mm: memcontrol: prepare uncharging for removal of private page type counters

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@cmpxchg.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Reviewed-by: Alex Shi <alex.shi@linux.alibaba.com>
Reviewed-by: Joonsoo Kim <iamjoonsoo.kim@lge.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/20200508183105.225460-7-hannes@cmpxchg.org
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

diff --git a/mm/memcontrol.c b/mm/memcontrol.c
index c414b7f85e48c6a7b74a236461188175d6761456..ff45bef46ffe1b66f6b061ca9d8d3de49548c20f 100644 (file)
--- a/mm/memcontrol.c
+++ b/mm/memcontrol.c
@@ -6666,6 +6666,7 @@ 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;
@@ -6682,13 +6683,12 @@ 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);
@@ -6700,16 +6700,18 @@ 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)
@@ -6729,13 +6731,12 @@ 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 {
@@ -6745,7 +6746,7 @@ 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);
        }