Re: [RFC PATCH v4 4/5] btrfs: ioctl: introduce btrfs_uring_import_iovec()

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

On Mon, Mar 17, 2025 at 7:00 AM Sidong Yang <sidong.yang@furiosa.ai> wrote:
>
> This patch introduces btrfs_uring_import_iovec(). In encoded read/write
> with uring cmd, it uses import_iovec without supporting fixed buffer.
> btrfs_using_import_iovec() could use fixed buffer if cmd flags has
> IORING_URING_CMD_FIXED.
>
> Signed-off-by: Sidong Yang <sidong.yang@furiosa.ai>
> ---
>  fs/btrfs/ioctl.c | 32 ++++++++++++++++++++++++--------
>  1 file changed, 24 insertions(+), 8 deletions(-)
>
> diff --git a/fs/btrfs/ioctl.c b/fs/btrfs/ioctl.c
> index 6c18bad53cd3..a7b52fd99059 100644
> --- a/fs/btrfs/ioctl.c
> +++ b/fs/btrfs/ioctl.c
> @@ -4802,6 +4802,28 @@ struct btrfs_uring_encoded_data {
>         struct iov_iter iter;
>  };
>
> +static int btrfs_uring_import_iovec(struct io_uring_cmd *cmd,
> +                                   unsigned int issue_flags, int rw)
> +{
> +       struct btrfs_uring_encoded_data *data =
> +               io_uring_cmd_get_async_data(cmd)->op_data;
> +       int ret;
> +
> +       if (cmd && (cmd->flags & IORING_URING_CMD_FIXED)) {
> +               data->iov = NULL;
> +               ret = io_uring_cmd_import_fixed_vec(cmd, data->args.iov,
> +                                                   data->args.iovcnt,
> +                                                   ITER_DEST, issue_flags,

Why ITER_DEST instead of rw?

Best,
Caleb

> +                                                   &data->iter);
> +       } else {
> +               data->iov = data->iovstack;
> +               ret = import_iovec(rw, data->args.iov, data->args.iovcnt,
> +                                  ARRAY_SIZE(data->iovstack), &data->iov,
> +                                  &data->iter);
> +       }
> +       return ret;
> +}
> +
>  static int btrfs_uring_encoded_read(struct io_uring_cmd *cmd, unsigned int issue_flags)
>  {
>         size_t copy_end_kernel = offsetofend(struct btrfs_ioctl_encoded_io_args, flags);
> @@ -4874,10 +4896,7 @@ static int btrfs_uring_encoded_read(struct io_uring_cmd *cmd, unsigned int issue
>                         goto out_acct;
>                 }
>
> -               data->iov = data->iovstack;
> -               ret = import_iovec(ITER_DEST, data->args.iov, data->args.iovcnt,
> -                                  ARRAY_SIZE(data->iovstack), &data->iov,
> -                                  &data->iter);
> +               ret = btrfs_uring_import_iovec(cmd, issue_flags, ITER_DEST);
>                 if (ret < 0)
>                         goto out_acct;
>
> @@ -5022,10 +5041,7 @@ static int btrfs_uring_encoded_write(struct io_uring_cmd *cmd, unsigned int issu
>                 if (data->args.len > data->args.unencoded_len - data->args.unencoded_offset)
>                         goto out_acct;
>
> -               data->iov = data->iovstack;
> -               ret = import_iovec(ITER_SOURCE, data->args.iov, data->args.iovcnt,
> -                                  ARRAY_SIZE(data->iovstack), &data->iov,
> -                                  &data->iter);
> +               ret = btrfs_uring_import_iovec(cmd, issue_flags, ITER_SOURCE);
>                 if (ret < 0)
>                         goto out_acct;
>
> --
> 2.43.0
>
>