1 files changed, 29 insertions, 3 deletions

diff --git a/mm/memcontrol.c b/mm/memcontrol.c
index a7a6a1a23c7d..d2ceadd11b10 100644
--- a/mm/memcontrol.c
+++ b/mm/memcontrol.c
@@ -5873,6 +5873,8 @@ static int mem_cgroup_move_account(struct page *page,
 	css_get(&to->css);
 	css_put(&from->css);
 
+	/* Warning should never happen, so don't worry about refcount non-0 */
+	WARN_ON_ONCE(folio_unqueue_deferred_split(folio));
 	folio->memcg_data = (unsigned long)to;
 
 	__folio_memcg_unlock(from);
@@ -6237,7 +6239,10 @@ static int mem_cgroup_move_charge_pte_range(pmd_t *pmd,
 	enum mc_target_type target_type;
 	union mc_target target;
 	struct page *page;
+	struct folio *folio;
+	bool tried_split_before = false;
 
+retry_pmd:
 	ptl = pmd_trans_huge_lock(pmd, vma);
 	if (ptl) {
 		if (mc.precharge < HPAGE_PMD_NR) {
@@ -6247,6 +6252,28 @@ static int mem_cgroup_move_charge_pte_range(pmd_t *pmd,
 		target_type = get_mctgt_type_thp(vma, addr, *pmd, &target);
 		if (target_type == MC_TARGET_PAGE) {
 			page = target.page;
+			folio = page_folio(page);
+			/*
+			 * Deferred split queue locking depends on memcg,
+			 * and unqueue is unsafe unless folio refcount is 0:
+			 * split or skip if on the queue? first try to split.
+			 */
+			if (!list_empty(&folio->_deferred_list)) {
+				spin_unlock(ptl);
+				if (!tried_split_before)
+					split_folio(folio);
+				folio_unlock(folio);
+				folio_put(folio);
+				if (tried_split_before)
+					return 0;
+				tried_split_before = true;
+				goto retry_pmd;
+			}
+			/*
+			 * So long as that pmd lock is held, the folio cannot
+			 * be racily added to the _deferred_list, because
+			 * page_remove_rmap() will find it still pmdmapped.
+			 */
 			if (isolate_lru_page(page)) {
 				if (!mem_cgroup_move_account(page, true,
 							     mc.from, mc.to)) {
@@ -7153,9 +7180,6 @@ static void uncharge_folio(struct folio *folio, struct uncharge_gather *ug)
 	struct obj_cgroup *objcg;
 
 	VM_BUG_ON_FOLIO(folio_test_lru(folio), folio);
-	VM_BUG_ON_FOLIO(folio_order(folio) > 1 &&
-			!folio_test_hugetlb(folio) &&
-			!list_empty(&folio->_deferred_list), folio);
 
 	/*
 	 * Nobody should be changing or seriously looking at
@@ -7202,6 +7226,7 @@ static void uncharge_folio(struct folio *folio, struct uncharge_gather *ug)
 			ug->nr_memory += nr_pages;
 		ug->pgpgout++;
 
+		WARN_ON_ONCE(folio_unqueue_deferred_split(folio));
 		folio->memcg_data = 0;
 	}
 
@@ -7495,6 +7520,7 @@ void mem_cgroup_swapout(struct folio *folio, swp_entry_t entry)
 	VM_BUG_ON_FOLIO(oldid, folio);
 	mod_memcg_state(swap_memcg, MEMCG_SWAP, nr_entries);
 
+	folio_unqueue_deferred_split(folio);
 	folio->memcg_data = 0;
 
 	if (!mem_cgroup_is_root(memcg))