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Commit 1c2d479a authored by Kirill Tkhai's avatar Kirill Tkhai Committed by Linus Torvalds
Browse files

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: default avatarKirill Tkhai <ktkhai@virtuozzo.com>
Reviewed-by: default avatarAndrew Morton <akpm@linux-foundation.org>
Acked-by: default avatarMichal 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: default avatarAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: default avatarLinus Torvalds <torvalds@linux-foundation.org>
parent 4a222127

include/linux/memcontrol.h

+1 −1
Original line number Diff line number Diff line
@@ -78,7 +78,7 @@ struct mem_cgroup_reclaim_cookie { 


struct mem_cgroup_id {

	int id;

	atomic_t ref;

	refcount_t ref;

};



/*

mm/memcontrol.c

+4 −6
Original line number Diff line number Diff line
@@ -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.