linux-kernel - Re: [PATCH v2] IB/umem: ib_ucontext already have tgid, remove pid from ib

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Date:   Tue, 15 May 2018 17:14:45 -0600
From:   Jason Gunthorpe <jgg@...pe.ca>
To:     Lidong Chen <jemmy858585@...il.com>
Cc:     dledford@...hat.com, akpm@...ux-foundation.org,
        qing.huang@...cle.com, leon@...nel.org, artemyko@...lanox.com,
        dan.j.williams@...el.com, linux-rdma@...r.kernel.org,
        linux-kernel@...r.kernel.org, adido@...lanox.com,
        galsha@...lanox.com, aviadye@...lanox.com,
        Lidong Chen <lidongchen@...cent.com>
Subject: Re: [PATCH v2] IB/umem: ib_ucontext already have tgid, remove pid
 from ib_umem structure

On Tue, May 08, 2018 at 04:50:16PM +0800, Lidong Chen wrote:
> The userspace may invoke ibv_reg_mr and ibv_dereg_mr by different threads.
> If when ibv_dereg_mr invoke and the thread which invoked ibv_reg_mr has
> exited, get_pid_task will return NULL, ib_umem_release does not decrease
> mm->pinned_vm. This patch fixes it by use tgid in ib_ucontext struct.
> 
> Signed-off-by: Lidong Chen <lidongchen@...cent.com>
> ---
>  [v2]
>  - use ib_ucontext tgid instread of tgid in ib_umem structure
>  
>  drivers/infiniband/core/umem.c | 7 +------
>  include/rdma/ib_umem.h         | 1 -
>  2 files changed, 1 insertion(+), 7 deletions(-)

Applied to for-rc, thanks.

It would be nice to send a cleanup to have all the users of tgid doing
this pattern

	task = get_pid_task(umem->context->tgid, PIDTYPE_PID);
  	if (!task)
  		goto out;
  	mm = get_task_mm(task);

To call some kind of common function like ib_get_mr_mm(), just to make
it really clear what is happening. 

Jason