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authorShaohua Li <shli@fb.com>2017-10-03 16:15:29 -0700
committerLinus Torvalds <torvalds@linux-foundation.org>2017-10-03 17:54:24 -0700
commit24c92eb7dce0a299b8e1a8c5fa585844a53bf7f0 (patch)
tree5e75ce81b94c109243b85e51f8e0c1c9ba5e126d
parentf4e222c56c83b2aed7cc2b329fca7435508eefa1 (diff)
mm: avoid marking swap cached page as lazyfree
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.shli@fb.com Signed-off-by: Shaohua Li <shli@fb.com> Reported-by: Artem Savkov <asavkov@redhat.com> Tested-by: Artem Savkov <asavkov@redhat.com> Reviewed-by: Rik van Riel <riel@redhat.com> Acked-by: Johannes Weiner <hannes@cmpxchg.org> Acked-by: Michal Hocko <mhocko@suse.com> Acked-by: Minchan Kim <minchan@kernel.org> Cc: Hillf Danton <hdanton@sina.com> Cc: Hugh Dickins <hughd@google.com> Cc: Mel Gorman <mgorman@techsingularity.net> Cc: <stable@vger.kernel.org> [4.12+] Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
-rw-r--r--mm/swap.c4
1 files changed, 2 insertions, 2 deletions
diff --git a/mm/swap.c b/mm/swap.c
index 9295ae960d66..a77d68f2c1b6 100644
--- a/mm/swap.c
+++ b/mm/swap.c
@@ -575,7 +575,7 @@ static void lru_lazyfree_fn(struct page *page, struct lruvec *lruvec,
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 *page)
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);