
David Howells <dhowells@redhat.com> wrote:
> This would only affect cifs.
Actually, that's not quite true: it changes the flags argument to
iov_iter_get_pages*().
David
On 2/14/23 3:56 PM, David Howells wrote: > Hi Jens, > > If you decide not to take my patches in this merge window, would you have any > objection to my patches 1-3 and 10-11 in this series going through Steve > French's cifs tree so that he can take my cifs iteratorisation patches? > > Patches 1-3 would add filemap_splice_read() and direct_splice_read(), but not > connect them up to anything and 10-11 would add iov_iter_extract_pages(). I > can then give Steve a patch to make cifs use them as part of my patches for > that. > > This would only affect cifs. See my iov-cifs branch: > > https://git.kernel.org/pub/scm/linux/kernel/git/dhowells/linux-fs.git/log/?h=iov-cifs > > for an example of how this would look. Let's update the branch and see how it goes... If there's more fallout, then let's make a fallback plan for the first few.
Jens Axboe <axboe@kernel.dk> wrote: > Let's update the branch and see how it goes... If there's more fallout, then > let's make a fallback plan for the first few. I forgot to export the new functions, as Steve found out. Fix attached. David --- splice: Export filemap/direct_splice_read() filemap_splice_read() and direct_splice_read() should be exported. Signed-off-by: David Howells <dhowells@redhat.com> cc: Steve French <sfrench@samba.org> cc: Jens Axboe <axboe@kernel.dk> cc: Christoph Hellwig <hch@lst.de> cc: Al Viro <viro@zeniv.linux.org.uk> cc: David Hildenbrand <david@redhat.com> cc: John Hubbard <jhubbard@nvidia.com> cc: linux-cifs@vger.kernel.org cc: linux-mm@kvack.org cc: linux-block@vger.kernel.org cc: linux-fsdevel@vger.kernel.org --- fs/splice.c | 1 + mm/filemap.c | 1 + 2 files changed, 2 insertions(+) diff --git a/fs/splice.c b/fs/splice.c index 4c6332854b63..928c7be2f318 100644 --- a/fs/splice.c +++ b/fs/splice.c @@ -373,6 +373,7 @@ ssize_t direct_splice_read(struct file *in, loff_t *ppos, kfree(bv); return ret; } +EXPORT_SYMBOL(direct_splice_read); /** * generic_file_splice_read - splice data from file to a pipe diff --git a/mm/filemap.c b/mm/filemap.c index 8c7b135c8e23..570f86578f7c 100644 --- a/mm/filemap.c +++ b/mm/filemap.c @@ -2969,6 +2969,7 @@ ssize_t filemap_splice_read(struct file *in, loff_t *ppos, return total_spliced ? total_spliced : error; } +EXPORT_SYMBOL(filemap_splice_read); static inline loff_t folio_seek_hole_data(struct xa_state *xas, struct address_space *mapping, struct folio *folio,
David Howells <dhowells@redhat.com> wrote: > Jens Axboe <axboe@kernel.dk> wrote: > > > Let's update the branch and see how it goes... If there's more fallout, then > > let's make a fallback plan for the first few. > > I forgot to export the new functions, as Steve found out. Fix attached. That said, nothing in your tree that calls these functions directly can be built as a module, so this can be left to the cifs tree for now. David
On Wed, Feb 15, 2023 at 08:07:58AM +0000, David Howells wrote: > return total_spliced ? total_spliced : error; > } > +EXPORT_SYMBOL(filemap_splice_read); EXPORT_SYMBOL_GPL for filemap internals, please.
And who is using filemap_splice_read directly anyway? I can't find a modular user in any of the branches.
