4.8-stable review patch.  If anyone has any objections, please let me know.

------------------

From: Hugh Dickins <[email protected]>

commit 9956edf37e65e93fbb76dcff1236dff2323d306a upstream.

If shmem_alloc_page() does not set PageLocked and PageSwapBacked, then
shmem_replace_page() needs to do so for itself.  Without this, it puts
newpage on the wrong lru, re-unlocks the unlocked newpage, and system
descends into "Bad page" reports and freeze; or if CONFIG_DEBUG_VM=y, it
hits an earlier VM_BUG_ON_PAGE(!PageLocked), depending on config.

But shmem_replace_page() is not a common path: it's only called when
swapin (or swapoff) finds the page was already read into an unsuitable
zone: usually all zones are suitable, but gem objects for a few drm
devices (gma500, omapdrm, crestline, broadwater) require zone DMA32 if
there's more than 4GB of ram.

Fixes: 800d8c63b2e9 ("shmem: add huge pages support")
Link: http://lkml.kernel.org/r/[email protected]
Signed-off-by: Hugh Dickins <[email protected]>
Acked-by: Kirill A. Shutemov <[email protected]>
Signed-off-by: Andrew Morton <[email protected]>
Signed-off-by: Linus Torvalds <[email protected]>
Signed-off-by: Greg Kroah-Hartman <[email protected]>

---
 mm/shmem.c |    2 ++
 1 file changed, 2 insertions(+)

--- a/mm/shmem.c
+++ b/mm/shmem.c
@@ -1483,6 +1483,8 @@ static int shmem_replace_page(struct pag
        copy_highpage(newpage, oldpage);
        flush_dcache_page(newpage);
 
+       __SetPageLocked(newpage);
+       __SetPageSwapBacked(newpage);
        SetPageUptodate(newpage);
        set_page_private(newpage, swap_index);
        SetPageSwapCache(newpage);


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