[PATCH v2] mm: Fix __dump_page when mapping->host is not set

[Oscar Salvador]

Swap mapping->host is NULL, so let us protect __dump_page() for such cases.

Fixes: 1c6fb1d89e73c ("mm: print more information about mapping in __dump_page")
Signed-off-by: Oscar Salvador <osalvador@xxxxxxx>
Acked-by: Michal Hocko <mhocko@xxxxxxxx>
---
 mm/debug.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/mm/debug.c b/mm/debug.c
index c0b31b6c3877..7759f12a8fbb 100644
--- a/mm/debug.c
+++ b/mm/debug.c
@@ -79,7 +79,7 @@ void __dump_page(struct page *page, const char *reason)
 		pr_warn("ksm ");
 	else if (mapping) {
 		pr_warn("%ps ", mapping->a_ops);
-		if (mapping->host->i_dentry.first) {
+		if (mapping->host && mapping->host->i_dentry.first) {
 			struct dentry *dentry;
 			dentry = container_of(mapping->host->i_dentry.first, struct dentry, d_u.d_alias);
 			pr_warn("name:\"%pd\" ", dentry);
-- 
2.13.7