1 files changed, 12 insertions, 2 deletions

diff --git a/mm/memcontrol.c b/mm/memcontrol.c
index cb1c9dedf9b6..010d6c14129a 100644
--- a/mm/memcontrol.c
+++ b/mm/memcontrol.c
@@ -4108,8 +4108,6 @@ __mem_cgroup_uncharge_common(struct page *page, enum charge_type ctype,
         if (mem_cgroup_disabled())
                 return NULL;
 
-        VM_BUG_ON(PageSwapCache(page));
-
         if (PageTransHuge(page)) {
                 nr_pages <<= compound_order(page);
                 VM_BUG_ON(!PageTransHuge(page));
@@ -4205,6 +4203,18 @@ void mem_cgroup_uncharge_page(struct page *page)
         if (page_mapped(page))
                 return;
         VM_BUG_ON(page->mapping && !PageAnon(page));
+        /*
+         * If the page is in swap cache, uncharge should be deferred
+         * to the swap path, which also properly accounts swap usage
+         * and handles memcg lifetime.
+         *
+         * Note that this check is not stable and reclaim may add the
+         * page to swap cache at any time after this.  However, if the
+         * page is not in swap cache by the time page->mapcount hits
+         * 0, there won't be any page table references to the swap
+         * slot, and reclaim will free it and not actually write the
+         * page to disk.
+         */
         if (PageSwapCache(page))
                 return;
         __mem_cgroup_uncharge_common(page, MEM_CGROUP_CHARGE_TYPE_ANON, false);