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 <jhubbard@nvidia.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Acked-by: David Hildenbrand <david@redhat.com>
Cc: Daniel Vetter <daniel@ffwll.ch>
Cc: Jérôme Glisse <jglisse@redhat.com>
Cc: Vlastimil Babka <vbabka@suse.cz>
Cc: Jan Kara <jack@suse.cz>
Cc: Dave Chinner <david@fromorbit.com>
Cc: Pankaj Gupta <pankaj.gupta.linux@gmail.com>
Cc: Souptick Joarder <jrdr.linux@gmail.com>
Link: http://lkml.kernel.org/r/20200527223243.884385-3-jhubbard@nvidia.com
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

diff --git a/mm/frame_vector.c b/mm/frame_vector.c
index c431ca81dad5514a2ecc468c30eaa98b1363643f..4107dbca0056b1d32bc99d8eecdb3b12aea7e73f 100644 (file)
--- a/mm/frame_vector.c
+++ b/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;