On Wed, Jun 8, 2022 at 6:48 AM Al Viro <viro@xxxxxxxxxxxxxxxxxx> wrote:
>
> Rebased to -rc1 and reordered. Sits in vfs.git #work.iov_iter,
> individual patches in followups
>
> 1/9: No need of likely/unlikely on calls of check_copy_size()
> not just in uio.h; the thing is inlined and it has unlikely on
> all paths leading to return false
>
> 2/9: btrfs_direct_write(): cleaner way to handle generic_write_sync() suppression
> new flag for iomap_dio_rw(), telling it to suppress generic_write_sync()
>
> 3/9: struct file: use anonymous union member for rcuhead and llist
> "f_u" might have been an amusing name, but... we expect anon unions to
> work.
>
> 4/9: iocb: delay evaluation of IS_SYNC(...) until we want to check IOCB_DSYNC
> makes iocb_flags() much cheaper, and it's easier to keep track of
> the places where it can change.
>
> 5/9: keep iocb_flags() result cached in struct file
> that, along with the previous commit, reduces the overhead of
> new_sync_{read,write}(). struct file doesn't grow - we can keep that
> thing in the same anon union where rcuhead and llist live; that field
> gets used only before ->f_count reaches zero while the other two are
> used only after ->f_count has reached zero.
>
> 6/9: copy_page_{to,from}_iter(): switch iovec variants to generic
> kmap_local_page() allows that. And it kills quite a bit of
> code.
>
> 7/9: new iov_iter flavour - ITER_UBUF
> iovec analogue, with single segment. That case is fairly common and it
> can be handled with less overhead than full-blown iovec.
>
> 8/9: switch new_sync_{read,write}() to ITER_UBUF
> ... and this is why it is so common. Further reduction of overhead
> for new_sync_{read,write}().
>
> 9/9: iov_iter_bvec_advance(): don't bother with bvec_iter
> AFAICS, variant similar to what we do for iovec/kvec generates better
> code. Needs profiling, obviously.
>
I have pulled this on top of Linux v5.19-rc1... plus assorted patches
to fix issues with LLVM/Clang version 14.
No (new) warnings in my build-log.
Boots fine on bare metal on my Debian/unstable AMD64 system.
Any hints for testing - to see improvements?
-Sedat-
> Diffstat:
> arch/powerpc/include/asm/uaccess.h | 2 +-
> arch/s390/include/asm/uaccess.h | 4 +-
> block/fops.c | 8 +-
> drivers/nvme/target/io-cmd-file.c | 2 +-
> fs/aio.c | 2 +-
> fs/btrfs/file.c | 19 +--
> fs/btrfs/inode.c | 2 +-
> fs/ceph/file.c | 2 +-
> fs/cifs/file.c | 2 +-
> fs/direct-io.c | 4 +-
> fs/fcntl.c | 1 +
> fs/file_table.c | 17 +-
> fs/fuse/dev.c | 4 +-
> fs/fuse/file.c | 4 +-
> fs/gfs2/file.c | 2 +-
> fs/io_uring.c | 2 +-
> fs/iomap/direct-io.c | 24 +--
> fs/nfs/direct.c | 2 +-
> fs/open.c | 1 +
> fs/read_write.c | 6 +-
> fs/zonefs/super.c | 2 +-
> include/linux/fs.h | 21 ++-
> include/linux/iomap.h | 2 +
> include/linux/uaccess.h | 4 +-
> include/linux/uio.h | 41 +++--
> lib/iov_iter.c | 308 +++++++++++--------------------------
> mm/shmem.c | 2 +-
> 27 files changed, 191 insertions(+), 299 deletions(-)
