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Subject[PATCH] shmem: fix pageflags after swapping DMA32 object
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")
Cc: stable@vger.kernel.org # v4.8
Signed-off-by: Hugh Dickins <hughd@google.com>
---

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

--- 4.9-rc4/mm/shmem.c 2016-10-15 12:52:13.157533478 -0700
+++ linux/mm/shmem.c 2016-11-06 12:45:49.626193769 -0800
@@ -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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