[PATCH v21 00/30] splice: Kill ITER_PIPE

David Howells
2023-05-20T00:01:01Z

Hi Jens, Al, Christoph,

I've split off splice patchset and moved the block patches to a separate
branch (though they are dependent on this one).

This patchset kills off ITER_PIPE to avoid a race between truncate,
iov_iter_revert() on the pipe and an as-yet incomplete DMA to a bio with
unpinned/unref'ed pages from an O_DIRECT splice read. This causes memory
corruption[2]. Instead, we use filemap_splice_read(), which invokes the
buffered file reading code and splices from the pagecache into the pipe;
copy_splice_read(), which bulk-allocates a buffer, reads into it and then
pushes the filled pages into the pipe; or handle it in filesystem-specific
code.

(1) Rename direct_splice_read() to copy_splice_read().

(2) Simplify the calculations for the number of pages to be reclaimed in
copy_splice_read().

(3) Turn do_splice_to() into a helper, vfs_splice_read(), so that it can
be used by overlayfs and coda to perform the checks on the lower fs.

(4) Make vfs_splice_read() jump to copy_splice_read() to handle direct-I/O
and DAX.

(5) Provide shmem with its own splice_read to handle non-existent pages
in the pagecache. We don't want a ->read_folio() as we don't want to
populate holes, but filemap_get_pages() requires it.

(6) Provide overlayfs with its own splice_read to call down to a lower
layer as overlayfs doesn't provide ->read_folio().

(7) Provide coda with its own splice_read to call down to a lower layer as
coda doesn't provide ->read_folio().

(8) Direct ->splice_read to copy_splice_read() in tty, procfs, kernfs
and random files as they just copy to the output buffer and don't
splice pages.

(9) Provide stubs for afs, ceph, ecryptfs, ext4, f2fs, nfs, ntfs3, ocfs2,
orangefs, xfs and zonefs to do locking and/or revalidation.

(10) Make cifs use filemap_splice_read().

(11) Replace pointers to generic_file_splice_read() with pointers to
filemap_splice_read() as DIO and DAX are handled in the caller;
filesystems can still provide their own alternate ->splice_read() op.

(12) Remove generic_file_splice_read().

(13) Remove ITER_PIPE and its paraphernalia as generic_file_splice_read()
was the only user.

I've pushed the patches here also:

https://git.kernel.org/pub/scm/linux/kernel/git/dhowells/linux-fs.git/log/?h=kill-iter-pipe

David

Changes:
========
ver #21)
- Split off the block-layer changes into a separate branch.
- Check for zero len in vfs_splice_read().
- Check s_maxbytes in filemap_splice_read().
- Rename direct_splice_read() to copy_splice_read().
- The direct I/O and DAX handling needs to be in vfs_splice_read(), not
generic_file_splice_read(), before ->splice_read() is called.
- Don't need #ifdef CONFIG_FS_DAX as IS_DAX() is false if !CONFIG_FS_DAX.
- Replace pointers to generic_file_splice_read() to filemap_splice_read().
- Remove generic_file_splice_read().
- In ceph, drop the caps ref.
- In NFS, Fix pos -> ppos in dprintk().

ver #20)
- Make direct_splice_read() limit the read to eof for regular files and
blockdevs.
- Check against s_maxbytes on the backing store, not a devnode inode.
- Provide stubs for afs, ceph, ecryptfs, ext4, f2fs, nfs, ntfs3, ocfs2,
orangefs, xfs and zonefs.
- Always use direct_splice_read() for 9p, trace and sockets.

ver #19)
- Remove a missed get_page() on the zeropage in shmem_splice_read().

ver #18)
- Split out the cifs bits from the patch the switches
generic_file_splice_read() over to using the non-ITER_PIPE splicing.
- Don't get/put refs on the zeropage in shmem_splice_read().

ver #17)
- Rename do_splice_to() to vfs_splice_read() and export it so that it can
be a helper and make overlayfs and coda use it, allowing duplicate
checks to be removed.

ver #16)
- The filemap_get_pages() changes are now upstream.
- filemap_splice_read() and direct_splice_read() are now upstream.
- iov_iter_extract_pages() is now upstream.

ver #15)
- Fixed up some errors in overlayfs_splice_read().

