[RFC PATCH v4 0/5] introduce io_uring_cmd_import_fixed_vec

[Sidong Yang <sidong.yang@furiosa.ai>]

This patche series introduce io_uring_cmd_import_vec. With this function,
Multiple fixed buffer could be used in uring cmd. It's vectored version
for io_uring_cmd_import_fixed(). Also this patch series includes a usage
for new api for encoded read/write in btrfs by using uring cmd.

There was approximately 10 percent of performance improvements through benchmark.
The benchmark code is in
https://github.com/SidongYang/btrfs-encoded-io-test/blob/main/main.c

./main -l
Elapsed time: 0.598997 seconds
./main -l -f
Elapsed time: 0.540332 seconds

Additionally, There is a commit that fixed a memory bug in btrfs uring encoded
read.

v2:
 - don't export iou_vc, use bvec for btrfs
 - use io_is_compat for checking compat
 - reduce allocation/free for import fixed vec

v3:
 - add iou_vec cache in io_uring_cmd and use it
 - also encoded write fixed supported

v4:
 - add a patch that introduce io_async_cmd
 - add a patch that fixes a bug in btrfs encoded read

Sidong Yang (5):
  io_uring/cmd: introduce io_async_cmd for hide io_uring_cmd_data
  io-uring/cmd: add iou_vec field for io_uring_cmd
  io-uring/cmd: introduce io_uring_cmd_import_fixed_vec
  btrfs: ioctl: introduce btrfs_uring_import_iovec()
  btrfs: ioctl: don't free iov when -EAGAIN in uring encoded read

 fs/btrfs/ioctl.c             | 35 ++++++++++++++++-----
 include/linux/io_uring/cmd.h | 14 +++++++++
 io_uring/io_uring.c          |  4 +--
 io_uring/opdef.c             |  3 +-
 io_uring/uring_cmd.c         | 60 +++++++++++++++++++++++++++++++-----
 io_uring/uring_cmd.h         | 10 ++++++
 6 files changed, 108 insertions(+), 18 deletions(-)

-- 
2.43.0