Re: [PATCH v3 03/19] ublk: support UBLK_PARAM_TYPE_INTEGRITY in device creation

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

On Tue, Jan 06, 2026 at 08:32:08AM -0800, Caleb Sander Mateos wrote:
> On Tue, Jan 6, 2026 at 5:09 AM Ming Lei <ming.lei@redhat.com> wrote:
> >
> > On Mon, Jan 05, 2026 at 05:57:35PM -0700, Caleb Sander Mateos wrote:
> > > From: Stanley Zhang <stazhang@purestorage.com>
> > >
> > > Add a feature flag UBLK_F_INTEGRITY for a ublk server to request
> > > integrity/metadata support when creating a ublk device. The ublk server
> > > can also check for the feature flag on the created device or the result
> > > of UBLK_U_CMD_GET_FEATURES to tell if the ublk driver supports it.
> > > UBLK_F_INTEGRITY requires UBLK_F_USER_COPY, as user copy is the only
> > > data copy mode initially supported for integrity data.
> > > Add UBLK_PARAM_TYPE_INTEGRITY and struct ublk_param_integrity to struct
> > > ublk_params to specify the integrity params of a ublk device.
> > > UBLK_PARAM_TYPE_INTEGRITY requires UBLK_F_INTEGRITY and a nonzero
> > > metadata_size. The LBMD_PI_CAP_* and LBMD_PI_CSUM_* values from the
> > > linux/fs.h UAPI header are used for the flags and csum_type fields.
> > > If the UBLK_PARAM_TYPE_INTEGRITY flag is set, validate the integrity
> > > parameters and apply them to the blk_integrity limits.
> > > The struct ublk_param_integrity validations are based on the checks in
> > > blk_validate_integrity_limits(). Any invalid parameters should be
> > > rejected before being applied to struct blk_integrity.
> > >
> > > Signed-off-by: Stanley Zhang <stazhang@purestorage.com>
> > > [csander: drop redundant pi_tuple_size field, use block metadata UAPI
> > >  constants, add param validation]
> > > Signed-off-by: Caleb Sander Mateos <csander@purestorage.com>
> > > ---
> > >  drivers/block/ublk_drv.c      | 94 ++++++++++++++++++++++++++++++++++-
> > >  include/uapi/linux/ublk_cmd.h | 18 +++++++
> > >  2 files changed, 111 insertions(+), 1 deletion(-)
> > >
> > > diff --git a/drivers/block/ublk_drv.c b/drivers/block/ublk_drv.c
> > > index 8e3da9b2b93a..066c6ae062a0 100644
> > > --- a/drivers/block/ublk_drv.c
> > > +++ b/drivers/block/ublk_drv.c
> > > @@ -42,10 +42,12 @@
> > >  #include <linux/mm.h>
> > >  #include <asm/page.h>
> > >  #include <linux/task_work.h>
> > >  #include <linux/namei.h>
> > >  #include <linux/kref.h>
> > > +#include <linux/blk-integrity.h>
> > > +#include <uapi/linux/fs.h>
> > >  #include <uapi/linux/ublk_cmd.h>
> > >
> > >  #define UBLK_MINORS          (1U << MINORBITS)
> > >
> > >  #define UBLK_INVALID_BUF_IDX         ((u16)-1)
> > > @@ -81,11 +83,12 @@
> > >
> > >  /* All UBLK_PARAM_TYPE_* should be included here */
> > >  #define UBLK_PARAM_TYPE_ALL                                \
> > >       (UBLK_PARAM_TYPE_BASIC | UBLK_PARAM_TYPE_DISCARD | \
> > >        UBLK_PARAM_TYPE_DEVT | UBLK_PARAM_TYPE_ZONED |    \
> > > -      UBLK_PARAM_TYPE_DMA_ALIGN | UBLK_PARAM_TYPE_SEGMENT)
> > > +      UBLK_PARAM_TYPE_DMA_ALIGN | UBLK_PARAM_TYPE_SEGMENT | \
> > > +      UBLK_PARAM_TYPE_INTEGRITY)
> > >
> > >  struct ublk_uring_cmd_pdu {
> > >       /*
> > >        * Store requests in same batch temporarily for queuing them to
> > >        * daemon context.
> > > @@ -628,10 +631,57 @@ static void ublk_dev_param_basic_apply(struct ublk_device *ub)
> > >               set_disk_ro(ub->ub_disk, true);
> > >
> > >       set_capacity(ub->ub_disk, p->dev_sectors);
> > >  }
> > >
> > > +static int ublk_integrity_flags(u32 flags)
> > > +{
> > > +     int ret_flags = 0;
> > > +
