linux-kernel - Re: [PATCH rdma-next 1/5] RDMA/hns: Implement the disassociate

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Date:   Thu, 17 May 2018 09:00:19 -0600
From:   Jason Gunthorpe <jgg@...pe.ca>
To:     "Wei Hu (Xavier)" <xavier.huwei@...wei.com>
Cc:     dledford@...hat.com, linux-rdma@...r.kernel.org,
        linux-kernel@...r.kernel.org, xavier.huwei@....com,
        lijun_nudt@....com
Subject: Re: [PATCH rdma-next 1/5] RDMA/hns: Implement the
 disassociate_ucontext API

On Thu, May 17, 2018 at 04:02:49PM +0800, Wei Hu (Xavier) wrote:
> This patch Implements the IB core disassociate_ucontext API.
> 
> Signed-off-by: Wei Hu (Xavier) <xavier.huwei@...wei.com>
>  drivers/infiniband/hw/hns/hns_roce_main.c | 36 +++++++++++++++++++++++++++++++
>  1 file changed, 36 insertions(+)
> 
> diff --git a/drivers/infiniband/hw/hns/hns_roce_main.c b/drivers/infiniband/hw/hns/hns_roce_main.c
> index 96fb6a9..7fafe9d 100644
> +++ b/drivers/infiniband/hw/hns/hns_roce_main.c
> @@ -33,6 +33,9 @@
>  #include <linux/acpi.h>
>  #include <linux/of_platform.h>
>  #include <linux/module.h>
> +#include <linux/sched.h>
> +#include <linux/sched/mm.h>
> +#include <linux/sched/task.h>
>  #include <rdma/ib_addr.h>
>  #include <rdma/ib_smi.h>
>  #include <rdma/ib_user_verbs.h>
> @@ -422,6 +425,38 @@ static int hns_roce_port_immutable(struct ib_device *ib_dev, u8 port_num,
>  	return 0;
>  }
>  
> +static void hns_roce_disassociate_ucontext(struct ib_ucontext *ibcontext)
> +{
> +	struct task_struct *process;
> +	struct mm_struct   *mm;
> +
> +	process = get_pid_task(ibcontext->tgid, PIDTYPE_PID);
> +	if (!process)
> +		return;
> +
> +	mm = get_task_mm(process);
> +	if (!mm) {
> +		pr_info("no mm, disassociate ucontext is pending task termination\n");
> +		while (1) {
> +			put_task_struct(process);
> +			usleep_range(1000, 2000);
> +			process = get_pid_task(ibcontext->tgid, PIDTYPE_PID);
> +			if (!process || process->state == TASK_DEAD) {
> +				pr_info("disassociate ucontext done, task was terminated\n");
> +				/* if task was dead, need to release the task
> +				 * struct.
> +				 */
> +				if (process)
> +					put_task_struct(process);
> +				return;
> +			}
> +		}
> +	}

I don't want to see this boilerplate code copied into every
driver. Hoist it into the core code, have the disassociate driver callback
accept a mm_struct parameter, and refactor the other drivers using this.

> +	mmput(mm);
> +	put_task_struct(process);
> +}

This can't be right, disassociate requires the driver to replace all
the mmaps it make to user space with the 0 page, I see hns does use
mmaps, so it must zap them here.

Jason