The last patch has a problem on define. this version could fix it.
BTW, I see some !memcg happens when MEMCG compilered but disabled by cgroup_disable
[ 94.657666] ---[ end trace f1f34bfc3b32ed2f ]---
[ 95.138995] anon flags: 0x5005b48008000d(locked|uptodate|dirty|swapbacked)
[ 95.146220] raw: 005005b48008000d dead000000000100 dead000000000122 ffff8897c7c76ad1
[ 95.154549] raw: 0000000000000022 0000000000000000 0000000200000000 0000000000000000
[ 95.162876] page dumped because: VM_WARN_ON_ONCE_PAGE(!memcg)
>From 2ca3e87fd3878ab729551682ad083a70f15bb3fc Mon Sep 17 00:00:00 2001
From: Alex Shi <alex.shi@xxxxxxxxxxxxxxxxx>
Date: Sat, 1 Aug 2020 10:43:55 +0800
Subject: [PATCH v3] mm/memcg: warning on !memcg after readahead page charged
Since readahead page is charged on memcg too, in theory we don't have to
check this exception now. Before safely remove them all, add a warning
for the unexpected !memcg.
Signed-off-by: Alex Shi <alex.shi@xxxxxxxxxxxxxxxxx>
Cc: Johannes Weiner <hannes@xxxxxxxxxxx>
Cc: Michal Hocko <mhocko@xxxxxxxxxx>
Cc: Vladimir Davydov <vdavydov.dev@xxxxxxxxx>
Cc: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
Cc: cgroups@xxxxxxxxxxxxxxx
Cc: linux-mm@xxxxxxxxx
Cc: linux-kernel@xxxxxxxxxxxxxxx
---
include/linux/mmdebug.h | 13 +++++++++++++
mm/memcontrol.c | 15 ++++++++-------
2 files changed, 21 insertions(+), 7 deletions(-)
diff --git a/include/linux/mmdebug.h b/include/linux/mmdebug.h
index 2ad72d2c8cc5..4ed52879ce55 100644
--- a/include/linux/mmdebug.h
+++ b/include/linux/mmdebug.h
@@ -37,6 +37,18 @@
BUG(); \
} \
} while (0)
+#define VM_WARN_ON_ONCE_PAGE(cond, page) ({ \
+ static bool __section(.data.once) __warned; \
+ int __ret_warn_once = !!(cond); \
+ \
+ if (unlikely(__ret_warn_once && !__warned)) { \
+ dump_page(page, "VM_WARN_ON_ONCE_PAGE(" __stringify(cond)")");\
+ __warned = true; \
+ WARN_ON(1); \
+ } \
+ unlikely(__ret_warn_once); \
+})
+
#define VM_WARN_ON(cond) (void)WARN_ON(cond)
#define VM_WARN_ON_ONCE(cond) (void)WARN_ON_ONCE(cond)
#define VM_WARN_ONCE(cond, format...) (void)WARN_ONCE(cond, format)
@@ -48,6 +60,7 @@
#define VM_BUG_ON_MM(cond, mm) VM_BUG_ON(cond)
#define VM_WARN_ON(cond) BUILD_BUG_ON_INVALID(cond)
#define VM_WARN_ON_ONCE(cond) BUILD_BUG_ON_INVALID(cond)
+#define VM_WARN_ON_ONCE_PAGE(cond, page) BUILD_BUG_ON_INVALID(cond)
#define VM_WARN_ONCE(cond, format...) BUILD_BUG_ON_INVALID(cond)
#define VM_WARN(cond, format...) BUILD_BUG_ON_INVALID(cond)
#endif
diff --git a/mm/memcontrol.c b/mm/memcontrol.c
index 130093bdf74b..299382fc55a9 100644
--- a/mm/memcontrol.c
+++ b/mm/memcontrol.c
@@ -1322,10 +1322,8 @@ struct lruvec *mem_cgroup_page_lruvec(struct page *page, struct pglist_data *pgd
}
memcg = page->mem_cgroup;
- /*
- * Swapcache readahead pages are added to the LRU - and
- * possibly migrated - before they are charged.
- */
+ /* Readahead page is charged too, to see if other page uncharged */
+ VM_WARN_ON_ONCE_PAGE(!memcg, page);
if (!memcg)
memcg = root_mem_cgroup;
@@ -6906,8 +6904,9 @@ void mem_cgroup_migrate(struct page *oldpage, struct page *newpage)
if (newpage->mem_cgroup)
return;
- /* Swapcache readahead pages can get replaced before being charged */
memcg = oldpage->mem_cgroup;
+ /* Readahead page is charged too, to see if other page uncharged */
+ VM_WARN_ON_ONCE_PAGE(!memcg, oldpage);
if (!memcg)
return;
@@ -7104,7 +7103,8 @@ void mem_cgroup_swapout(struct page *page, swp_entry_t entry)
memcg = page->mem_cgroup;
- /* Readahead page, never charged */
+ /* Readahead page is charged too, to see if other page uncharged */
+ VM_WARN_ON_ONCE_PAGE(!memcg, page);
if (!memcg)
return;
@@ -7168,7 +7168,8 @@ int mem_cgroup_try_charge_swap(struct page *page, swp_entry_t entry)
memcg = page->mem_cgroup;
- /* Readahead page, never charged */
+ /* Readahead page is charged too, to see if other page uncharged */
+ VM_WARN_ON_ONCE_PAGE(!memcg, page);
if (!memcg)
return 0;
--
1.8.3.1
