[070/178] mm: memcontrol: directly access page->memcg_data in mm/page_alloc.c

Commit Message

Andrew Morton April 30, 2021, 5:56 a.m. UTC

From: Muchun Song <[e-mail]>
Subject: mm: memcontrol: directly access page->memcg_data in mm/page_alloc.c

page_memcg() is not suitable for use by page_expected_state() and
page_bad_reason().  Because it can BUG_ON() for the slab pages when
CONFIG_DEBUG_VM is enabled.  As neither lru, nor kmem, nor slab page
should have anything left in there by the time the page is freed, what we
care about is whether the value of page->memcg_data is 0.  So just
directly access page->memcg_data here.

Link: https://lkml.kernel.org/r/[e-mail]
Signed-off-by: Muchun Song <[e-mail]>
Acked-by: Johannes Weiner <[e-mail]>
Reviewed-by: Shakeel Butt <[e-mail]>
Cc: Michal Hocko <[e-mail]>
Cc: Roman Gushchin <[e-mail]>
Cc: Vladimir Davydov <[e-mail]>
Cc: Xiongchun Duan <[e-mail]>
Signed-off-by: Andrew Morton <[e-mail]>
---

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

Patch

--- a/mm/page_alloc.c~mm-memcontrol-directly-access-page-memcg_data-in-mm-page_allocc
+++ a/mm/page_alloc.c
@@ -1103,7 +1103,7 @@  static inline bool page_expected_state(s
 	if (unlikely((unsigned long)page->mapping |
 			page_ref_count(page) |
 #ifdef CONFIG_MEMCG
-			(unsigned long)page_memcg(page) |
+			page->memcg_data |
 #endif
 			(page->flags & check_flags)))
 		return false;
@@ -1128,7 +1128,7 @@  static const char *page_bad_reason(struc
 			bad_reason = "PAGE_FLAGS_CHECK_AT_FREE flag(s) set";
 	}
 #ifdef CONFIG_MEMCG
-	if (unlikely(page_memcg(page)))
+	if (unlikely(page->memcg_data))
 		bad_reason = "page still charged to cgroup";
 #endif
 	return bad_reason;