Commit eb94a878 authored May 03, 2017 by Minchan Kim Committed by Linus Torvalds May 03, 2017

mm: fix lazyfree BUG_ON check in try_to_unmap_one()

If a page is swapbacked, it means it should be in swapcache in
try_to_unmap_one's path.

If a page is !swapbacked, it mean it shouldn't be in swapcache in
try_to_unmap_one's path.

Check both two cases all at once and if it fails, warn and return
SWAP_FAIL.  Such bug never mean we should shut down the kernel.

[minchan@kernel.org: do not use VM_WARN_ON_ONCE as if condition[
  Link: http://lkml.kernel.org/r/20170309060226.GB854@bbox
Link: http://lkml.kernel.org/r/20170307055551.GC29458@bbox


Signed-off-by: Minchan Kim <minchan@kernel.org>
Suggested-by: Johannes Weiner <hannes@cmpxchg.org>
Acked-by: Michal Hocko <mhocko@suse.com>
Acked-by: Johannes Weiner <hannes@cmpxchg.org>
Cc: Shaohua Li <shli@fb.com>
Cc: Hillf Danton <hillf.zj@alibaba-inc.com>
Cc: Hugh Dickins <hughd@google.com>
Cc: Rik van Riel <riel@redhat.com>
Cc: Mel Gorman <mgorman@techsingularity.net>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

parent 802a3a92

mm/rmap.c

+6 −2

Original line number	Diff line number	Diff line
		@@ -1418,8 +1418,12 @@ static int try_to_unmap_one(struct page page, struct vm_area_struct vma,
		* Store the swap location in the pte.
		* See handle_pte_fault() ...
		*/
		VM_BUG_ON_PAGE(!PageSwapCache(page) && PageSwapBacked(page),
		page);
		if (unlikely(PageSwapBacked(page) != PageSwapCache(page))) {
		WARN_ON_ONCE(1);
		ret = SWAP_FAIL;
		page_vma_mapped_walk_done(&pvmw);
		break;
		}

		/* MADV_FREE page check */
		if (!PageSwapBacked(page)) {

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