mm: memcontrol: prepare cgroup vmstat infrastructure for native anon counters

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>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Reviewed-by: Joonsoo Kim <iamjoonsoo.kim@lge.com>
Cc: Alex Shi <alex.shi@linux.alibaba.com>
Cc: Hugh Dickins <hughd@google.com>
Cc: "Kirill A. Shutemov" <kirill@shutemov.name>
Cc: Michal Hocko <mhocko@suse.com>
Cc: Roman Gushchin <guro@fb.com>
Cc: Shakeel Butt <shakeelb@google.com>
Cc: Balbir Singh <bsingharora@gmail.com>
Link: http://lkml.kernel.org/r/20200508183105.225460-9-hannes@cmpxchg.org
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

diff --git a/include/linux/memcontrol.h b/include/linux/memcontrol.h
index 898925b..8f00dd7 100644 (file)
--- a/include/linux/memcontrol.h
+++ b/include/linux/memcontrol.h
@@ -709,16 +709,17 @@ 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 f82ae37..a875a97 100644 (file)
--- a/mm/memcontrol.c
+++ b/mm/memcontrol.c
@@ -1981,6 +1981,7 @@ 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;
 
@@ -2000,7 +2001,7 @@ 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;
 
@@ -2008,7 +2009,7 @@ again:
                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;
        }
@@ -2051,7 +2052,9 @@ 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);