Merge branch 'for-4.8' of git://git.kernel.org/pub/scm/linux/kernel/git/tj/cgroup

Pull cgroup updates from Tejun Heo:
 "Nothing too exciting.

   - updates to the pids controller so that pid limit breaches can be
     noticed and monitored from userland.

   - cleanups and non-critical bug fixes"

* 'for-4.8' of git://git.kernel.org/pub/scm/linux/kernel/git/tj/cgroup:
  cgroup: remove duplicated include from cgroup.c
  cgroup: Use lld instead of ld when printing pids controller events_limit
  cgroup: Add pids controller event when fork fails because of pid limit
  cgroup: allow NULL return from ss->css_alloc()
  cgroup: remove unnecessary 0 check from css_from_id()
  cgroup: fix idr leak for the first cgroup root

diff --git a/kernel/cgroup.c b/kernel/cgroup.c
index 75c0ff00aca60d298062755539e83cbfeaffaaf2..33a2f63d4a1006566c28a2ce0f137dad9e921e8f 100644 (file)
--- a/kernel/cgroup.c
+++ b/kernel/cgroup.c
@@ -61,7 +61,6 @@
 #include <linux/cpuset.h>
 #include <linux/proc_ns.h>
 #include <linux/nsproxy.h>
-#include <linux/proc_ns.h>
 #include <net/sock.h>
 
 /*
@@ -1160,18 +1159,12 @@ static void cgroup_exit_root_id(struct cgroup_root *root)
 {
        lockdep_assert_held(&cgroup_mutex);
 
-       if (root->hierarchy_id) {
-               idr_remove(&cgroup_hierarchy_idr, root->hierarchy_id);
-               root->hierarchy_id = 0;
-       }
+       idr_remove(&cgroup_hierarchy_idr, root->hierarchy_id);
 }
 
 static void cgroup_free_root(struct cgroup_root *root)
 {
        if (root) {
-               /* hierarchy ID should already have been released */
-               WARN_ON_ONCE(root->hierarchy_id);
-
                idr_destroy(&root->cgroup_idr);
                kfree(root);
        }
@@ -5146,6 +5139,8 @@ static struct cgroup_subsys_state *css_create(struct cgroup *cgrp,
        lockdep_assert_held(&cgroup_mutex);
 
        css = ss->css_alloc(parent_css);
+       if (!css)
+               css = ERR_PTR(-ENOMEM);
        if (IS_ERR(css))
                return css;
 
@@ -6172,7 +6167,7 @@ struct cgroup_subsys_state *css_tryget_online_from_dir(struct dentry *dentry,
 struct cgroup_subsys_state *css_from_id(int id, struct cgroup_subsys *ss)
 {
        WARN_ON_ONCE(!rcu_read_lock_held());
-       return id > 0 ? idr_find(&ss->css_idr, id) : NULL;
+       return idr_find(&ss->css_idr, id);
 }
 
 /**

diff --git a/kernel/cgroup_pids.c b/kernel/cgroup_pids.c
index 303097b374294cf4eb59d4d1a28e4a4a69e4d480..2bd673783f1a9520bddd689da959217d77797ce4 100644 (file)
--- a/kernel/cgroup_pids.c
+++ b/kernel/cgroup_pids.c
@@ -49,6 +49,12 @@ struct pids_cgroup {
         */
        atomic64_t                      counter;
        int64_t                         limit;
+
+       /* Handle for "pids.events" */
+       struct cgroup_file              events_file;
+
+       /* Number of times fork failed because limit was hit. */
+       atomic64_t                      events_limit;
 };
 
 static struct pids_cgroup *css_pids(struct cgroup_subsys_state *css)
@@ -72,6 +78,7 @@ pids_css_alloc(struct cgroup_subsys_state *parent)
 
        pids->limit = PIDS_MAX;
        atomic64_set(&pids->counter, 0);
+       atomic64_set(&pids->events_limit, 0);
        return &pids->css;
 }
 
@@ -213,10 +220,21 @@ static int pids_can_fork(struct task_struct *task)
 {
        struct cgroup_subsys_state *css;
        struct pids_cgroup *pids;
+       int err;
 
        css = task_css_check(current, pids_cgrp_id, true);
        pids = css_pids(css);
-       return pids_try_charge(pids, 1);
+       err = pids_try_charge(pids, 1);
+       if (err) {
+               /* Only log the first time events_limit is incremented. */
+               if (atomic64_inc_return(&pids->events_limit) == 1) {
+                       pr_info("cgroup: fork rejected by pids controller in ");
+                       pr_cont_cgroup_path(task_cgroup(current, pids_cgrp_id));
+                       pr_cont("\n");
+               }
+               cgroup_file_notify(&pids->events_file);
+       }
+       return err;
 }
 
 static void pids_cancel_fork(struct task_struct *task)
@@ -288,6 +306,14 @@ static s64 pids_current_read(struct cgroup_subsys_state *css,
        return atomic64_read(&pids->counter);
 }
 
+static int pids_events_show(struct seq_file *sf, void *v)
+{
+       struct pids_cgroup *pids = css_pids(seq_css(sf));
+
+       seq_printf(sf, "max %lld\n", (s64)atomic64_read(&pids->events_limit));
+       return 0;
+}
+
 static struct cftype pids_files[] = {
        {
                .name = "max",
@@ -300,6 +326,12 @@ static struct cftype pids_files[] = {
                .read_s64 = pids_current_read,
                .flags = CFTYPE_NOT_ON_ROOT,
        },
+       {
+               .name = "events",
+               .seq_show = pids_events_show,
+               .file_offset = offsetof(struct pids_cgroup, events_file),
+               .flags = CFTYPE_NOT_ON_ROOT,
+       },
        { }     /* terminate */
 };