Re: [PATCH V3 09/27] ublk: add new batch command UBLK_U_IO_PREP_IO_CMDS & UBLK_U_IO_COMMIT_IO_CMDS

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

On Tue, Nov 18, 2025 at 06:39:09PM -0800, Caleb Sander Mateos wrote:
> On Tue, Nov 18, 2025 at 6:37 PM Caleb Sander Mateos
> <csander@purestorage.com> wrote:
> >
> > On Wed, Nov 12, 2025 at 1:39 AM Ming Lei <ming.lei@redhat.com> wrote:
> > >
> > > Add new command UBLK_U_IO_PREP_IO_CMDS, which is the batch version of
> > > UBLK_IO_FETCH_REQ.
> > >
> > > Add new command UBLK_U_IO_COMMIT_IO_CMDS, which is for committing io command
> > > result only, still the batch version.
> > >
> > > The new command header type is `struct ublk_batch_io`, and fixed buffer is
> > > required for these two uring_cmd.
> > >
> > > This patch doesn't actually implement these commands yet, just validates the
> > > SQE fields.
> > >
> > > Signed-off-by: Ming Lei <ming.lei@redhat.com>
> > > ---
> > >  drivers/block/ublk_drv.c      | 107 +++++++++++++++++++++++++++++++++-
> > >  include/uapi/linux/ublk_cmd.h |  49 ++++++++++++++++
> > >  2 files changed, 155 insertions(+), 1 deletion(-)
> > >
> > > diff --git a/drivers/block/ublk_drv.c b/drivers/block/ublk_drv.c
> > > index c62b2f2057fe..5f9d7ec9daa4 100644
> > > --- a/drivers/block/ublk_drv.c
> > > +++ b/drivers/block/ublk_drv.c
> > > @@ -85,6 +85,11 @@
> > >          UBLK_PARAM_TYPE_DEVT | UBLK_PARAM_TYPE_ZONED |    \
> > >          UBLK_PARAM_TYPE_DMA_ALIGN | UBLK_PARAM_TYPE_SEGMENT)
> > >
> > > +#define UBLK_BATCH_F_ALL  \
> > > +       (UBLK_BATCH_F_HAS_ZONE_LBA | \
> > > +        UBLK_BATCH_F_HAS_BUF_ADDR | \
> > > +        UBLK_BATCH_F_AUTO_BUF_REG_FALLBACK)
> > > +
> > >  struct ublk_uring_cmd_pdu {
> > >         /*
> > >          * Store requests in same batch temporarily for queuing them to
> > > @@ -108,6 +113,12 @@ struct ublk_uring_cmd_pdu {
> > >         u16 tag;
> > >  };
> > >
> > > +struct ublk_batch_io_data {
> > > +       struct ublk_device *ub;
> > > +       struct io_uring_cmd *cmd;
> > > +       struct ublk_batch_io header;
> > > +};
> > > +
> > >  /*
> > >   * io command is active: sqe cmd is received, and its cqe isn't done
> > >   *
> > > @@ -2520,10 +2531,104 @@ static int ublk_ch_uring_cmd(struct io_uring_cmd *cmd, unsigned int issue_flags)
> > >         return ublk_ch_uring_cmd_local(cmd, issue_flags);
> > >  }
> > >
> > > +static int ublk_check_batch_cmd_flags(const struct ublk_batch_io *uc)
> > > +{
> > > +       const u16 mask = UBLK_BATCH_F_HAS_BUF_ADDR | UBLK_BATCH_F_HAS_ZONE_LBA;
> > > +       const unsigned header_len = sizeof(struct ublk_elem_header);
> > > +
> > > +       if (uc->flags & ~UBLK_BATCH_F_ALL)
> > > +               return -EINVAL;
> > > +
> > > +       /* UBLK_BATCH_F_AUTO_BUF_REG_FALLBACK requires buffer index */
> > > +       if ((uc->flags & UBLK_BATCH_F_AUTO_BUF_REG_FALLBACK) &&
> > > +                       (uc->flags & UBLK_BATCH_F_HAS_BUF_ADDR))
> > > +               return -EINVAL;
> > > +
> > > +       switch (uc->flags & mask) {
> > > +       case 0:
> > > +               if (uc->elem_bytes != header_len)
> > > +                       return -EINVAL;
> > > +               break;
> > > +       case UBLK_BATCH_F_HAS_ZONE_LBA:
> > > +       case UBLK_BATCH_F_HAS_BUF_ADDR:
> > > +               if (uc->elem_bytes != header_len + sizeof(u64))
> > > +                       return -EINVAL;
> > > +               break;
> > > +       case UBLK_BATCH_F_HAS_ZONE_LBA | UBLK_BATCH_F_HAS_BUF_ADDR:
> > > +               if (uc->elem_bytes != header_len + sizeof(u64) + sizeof(u64))
> > > +                       return -EINVAL;
> > > +               break;
> > > +       }
> > > +
> > > +       return 0;
> > > +}
> > > +
> > > +static int ublk_check_batch_cmd(const struct ublk_batch_io_data *data)
> > > +{
> > > +
> > > +       const struct ublk_batch_io *uc = &data->header;
> > > +
> > > +       if (!(data->cmd->flags & IORING_URING_CMD_FIXED))
> > > +               return -EINVAL;
> > > +
> > > +       if (uc->nr_elem * uc->elem_bytes > data->cmd->sqe->len)
> >
> > sqe->len should be accessed with READ_ONCE() since it may point to
> > user-mapped memory.
> 
> Actually, is there any point in this check since sqe->len is no longer
> used anywhere?

Right, will remove it in next version.


Thanks, 
Ming