linux-kernel - Re: [PATCH 3/6] PCI/P2PDMA: create VMA without page

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Date: Wed, 5 Jun 2024 16:45:00 -0500
From: Bjorn Helgaas <helgaas@...nel.org>
To: Martin Oliveira <martin.oliveira@...eticom.com>
Cc: linux-rdma@...r.kernel.org, linux-kernel@...r.kernel.org,
	linux-pci@...r.kernel.org, linux-mm@...ck.org,
	Jason Gunthorpe <jgg@...pe.ca>, Leon Romanovsky <leon@...nel.org>,
	Bjorn Helgaas <bhelgaas@...gle.com>,
	Logan Gunthorpe <logang@...tatee.com>,
	Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
	Tejun Heo <tj@...nel.org>, "Rafael J. Wysocki" <rafael@...nel.org>,
	Andrew Morton <akpm@...ux-foundation.org>,
	Mike Marciniszyn <mike.marciniszyn@...el.com>,
	Michael Guralnik <michaelgur@...dia.com>,
	Dan Williams <dan.j.williams@...el.com>,
	Ard Biesheuvel <ardb@...nel.org>,
	Valentine Sinitsyn <valesini@...dex-team.ru>,
	Lukas Wunner <lukas@...ner.de>
Subject: Re: [PATCH 3/6] PCI/P2PDMA: create VMA without page_mkwrite()
 operator

On Wed, Jun 05, 2024 at 01:29:31PM -0600, Martin Oliveira wrote:
> The P2PDMA code does not need (or want) a page_mkwrite() operator on its
> VMA.
> 
> Furthermore, having the page_mkwrite() operator causes
> writable_file_mapping_allowed() to fail due to
> vma_needs_dirty_tracking() on the gup flow, which is a pre-requisite for
> enabling P2PDMA with FOLL_LONGTERM use cases.
> 
> Co-developed-by: Logan Gunthorpe <logang@...tatee.com>
> Signed-off-by: Logan Gunthorpe <logang@...tatee.com>
> Signed-off-by: Martin Oliveira <martin.oliveira@...eticom.com>

Fine with me, but please s/create/Create/ in the subject to match
history of the file.

Acked-by: Bjorn Helgaas <bhelgaas@...gle.com>

> ---
>  drivers/pci/p2pdma.c | 1 +
>  1 file changed, 1 insertion(+)
> 
> diff --git a/drivers/pci/p2pdma.c b/drivers/pci/p2pdma.c
> index 4f47a13cb500..ac07053abfea 100644
> --- a/drivers/pci/p2pdma.c
> +++ b/drivers/pci/p2pdma.c
> @@ -171,6 +171,7 @@ static struct bin_attribute p2pmem_alloc_attr = {
>  	 * to be very large.
>  	 */
>  	.size = SZ_1T,
> +	.mmap_allocates = true,
>  };
>  
>  static struct attribute *p2pmem_attrs[] = {
> -- 
> 2.34.1
>