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
Link: https://lore.kernel.org/r/20230214171330.2722188-1-dhowells@redhat.com/ # v14
Link: https://lore.kernel.org/r/20230308143754.1976726-1-dhowells@redhat.com/ # v16
Link: https://lore.kernel.org/r/20230308165251.2078898-1-dhowells@redhat.com/ # v17
Link: https://lore.kernel.org/r/20230314220757.3827941-1-dhowells@redhat.com/ # v18
Link: https://lore.kernel.org/r/20230315163549.295454-1-dhowells@redhat.com/ # v19
Link: https://lore.kernel.org/r/20230519074047.1739879-1-dhowells@redhat.com/ #v20

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

David Howells (30):
splice: Fix filemap of a blockdev
splice: Make filemap_splice_read() check s_maxbytes
splice: Rename direct_splice_read() to copy_splice_read()
splice: Clean up copy_splice_read() a bit
splice: Make do_splice_to() generic and export it
splice: Check for zero count in vfs_splice_read()
splice: Make splice from an O_DIRECT fd use copy_splice_read()
splice: Make splice from a DAX file use copy_splice_read()
shmem: Implement splice-read
overlayfs: Implement splice-read
coda: Implement splice-read
tty, proc, kernfs, random: Use copy_splice_read()
net: Make sock_splice_read() use copy_splice_read() by default
9p: Add splice_read stub
afs: Provide a splice-read stub
ceph: Provide a splice-read stub
ecryptfs: Provide a splice-read stub
ext4: Provide a splice-read stub
f2fs: Provide a splice-read stub
nfs: Provide a splice-read stub
ntfs3: Provide a splice-read stub
ocfs2: Provide a splice-read stub
orangefs: Provide a splice-read stub
xfs: Provide a splice-read stub
zonefs: Provide a splice-read stub
splice: Convert trace/seq to use copy_splice_read()
cifs: Use filemap_splice_read()
splice: Use filemap_splice_read() instead of
generic_file_splice_read()
splice: Remove generic_file_splice_read()
iov_iter: Kill ITER_PIPE

block/fops.c | 2 +-
drivers/char/random.c | 4 +-
drivers/tty/tty_io.c | 4 +-
fs/9p/vfs_file.c | 26 ++-
fs/adfs/file.c | 2 +-
fs/affs/file.c | 2 +-
fs/afs/file.c | 20 +-
fs/bfs/file.c | 2 +-
fs/btrfs/file.c | 2 +-
fs/ceph/file.c | 65 +++++-
fs/cifs/cifsfs.c | 12 +-
fs/cifs/cifsfs.h | 3 -
fs/cifs/file.c | 16 --
fs/coda/file.c | 29 ++-
fs/cramfs/inode.c | 2 +-
fs/ecryptfs/file.c | 27 ++-
fs/erofs/data.c | 2 +-
fs/exfat/file.c | 2 +-
fs/ext2/file.c | 2 +-
fs/ext4/file.c | 13 +-
fs/f2fs/file.c | 43 +++-
fs/fat/file.c | 2 +-
fs/fuse/file.c | 2 +-
fs/gfs2/file.c | 4 +-
fs/hfs/inode.c | 2 +-
fs/hfsplus/inode.c | 2 +-
fs/hostfs/hostfs_kern.c | 2 +-
fs/hpfs/file.c | 2 +-
fs/jffs2/file.c | 2 +-
fs/jfs/file.c | 2 +-
fs/kernfs/file.c | 2 +-
fs/minix/file.c | 2 +-
fs/nfs/file.c | 23 ++-
fs/nfs/internal.h | 2 +
fs/nfs/nfs4file.c | 2 +-
fs/nilfs2/file.c | 2 +-
fs/ntfs/file.c | 2 +-
fs/ntfs3/file.c | 31 ++-
fs/ocfs2/file.c | 41 +++-
fs/ocfs2/ocfs2_trace.h | 3 +
fs/omfs/file.c | 2 +-
fs/orangefs/file.c | 22 +-
fs/overlayfs/file.c | 23 ++-
fs/proc/inode.c | 4 +-
fs/proc/proc_sysctl.c | 2 +-
fs/proc_namespace.c | 6 +-
fs/ramfs/file-mmu.c | 2 +-
fs/ramfs/file-nommu.c | 2 +-
fs/read_write.c | 2 +-
fs/reiserfs/file.c | 2 +-
fs/romfs/mmap-nommu.c | 2 +-
fs/splice.c | 108 ++++------
fs/sysv/file.c | 2 +-
fs/ubifs/file.c | 2 +-
fs/udf/file.c | 2 +-
fs/ufs/file.c | 2 +-
fs/vboxsf/file.c | 2 +-
fs/xfs/xfs_file.c | 30 ++-
fs/xfs/xfs_trace.h | 2 +-
fs/zonefs/file.c | 40 +++-
include/linux/fs.h | 8 +-
include/linux/splice.h | 3 +
include/linux/uio.h | 14 --
kernel/trace/trace.c | 2 +-
lib/iov_iter.c | 431 +---------------------------------------
mm/filemap.c | 10 +-
mm/shmem.c | 134 ++++++++++++-
net/socket.c | 2 +-
68 files changed, 657 insertions(+), 616 deletions(-)