[PATCH 08/18] mm: memcontrol: prepare cgroup vmstat infrastructure for native anon counters

Johannes Weiner
2020-04-20T22:12:03Z

Anonymous compound pages can be mapped by ptes, which means that if we
want to track NR_MAPPED_ANON, NR_ANON_THPS on a per-cgroup basis, we
have to be prepared to see tail pages in our accounting functions.

Make mod_lruvec_page_state() and lock_page_memcg() deal with tail
pages correctly, namely by redirecting to the head page which has the
page->mem_cgroup set up.

Signed-off-by: Johannes Weiner <hannes@cmpxchg.org>
---
include/linux/memcontrol.h | 5 +++--
mm/memcontrol.c | 9 ++++++---
2 files changed, 9 insertions(+), 5 deletions(-)

diff --git a/include/linux/memcontrol.h b/include/linux/memcontrol.h
index 5e8b0e38f145..5a1b5a7b7728 100644
--- a/include/linux/memcontrol.h
+++ b/include/linux/memcontrol.h
@@ -711,16 +711,17 @@ static inline void mod_lruvec_state(struct lruvec *lruvec,
static inline void __mod_lruvec_page_state(struct page *page,
enum node_stat_item idx, int val)
{
+ struct page *head = compound_head(page); /* rmap on tail pages */
pg_data_t *pgdat = page_pgdat(page);
struct lruvec *lruvec;

/* Untracked pages have no memcg, no lruvec. Update only the node */
- if (!page->mem_cgroup) {
+ if (!head->mem_cgroup) {
__mod_node_page_state(pgdat, idx, val);
return;
}

- lruvec = mem_cgroup_lruvec(page->mem_cgroup, pgdat);
+ lruvec = mem_cgroup_lruvec(head->mem_cgroup, pgdat);
__mod_lruvec_state(lruvec, idx, val);
}

diff --git a/mm/memcontrol.c b/mm/memcontrol.c
index ac6f2b073a5a..e9e22c86a118 100644
--- a/mm/memcontrol.c
+++ b/mm/memcontrol.c
@@ -1979,6 +1979,7 @@ void mem_cgroup_print_oom_group(struct mem_cgroup *memcg)
*/
struct mem_cgroup *lock_page_memcg(struct page *page)
{
+ struct page *head = compound_head(page); /* rmap on tail pages */
struct mem_cgroup *memcg;
unsigned long flags;

@@ -1998,7 +1999,7 @@ struct mem_cgroup *lock_page_memcg(struct page *page)
if (mem_cgroup_disabled())
return NULL;
again:
- memcg = page->mem_cgroup;
+ memcg = head->mem_cgroup;
if (unlikely(!memcg))
return NULL;

@@ -2006,7 +2007,7 @@ struct mem_cgroup *lock_page_memcg(struct page *page)
return memcg;

spin_lock_irqsave(&memcg->move_lock, flags);
- if (memcg != page->mem_cgroup) {
+ if (memcg != head->mem_cgroup) {
spin_unlock_irqrestore(&memcg->move_lock, flags);
goto again;
}
@@ -2049,7 +2050,9 @@ void __unlock_page_memcg(struct mem_cgroup *memcg)
*/
void unlock_page_memcg(struct page *page)
{
- __unlock_page_memcg(page->mem_cgroup);
+ struct page *head = compound_head(page);
+
+ __unlock_page_memcg(head->mem_cgroup);
}
EXPORT_SYMBOL(unlock_page_memcg);

--
2.26.0