Re: [PATCHv5 09/11] ublk: zc register/unregister bvec

[Ming Lei <ming.lei@redhat.com>]

On Mon, Feb 24, 2025 at 01:31:14PM -0800, Keith Busch wrote:
> From: Keith Busch <kbusch@kernel.org>
> 
> Provide new operations for the user to request mapping an active request
> to an io uring instance's buf_table. The user has to provide the index
> it wants to install the buffer.
> 
> A reference count is taken on the request to ensure it can't be
> completed while it is active in a ring's buf_table.
> 
> Signed-off-by: Keith Busch <kbusch@kernel.org>
> ---
>  drivers/block/ublk_drv.c      | 117 +++++++++++++++++++++++-----------
>  include/uapi/linux/ublk_cmd.h |   4 ++
>  2 files changed, 85 insertions(+), 36 deletions(-)
> 
> diff --git a/drivers/block/ublk_drv.c b/drivers/block/ublk_drv.c
> index 529085181f355..a719d873e3882 100644
> --- a/drivers/block/ublk_drv.c
> +++ b/drivers/block/ublk_drv.c
> @@ -51,6 +51,9 @@
>  /* private ioctl command mirror */
>  #define UBLK_CMD_DEL_DEV_ASYNC	_IOC_NR(UBLK_U_CMD_DEL_DEV_ASYNC)
>  
> +#define UBLK_IO_REGISTER_IO_BUF		_IOC_NR(UBLK_U_IO_REGISTER_IO_BUF)
> +#define UBLK_IO_UNREGISTER_IO_BUF	_IOC_NR(UBLK_U_IO_UNREGISTER_IO_BUF)
> +
>  /* All UBLK_F_* have to be included into UBLK_F_ALL */
>  #define UBLK_F_ALL (UBLK_F_SUPPORT_ZERO_COPY \
>  		| UBLK_F_URING_CMD_COMP_IN_TASK \
> @@ -201,7 +204,7 @@ static inline struct ublksrv_io_desc *ublk_get_iod(struct ublk_queue *ubq,
>  						   int tag);
>  static inline bool ublk_dev_is_user_copy(const struct ublk_device *ub)
>  {
> -	return ub->dev_info.flags & UBLK_F_USER_COPY;
> +	return ub->dev_info.flags & (UBLK_F_USER_COPY | UBLK_F_SUPPORT_ZERO_COPY);
>  }

I'd suggest to set UBLK_F_USER_COPY explicitly either from userspace or
kernel side.

One reason is that UBLK_F_UNPRIVILEGED_DEV mode can't work for both.



Thanks,
Ming