[PATCH v2] cgroup/cpuset: call fmeter_init() when cpuset.memory_pressure disabled

[Jin Guojie]

When running LTP's cpuset_memory_pressure program, the following error occurs:

(1) Create a cgroup, enable cpuset subsystem, set memory limit, and
then set cpuset_memory_pressure to 1
(2) In this cgroup, create a process to allocate a large amount of
memory and generate pressure counts
(3) Set cpuset_memory_pressure to 0
(4) Check cpuset.memory_pressure: LTP thinks it should be 0, but the
current kernel returns a value of 1, so LTP determines it as FAIL

V2:
* call fmeter_init() when writing 0 to the memory_pressure_enabled

Compared with patch v1 [1], this version implements clearer logic.

[1] https://lore.kernel.org/cgroups/CA+B+MYRNsdKcYxC8kbyzVrdH9fT8c2if5UxGguKep36ZHe6HMQ@xxxxxxxxxxxxxx/T/#u

Signed-off-by: Jin Guojie <guojie.jin@xxxxxxxxx>
Suggested-by: Michal Koutný <mkoutny@xxxxxxxx>
Suggested-by: Waiman Long <longman@xxxxxxxxxx>
---
 kernel/cgroup/cpuset-v1.c | 4 +++-
 kernel/cgroup/cpuset.c    | 2 ++
 2 files changed, 5 insertions(+), 1 deletion(-)

diff --git a/kernel/cgroup/cpuset-v1.c b/kernel/cgroup/cpuset-v1.c
index 25c1d7b77e2f..7520eb31598a 100644
--- a/kernel/cgroup/cpuset-v1.c
+++ b/kernel/cgroup/cpuset-v1.c
@@ -66,7 +66,6 @@ void fmeter_init(struct fmeter *fmp)
        fmp->cnt = 0;
        fmp->val = 0;
        fmp->time = 0;
-       spin_lock_init(&fmp->lock);
 }

 /* Internal meter update - process cnt events and update value */
@@ -437,6 +436,9 @@ static int cpuset_write_u64(struct
cgroup_subsys_state *css, struct cftype *cft,
                break;
        case FILE_MEMORY_PRESSURE_ENABLED:
                cpuset_memory_pressure_enabled = !!val;
+               if (cpuset_memory_pressure_enabled == 0) {
+                       fmeter_init(&cs->fmeter);
+               }
                break;
        case FILE_SPREAD_PAGE:
                retval = cpuset_update_flag(CS_SPREAD_PAGE, cs, val);
diff --git a/kernel/cgroup/cpuset.c b/kernel/cgroup/cpuset.c
index 0f910c828973..3583c898ff77 100644
--- a/kernel/cgroup/cpuset.c
+++ b/kernel/cgroup/cpuset.c
@@ -3378,6 +3378,7 @@ cpuset_css_alloc(struct cgroup_subsys_state *parent_css)

        __set_bit(CS_SCHED_LOAD_BALANCE, &cs->flags);
        fmeter_init(&cs->fmeter);
+       spin_lock_init(&cs->fmeter.lock);
        cs->relax_domain_level = -1;
        INIT_LIST_HEAD(&cs->remote_sibling);

@@ -3650,6 +3651,7 @@ int __init cpuset_init(void)
        nodes_setall(top_cpuset.effective_mems);

        fmeter_init(&top_cpuset.fmeter);
+       spin_lock_init(&top_cpuset.fmeter.lock);
        INIT_LIST_HEAD(&remote_children);

        BUG_ON(!alloc_cpumask_var(&cpus_attach, GFP_KERNEL));
--
2.34.1