Patch "mm: avoid marking swap cached page as lazyfree" has been added to the 4.13-stable tree

This is a note to let you know that I've just added the patch titled

mm: avoid marking swap cached page as lazyfree

to the 4.13-stable tree which can be found at:
http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary

The filename of the patch is:
mm-avoid-marking-swap-cached-page-as-lazyfree.patch
and it can be found in the queue-4.13 subdirectory.

If you, or anyone else, feels it should not be added to the stable tree, please let <[email protected]> know about it.

From: Shaohua Li <[email protected]>
Date: Tue, 3 Oct 2017 16:15:29 -0700
Subject: mm: avoid marking swap cached page as lazyfree

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.

---
 mm/swap.c |    4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

@@ -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);

Patches currently in stable-queue which might be from [email protected] are

queue-4.13/mm-hugetlb-soft_offline-save-compound-page-order-before-page-migration.patch queue-4.13/mm-fix-data-corruption-caused-by-lazyfree-page.patch queue-4.13/mm-avoid-marking-swap-cached-page-as-lazyfree.patch