4.13-stable review patch. If anyone has any objections, please let me know.
------------------ From: Shaohua Li <[email protected]> commit 24c92eb7dce0a299b8e1a8c5fa585844a53bf7f0 upstream. MADV_FREE clears pte dirty bit and then marks the page lazyfree (clear SwapBacked). There is no lock to prevent the page is added to swap cache between these two steps by page reclaim. Page reclaim could add the page to swap cache and unmap the page. After page reclaim, the page is added back to lru. At that time, we probably start draining per-cpu pagevec and mark the page lazyfree. So the page could be in a state with SwapBacked cleared and PG_swapcache set. Next time there is a refault in the virtual address, do_swap_page can find the page from swap cache but the page has PageSwapCache false because SwapBacked isn't set, so do_swap_page will bail out and do nothing. The task will keep running into fault handler. Fixes: 802a3a92ad7a ("mm: reclaim MADV_FREE pages") Link: http://lkml.kernel.org/r/6537ef3814398c0073630b03f176263bc81f0902.1506446061.git.s...@fb.com Signed-off-by: Shaohua Li <[email protected]> Reported-by: Artem Savkov <[email protected]> Tested-by: Artem Savkov <[email protected]> Reviewed-by: Rik van Riel <[email protected]> Acked-by: Johannes Weiner <[email protected]> Acked-by: Michal Hocko <[email protected]> Acked-by: Minchan Kim <[email protected]> Cc: Hillf Danton <[email protected]> Cc: Hugh Dickins <[email protected]> Cc: Mel Gorman <[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/swap.c | 4 ++-- 1 file changed, 2 insertions(+), 2 deletions(-) --- a/mm/swap.c +++ b/mm/swap.c @@ -575,7 +575,7 @@ static void lru_lazyfree_fn(struct page void *arg) { if (PageLRU(page) && PageAnon(page) && PageSwapBacked(page) && - !PageUnevictable(page)) { + !PageSwapCache(page) && !PageUnevictable(page)) { bool active = PageActive(page); del_page_from_lru_list(page, lruvec, @@ -665,7 +665,7 @@ void deactivate_file_page(struct page *p void mark_page_lazyfree(struct page *page) { if (PageLRU(page) && PageAnon(page) && PageSwapBacked(page) && - !PageUnevictable(page)) { + !PageSwapCache(page) && !PageUnevictable(page)) { struct pagevec *pvec = &get_cpu_var(lru_lazyfree_pvecs); get_page(page);
