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 @@ -1362,10 +1362,7 @@ 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; @@ -6987,6 +6984,7 @@ void mem_cgroup_migrate(struct page *old 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 *pag 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 pa memcg = page_memcg(page); - /* Readahead page, never charged */ + VM_WARN_ON_ONCE_PAGE(!memcg, page); if (!memcg) return 0; _