> > > +     if (flags & LBMD_PI_CAP_INTEGRITY) {
> > > +             flags &= ~LBMD_PI_CAP_INTEGRITY;
> > > +             ret_flags |= BLK_INTEGRITY_DEVICE_CAPABLE;
> > > +     }
> > > +     if (flags & LBMD_PI_CAP_REFTAG) {
> > > +             flags &= ~LBMD_PI_CAP_REFTAG;
> > > +             ret_flags |= BLK_INTEGRITY_REF_TAG;
> > > +     }
> > > +     return flags ? -EINVAL : ret_flags;
> > > +}
> > > +
> > > +static int ublk_integrity_pi_tuple_size(u8 csum_type)
> > > +{
> > > +     switch (csum_type) {
> > > +     case LBMD_PI_CSUM_NONE:
> > > +             return 0;
> > > +     case LBMD_PI_CSUM_IP:
> > > +     case LBMD_PI_CSUM_CRC16_T10DIF:
> > > +             return 8;
> > > +     case LBMD_PI_CSUM_CRC64_NVME:
> > > +             return 16;
> > > +     default:
> > > +             return -EINVAL;
> > > +     }
> > > +}
> > > +
> > > +static enum blk_integrity_checksum ublk_integrity_csum_type(u8 csum_type)
> > > +{
> > > +     switch (csum_type) {
> > > +     case LBMD_PI_CSUM_NONE:
> > > +             return BLK_INTEGRITY_CSUM_NONE;
> > > +     case LBMD_PI_CSUM_IP:
> > > +             return BLK_INTEGRITY_CSUM_IP;
> > > +     case LBMD_PI_CSUM_CRC16_T10DIF:
> > > +             return BLK_INTEGRITY_CSUM_CRC;
> > > +     case LBMD_PI_CSUM_CRC64_NVME:
> > > +             return BLK_INTEGRITY_CSUM_CRC64;
> > > +     default:
> > > +             WARN_ON_ONCE(1);
> > > +             return BLK_INTEGRITY_CSUM_NONE;
> > > +     }
> > > +}
> > > +
> > >  static int ublk_validate_params(const struct ublk_device *ub)
> > >  {
> > >       /* basic param is the only one which must be set */
> > >       if (ub->params.types & UBLK_PARAM_TYPE_BASIC) {
> > >               const struct ublk_param_basic *p = &ub->params.basic;
> > > @@ -690,10 +740,33 @@ static int ublk_validate_params(const struct ublk_device *ub)
> > >                       return -EINVAL;
> > >               if (p->max_segment_size < UBLK_MIN_SEGMENT_SIZE)
> > >                       return -EINVAL;
> > >       }
> > >
> > > +     if (ub->params.types & UBLK_PARAM_TYPE_INTEGRITY) {
> > > +             const struct ublk_param_integrity *p = &ub->params.integrity;
> > > +             int pi_tuple_size = ublk_integrity_pi_tuple_size(p->csum_type);
> > > +             int flags = ublk_integrity_flags(p->flags);
> > > +
> > > +             if (!(ub->dev_info.flags & UBLK_F_INTEGRITY))
> > > +                     return -EINVAL;
> > > +             if (flags < 0)
> > > +                     return flags;
> > > +             if (pi_tuple_size < 0)
> > > +                     return pi_tuple_size;
> > > +             if (!p->metadata_size)
> > > +                     return -EINVAL;
> > > +             if (p->csum_type == LBMD_PI_CSUM_NONE &&
> > > +                 p->flags & LBMD_PI_CAP_REFTAG)
> > > +                     return -EINVAL;
> > > +             if (p->pi_offset + pi_tuple_size > p->metadata_size)
> > > +                     return -EINVAL;
> > > +             if (p->interval_exp < SECTOR_SHIFT ||
> > > +                 p->interval_exp > ub->params.basic.logical_bs_shift)
> > > +                     return -EINVAL;
> > > +     }
> > > +
> > >       return 0;
> > >  }
> > >
> > >  static void ublk_apply_params(struct ublk_device *ub)
> > >  {
> > > @@ -2941,10 +3014,25 @@ static int ublk_ctrl_start_dev(struct ublk_device *ub,
> > >               lim.seg_boundary_mask = ub->params.seg.seg_boundary_mask;
> > >               lim.max_segment_size = ub->params.seg.max_segment_size;
> > >               lim.max_segments = ub->params.seg.max_segments;
> > >       }
> > >
