memcg: replace cgroup_lock with memcg specific memcg_lock
After the preparation work done in earlier patches, the cgroup_lock can
be trivially replaced with a memcg-specific lock. This is an automatic
translation at every site where the values involved were queried.
The sites where values are written, however, used to be naturally called
under cgroup_lock. This is the case for instance in the css_online
callback. For those, we now need to explicitly add the memcg lock.
With this, all the calls to cgroup_lock outside cgroup core are gone.
Signed-off-by: Glauber Costa <glommer@parallels.com>
Acked-by: Michal Hocko <mhocko@suse.cz>
Cc: Tejun Heo <tj@kernel.org>
Cc: Hiroyuki Kamezawa <kamezawa.hiroyuki@gmail.com>
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 2bc3fbe..46cdaef 100644
--- a/mm/memcontrol.c
+++ b/mm/memcontrol.c
@@ -488,6 +488,13 @@
#define MEM_CGROUP_RECLAIM_SHRINK_BIT 0x1
#define MEM_CGROUP_RECLAIM_SHRINK (1 << MEM_CGROUP_RECLAIM_SHRINK_BIT)
+/*
+ * The memcg_create_mutex will be held whenever a new cgroup is created.
+ * As a consequence, any change that needs to protect against new child cgroups
+ * appearing has to hold it as well.
+ */
+static DEFINE_MUTEX(memcg_create_mutex);
+
static void mem_cgroup_get(struct mem_cgroup *memcg);
static void mem_cgroup_put(struct mem_cgroup *memcg);
@@ -4778,8 +4785,8 @@
}
/*
- * Must be called with cgroup_lock held, unless the cgroup is guaranteed to be
- * already dead (in mem_cgroup_force_empty(), for instance). This is different
+ * Must be called with memcg_create_mutex held, unless the cgroup is guaranteed
+ * to be already dead (as in mem_cgroup_force_empty, for instance). This is
* from mem_cgroup_count_children(), in the sense that we don't really care how
* many children we have; we only need to know if we have any. It also counts
* any memcg without hierarchy as infertile.
@@ -4859,7 +4866,7 @@
if (parent)
parent_memcg = mem_cgroup_from_cont(parent);
- cgroup_lock();
+ mutex_lock(&memcg_create_mutex);
if (memcg->use_hierarchy == val)
goto out;
@@ -4882,7 +4889,7 @@
retval = -EINVAL;
out:
- cgroup_unlock();
+ mutex_unlock(&memcg_create_mutex);
return retval;
}
@@ -4981,14 +4988,8 @@
*
* After it first became limited, changes in the value of the limit are
* of course permitted.
- *
- * Taking the cgroup_lock is really offensive, but it is so far the only
- * way to guarantee that no children will appear. There are plenty of
- * other offenders, and they should all go away. Fine grained locking
- * is probably the way to go here. When we are fully hierarchical, we
- * can also get rid of the use_hierarchy check.
*/
- cgroup_lock();
+ mutex_lock(&memcg_create_mutex);
mutex_lock(&set_limit_mutex);
if (!memcg->kmem_account_flags && val != RESOURCE_MAX) {
if (cgroup_task_count(cont) || memcg_has_children(memcg)) {
@@ -5015,7 +5016,7 @@
ret = res_counter_set_limit(&memcg->kmem, val);
out:
mutex_unlock(&set_limit_mutex);
- cgroup_unlock();
+ mutex_unlock(&memcg_create_mutex);
/*
* We are by now familiar with the fact that we can't inc the static
@@ -5396,17 +5397,17 @@
parent = mem_cgroup_from_cont(cgrp->parent);
- cgroup_lock();
+ mutex_lock(&memcg_create_mutex);
/* If under hierarchy, only empty-root can set this value */
if ((parent->use_hierarchy) || memcg_has_children(memcg)) {
- cgroup_unlock();
+ mutex_unlock(&memcg_create_mutex);
return -EINVAL;
}
memcg->swappiness = val;
- cgroup_unlock();
+ mutex_unlock(&memcg_create_mutex);
return 0;
}
@@ -5732,16 +5733,16 @@
parent = mem_cgroup_from_cont(cgrp->parent);
- cgroup_lock();
+ mutex_lock(&memcg_create_mutex);
/* oom-kill-disable is a flag for subhierarchy. */
if ((parent->use_hierarchy) || memcg_has_children(memcg)) {
- cgroup_unlock();
+ mutex_unlock(&memcg_create_mutex);
return -EINVAL;
}
memcg->oom_kill_disable = val;
if (!val)
memcg_oom_recover(memcg);
- cgroup_unlock();
+ mutex_unlock(&memcg_create_mutex);
return 0;
}
@@ -6170,6 +6171,7 @@
if (!cont->parent)
return 0;
+ mutex_lock(&memcg_create_mutex);
memcg = mem_cgroup_from_cont(cont);
parent = mem_cgroup_from_cont(cont->parent);
@@ -6203,6 +6205,7 @@
}
error = memcg_init_kmem(memcg, &mem_cgroup_subsys);
+ mutex_unlock(&memcg_create_mutex);
if (error) {
/*
* We call put now because our (and parent's) refcnts