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

[Jens Axboe <axboe@kernel.dk>]

On 3/17/25 7:57 AM, Sidong Yang 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,
> +						    &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;
> +}

How can 'cmd' be NULL here?


-- 
Jens Axboe