[PATCH v2 0/4] io_uring/btrfs: remove struct io_uring_cmd_data

[Caleb Sander Mateos <csander@purestorage.com>]

btrfs's ->uring_cmd() implementations are the only ones using io_uring_cmd_data
to store data that lasts for the lifetime of the uring_cmd. But all uring_cmds
have to pay the memory and CPU cost of initializing this field and freeing the
pointer if necessary when the uring_cmd ends. There is already a pdu field in
struct io_uring_cmd that ->uring_cmd() implementations can use for storage. The
only benefit of op_data seems to be that io_uring initializes it, so
->uring_cmd() can read it to tell if there was a previous call to ->uring_cmd().

Introduce a flag IORING_URING_CMD_REISSUE that ->uring_cmd() implementations can
use to tell if this is the first call to ->uring_cmd() or a reissue of the
uring_cmd. Switch btrfs to use the pdu storage for its btrfs_uring_encoded_data.
If IORING_URING_CMD_REISSUE is unset, allocate a new btrfs_uring_encoded_data.
If it's set, use the existing one in op_data. Free the btrfs_uring_encoded_data
in the btrfs layer instead of relying on io_uring to free op_data. Finally,
remove io_uring_cmd_data since it's now unused.

Caleb Sander Mateos (4):
  btrfs/ioctl: don't skip accounting in early ENOTTY return
  io_uring/cmd: introduce IORING_URING_CMD_REISSUE flag
  btrfs/ioctl: store btrfs_uring_encoded_data in io_btrfs_cmd
  io_uring/cmd: remove struct io_uring_cmd_data

 fs/btrfs/ioctl.c             | 41 +++++++++++++++++++++++++-----------
 include/linux/io_uring/cmd.h | 11 ++--------
 io_uring/uring_cmd.c         | 18 ++++++----------
 io_uring/uring_cmd.h         |  1 -
 4 files changed, 37 insertions(+), 34 deletions(-)

v2:
- Don't branch twice on -EAGAIN in io_uring_cmd() (Jens)
- Rebase on for-6.17/io_uring

-- 
2.45.2