cgroup: remove cgroup->name
cgroup->name handling became quite complicated over time involving
dedicated struct cgroup_name for RCU protection. Now that cgroup is
on kernfs, we can drop all of it and simply use kernfs_name/path() and
friends. Replace cgroup->name and all related code with kernfs
name/path constructs.
* Reimplement cgroup_name() and cgroup_path() as thin wrappers on top
of kernfs counterparts, which involves semantic changes.
pr_cont_cgroup_name() and pr_cont_cgroup_path() added.
* cgroup->name handling dropped from cgroup_rename().
* All users of cgroup_name/path() updated to the new semantics. Users
which were formatting the string just to printk them are converted
to use pr_cont_cgroup_name/path() instead, which simplifies things
quite a bit. As cgroup_name() no longer requires RCU read lock
around it, RCU lockings which were protecting only cgroup_name() are
removed.
v2: Comment above oom_info_lock updated as suggested by Michal.
v3: dummy_top doesn't have a kn associated and
pr_cont_cgroup_name/path() ended up calling the matching kernfs
functions with NULL kn leading to oops. Test for NULL kn and
print "/" if so. This issue was reported by Fengguang Wu.
v4: Rebased on top of 0ab02ca8f887 ("cgroup: protect modifications to
cgroup_idr with cgroup_mutex").
Signed-off-by: Tejun Heo <tj@kernel.org>
Acked-by: Peter Zijlstra <peterz@infradead.org>
Acked-by: Michal Hocko <mhocko@suse.cz>
Acked-by: Li Zefan <lizefan@huawei.com>
Cc: Fengguang Wu <fengguang.wu@intel.com>
Cc: Ingo Molnar <mingo@redhat.com>
Cc: Johannes Weiner <hannes@cmpxchg.org>
Cc: Balbir Singh <bsingharora@gmail.com>
Cc: KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com>
diff --git a/mm/memcontrol.c b/mm/memcontrol.c
index 102ab48..c1c2549 100644
--- a/mm/memcontrol.c
+++ b/mm/memcontrol.c
@@ -1683,15 +1683,8 @@
*/
void mem_cgroup_print_oom_info(struct mem_cgroup *memcg, struct task_struct *p)
{
- /*
- * protects memcg_name and makes sure that parallel ooms do not
- * interleave
- */
+ /* oom_info_lock ensures that parallel ooms do not interleave */
static DEFINE_SPINLOCK(oom_info_lock);
- struct cgroup *task_cgrp;
- struct cgroup *mem_cgrp;
- static char memcg_name[PATH_MAX];
- int ret;
struct mem_cgroup *iter;
unsigned int i;
@@ -1701,36 +1694,14 @@
spin_lock(&oom_info_lock);
rcu_read_lock();
- mem_cgrp = memcg->css.cgroup;
- task_cgrp = task_cgroup(p, memory_cgrp_id);
+ pr_info("Task in ");
+ pr_cont_cgroup_path(task_cgroup(p, memory_cgrp_id));
+ pr_info(" killed as a result of limit of ");
+ pr_cont_cgroup_path(memcg->css.cgroup);
+ pr_info("\n");
- ret = cgroup_path(task_cgrp, memcg_name, PATH_MAX);
- if (ret < 0) {
- /*
- * Unfortunately, we are unable to convert to a useful name
- * But we'll still print out the usage information
- */
- rcu_read_unlock();
- goto done;
- }
rcu_read_unlock();
- pr_info("Task in %s killed", memcg_name);
-
- rcu_read_lock();
- ret = cgroup_path(mem_cgrp, memcg_name, PATH_MAX);
- if (ret < 0) {
- rcu_read_unlock();
- goto done;
- }
- rcu_read_unlock();
-
- /*
- * Continues from above, so we don't need an KERN_ level
- */
- pr_cont(" as a result of limit of %s\n", memcg_name);
-done:
-
pr_info("memory: usage %llukB, limit %llukB, failcnt %llu\n",
res_counter_read_u64(&memcg->res, RES_USAGE) >> 10,
res_counter_read_u64(&memcg->res, RES_LIMIT) >> 10,
@@ -1745,13 +1716,8 @@
res_counter_read_u64(&memcg->kmem, RES_FAILCNT));
for_each_mem_cgroup_tree(iter, memcg) {
- pr_info("Memory cgroup stats");
-
- rcu_read_lock();
- ret = cgroup_path(iter->css.cgroup, memcg_name, PATH_MAX);
- if (!ret)
- pr_cont(" for %s", memcg_name);
- rcu_read_unlock();
+ pr_info("Memory cgroup stats for ");
+ pr_cont_cgroup_path(iter->css.cgroup);
pr_cont(":");
for (i = 0; i < MEM_CGROUP_STAT_NSTATS; i++) {
@@ -3401,7 +3367,7 @@
struct kmem_cache *s)
{
struct kmem_cache *new = NULL;
- static char *tmp_name = NULL;
+ static char *tmp_path = NULL, *tmp_name = NULL;
static DEFINE_MUTEX(mutex); /* protects tmp_name */
BUG_ON(!memcg_can_account_kmem(memcg));
@@ -3413,18 +3379,20 @@
* This static temporary buffer is used to prevent from
* pointless shortliving allocation.
*/
- if (!tmp_name) {
- tmp_name = kmalloc(PATH_MAX, GFP_KERNEL);
+ if (!tmp_path || !tmp_name) {
+ if (!tmp_path)
+ tmp_path = kmalloc(PATH_MAX, GFP_KERNEL);
if (!tmp_name)
+ tmp_name = kmalloc(NAME_MAX + 1, GFP_KERNEL);
+ if (!tmp_path || !tmp_name)
goto out;
}
- rcu_read_lock();
- snprintf(tmp_name, PATH_MAX, "%s(%d:%s)", s->name,
- memcg_cache_id(memcg), cgroup_name(memcg->css.cgroup));
- rcu_read_unlock();
+ cgroup_name(memcg->css.cgroup, tmp_name, NAME_MAX + 1);
+ snprintf(tmp_path, PATH_MAX, "%s(%d:%s)", s->name,
+ memcg_cache_id(memcg), tmp_name);
- new = kmem_cache_create_memcg(memcg, tmp_name, s->object_size, s->align,
+ new = kmem_cache_create_memcg(memcg, tmp_path, s->object_size, s->align,
(s->flags & ~SLAB_PANIC), s->ctor, s);
if (new)
new->allocflags |= __GFP_KMEMCG;