Re: [PATCH v3 for-next 01/12] RDMA/hns: Introduce DCA for RC QP

[Leon Romanovsky <leon@kernel.org>]

On Tue, Jul 27, 2021 at 11:27:21AM +0800, Wenpeng Liang wrote:
> From: Xi Wang <wangxi11@huawei.com>
> 
> The hip09 introduces the DCA(Dynamic context attachment) feature which
> supports many RC QPs to share the WQE buffer in a memory pool, this will
> reduce the memory consumption when there are too many QPs are inactive.
> 
> If a QP enables DCA feature, the WQE's buffer will not be allocated when
> creating. But when the users start to post WRs, the hns driver will
> allocate a buffer from the memory pool and then fill WQEs which tagged with
> this QP's number.
> 
> The hns ROCEE will stop accessing the WQE buffer when the user polled all
> of the CQEs for a DCA QP, then the driver will recycle this WQE's buffer
> to the memory pool.
> 
> This patch adds a group of methods to support the user space register
> buffers to a memory pool which belongs to the user context. The hns kernel
> driver will update the pages state in this pool when the user calling the
> post/poll methods and the user driver can get the QP's WQE buffer address
> by the key and offset which queried from kernel.
> 
> Signed-off-by: Xi Wang <wangxi11@huawei.com>
> Signed-off-by: Wenpeng Liang <liangwenpeng@huawei.com>
> ---
>  drivers/infiniband/hw/hns/Makefile          |   2 +-
>  drivers/infiniband/hw/hns/hns_roce_dca.c    | 343 ++++++++++++++++++++++++++++
>  drivers/infiniband/hw/hns/hns_roce_dca.h    |  22 ++
>  drivers/infiniband/hw/hns/hns_roce_device.h |   9 +
>  drivers/infiniband/hw/hns/hns_roce_main.c   |  27 ++-
>  include/uapi/rdma/hns-abi.h                 |  27 +++
>  6 files changed, 427 insertions(+), 3 deletions(-)
>  create mode 100644 drivers/infiniband/hw/hns/hns_roce_dca.c
>  create mode 100644 drivers/infiniband/hw/hns/hns_roce_dca.h

<...>

> +static struct hns_dca_page_state *alloc_dca_states(void *pages, int count)
> +{
> +	struct hns_dca_page_state *states;
> +
> +	states = kcalloc(count, sizeof(*states), GFP_NOWAIT);

GFP_NOWAIT ????
Why do you use this flag while in the function before you used classic GFP_KERNEL?

Thanks