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@deltatee.com>
Reviewed-by: Christoph Hellwig <hch@lst.de>
Link: https://lore.kernel.org/r/20221021174116.7200-4-logang@deltatee.com
Signed-off-by: Jens Axboe <axboe@kernel.dk>

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(struct iov_iter *i, struct page **pages,
+		size_t maxsize, unsigned maxpages, size_t *start,
+		unsigned 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(struct iov_iter *i,
+		struct page ***pages, size_t maxsize, size_t *start,
+		unsigned 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);

lib/iov_iter.c

@@ -1430,7 +1430,8 @@ 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;
 
@@ -1442,7 +1443,6 @@ 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;
 
@@ -1492,33 +1492,49 @@ static ssize_t __iov_iter_get_pages_alloc(struct iov_iter *i,
 	return -EFAULT;
 }
 
-ssize_t iov_iter_get_pages2(struct iov_iter *i,
+ssize_t iov_iter_get_pages(struct iov_iter *i,
 		   struct page **pages, size_t maxsize, unsigned maxpages,
-		   size_t *start)
+		   size_t *start, unsigned gup_flags)
 {
 	if (!maxpages)
 		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, gup_flags);
+}
+EXPORT_SYMBOL_GPL(iov_iter_get_pages);
+
+ssize_t iov_iter_get_pages2(struct iov_iter *i, struct page **pages,
+		size_t maxsize, unsigned maxpages, size_t *start)
+{
+	return iov_iter_get_pages(i, pages, maxsize, maxpages, start, 0);
 }
 EXPORT_SYMBOL(iov_iter_get_pages2);
 
-ssize_t iov_iter_get_pages_alloc2(struct iov_iter *i,
+ssize_t iov_iter_get_pages_alloc(struct iov_iter *i,
 		   struct page ***pages, size_t maxsize,
-		   size_t *start)
+		   size_t *start, unsigned gup_flags)
 {
 	ssize_t len;
 
 	*pages = NULL;
 
-	len = __iov_iter_get_pages_alloc(i, pages, maxsize, ~0U, start);
+	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);
+
+ssize_t iov_iter_get_pages_alloc2(struct iov_iter *i,
+		struct page ***pages, size_t maxsize, size_t *start)
+{
+	return iov_iter_get_pages_alloc(i, pages, maxsize, start, 0);
+}
 EXPORT_SYMBOL(iov_iter_get_pages_alloc2);
 
 size_t csum_and_copy_from_iter(void *addr, size_t bytes, __wsum *csum,