Re: [PATCH for-next] RDMA/core: Add writev to uverbs file descriptor

[Leon Romanovsky <leon@kernel.org>]

On Wed, Mar 11, 2026 at 01:33:37PM -0400, Dennis Dalessandro wrote:
> From: Dean Luick <dean.luick@cornelisnetworks.com>
> 
> Add a writev pass-through between the uverbs file descriptor and
> infiniband devices.  Interested devices may subscribe to this
> functionality.
> 
> The goal is to keep all the semantics of the user interface the same so
> it's an easy migration to the uverbs cdev from the private cdev. The idea
> is that all the command and control is still ioctl, but the "data path" is
> still using the writev() to pass in the iovecs.
> 
> Signed-off-by: Dean Luick <dean.luick@cornelisnetworks.com>
> Signed-off-by: Dennis Dalessandro <dennis.dalessandro@cornelisnetworks.com>
> 
> ---
> Changes since v1:
> Updated commit message to indiate why we are keeping the
> writev semantic.
> ---
>  drivers/infiniband/core/device.c      |    1 +
>  drivers/infiniband/core/uverbs_main.c |   22 ++++++++++++++++++++++
>  include/rdma/ib_verbs.h               |    2 ++
>  3 files changed, 25 insertions(+)
> 
> diff --git a/drivers/infiniband/core/device.c b/drivers/infiniband/core/device.c
> index 1b5f1ee0a557..e94aebea16e1 100644
> --- a/drivers/infiniband/core/device.c
> +++ b/drivers/infiniband/core/device.c
> @@ -2805,6 +2805,7 @@ void ib_set_device_ops(struct ib_device *dev, const struct ib_device_ops *ops)
>  	SET_DEVICE_OP(dev_ops, set_vf_link_state);
>  	SET_DEVICE_OP(dev_ops, ufile_hw_cleanup);
>  	SET_DEVICE_OP(dev_ops, report_port_event);
> +	SET_DEVICE_OP(dev_ops, write_iter);
>  
>  	SET_OBJ_SIZE(dev_ops, ib_ah);
>  	SET_OBJ_SIZE(dev_ops, ib_counters);
> diff --git a/drivers/infiniband/core/uverbs_main.c b/drivers/infiniband/core/uverbs_main.c
> index 7b68967a6301..b393d3a0f11c 100644
> --- a/drivers/infiniband/core/uverbs_main.c
> +++ b/drivers/infiniband/core/uverbs_main.c
> @@ -713,6 +713,26 @@ static int ib_uverbs_mmap(struct file *filp, struct vm_area_struct *vma)
>  	return ret;
>  }
>  
> +static ssize_t ib_uverbs_write_iter(struct kiocb *kiocb, struct iov_iter *from)
> +{
> +	struct ib_uverbs_file *file = kiocb->ki_filp->private_data;
> +	struct ib_ucontext *ucontext;
> +	ssize_t ret = -EOPNOTSUPP;
> +	int srcu_key;

I see that this function is modeled after ib_uverbs_mmap(), not
ib_uverbs_write(). Why is ib_safe_file_access(ki_filp) not used here?

Also, this should be documented as a narrow, migration‑only path for the
legacy hfi1 driver, and it must not be used by any other new code.

Thanks