> > > +     if (ub->params.types & UBLK_PARAM_TYPE_INTEGRITY) {
> > > +             const struct ublk_param_integrity *p = &ub->params.integrity;
> > > +             int pi_tuple_size = ublk_integrity_pi_tuple_size(p->csum_type);
> > > +
> > > +             lim.integrity = (struct blk_integrity) {
> > > +                     .flags = ublk_integrity_flags(p->flags),
> > > +                     .csum_type = ublk_integrity_csum_type(p->csum_type),
> > > +                     .metadata_size = p->metadata_size,
> > > +                     .pi_offset = p->pi_offset,
> > > +                     .interval_exp = p->interval_exp,
> > > +                     .tag_size = p->tag_size,
> > > +                     .pi_tuple_size = pi_tuple_size,
> > > +             };
> > > +     }
> > > +
> > >       if (wait_for_completion_interruptible(&ub->completion) != 0)
> > >               return -EINTR;
> > >
> > >       if (ub->ublksrv_tgid != ublksrv_pid)
> > >               return -EINVAL;
> > > @@ -3131,10 +3219,14 @@ static int ublk_ctrl_add_dev(const struct ublksrv_ctrl_cmd *header)
> > >               if (info.flags & (UBLK_F_USER_COPY | UBLK_F_SUPPORT_ZERO_COPY |
> > >                                       UBLK_F_AUTO_BUF_REG))
> > >                       return -EINVAL;
> > >       }
> > >
> > > +     /* User copy is required to access integrity buffer */
> > > +     if (info.flags & UBLK_F_INTEGRITY && !(info.flags & UBLK_F_USER_COPY))
> > > +             return -EINVAL;
> > > +
> > >       /* the created device is always owned by current user */
> > >       ublk_store_owner_uid_gid(&info.owner_uid, &info.owner_gid);
> > >
> > >       if (header->dev_id != info.dev_id) {
> > >               pr_warn("%s: dev id not match %u %u\n",
> > > diff --git a/include/uapi/linux/ublk_cmd.h b/include/uapi/linux/ublk_cmd.h
> > > index ec77dabba45b..a54c47832fa2 100644
> > > --- a/include/uapi/linux/ublk_cmd.h
> > > +++ b/include/uapi/linux/ublk_cmd.h
> > > @@ -309,10 +309,16 @@
> > >   * the I/O's daemon task. The q_id and tag of the registered buffer are required
> > >   * in UBLK_U_IO_UNREGISTER_IO_BUF's ublksrv_io_cmd.
> > >   */
> > >  #define UBLK_F_BUF_REG_OFF_DAEMON (1ULL << 14)
> > >
> > > +/*
> > > + * ublk device supports requests with integrity/metadata buffer.
> > > + * Requires UBLK_F_USER_COPY.
> > > + */
> > > +#define UBLK_F_INTEGRITY (1ULL << 16)
> > > +
> > >  /* device state */
> > >  #define UBLK_S_DEV_DEAD      0
> > >  #define UBLK_S_DEV_LIVE      1
> > >  #define UBLK_S_DEV_QUIESCED  2
> > >  #define UBLK_S_DEV_FAIL_IO   3
> > > @@ -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; /* UBLK_PARAM_TYPE_INTEGRITY requires nonzero */
> > > +     __u8    pi_offset;
> > > +     __u8    csum_type; /* LBMD_PI_CSUM_* from linux/fs.h */
> > > +     __u8    tag_size;
> > > +     __u8    pad[7];
> > > +};
> >
> > Looks max_integrity_segments is missed, otherwise this patch is fine for me.
> 
> My thinking was that there isn't any reason why a ublk server would
> need to limit the number of integrity segments. The request integrity
> segments aren't directly exposed to the ublk server through user copy.
> And since zero copy isn't supported for integrity data, there's no
> concern about needing to align the ublk integrity limits with the
> backing device limits. What do you think?

Yeah, it isn't needed in current implementation, but things may change in
future.

How about adding it(__u16) to `ublk_param_integrity`? And document it is ignored for
user-copy based implementation. It is usually part of HW/SW interface wrt. PI.

Thanks,
Ming