Re: [PATCH 04/20] ublk: add integrity UAPI

Ming Lei
2025-12-22T14:26:42Z

On Tue, Dec 16, 2025 at 10:34:38PM -0700, Caleb Sander Mateos wrote:
> From: Stanley Zhang <stazhang@purestorage.com>
>
> Add UAPI definitions for metadata/integrity support in ublk.
> UBLK_PARAM_TYPE_INTEGRITY and struct ublk_param_integrity allow a ublk
> server to specify the integrity params of a ublk device.
> The ublk driver will set UBLK_IO_F_INTEGRITY in the op_flags field of
> struct ublksrv_io_desc for requests with integrity data.
> The ublk server uses user copy with UBLKSRV_IO_INTEGRITY_FLAG set in the
> offset parameter to access a request's integrity buffer.
>
> Signed-off-by: Stanley Zhang <stazhang@purestorage.com>
> [csander: drop feature flag and redundant pi_tuple_size field,
> add io_desc flag, use block metadata UAPI constants]
> Signed-off-by: Caleb Sander Mateos <csander@purestorage.com>
> ---
> include/uapi/linux/ublk_cmd.h | 20 +++++++++++++++++++-
> 1 file changed, 19 insertions(+), 1 deletion(-)
>
> diff --git a/include/uapi/linux/ublk_cmd.h b/include/uapi/linux/ublk_cmd.h
> index ec77dabba45b..5bfb9a0521c3 100644
> --- a/include/uapi/linux/ublk_cmd.h
> +++ b/include/uapi/linux/ublk_cmd.h
> @@ -129,11 +129,15 @@
> #define UBLK_QID_BITS 12
> #define UBLK_QID_BITS_MASK ((1ULL << UBLK_QID_BITS) - 1)
>
> #define UBLK_MAX_NR_QUEUES (1U << UBLK_QID_BITS)
>
> -#define UBLKSRV_IO_BUF_TOTAL_BITS (UBLK_QID_OFF + UBLK_QID_BITS)
> +/* Copy to/from request integrity buffer instead of data buffer */
> +#define UBLK_INTEGRITY_FLAG_OFF (UBLK_QID_OFF + UBLK_QID_BITS)
> +#define UBLKSRV_IO_INTEGRITY_FLAG (1ULL << UBLK_INTEGRITY_FLAG_OFF)
> +

I feel it is more readable to move the definition into the patch which uses
them.

> +#define UBLKSRV_IO_BUF_TOTAL_BITS (UBLK_INTEGRITY_FLAG_OFF + 1)

It is UAPI, UBLKSRV_IO_BUF_TOTAL_BITS shouldn't be changed, or can you
explain this way is safe?

> #define UBLKSRV_IO_BUF_TOTAL_SIZE (1ULL << UBLKSRV_IO_BUF_TOTAL_BITS)
>
> /*
> * ublk server can register data buffers for incoming I/O requests with a sparse
> * io_uring buffer table. The request buffer can then be used as the data buffer
> @@ -406,10 +410,12 @@ struct ublksrv_ctrl_dev_info {
> *
> * ublk server has to check this flag if UBLK_AUTO_BUF_REG_FALLBACK is
> * passed in.
> */
> #define UBLK_IO_F_NEED_REG_BUF (1U << 17)
> +/* Request has an integrity data buffer */
> +#define UBLK_IO_F_INTEGRITY (1U << 18)
>
> /*
> * io cmd is described by this structure, and stored in share memory, indexed
> * by request tag.
> *
> @@ -598,10 +604,20 @@ struct ublk_param_segment {
> __u32 max_segment_size;
> __u16 max_segments;
> __u8 pad[2];
> };
>
> +struct ublk_param_integrity {
> + __u32 flags; /* LBMD_PI_CAP_* from linux/fs.h */
> + __u8 interval_exp;
> + __u8 metadata_size;
> + __u8 pi_offset;
> + __u8 csum_type; /* LBMD_PI_CSUM_* from linux/fs.h */
> + __u8 tag_size;
> + __u8 pad[7];
> +};
> +

Just be curious, `pi_tuple_size` isn't defined, instead it is hard-coded in
ublk_integrity_pi_tuple_size().

However, both scsi and nvme sets `pi_tuple_size`, so it means that ublk PI
supports one `subset` or scsi/nvme `pi_tuple_size` can be removed too?

Thanks,
Ming