Christoph Hellwig <hch@infradead.org> wrote: > And who is using filemap_splice_read directly anyway? I can't find a > modular user in any of the branches. Fair point. I have a subset of the patches on my iov-cifs branch that doesn't make the change to generic_file_read_splice(), but rather does that bit in cifs.ko - that does require access to filemap_splice_read(). David
Hi Jens, Al, Christoph, Here are patches to provide support for extracting pages from an iov_iter and to use this in the extraction functions in the block layer bio code. The patches make the following changes: (1) Change generic_file_splice_read() to no longer use ITER_PIPE for doing a read from an O_DIRECT file fd, but rather load up an ITER_BVEC iterator with sufficient pages and use that rather than using an ITER_PIPE. This avoids a problem[2] when __iomap_dio_rw() calls iov_iter_revert() to shorten an iterator when it races with truncation. The reversion causes the pipe iterator to prematurely release the pages it was retaining - despite the read still being in progress. This caused memory corruption. (2) Change generic_file_splice_read() to no longer use ITER_PIPE for doing a read from a buffered file fd, but rather get pages directly from the pagecache using filemap_get_pages() do all the readahead, reading, waiting and extraction, and then feed the pages directly into the pipe. (3) filemap_get_pages() is altered so that it doesn't take an iterator (which we don't have in (2)), but rather the count and a flag indicating if we can handle partially uptodate pages are passed in and down to its subsidiary functions. (4) Remove ITER_PIPE and its paraphernalia as generic_file_splice_read() was the only user. (5) Add a function, iov_iter_extract_pages() to replace iov_iter_get_pages*() that gets refs, pins or just lists the pages as appropriate to the iterator type. Add a function, iov_iter_extract_will_pin() that will indicate from the iterator type how the cleanup is to be performed, returning true if the pages will need unpinning, false otherwise. (6) Make the bio struct carry a pair of flags to indicate the cleanup mode. BIO_NO_PAGE_REF is replaced with BIO_PAGE_REFFED (indicating FOLL_GET was used) and BIO_PAGE_PINNED (indicating FOLL_PIN was used) is added. BIO_PAGE_REFFED will go away, but at the moment fs/direct-io.c sets it and this series does not fully address that file. (7) Add a function, bio_release_page(), to release a page appropriately to the cleanup mode indicated by the BIO_PAGE_* flags. (8) Make the iter-to-bio code use iov_iter_extract_pages() to retain the pages appropriately and clean them up later. (9) Fix bio_flagged() so that it doesn't prevent a gcc optimisation. I've pushed the patches here also: https://git.kernel.org/pub/scm/linux/kernel/git/dhowells/linux-fs.git/log/?h=iov-extract David Changes: ======== ver #14) - Some changes to generic_file_buffered_splice_read(): - Rename to filemap_splice_read() and move to mm/filemap.c. - Create a helper, pipe_head_buf(). - Use init_sync_kiocb(). - Some changes to generic_file_direct_splice_read(): - Use alloc_pages_bulk_array() rather than alloc_pages_bulk_list(). - Use release_pages() instead of __free_page() in a loop. - Rename to direct_splice_read(). - Rearrange the patches to implement filemap_splice_read() and direct_splice_read() separately to changing generic_file_splice_read(). - Don't call generic_file_splice_read() when there isn't a ->read_folio(). - Insert patches to fix read_folio-less cases: - Make tty, procfs, kernfs and (u)random use direct_splice_read(). - Make overlayfs and coda call down to a lower layer. - Give shmem its own splice-read that doesn't insert missing pages. - Fixed a min() with mixed type args on some arches. ver #13) - Only use allocation in advance and ITER_BVEC for DIO read-splice. - Make buffered read-splice get pages directly from the