When memcg uses the generic vmstat counters, it doesn't need to do
anything at charging and uncharging time. It does, however, need to
migrate counts when pages move to a different cgroup in move_account.

Prepare the move_account function for the arrival of NR_FILE_PAGES,
NR_ANON_MAPPED, NR_ANON_THPS etc. by having a branch for files and a
branch for anon, which can then divided into sub-branches.

Signed-off-by: Johannes Weiner <[email protected]>
Reviewed-by: Alex Shi <[email protected]>
Reviewed-by: Joonsoo Kim <[email protected]>
---
 mm/memcontrol.c | 25 +++++++++++++------------
 1 file changed, 13 insertions(+), 12 deletions(-)

diff --git a/mm/memcontrol.c b/mm/memcontrol.c
index a5efdad77be4..fe4212db8411 100644
--- a/mm/memcontrol.c
+++ b/mm/memcontrol.c
@@ -5378,7 +5378,6 @@ static int mem_cgroup_move_account(struct page *page,
        struct pglist_data *pgdat;
        unsigned int nr_pages = compound ? hpage_nr_pages(page) : 1;
        int ret;
-       bool anon;
 
        VM_BUG_ON(from == to);
        VM_BUG_ON_PAGE(PageLRU(page), page);
@@ -5396,25 +5395,27 @@ static int mem_cgroup_move_account(struct page *page,
        if (page->mem_cgroup != from)
                goto out_unlock;
 
-       anon = PageAnon(page);
-
        pgdat = page_pgdat(page);
        from_vec = mem_cgroup_lruvec(from, pgdat);
        to_vec = mem_cgroup_lruvec(to, pgdat);
 
        lock_page_memcg(page);
 
-       if (!anon && page_mapped(page)) {
-               __mod_lruvec_state(from_vec, NR_FILE_MAPPED, -nr_pages);
-               __mod_lruvec_state(to_vec, NR_FILE_MAPPED, nr_pages);
-       }
+       if (!PageAnon(page)) {
+               if (page_mapped(page)) {
+                       __mod_lruvec_state(from_vec, NR_FILE_MAPPED, -nr_pages);
+                       __mod_lruvec_state(to_vec, NR_FILE_MAPPED, nr_pages);
+               }
 
-       if (!anon && PageDirty(page)) {
-               struct address_space *mapping = page_mapping(page);
+               if (PageDirty(page)) {
+                       struct address_space *mapping = page_mapping(page);
 
-               if (mapping_cap_account_dirty(mapping)) {
-                       __mod_lruvec_state(from_vec, NR_FILE_DIRTY, -nr_pages);
-                       __mod_lruvec_state(to_vec, NR_FILE_DIRTY, nr_pages);
+                       if (mapping_cap_account_dirty(mapping)) {
+                               __mod_lruvec_state(from_vec, NR_FILE_DIRTY,
+                                                  -nr_pages);
+                               __mod_lruvec_state(to_vec, NR_FILE_DIRTY,
+                                                  nr_pages);
+                       }
                }
        }
 
-- 
2.26.2

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