linux-kernel - [RFC PATCH 13/15] block: Set FOLL_PCI_P2PDMA in bio_map_user

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Message-Id: <20201106170036.18713-14-logang@deltatee.com>
Date:   Fri,  6 Nov 2020 10:00:34 -0700
From:   Logan Gunthorpe <logang@...tatee.com>
To:     linux-kernel@...r.kernel.org, linux-nvme@...ts.infradead.org,
        linux-block@...r.kernel.org, linux-pci@...r.kernel.org,
        linux-mm@...ck.org, iommu@...ts.linux-foundation.org
Cc:     Stephen Bates <sbates@...thlin.com>,
        Christoph Hellwig <hch@....de>,
        Dan Williams <dan.j.williams@...el.com>,
        Jason Gunthorpe <jgg@...pe.ca>,
        Christian König <christian.koenig@....com>,
        Ira Weiny <iweiny@...el.com>,
        John Hubbard <jhubbard@...dia.com>,
        Don Dutile <ddutile@...hat.com>,
        Matthew Wilcox <willy@...radead.org>,
        Daniel Vetter <daniel.vetter@...ll.ch>,
        Logan Gunthorpe <logang@...tatee.com>
Subject: [RFC PATCH 13/15] block: Set FOLL_PCI_P2PDMA in bio_map_user_iov()

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 NVMe passthru requests to
use P2PDMA pages.

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

diff --git a/block/blk-map.c b/block/blk-map.c
index 21630dccac62..cad8fcfe4f17 100644
--- a/block/blk-map.c
+++ b/block/blk-map.c
@@ -245,6 +245,7 @@ static int bio_map_user_iov(struct request *rq, struct iov_iter *iter,
 {
 	unsigned int max_sectors = queue_max_hw_sectors(rq->q);
 	struct bio *bio, *bounce_bio;
+	unsigned int flags = 0;
 	int ret;
 	int j;
 
@@ -256,13 +257,17 @@ static int bio_map_user_iov(struct request *rq, struct iov_iter *iter,
 		return -ENOMEM;
 	bio->bi_opf |= req_op(rq);
 
+	if (blk_queue_pci_p2pdma(rq->q))
+		flags |= FOLL_PCI_P2PDMA;
+
 	while (iov_iter_count(iter)) {
 		struct page **pages;
 		ssize_t bytes;
 		size_t offs, added = 0;
 		int npages;
 
-		bytes = iov_iter_get_pages_alloc(iter, &pages, LONG_MAX, &offs);
+		bytes = iov_iter_get_pages_alloc_flags(iter, &pages, LONG_MAX,
+						       &offs, flags);
 		if (unlikely(bytes <= 0)) {
 			ret = bytes ? bytes : -EFAULT;
 			goto out_unmap;
-- 
2.20.1