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

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Message-Id: <20240605192934.742369-4-martin.oliveira@eideticom.com>
Date: Wed,  5 Jun 2024 13:29:31 -0600
From: Martin Oliveira <martin.oliveira@...eticom.com>
To: linux-rdma@...r.kernel.org,
	linux-kernel@...r.kernel.org,
	linux-pci@...r.kernel.org,
	linux-mm@...ck.org
Cc: 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>,
	Martin Oliveira <martin.oliveira@...eticom.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: [PATCH 3/6] PCI/P2PDMA: create VMA without page_mkwrite() operator

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>
---
 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