mm/memcontrol.c: convert mem_cgroup_id::ref to refcount_t type

This will allow to use generic refcount_t interfaces to check counters
overflow instead of currently existing VM_BUG_ON().  The only difference
after the patch is VM_BUG_ON() may cause BUG(), while refcount_t fires
with WARN().  But this seems not to be significant here, since such the
problems are usually caught by syzbot with panic-on-warn enabled.

Link: http://lkml.kernel.org/r/153910718919.7006.13400779039257185427.stgit@localhost.localdomain
Signed-off-by: Kirill Tkhai <ktkhai@virtuozzo.com>
Reviewed-by: Andrew Morton <akpm@linux-foundation.org>
Acked-by: Michal Hocko <mhocko@suse.com>
Cc: Johannes Weiner <hannes@cmpxchg.org>
Cc: Vladimir Davydov <vdavydov.dev@gmail.com>
Cc: Andrea Parri <andrea.parri@amarulasolutions.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

diff --git a/include/linux/memcontrol.h b/include/linux/memcontrol.h
index 4399cc3..7ab2120 100644 (file)
--- a/include/linux/memcontrol.h
+++ b/include/linux/memcontrol.h
@@ -78,7 +78,7 @@ struct mem_cgroup_reclaim_cookie {
 
 struct mem_cgroup_id {
        int id;
-       atomic_t ref;
+       refcount_t ref;
 };
 
 /*

diff --git a/mm/memcontrol.c b/mm/memcontrol.c
index 645ede7..92d38c8 100644 (file)
--- a/mm/memcontrol.c
+++ b/mm/memcontrol.c
@@ -4299,14 +4299,12 @@ static void mem_cgroup_id_remove(struct mem_cgroup *memcg)
 
 static void mem_cgroup_id_get_many(struct mem_cgroup *memcg, unsigned int n)
 {
-       VM_BUG_ON(atomic_read(&memcg->id.ref) <= 0);
-       atomic_add(n, &memcg->id.ref);
+       refcount_add(n, &memcg->id.ref);
 }
 
 static void mem_cgroup_id_put_many(struct mem_cgroup *memcg, unsigned int n)
 {
-       VM_BUG_ON(atomic_read(&memcg->id.ref) < n);
-       if (atomic_sub_and_test(n, &memcg->id.ref)) {
+       if (refcount_sub_and_test(n, &memcg->id.ref)) {
                mem_cgroup_id_remove(memcg);
 
                /* Memcg ID pins CSS */
@@ -4523,7 +4521,7 @@ static int mem_cgroup_css_online(struct cgroup_subsys_state *css)
        }
 
        /* Online state pins memcg ID, memcg ID pins CSS */
-       atomic_set(&memcg->id.ref, 1);
+       refcount_set(&memcg->id.ref, 1);
        css_get(css);
        return 0;
 }
@@ -6357,7 +6355,7 @@ subsys_initcall(mem_cgroup_init);
 #ifdef CONFIG_MEMCG_SWAP
 static struct mem_cgroup *mem_cgroup_id_get_online(struct mem_cgroup *memcg)
 {
-       while (!atomic_inc_not_zero(&memcg->id.ref)) {
+       while (!refcount_inc_not_zero(&memcg->id.ref)) {
                /*
                 * The root cgroup cannot be destroyed, so it's refcount must
                 * always be >= 1.