[PATCH 06/19] mm: memcontrol: prepare uncharging for removal of private page type counters

[Johannes Weiner <hannes@xxxxxxxxxxx>]

The uncharge batching code adds up the anon, file, kmem counts to
determine the total number of pages to uncharge and references to
drop. But the next patches will remove the anon and file counters.

Maintain an aggregate nr_pages in the uncharge_gather struct.

Signed-off-by: Johannes Weiner <hannes@xxxxxxxxxxx>
Reviewed-by: Alex Shi <alex.shi@xxxxxxxxxxxxxxxxx>
Reviewed-by: Joonsoo Kim <iamjoonsoo.kim@xxxxxxx>
---
 mm/memcontrol.c | 23 ++++++++++++-----------
 1 file changed, 12 insertions(+), 11 deletions(-)

diff --git a/mm/memcontrol.c b/mm/memcontrol.c
index 1d45a09b334f..a5efdad77be4 100644
--- a/mm/memcontrol.c
+++ b/mm/memcontrol.c
@@ -6607,6 +6607,7 @@ int mem_cgroup_charge(struct page *page, struct mm_struct *mm, gfp_t gfp_mask,
 
 struct uncharge_gather {
 	struct mem_cgroup *memcg;
+	unsigned long nr_pages;
 	unsigned long pgpgout;
 	unsigned long nr_anon;
 	unsigned long nr_file;
@@ -6623,13 +6624,12 @@ static inline void uncharge_gather_clear(struct uncharge_gather *ug)
 
 static void uncharge_batch(const struct uncharge_gather *ug)
 {
-	unsigned long nr_pages = ug->nr_anon + ug->nr_file + ug->nr_kmem;
 	unsigned long flags;
 
 	if (!mem_cgroup_is_root(ug->memcg)) {
-		page_counter_uncharge(&ug->memcg->memory, nr_pages);
+		page_counter_uncharge(&ug->memcg->memory, ug->nr_pages);
 		if (do_memsw_account())
-			page_counter_uncharge(&ug->memcg->memsw, nr_pages);
+			page_counter_uncharge(&ug->memcg->memsw, ug->nr_pages);
 		if (!cgroup_subsys_on_dfl(memory_cgrp_subsys) && ug->nr_kmem)
 			page_counter_uncharge(&ug->memcg->kmem, ug->nr_kmem);
 		memcg_oom_recover(ug->memcg);
@@ -6641,16 +6641,18 @@ static void uncharge_batch(const struct uncharge_gather *ug)
 	__mod_memcg_state(ug->memcg, MEMCG_RSS_HUGE, -ug->nr_huge);
 	__mod_memcg_state(ug->memcg, NR_SHMEM, -ug->nr_shmem);
 	__count_memcg_events(ug->memcg, PGPGOUT, ug->pgpgout);
-	__this_cpu_add(ug->memcg->vmstats_percpu->nr_page_events, nr_pages);
+	__this_cpu_add(ug->memcg->vmstats_percpu->nr_page_events, ug->nr_pages);
 	memcg_check_events(ug->memcg, ug->dummy_page);
 	local_irq_restore(flags);
 
 	if (!mem_cgroup_is_root(ug->memcg))
-		css_put_many(&ug->memcg->css, nr_pages);
+		css_put_many(&ug->memcg->css, ug->nr_pages);
 }
 
 static void uncharge_page(struct page *page, struct uncharge_gather *ug)
 {
+	unsigned long nr_pages;
+
 	VM_BUG_ON_PAGE(PageLRU(page), page);
 
 	if (!page->mem_cgroup)
@@ -6670,13 +6672,12 @@ static void uncharge_page(struct page *page, struct uncharge_gather *ug)
 		ug->memcg = page->mem_cgroup;
 	}
 
-	if (!PageKmemcg(page)) {
-		unsigned int nr_pages = 1;
+	nr_pages = compound_nr(page);
+	ug->nr_pages += nr_pages;
 
-		if (PageTransHuge(page)) {
-			nr_pages = compound_nr(page);
+	if (!PageKmemcg(page)) {
+		if (PageTransHuge(page))
 			ug->nr_huge += nr_pages;
-		}
 		if (PageAnon(page))
 			ug->nr_anon += nr_pages;
 		else {
@@ -6686,7 +6687,7 @@ static void uncharge_page(struct page *page, struct uncharge_gather *ug)
 		}
 		ug->pgpgout++;
 	} else {
-		ug->nr_kmem += compound_nr(page);
+		ug->nr_kmem += nr_pages;
 		__ClearPageKmemcg(page);
 	}
 
-- 
2.26.2