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@linux.alibaba.com
Signed-off-by: Alex Shi <alex.shi@linux.alibaba.com>
Acked-by: Michal Hocko <mhocko@suse.com>
Acked-by: Hugh Dickins <hughd@google.com>
Acked-by: Johannes Weiner <hannes@cmpxchg.org>
Cc: Vladimir Davydov <vdavydov.dev@gmail.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
diff --git a/mm/memcontrol.c b/mm/memcontrol.c
index 5c3b054..7b97667 100644
--- a/mm/memcontrol.c
+++ b/mm/memcontrol.c
@@ -1362,10 +1362,7 @@ struct lruvec *mem_cgroup_page_lruvec(struct page *page, struct pglist_data *pgd
}
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;
@@ -6987,6 +6984,7 @@ void mem_cgroup_migrate(struct page *oldpage, struct page *newpage)
return;
memcg = page_memcg(oldpage);
+ VM_WARN_ON_ONCE_PAGE(!memcg, oldpage);
if (!memcg)
return;
@@ -7186,7 +7184,7 @@ void mem_cgroup_swapout(struct page *page, swp_entry_t entry)
memcg = page_memcg(page);
- /* Readahead page, never charged */
+ VM_WARN_ON_ONCE_PAGE(!memcg, page);
if (!memcg)
return;
@@ -7253,7 +7251,7 @@ int mem_cgroup_try_charge_swap(struct page *page, swp_entry_t entry)
memcg = page_memcg(page);
- /* Readahead page, never charged */
+ VM_WARN_ON_ONCE_PAGE(!memcg, page);
if (!memcg)
return 0;