mm: memcontrol: implement lruvec stat functions on top of each other

The implementation of the lruvec stat functions and their variants for
accounting through a page, or accounting from a preemptible context, are
mostly identical and needlessly repetitive.

Implement the lruvec_page functions by looking up the page's lruvec and
then using the lruvec function.

Implement the functions for preemptible contexts by disabling preemption
before calling the atomic context functions.

Link: http://lkml.kernel.org/r/20171103153336.24044-2-hannes@cmpxchg.org
Signed-off-by: Johannes Weiner <hannes@cmpxchg.org>
Acked-by: Vladimir Davydov <vdavydov.dev@gmail.com>
Cc: Michal Hocko <mhocko@suse.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

include/linux/memcontrol.h

@@ -569,51 +569,51 @@ static inline void __mod_lruvec_state(struct lruvec *lruvec,
 {
 	struct mem_cgroup_per_node *pn;
 
+	/* Update node */
 	__mod_node_page_state(lruvec_pgdat(lruvec), idx, val);
+
 	if (mem_cgroup_disabled())
 		return;
+
 	pn = container_of(lruvec, struct mem_cgroup_per_node, lruvec);
+
+	/* Update memcg */
 	__mod_memcg_state(pn->memcg, idx, val);
+
+	/* Update lruvec */
 	__this_cpu_add(pn->lruvec_stat->count[idx], val);
 }
 
 static inline void mod_lruvec_state(struct lruvec *lruvec,
 				    enum node_stat_item idx, int val)
 {
-	struct mem_cgroup_per_node *pn;
-
-	mod_node_page_state(lruvec_pgdat(lruvec), idx, val);
-	if (mem_cgroup_disabled())
-		return;
-	pn = container_of(lruvec, struct mem_cgroup_per_node, lruvec);
-	mod_memcg_state(pn->memcg, idx, val);
-	this_cpu_add(pn->lruvec_stat->count[idx], val);
+	preempt_disable();
+	__mod_lruvec_state(lruvec, idx, val);
+	preempt_enable();
 }
 
 static inline void __mod_lruvec_page_state(struct page *page,
 					   enum node_stat_item idx, int val)
 {
-	struct mem_cgroup_per_node *pn;
+	pg_data_t *pgdat = page_pgdat(page);
+	struct lruvec *lruvec;
 
-	__mod_node_page_state(page_pgdat(page), idx, val);
-	if (mem_cgroup_disabled() || !page->mem_cgroup)
+	/* Untracked pages have no memcg, no lruvec. Update only the node */
+	if (!page->mem_cgroup) {
+		__mod_node_page_state(pgdat, idx, val);
 		return;
-	__mod_memcg_state(page->mem_cgroup, idx, val);
-	pn = page->mem_cgroup->nodeinfo[page_to_nid(page)];
-	__this_cpu_add(pn->lruvec_stat->count[idx], val);
+	}
+
+	lruvec = mem_cgroup_lruvec(pgdat, page->mem_cgroup);
+	__mod_lruvec_state(lruvec, idx, val);
 }
 
 static inline void mod_lruvec_page_state(struct page *page,
 					 enum node_stat_item idx, int val)
 {
-	struct mem_cgroup_per_node *pn;
-
-	mod_node_page_state(page_pgdat(page), idx, val);
-	if (mem_cgroup_disabled() || !page->mem_cgroup)
-		return;
-	mod_memcg_state(page->mem_cgroup, idx, val);
-	pn = page->mem_cgroup->nodeinfo[page_to_nid(page)];
-	this_cpu_add(pn->lruvec_stat->count[idx], val);
+	preempt_disable();
+	__mod_lruvec_page_state(page, idx, val);
+	preempt_enable();
 }
 
 unsigned long mem_cgroup_soft_limit_reclaim(pg_data_t *pgdat, int order,