linux-kernel - [PATCH v9 2/8] iov_iter: introduce iov_iter_get_pages_[alloc

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Date:   Thu, 25 Aug 2022 09:24:19 -0600
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
Cc:     Christoph Hellwig <hch@....de>,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        Dan Williams <dan.j.williams@...el.com>,
        Jason Gunthorpe <jgg@...pe.ca>,
        Christian König <christian.koenig@....com>,
        John Hubbard <jhubbard@...dia.com>,
        Don Dutile <ddutile@...hat.com>,
        Matthew Wilcox <willy@...radead.org>,
        Daniel Vetter <daniel.vetter@...ll.ch>,
        Minturn Dave B <dave.b.minturn@...el.com>,
        Jason Ekstrand <jason@...kstrand.net>,
        Dave Hansen <dave.hansen@...ux.intel.com>,
        Xiong Jianxin <jianxin.xiong@...el.com>,
        Bjorn Helgaas <helgaas@...nel.org>,
        Ira Weiny <ira.weiny@...el.com>,
        Robin Murphy <robin.murphy@....com>,
        Martin Oliveira <martin.oliveira@...eticom.com>,
        Chaitanya Kulkarni <ckulkarnilinux@...il.com>,
        Ralph Campbell <rcampbell@...dia.com>,
        Stephen Bates <sbates@...thlin.com>,
        Logan Gunthorpe <logang@...tatee.com>
Subject: [PATCH v9 2/8] iov_iter: introduce iov_iter_get_pages_[alloc_]flags()

Add iov_iter_get_pages_flags() and iov_iter_get_pages_alloc_flags()
which take a flags argument that is passed to get_user_pages_fast().

This is so that FOLL_PCI_P2PDMA can be passed when appropriate.

Signed-off-by: Logan Gunthorpe <logang@...tatee.com>
---
 include/linux/uio.h |  6 ++++++
 lib/iov_iter.c      | 40 ++++++++++++++++++++++++++++++++++++----
 2 files changed, 42 insertions(+), 4 deletions(-)

diff --git a/include/linux/uio.h b/include/linux/uio.h
index 5896af36199c..76ba69edb8c5 100644
--- a/include/linux/uio.h
+++ b/include/linux/uio.h
@@ -247,8 +247,14 @@ void iov_iter_pipe(struct iov_iter *i, unsigned int direction, struct pipe_inode
 void iov_iter_discard(struct iov_iter *i, unsigned int direction, size_t count);
 void iov_iter_xarray(struct iov_iter *i, unsigned int direction, struct xarray *xarray,
 		     loff_t start, size_t count);
+ssize_t iov_iter_get_pages_flags(struct iov_iter *i, struct page **pages,
+		size_t maxsize, unsigned maxpages, size_t *start,
+		unsigned int gup_flags);
 ssize_t iov_iter_get_pages2(struct iov_iter *i, struct page **pages,
 			size_t maxsize, unsigned maxpages, size_t *start);
+ssize_t iov_iter_get_pages_alloc_flags(struct iov_iter *i,
+		struct page ***pages, size_t maxsize, size_t *start,
+		unsigned int gup_flags);
 ssize_t iov_iter_get_pages_alloc2(struct iov_iter *i, struct page ***pages,
 			size_t maxsize, size_t *start);
 int iov_iter_npages(const struct iov_iter *i, int maxpages);
diff --git a/lib/iov_iter.c b/lib/iov_iter.c
index 4b7fce72e3e5..dedb78f3c655 100644
--- a/lib/iov_iter.c
+++ b/lib/iov_iter.c
@@ -1427,7 +1427,8 @@ static struct page *first_bvec_segment(const struct iov_iter *i,
 
 static ssize_t __iov_iter_get_pages_alloc(struct iov_iter *i,
 		   struct page ***pages, size_t maxsize,
-		   unsigned int maxpages, size_t *start)
+		   unsigned int maxpages, size_t *start,
+		   unsigned int gup_flags)
 {
 	unsigned int n;
 
@@ -1439,7 +1440,6 @@ static ssize_t __iov_iter_get_pages_alloc(struct iov_iter *i,
 		maxsize = MAX_RW_COUNT;
 
 	if (likely(user_backed_iter(i))) {
-		unsigned int gup_flags = 0;
 		unsigned long addr;
 		int res;
 
@@ -1497,10 +1497,24 @@ ssize_t iov_iter_get_pages2(struct iov_iter *i,
 		return 0;
 	BUG_ON(!pages);
 
-	return __iov_iter_get_pages_alloc(i, &pages, maxsize, maxpages, start);
+	return __iov_iter_get_pages_alloc(i, &pages, maxsize, maxpages,
+					  start, 0);
 }
 EXPORT_SYMBOL(iov_iter_get_pages2);
 
+ssize_t iov_iter_get_pages_flags(struct iov_iter *i, struct page **pages,
+		size_t maxsize, unsigned maxpages, size_t *start,
+		unsigned int gup_flags)
+{
+	if (!maxpages)
+		return 0;
+	BUG_ON(!pages);
+
+	return __iov_iter_get_pages_alloc(i, &pages, maxsize, maxpages,
+					  start, gup_flags);
+}
+EXPORT_SYMBOL_GPL(iov_iter_get_pages_flags);
+
 ssize_t iov_iter_get_pages_alloc2(struct iov_iter *i,
 		   struct page ***pages, size_t maxsize,
 		   size_t *start)
@@ -1509,7 +1523,7 @@ ssize_t iov_iter_get_pages_alloc2(struct iov_iter *i,
 
 	*pages = NULL;
 
-	len = __iov_iter_get_pages_alloc(i, pages, maxsize, ~0U, start);
+	len = __iov_iter_get_pages_alloc(i, pages, maxsize, ~0U, start, 0);
 	if (len <= 0) {
 		kvfree(*pages);
 		*pages = NULL;
@@ -1518,6 +1532,24 @@ ssize_t iov_iter_get_pages_alloc2(struct iov_iter *i,
 }
 EXPORT_SYMBOL(iov_iter_get_pages_alloc2);
 
+ssize_t iov_iter_get_pages_alloc_flags(struct iov_iter *i,
+		struct page ***pages, size_t maxsize,
+		size_t *start, unsigned int gup_flags)
+{
+	ssize_t len;
+
+	*pages = NULL;
+
+	len = __iov_iter_get_pages_alloc(i, pages, maxsize, ~0U, start,
+					 gup_flags);
+	if (len <= 0) {
+		kvfree(*pages);
+		*pages = NULL;
+	}
+	return len;
+}
+EXPORT_SYMBOL_GPL(iov_iter_get_pages_alloc_flags);
+
 size_t csum_and_copy_from_iter(void *addr, size_t bytes, __wsum *csum,
 			       struct iov_iter *i)
 {
-- 
2.30.2