linux-kernel - Re: [PATCH v4 for-next 1/2] RDMA/core: Provide rdma_user_mmap_disassociate() to disassociate mmap pages

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Message-ID: <20240911102018.GF4026@unreal>
Date: Wed, 11 Sep 2024 13:20:18 +0300
From: Leon Romanovsky <leon@...nel.org>
To: Junxian Huang <huangjunxian6@...ilicon.com>
Cc: Jason Gunthorpe <jgg@...pe.ca>, linux-rdma@...r.kernel.org,
	linuxarm@...wei.com, linux-kernel@...r.kernel.org
Subject: Re: [PATCH v4 for-next 1/2] RDMA/core: Provide
 rdma_user_mmap_disassociate() to disassociate mmap pages

On Mon, Sep 09, 2024 at 04:41:00PM +0800, Junxian Huang wrote:
> 
> 
> On 2024/9/7 20:12, Jason Gunthorpe wrote:
> > On Thu, Sep 05, 2024 at 09:11:54PM +0800, Junxian Huang wrote:
> > 
> >> @@ -698,11 +700,20 @@ static int ib_uverbs_mmap(struct file *filp, struct vm_area_struct *vma)
> >>  	ucontext = ib_uverbs_get_ucontext_file(file);
> >>  	if (IS_ERR(ucontext)) {
> >>  		ret = PTR_ERR(ucontext);
> >> -		goto out;
> >> +		goto out_srcu;
> >>  	}
> >> +
> >> +	mutex_lock(&file->disassociation_lock);
> >> +	if (file->disassociated) {
> >> +		ret = -EPERM;
> >> +		goto out_mutex;
> >> +	}
> > 
> > What sets disassociated back to false once the driver reset is
> > completed?
> > 
> > I think you should probably drop this and instead add a lock and test
> > inside the driver within its mmap op. While reset is ongoing fail all
> > new mmaps.
> > 
> 
> disassociated won't be set back to false. This is to stop new mmaps on
> this ucontext even after reset is completed, because during hns reset,
> all resources will be destroyed, and the ucontexts will become unavailable.

ucontext is SW object and not HW object, why will it become unavailable?

Thanks