The patch titled
Subject: mm/memcg: warning on !memcg after readahead page charged
has been added to the -mm tree. Its filename is
mm-memcg-warning-on-memcg-after-readahead-page-charged.patch
This patch should soon appear at
https://ozlabs.org/~akpm/mmots/broken-out/mm-memcg-warning-on-memcg-after-readahead-page-charged.patch
and later at
https://ozlabs.org/~akpm/mmotm/broken-out/mm-memcg-warning-on-memcg-after-readahead-page-charged.patch
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*** Remember to use Documentation/process/submit-checklist.rst when testing your code ***
The -mm tree is included into linux-next and is updated
there every 3-4 working days
------------------------------------------------------
From: Alex Shi <alex.shi@xxxxxxxxxxxxxxxxx>
Subject: mm/memcg: warning on !memcg after readahead page charged
Add VM_WARN_ON_ONCE_PAGE() macro.
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.
Link: https://lkml.kernel.org/r/1604283436-18880-3-git-send-email-alex.shi@xxxxxxxxxxxxxxxxx
Signed-off-by: Alex Shi <alex.shi@xxxxxxxxxxxxxxxxx>
Acked-by: Michal Hocko <mhocko@xxxxxxxx>
Acked-by: Hugh Dickins <hughd@xxxxxxxxxx>
Acked-by: Johannes Weiner <hannes@xxxxxxxxxxx>
Cc: Vladimir Davydov <vdavydov.dev@xxxxxxxxx>
Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
---
include/linux/mmdebug.h | 13 +++++++++++++
mm/memcontrol.c | 10 ++++------
2 files changed, 17 insertions(+), 6 deletions(-)
--- a/include/linux/mmdebug.h~mm-memcg-warning-on-memcg-after-readahead-page-charged
+++ a/include/linux/mmdebug.h
@@ -37,6 +37,18 @@ void dump_mm(const struct mm_struct *mm)
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 @@ void dump_mm(const struct mm_struct *mm)
#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
--- a/mm/memcontrol.c~mm-memcg-warning-on-memcg-after-readahead-page-charged
+++ a/mm/memcontrol.c
@@ -1325,10 +1325,7 @@ struct lruvec *mem_cgroup_page_lruvec(st
}
memcg = page_memcg(page);
- /*
- * Swapcache readahead pages are added to the LRU - and
- * possibly migrated - before they are charged.
- */
+ VM_WARN_ON_ONCE_PAGE(!memcg, page);
if (!memcg)
memcg = root_mem_cgroup;
@@ -6966,6 +6963,7 @@ void mem_cgroup_migrate(struct page *old
/* Swapcache readahead pages can get replaced before being charged */
memcg = page_memcg(oldpage);
+ VM_WARN_ON_ONCE_PAGE(!memcg, oldpage);
if (!memcg)
return;
@@ -7165,7 +7163,7 @@ void mem_cgroup_swapout(struct page *pag
memcg = page_memcg(page);
- /* Readahead page, never charged */
+ VM_WARN_ON_ONCE_PAGE(!memcg, page);
if (!memcg)
return;
@@ -7232,7 +7230,7 @@ int mem_cgroup_try_charge_swap(struct pa
memcg = page_memcg(page);
- /* Readahead page, never charged */
+ VM_WARN_ON_ONCE_PAGE(!memcg, page);
if (!memcg)
return 0;
_
Patches currently in -mm which might be from alex.shi@xxxxxxxxxxxxxxxxx are
mm-memcg-bail-early-from-swap-accounting-if-memcg-disabled.patch
mm-memcg-warning-on-memcg-after-readahead-page-charged.patch
