[PATCH] dbg xa head

[Huang Ying]

---
 mm/huge_memory.c | 18 ++++++++++++++++--
 1 file changed, 16 insertions(+), 2 deletions(-)

diff --git a/mm/huge_memory.c b/mm/huge_memory.c
index 9f8bce9a6b32..c6ca1c7157ed 100644
--- a/mm/huge_memory.c
+++ b/mm/huge_memory.c
@@ -2482,6 +2482,8 @@ static void __split_huge_page(struct page *page, struct list_head *list,
 	struct page *head = compound_head(page);
 	pg_data_t *pgdat = page_pgdat(head);
 	struct lruvec *lruvec;
+	struct address_space *swap_cache = NULL;
+	unsigned long offset;
 	int i;
 
 	lruvec = mem_cgroup_page_lruvec(head, pgdat);
@@ -2489,6 +2491,14 @@ static void __split_huge_page(struct page *page, struct list_head *list,
 	/* complete memcg works before add pages to LRU */
 	mem_cgroup_split_huge_fixup(head);
 
+	if (PageAnon(head) && PageSwapCache(head)) {
+		swp_entry_t entry = { .val = page_private(head) };
+
+		offset = swp_offset(entry);
+		swap_cache = swap_address_space(entry);
+		xa_lock(&swap_cache->i_pages);
+	}
+
 	for (i = HPAGE_PMD_NR - 1; i >= 1; i--) {
 		__split_huge_page_tail(head, i, lruvec, list);
 		/* Some pages can be beyond i_size: drop them from page cache */
@@ -2501,6 +2511,9 @@ static void __split_huge_page(struct page *page, struct list_head *list,
 		} else if (!PageAnon(page)) {
 			__xa_store(&head->mapping->i_pages, head[i].index,
 					head + i, 0);
+		} else if (swap_cache) {
+			__xa_store(&swap_cache->i_pages, offset + i,
+				   head + i, 0);
 		}
 	}
 
@@ -2508,9 +2521,10 @@ static void __split_huge_page(struct page *page, struct list_head *list,
 	/* See comment in __split_huge_page_tail() */
 	if (PageAnon(head)) {
 		/* Additional pin to swap cache */
-		if (PageSwapCache(head))
+		if (PageSwapCache(head)) {
 			page_ref_add(head, 2);
-		else
+			xa_unlock(&swap_cache->i_pages);
+		} else
 			page_ref_inc(head);
 	} else {
 		/* Additional pin to page cache */
-- 
2.20.1