mm/gup: frame_vector: convert get_user_pages() --> pin_user_pages()

This code was using get_user_pages*(), and all of the callers so far
were in a "Case 2" scenario (DMA/RDMA), using the categorization from [1].

That means that it's time to convert the get_user_pages*() + put_page()
calls to pin_user_pages*() + unpin_user_pages() calls.

There is some helpful background in [2]: basically, this is a small part
of fixing a long-standing disconnect between pinning pages, and file
systems' use of those pages.

[1] Documentation/core-api/pin_user_pages.rst

[2] "Explicit pinning of user-space pages":
    https://lwn.net/Articles/807108/

Signed-off-by: John Hubbard <[email protected]>
Signed-off-by: Andrew Morton <[email protected]>
Acked-by: David Hildenbrand <[email protected]>
Cc: Daniel Vetter <[email protected]>
Cc: Jérôme Glisse <[email protected]>
Cc: Vlastimil Babka <[email protected]>
Cc: Jan Kara <[email protected]>
Cc: Dave Chinner <[email protected]>
Cc: Pankaj Gupta <[email protected]>
Cc: Souptick Joarder <[email protected]>
Link: http://lkml.kernel.org/r/[email protected]
Signed-off-by: Linus Torvalds <[email protected]>

mm/frame_vector.c

@@ -72,7 +72,7 @@ int get_vaddr_frames(unsigned long start, unsigned int nr_frames,
 	if (!(vma->vm_flags & (VM_IO | VM_PFNMAP))) {
 		vec->got_ref = true;
 		vec->is_pfns = false;
-		ret = get_user_pages_locked(start, nr_frames,
+		ret = pin_user_pages_locked(start, nr_frames,
 			gup_flags, (struct page **)(vec->ptrs), &locked);
 		goto out;
 	}
@@ -122,7 +122,6 @@ EXPORT_SYMBOL(get_vaddr_frames);
  */
 void put_vaddr_frames(struct frame_vector *vec)
 {
-	int i;
 	struct page **pages;
 
 	if (!vec->got_ref)
@@ -135,8 +134,8 @@ void put_vaddr_frames(struct frame_vector *vec)
 	 */
 	if (WARN_ON(IS_ERR(pages)))
 		goto out;
-	for (i = 0; i < vec->nr_frames; i++)
-		put_page(pages[i]);
+
+	unpin_user_pages(pages, vec->nr_frames);
 	vec->got_ref = false;
 out:
 	vec->nr_frames = 0;