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SubjectRe: [PATCH V8 00/33] loop: Issue O_DIRECT aio using bio_vec
Hello Dave,

On Thu, Jul 25, 2013 at 12:50:26PM -0500, Dave Kleikamp wrote:
> This patch series adds a kernel interface to fs/aio.c so that kernel code can
> issue concurrent asynchronous IO to file systems. It adds an aio command and
> file system methods which specify io memory with pages instead of userspace
> addresses.

First off, have you tested that this series actually works when merged with
the pending AIO changes from Kent? There a git tree with those pending
changes at git://git.kvack.org/~bcrl/aio-next.git , and they're in
linux-next.

One of the major problems your changeset continues to carry is that your
new read_iter/write_iter operations permit blocking (implicitely), which
really isn't what we want for aio. If you're going to introduce a new api,
it should be made non-blocking, and enforce that non-blocking requirement
(ie warn when read_iter/write_iter methods perform blockin operations,
similar to the warnings when scheduling in atomic mode). This means more
changes for some filesystem code involved, something that people have been
avoiding for years, but which really needs to be done.

-ben

> This series was written to reduce the current overhead loop imposes by
> performing synchronus buffered file system IO from a kernel thread. These
> patches turn loop into a light weight layer that translates bios into iocbs.
>
> It introduces new file ops, read_iter() and write_iter(), that replace the
> aio_read() and aio_write() operations. The iov_iter structure can now contain
> either a user-space iovec or a kernel-space bio_vec. Since it would be
> overly complicated to replace every instance of aio_read() and aio_write(),
> the old operations are not removed, but file systems implementing the new
> ones need not keep the old ones.
>
> Verion 8 is little changed from Version 7 that I send out in March, just
> updated to the latest kernel. These patches apply to 3.11-rc2 and can
> also be found at:
>
> git://github.com/kleikamp/linux-shaggy.git aio_loop
>
> Asias He (1):
> block_dev: add support for read_iter, write_iter
>
> Dave Kleikamp (22):
> iov_iter: iov_iter_copy_from_user() should use non-atomic copy
> iov_iter: add __iovec_copy_to_user()
> fuse: convert fuse to use iov_iter_copy_[to|from]_user
> iov_iter: ii_iovec_copy_to_user should pre-fault user pages
> dio: Convert direct_IO to use iov_iter
> dio: add bio_vec support to __blockdev_direct_IO()
> aio: add aio_kernel_() interface
> aio: add aio support for iov_iter arguments
> fs: create file_readable() and file_writable() functions
> fs: use read_iter and write_iter rather than aio_read and aio_write
> fs: add read_iter and write_iter to several file systems
> ocfs2: add support for read_iter and write_iter
> ext4: add support for read_iter and write_iter
> nfs: add support for read_iter, write_iter
> nfs: simplify swap
> btrfs: add support for read_iter and write_iter
> xfs: add support for read_iter and write_iter
> gfs2: Convert aio_read/write ops to read/write_iter
> udf: convert file ops from aio_read/write to read/write_iter
> afs: add support for read_iter and write_iter
