mm: vmscan: do not scan anon pages if memcg swap limit is hit

We don't scan anonymous memory if we ran out of swap, neither should we do
it in case memcg swap limit is hit, because swap out is impossible anyway.

Signed-off-by: Vladimir Davydov <vdavydov@virtuozzo.com>
Acked-by: Johannes Weiner <hannes@cmpxchg.org>
Cc: Michal Hocko <mhocko@kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

2 files changed, 14 insertions, 1 deletions

diff --git a/mm/memcontrol.c b/mm/memcontrol.c
index 1ff552e3722b..bcb38718e174 100644
--- a/mm/memcontrol.c
+++ b/mm/memcontrol.c
@@ -5748,6 +5748,19 @@ void mem_cgroup_uncharge_swap(swp_entry_t entry)
         rcu_read_unlock();
 }
 
+long mem_cgroup_get_nr_swap_pages(struct mem_cgroup *memcg)
+{
+        long nr_swap_pages = get_nr_swap_pages();
+
+        if (!do_swap_account || !cgroup_subsys_on_dfl(memory_cgrp_subsys))
+                return nr_swap_pages;
+        for (; memcg != root_mem_cgroup; memcg = parent_mem_cgroup(memcg))
+                nr_swap_pages = min_t(long, nr_swap_pages,
+                                      READ_ONCE(memcg->swap.limit) -
+                                      page_counter_read(&memcg->swap));
+        return nr_swap_pages;
+}
+
 /* for remember boot option*/
 #ifdef CONFIG_MEMCG_SWAP_ENABLED
 static int really_do_swap_account __initdata = 1;
diff --git a/mm/vmscan.c b/mm/vmscan.c
index 9a8556e49cd9..3be5f9db6c42 100644
--- a/mm/vmscan.c
+++ b/mm/vmscan.c
@@ -2004,7 +2004,7 @@ static void get_scan_count(struct lruvec *lruvec, struct mem_cgroup *memcg,
                 force_scan = true;
 
         /* If we have no swap space, do not bother scanning anon pages. */
-        if (!sc->may_swap || (get_nr_swap_pages() <= 0)) {
+        if (!sc->may_swap || mem_cgroup_get_nr_swap_pages(memcg) <= 0) {
                 scan_balance = SCAN_FILE;
                 goto out;
         }