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

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

Hi Jens,
Are you satisfied with the updated version of this series? Let me know
if there's anything else you'd like to see.

Thanks,
Caleb

On Tue, Jul 8, 2025 at 4:22 PM Caleb Sander Mateos
<csander@purestorage.com> wrote:
>
> 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
>