memcg: use css_get/put for swap memcg
Use css_get/put instead of mem_cgroup_get/put. A simple replacement
will do.
The historical reason that memcg has its own refcnt instead of always
using css_get/put, is that cgroup couldn't be removed if there're still
css refs, so css refs can't be used as long-lived reference. The
situation has changed so that rmdir a cgroup will succeed regardless css
refs, but won't be freed until css refs goes down to 0.
Signed-off-by: Li Zefan <lizefan@huawei.com>
Acked-by: Michal Hocko <mhocko@suse.cz>
Acked-by: KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com>
Cc: Hugh Dickins <hughd@google.com>
Cc: Tejun Heo <tj@kernel.org>
Cc: Glauber Costa <glommer@openvz.org>
Cc: Johannes Weiner <hannes@cmpxchg.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
diff --git a/mm/memcontrol.c b/mm/memcontrol.c
index bdc9582..76c0c99b 100644
--- a/mm/memcontrol.c
+++ b/mm/memcontrol.c
@@ -4231,12 +4231,12 @@
unlock_page_cgroup(pc);
/*
* even after unlock, we have memcg->res.usage here and this memcg
- * will never be freed.
+ * will never be freed, so it's safe to call css_get().
*/
memcg_check_events(memcg, page);
if (do_swap_account && ctype == MEM_CGROUP_CHARGE_TYPE_SWAPOUT) {
mem_cgroup_swap_statistics(memcg, true);
- mem_cgroup_get(memcg);
+ css_get(&memcg->css);
}
/*
* Migration does not charge the res_counter for the
@@ -4348,7 +4348,7 @@
/*
* record memcg information, if swapout && memcg != NULL,
- * mem_cgroup_get() was called in uncharge().
+ * css_get() was called in uncharge().
*/
if (do_swap_account && swapout && memcg)
swap_cgroup_record(ent, css_id(&memcg->css));
@@ -4379,7 +4379,7 @@
if (!mem_cgroup_is_root(memcg))
res_counter_uncharge(&memcg->memsw, PAGE_SIZE);
mem_cgroup_swap_statistics(memcg, false);
- mem_cgroup_put(memcg);
+ css_put(&memcg->css);
}
rcu_read_unlock();
}
@@ -4413,11 +4413,14 @@
* This function is only called from task migration context now.
* It postpones res_counter and refcount handling till the end
* of task migration(mem_cgroup_clear_mc()) for performance
- * improvement. But we cannot postpone mem_cgroup_get(to)
- * because if the process that has been moved to @to does
- * swap-in, the refcount of @to might be decreased to 0.
+ * improvement. But we cannot postpone css_get(to) because if
+ * the process that has been moved to @to does swap-in, the
+ * refcount of @to might be decreased to 0.
+ *
+ * We are in attach() phase, so the cgroup is guaranteed to be
+ * alive, so we can just call css_get().
*/
- mem_cgroup_get(to);
+ css_get(&to->css);
return 0;
}
return -EINVAL;
@@ -6718,6 +6721,7 @@
{
struct mem_cgroup *from = mc.from;
struct mem_cgroup *to = mc.to;
+ int i;
/* we must uncharge all the leftover precharges from mc.to */
if (mc.precharge) {
@@ -6738,7 +6742,9 @@
if (!mem_cgroup_is_root(mc.from))
res_counter_uncharge(&mc.from->memsw,
PAGE_SIZE * mc.moved_swap);
- __mem_cgroup_put(mc.from, mc.moved_swap);
+
+ for (i = 0; i < mc.moved_swap; i++)
+ css_put(&mc.from->css);
if (!mem_cgroup_is_root(mc.to)) {
/*
@@ -6748,7 +6754,7 @@
res_counter_uncharge(&mc.to->res,
PAGE_SIZE * mc.moved_swap);
}
- /* we've already done mem_cgroup_get(mc.to) */
+ /* we've already done css_get(mc.to) */
mc.moved_swap = 0;
}
memcg_oom_recover(from);
