[RFC PATCH 12/15] block: Set FOLL_PCI_P2PDMA in __bio_iov_iter_get_pages()

From: Logan Gunthorpe <logang@deltatee.com>
To: linux-kernel@vger.kernel.org, linux-nvme@lists.infradead.org,
	linux-block@vger.kernel.org, linux-pci@vger.kernel.org,
	linux-mm@kvack.org, iommu@lists.linux-foundation.org
Cc: "Stephen Bates" <sbates@raithlin.com>,
	"Christoph Hellwig" <hch@lst.de>,
	"Dan Williams" <dan.j.williams@intel.com>,
	"Jason Gunthorpe" <jgg@ziepe.ca>,
	"Christian König" <christian.koenig@amd.com>,
	"Ira Weiny" <iweiny@intel.com>,
	"John Hubbard" <jhubbard@nvidia.com>,
	"Don Dutile" <ddutile@redhat.com>,
	"Matthew Wilcox" <willy@infradead.org>,
	"Daniel Vetter" <daniel.vetter@ffwll.ch>,
	"Logan Gunthorpe" <logang@deltatee.com>
Subject: [RFC PATCH 12/15] block: Set FOLL_PCI_P2PDMA in __bio_iov_iter_get_pages()
Date: Fri,  6 Nov 2020 10:00:33 -0700	[thread overview]
Message-ID: <20201106170036.18713-13-logang@deltatee.com> (raw)
In-Reply-To: <20201106170036.18713-1-logang@deltatee.com>

When a bio's queue supports PCI P2PDMA, set FOLL_PCI_P2PDMA for
iov_iter_get_pages_flags(). This allows PCI P2PDMA pages to be passed
from userspace and enables the O_DIRECT path in iomap based filesystems
and direct to block devices.

Signed-off-by: Logan Gunthorpe <logang@deltatee.com>
---
 block/bio.c | 7 ++++++-
 1 file changed, 6 insertions(+), 1 deletion(-)

diff --git a/block/bio.c b/block/bio.c
index fa01bef35bb1..6b28256a5575 100644
--- a/block/bio.c
+++ b/block/bio.c
@@ -997,6 +997,7 @@ static int __bio_iov_iter_get_pages(struct bio *bio, struct iov_iter *iter)
 	struct bio_vec *bv = bio->bi_io_vec + bio->bi_vcnt;
 	struct page **pages = (struct page **)bv;
 	bool same_page = false;
+	unsigned int flags = 0;
 	ssize_t size, left;
 	unsigned len, i;
 	size_t offset;
@@ -1009,7 +1010,11 @@ static int __bio_iov_iter_get_pages(struct bio *bio, struct iov_iter *iter)
 	BUILD_BUG_ON(PAGE_PTRS_PER_BVEC < 2);
 	pages += entries_left * (PAGE_PTRS_PER_BVEC - 1);
 
-	size = iov_iter_get_pages(iter, pages, LONG_MAX, nr_pages, &offset);
+	if (bio->bi_disk && blk_queue_pci_p2pdma(bio->bi_disk->queue))
+		flags |= FOLL_PCI_P2PDMA;
+
+	size = iov_iter_get_pages_flags(iter, pages, LONG_MAX, nr_pages,
+					&offset, flags);
 	if (unlikely(size <= 0))
 		return size ? size : -EFAULT;
 
-- 
2.20.1