pagecache. - Alter filemap_get_pages() & co. so that it doesn't need an iterator. ver #12) - Added the missing __bitwise on the iov_iter_extraction_t typedef. - Rebased on -rc7. - Don't specify FOLL_PIN to pin_user_pages_fast(). - Inserted patch at front to fix race between DIO read and truncation that caused memory corruption when iov_iter_revert() got called on an ITER_PIPE iterator[2]. - Inserted a patch after that to remove the now-unused ITER_PIPE and its helper functions. - Removed the ITER_PIPE bits from iov_iter_extract_pages(). ver #11) - Fix iov_iter_extract_kvec_pages() to include the offset into the page in the returned starting offset. - Use __bitwise for the extraction flags ver #10) - Fix use of i->kvec in iov_iter_extract_bvec_pages() to be i->bvec. - Drop bio_set_cleanup_mode(), open coding it instead. ver #9) - It's now not permitted to use FOLL_PIN outside of mm/, so: - Change iov_iter_extract_mode() into iov_iter_extract_will_pin() and return true/false instead of FOLL_PIN/0. - Drop of folio_put_unpin() and page_put_unpin() and instead call unpin_user_page() (and put_page()) directly as necessary. - Make __bio_release_pages() call bio_release_page() instead of unpin_user_page() as there's no BIO_* -> FOLL_* translation to do. - Drop the FOLL_* renumbering patch. - Change extract_flags to extraction_flags. ver #8) - Import Christoph Hellwig's changes. - Split the conversion-to-extraction patch. - Drop the extract_flags arg from iov_iter_extract_mode(). - Don't default bios to BIO_PAGE_REFFED, but set explicitly. - Switch FOLL_PIN and FOLL_GET when renumbering so PIN is at bit 0. - Switch BIO_PAGE_PINNED and BIO_PAGE_REFFED so PINNED is at bit 0. - We should always be using FOLL_PIN (not FOLL_GET) for DIO, so adjust the patches for that. ver #7) - For now, drop the parts to pass the I/O direction to iov_iter_*pages*() as it turned out to be a lot more complicated, with places not setting IOCB_WRITE when they should, for example. - Drop all the patches that changed things other then the block layer's bio handling. The netfslib and cifs changes can go into a separate patchset. - Add support for extracting pages from KVEC-type iterators. - When extracting from BVEC/KVEC, skip over empty vecs at the front. ver #6) - Fix write() syscall and co. not setting IOCB_WRITE. - Added iocb_is_read() and iocb_is_write() to check IOCB_WRITE. - Use op_is_write() in bio_copy_user_iov(). - Drop the iterator direction checks from smbd_recv(). - Define FOLL_SOURCE_BUF and FOLL_DEST_BUF and pass them in as part of gup_flags to iov_iter_get/extract_pages*(). - Replace iov_iter_get_pages*2() with iov_iter_get_pages*() and remove. - Add back the function to indicate the cleanup mode. - Drop the cleanup_mode return arg to iov_iter_extract_pages(). - Provide a helper to clean up a page. - Renumbered FOLL_GET and FOLL_PIN and made BIO_PAGE_REFFED/PINNED have the same numerical values, enforced with an assertion. - Converted AF_ALG, SCSI vhost, generic DIO, FUSE, splice to pipe, 9P and NFS. - Added in the patches to make CIFS do top-to-bottom iterators and use various of the added extraction functions. - Added a pair of work-in-progess patches to make sk_buff fragments store FOLL_GET and FOLL_PIN. ver #5) - Replace BIO_NO_PAGE_REF with BIO_PAGE_REFFED and split into own patch. - Transcribe FOLL_GET/PIN into BIO_PAGE_REFFED/PINNED flags. - Add patch to allow bio_flagged() to be combined by gcc. ver #4) - Drop the patch to move the FOLL_* flags to linux/mm_types.h as they're no longer referenced by linux/uio.h. - Add ITER_SOURCE/DEST cleanup patches. - Make iov_iter/netfslib iter extraction patches use ITER_SOURCE/DEST. - Allow additional gup_flags to be passed into iov_iter_extract_pages(). - Add struct bio patch. ver #3) - Switch to using EXPORT_SYMBOL_GPL to prevent indirect 3rd-party access to get/pin_user_pages_fast()[1]. ver #2) - Rolled the extraction cleanup mode query function into the extraction function, returning the indication through the argument list. - Fixed patch 4 (extract to scatterlist) to actually use the new extraction API. Link: https://lore.kernel.org/r/Y3zFzdWnWlEJ8X8/@infradead.org/ [1] Link: https://lore.kernel.org/r/000000000000b0b3c005f3a09383@google.com/ [2] Link: https://lore.kernel.org/r/166697254399.61150.1256557652599252121.stgit@warthog.procyon.org.uk/ # rfc Link: https://lore.kernel.org/r/166722777223.2555743.162508599131141451.stgit@warthog.procyon.org.uk/ # rfc Link: https://lore.kernel.org/r/166732024173.3186319.18204305072070871546.stgit@warthog.procyon.org.uk/ # rfc Link: https://lore.kernel.org/r/166869687556.3723671.10061142538708346995.stgit@warthog.procyon.org.uk/ # rfc Link: https://lore.kernel.org/r/166920902005.1461876.2786264600108839814.stgit@warthog.procyon.org.uk/ # v2 Link: https://lore.kernel.org/r/166997419665.9475.15014699817597102032.stgit@warthog.procyon.org.uk/ # v3 Link: https://lore.kernel.org/r/167305160937.1521586.133299343565358971.stgit@warthog.procyon.org.uk/ # v4 Link: https://lore.kernel.org/r/167344725490.2425628.13771289553670112965.stgit@warthog.procyon.org.uk/ # v5 Link: https://lore.kernel.org/r/167391047703.2311931.8115712773222260073.stgit@warthog.procyon.org.uk/ # v6 Link: https://lore.kernel.org/r/20230120175556.3556978-1-dhowells@redhat.com/ # v7 Link: https://lore.kernel.org/r/20230123173007.325544-1-dhowells@redhat.com/ # v8 Link: https://lore.kernel.org/r/20230124170108.1070389-1-dhowells@redhat.com/ # v9 Link: https://lore.kernel.org/r/20230125210657.2335748-1-dhowells@redhat.com/ # v10 Link: https://lore.kernel.org/r/20230126141626.2809643-1-dhowells@redhat.com/ # v11 Link: https://lore.kernel.org/r/20230207171305.3716974-1-dhowells@redhat.com/ # v12 Link: https://lore.kernel.org/r/20230209102954.528942-1-dhowells@redhat.com/ # v13 Additional patches that got folded in: Link: https://lore.kernel.org/r/20230213134619.2198965-1-dhowells@redhat.com/ # v1 Link: https://lore.kernel.org/r/20230213153301.2338806-1-dhowells@redhat.com/ # v2 Link: https://lore.kernel.org/r/20230214083710.2547248-1-dhowells@redhat.com/ # v3 Christoph Hellwig (1): block: Replace BIO_NO_PAGE_REF with BIO_PAGE_REFFED with inverted logic David Howells (16): mm: Pass info, not iter, into filemap_get_pages() splice: Add a func to do a splice from a buffered file without ITER_PIPE splice: Add a func to do a splice from an O_DIRECT file without ITER_PIPE shmem: Implement splice-read overlayfs: Implement splice-read coda: Implement splice-read tty, proc, kernfs, random: Use direct_splice_read() splice: Do splice read from a file without using ITER_PIPE iov_iter: Kill ITER_PIPE iov_iter: Define flags to qualify page extraction. iov_iter: Add a function to extract a page list from an iterator iomap: Don't get an reference on ZERO_PAGE for direct I/O block zeroing block: Fix bio_flagged() so that gcc can better optimise it block: Add BIO_PAGE_PINNED and associated infrastructure block: Convert bio_iov_iter_get_pages to use iov_iter_extract_pages block: convert bio_map_user_iov to use iov_iter_extract_pages block/bio.c | 33 +- block/blk-map.c | 26 +- block/blk.h | 12 + drivers/char/random.c | 4 +- drivers/tty/tty_io.c | 4 +- fs/cifs/file.c | 8 +- fs/coda/file.c | 36 +- fs/direct-io.c | 2 + fs/iomap/direct-io.c | 1 - fs/kernfs/file.c | 2 +- fs/overlayfs/file.c | 36 +- fs/proc/inode.c | 4 +- fs/proc/proc_sysctl.c | 2 +- fs/proc_namespace.c | 6 +- fs/splice.c | 114 +++++- include/linux/bio.h | 5 +- include/linux/blk_types.h | 3 +- include/linux/fs.h | 6 + include/linux/pipe_fs_i.h | 20 ++ include/linux/uio.h | 49 ++- lib/iov_iter.c | 713 +++++++++++++++----------------------- mm/filemap.c | 154 +++++++- mm/internal.h | 6 + mm/shmem.c | 124 ++++++- 24 files changed, 830 insertions(+), 540 deletions(-)