[PATCH 05/13] mm: Move memcg stack accounting to account_kernel_stack

[Andy Lutomirski]

We should account for stacks regardless of stack size.  Move it into
account_kernel_stack.

Fixes: 12580e4b54ba8 ("mm: memcontrol: report kernel stack usage in cgroup2 
memory.stat")
Cc: Vladimir Davydov <vdavy...@virtuozzo.com>
Cc: Johannes Weiner <han...@cmpxchg.org>
Cc: Michal Hocko <mho...@kernel.org>
Cc: linux...@kvack.org
Signed-off-by: Andy Lutomirski <l...@kernel.org>
---
 kernel/fork.c | 15 ++++++---------
 1 file changed, 6 insertions(+), 9 deletions(-)

diff --git a/kernel/fork.c b/kernel/fork.c
index 95bebde59d79..59e52f2120a3 100644
--- a/kernel/fork.c
+++ b/kernel/fork.c
@@ -165,20 +165,12 @@ static struct thread_info *alloc_thread_info_node(struct 
task_struct *tsk,
        struct page *page = alloc_kmem_pages_node(node, THREADINFO_GFP,
                                                  THREAD_SIZE_ORDER);
 
-       if (page)
-               memcg_kmem_update_page_stat(page, MEMCG_KERNEL_STACK,
-                                           1 << THREAD_SIZE_ORDER);
-
        return page ? page_address(page) : NULL;
 }
 
 static inline void free_thread_info(struct thread_info *ti)
 {
-       struct page *page = virt_to_page(ti);
-
-       memcg_kmem_update_page_stat(page, MEMCG_KERNEL_STACK,
-                                   -(1 << THREAD_SIZE_ORDER));
-       __free_kmem_pages(page, THREAD_SIZE_ORDER);
+       free_kmem_pages((unsigned long)ti, THREAD_SIZE_ORDER);
 }
 # else
 static struct kmem_cache *thread_info_cache;
@@ -227,6 +219,11 @@ static void account_kernel_stack(struct thread_info *ti, 
int account)
 
        mod_zone_page_state(zone, NR_KERNEL_STACK,
                            THREAD_SIZE / PAGE_SIZE * account);
+
+       /* All stack pages belong to the same memcg. */
+       memcg_kmem_update_page_stat(
+               virt_to_page(ti), MEMCG_KERNEL_STACK,
+               account * (THREAD_SIZE / PAGE_SIZE));
 }
 
 void free_task(struct task_struct *tsk)
-- 
2.7.4