> ecrpytfs: Convert aio_read/write ops to read/write_iter
> ubifs: convert file ops from aio_read/write to read/write_iter
>
> Hugh Dickins (1):
> tmpfs: add support for read_iter and write_iter
>
> Zach Brown (9):
> iov_iter: move into its own file
> iov_iter: add copy_to_user support
> iov_iter: hide iovec details behind ops function pointers
> iov_iter: add bvec support
> iov_iter: add a shorten call
> iov_iter: let callers extract iovecs and bio_vecs
> fs: pull iov_iter use higher up the stack
> bio: add bvec_length(), like iov_length()
> loop: use aio to perform io on the underlying file
>
> Documentation/filesystems/Locking | 6 +-
> Documentation/filesystems/vfs.txt | 12 +-
> drivers/block/loop.c | 148 ++++++++----
> drivers/char/raw.c | 4 +-
> drivers/mtd/nand/nandsim.c | 4 +-
> drivers/usb/gadget/storage_common.c | 4 +-
> fs/9p/vfs_addr.c | 12 +-
> fs/9p/vfs_file.c | 8 +-
> fs/Makefile | 2 +-
> fs/adfs/file.c | 4 +-
> fs/affs/file.c | 4 +-
> fs/afs/file.c | 4 +-
> fs/afs/internal.h | 3 +-
> fs/afs/write.c | 9 +-
> fs/aio.c | 152 ++++++++++++-
> fs/bad_inode.c | 14 ++
> fs/bfs/file.c | 4 +-
> fs/block_dev.c | 27 ++-
> fs/btrfs/file.c | 42 ++--
> fs/btrfs/inode.c | 63 +++---
> fs/ceph/addr.c | 3 +-
> fs/cifs/file.c | 4 +-
> fs/direct-io.c | 223 +++++++++++++------
> fs/ecryptfs/file.c | 15 +-
> fs/exofs/file.c | 4 +-
> fs/ext2/file.c | 4 +-
> fs/ext2/inode.c | 8 +-
> fs/ext3/file.c | 4 +-
> fs/ext3/inode.c | 15 +-
> fs/ext4/ext4.h | 3 +-
> fs/ext4/file.c | 34 +--
> fs/ext4/indirect.c | 16 +-
> fs/ext4/inode.c | 23 +-
> fs/f2fs/data.c | 4 +-
> fs/f2fs/file.c | 4 +-
> fs/fat/file.c | 4 +-
> fs/fat/inode.c | 10 +-
> fs/fuse/cuse.c | 10 +-
> fs/fuse/file.c | 90 ++++----
> fs/fuse/fuse_i.h | 5 +-
> fs/gfs2/aops.c | 7 +-
> fs/gfs2/file.c | 21 +-
> fs/hfs/inode.c | 11 +-
> fs/hfsplus/inode.c | 10 +-
> fs/hostfs/hostfs_kern.c | 4 +-
> fs/hpfs/file.c | 4 +-
> fs/internal.h | 4 +
> fs/iov-iter.c | 411 ++++++++++++++++++++++++++++++++++
> fs/jffs2/file.c | 8 +-
> fs/jfs/file.c | 4 +-
> fs/jfs/inode.c | 7 +-
> fs/logfs/file.c | 4 +-
> fs/minix/file.c | 4 +-
> fs/nfs/direct.c | 302 ++++++++++++++++---------
> fs/nfs/file.c | 33 ++-
> fs/nfs/internal.h | 4 +-
> fs/nfs/nfs4file.c | 4 +-
> fs/nilfs2/file.c | 4 +-
> fs/nilfs2/inode.c | 8 +-
> fs/ocfs2/aops.c | 8 +-
> fs/ocfs2/aops.h | 2 +-
> fs/ocfs2/file.c | 55 ++---
> fs/ocfs2/ocfs2_trace.h | 6 +-
> fs/omfs/file.c | 4 +-
> fs/ramfs/file-mmu.c | 4 +-
> fs/ramfs/file-nommu.c | 4 +-
> fs/read_write.c | 78 +++++--
> fs/reiserfs/file.c | 4 +-
> fs/reiserfs/inode.c | 7 +-
> fs/romfs/mmap-nommu.c | 2 +-
> fs/sysv/file.c | 4 +-
> fs/ubifs/file.c | 12 +-
> fs/udf/file.c | 13 +-
> fs/udf/inode.c | 10 +-
> fs/ufs/file.c | 4 +-
> fs/xfs/xfs_aops.c | 13 +-
> fs/xfs/xfs_file.c | 51 ++---
> include/linux/aio.h | 20 +-
> include/linux/bio.h | 8 +
> include/linux/blk_types.h | 2 -
> include/linux/fs.h | 165 ++++++++++++--
> include/linux/nfs_fs.h | 13 +-
> include/uapi/linux/aio_abi.h | 2 +
> include/uapi/linux/loop.h | 1 +
> mm/filemap.c | 433 ++++++++++++++----------------------
> mm/page_io.c | 15 +-
> mm/shmem.c | 61 ++---
> 87 files changed, 1862 insertions(+), 1002 deletions(-)
> create mode 100644 fs/iov-iter.c
>
> --
> 1.8.3.4
>
> --
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