linux-kernel - Re: [PATCH 02/12] pci/p2pdma: Don't initialise page refcount to one

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Message-ID: <20240911135141.GA629523@bhelgaas>
Date: Wed, 11 Sep 2024 08:51:41 -0500
From: Bjorn Helgaas <helgaas@...nel.org>
To: Alistair Popple <apopple@...dia.com>
Cc: dan.j.williams@...el.com, linux-mm@...ck.org, vishal.l.verma@...el.com,
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Subject: Re: [PATCH 02/12] pci/p2pdma: Don't initialise page refcount to one

On Wed, Sep 11, 2024 at 11:07:51AM +1000, Alistair Popple wrote:
> 
> >> diff --git a/drivers/pci/p2pdma.c b/drivers/pci/p2pdma.c
> >> index 4f47a13..210b9f4 100644
> >> --- a/drivers/pci/p2pdma.c
> >> +++ b/drivers/pci/p2pdma.c
> >> @@ -129,6 +129,12 @@ static int p2pmem_alloc_mmap(struct file *filp, struct kobject *kobj,
> >>  	}
> >>  
> >>  	/*
> >> +	 * Initialise the refcount for the freshly allocated page. As we have
> >> +	 * just allocated the page no one else should be using it.
> >> +	 */
> >> +	set_page_count(virt_to_page(kaddr), 1);
> >
> > No doubt the subject line is true in some overall context, but it does
> > seem to say the opposite of what happens here.
> 
> Fair. It made sense to me from the mm context I was coming from (it was
> being initialised to 1 there) but not overall. Something like "move page
> refcount initialisation to p2pdma driver" would make more sense?

Definitely would, thanks.