Merge branch 'for-3.18' of git://git.kernel.org/pub/scm/linux/kernel/git/tj/cgroup

Pull cgroup updates from Tejun Heo:
 "Nothing too interesting.  Just a handful of cleanup patches"

* 'for-3.18' of git://git.kernel.org/pub/scm/linux/kernel/git/tj/cgroup:
  Revert "cgroup: remove redundant variable in cgroup_mount()"
  cgroup: remove redundant variable in cgroup_mount()
  cgroup: fix missing unlock in cgroup_release_agent()
  cgroup: remove CGRP_RELEASABLE flag
  perf/cgroup: Remove perf_put_cgroup()
  cgroup: remove redundant check in cgroup_ino()
  cpuset: simplify proc_cpuset_show()
  cgroup: simplify proc_cgroup_show()
  cgroup: use a per-cgroup work for release agent
  cgroup: remove bogus comments
  cgroup: remove redundant code in cgroup_rmdir()
  cgroup: remove some useless forward declarations
  cgroup: fix a typo in comment.

1 files changed, 53 insertions, 131 deletions

diff --git a/kernel/cgroup.c b/kernel/cgroup.c
index 3a73f995a81e..cab7dc4284dc 100644
--- a/kernel/cgroup.c
+++ b/kernel/cgroup.c
@@ -185,7 +185,6 @@ static int need_forkexit_callback __read_mostly;
 static struct cftype cgroup_dfl_base_files[];
 static struct cftype cgroup_legacy_base_files[];
 
-static void cgroup_put(struct cgroup *cgrp);
 static int rebind_subsystems(struct cgroup_root *dst_root,
                              unsigned int ss_mask);
 static int cgroup_destroy_locked(struct cgroup *cgrp);
@@ -195,7 +194,6 @@ static void css_release(struct percpu_ref *ref);
 static void kill_css(struct cgroup_subsys_state *css);
 static int cgroup_addrm_files(struct cgroup *cgrp, struct cftype cfts[],
                               bool is_add);
-static void cgroup_pidlist_destroy_all(struct cgroup *cgrp);
 
 /* IDR wrappers which synchronize using cgroup_idr_lock */
 static int cgroup_idr_alloc(struct idr *idr, void *ptr, int start, int end,
@@ -331,14 +329,6 @@ bool cgroup_is_descendant(struct cgroup *cgrp, struct cgroup *ancestor)
         return false;
 }
 
-static int cgroup_is_releasable(const struct cgroup *cgrp)
-{
-        const int bits =
-                (1 << CGRP_RELEASABLE) |
-                (1 << CGRP_NOTIFY_ON_RELEASE);
-        return (cgrp->flags & bits) == bits;
-}
-
 static int notify_on_release(const struct cgroup *cgrp)
 {
         return test_bit(CGRP_NOTIFY_ON_RELEASE, &cgrp->flags);
@@ -394,12 +384,7 @@ static int notify_on_release(const struct cgroup *cgrp)
                         ;                                               \
                 else
 
-/* the list of cgroups eligible for automatic release. Protected by
- * release_list_lock */
-static LIST_HEAD(release_list);
-static DEFINE_RAW_SPINLOCK(release_list_lock);
 static void cgroup_release_agent(struct work_struct *work);
-static DECLARE_WORK(release_agent_work, cgroup_release_agent);
 static void check_for_release(struct cgroup *cgrp);
 
 /*
@@ -498,7 +483,7 @@ static unsigned long css_set_hash(struct cgroup_subsys_state *css[])
         return key;
 }
 
-static void put_css_set_locked(struct css_set *cset, bool taskexit)
+static void put_css_set_locked(struct css_set *cset)
 {
         struct cgrp_cset_link *link, *tmp_link;
         struct cgroup_subsys *ss;
@@ -524,11 +509,7 @@ static void put_css_set_locked(struct css_set *cset, bool taskexit)
                 /* @cgrp can't go away while we're holding css_set_rwsem */
                 if (list_empty(&cgrp->cset_links)) {
                         cgroup_update_populated(cgrp, false);
-                        if (notify_on_release(cgrp)) {
-                                if (taskexit)
-                                        set_bit(CGRP_RELEASABLE, &cgrp->flags);
-                                check_for_release(cgrp);
-                        }
+                        check_for_release(cgrp);
                 }
 
                 kfree(link);
@@ -537,7 +518,7 @@ static void put_css_set_locked(struct css_set *cset, bool taskexit)
         kfree_rcu(cset, rcu_head);
 }
 
-static void put_css_set(struct css_set *cset, bool taskexit)
+static void put_css_set(struct css_set *cset)
 {
         /*
          * Ensure that the refcount doesn't hit zero while any readers
@@ -548,7 +529,7 @@ static void put_css_set(struct css_set *cset, bool taskexit)
                 return;
 
         down_write(&css_set_rwsem);
-        put_css_set_locked(cset, taskexit);
+        put_css_set_locked(cset);
         up_write(&css_set_rwsem);
 }
 
@@ -969,14 +950,6 @@ static struct cgroup *task_cgroup_from_root(struct task_struct *task,
  * knows that the cgroup won't be removed, as cgroup_rmdir()
  * needs that mutex.
  *
- * The fork and exit callbacks cgroup_fork() and cgroup_exit(), don't
- * (usually) take cgroup_mutex.  These are the two most performance
- * critical pieces of code here.  The exception occurs on cgroup_exit(),
- * when a task in a notify_on_release cgroup exits.  Then cgroup_mutex
- * is taken, and if the cgroup count is zero, a usermode call made
- * to the release agent with the name of the cgroup (path relative to
- * the root of cgroup file system) as the argument.
- *
  * A cgroup can only be deleted if both its 'count' of using tasks
  * is zero, and its list of 'children' cgroups is empty.  Since all
  * tasks in the system use _some_ cgroup, and since there is always at
@@ -1587,7 +1560,6 @@ static void init_cgroup_housekeeping(struct cgroup *cgrp)
         INIT_LIST_HEAD(&cgrp->self.sibling);
         INIT_LIST_HEAD(&cgrp->self.children);
         INIT_LIST_HEAD(&cgrp->cset_links);
-        INIT_LIST_HEAD(&cgrp->release_list);
         INIT_LIST_HEAD(&cgrp->pidlists);
         mutex_init(&cgrp->pidlist_mutex);
         cgrp->self.cgroup = cgrp;
@@ -1597,6 +1569,7 @@ static void init_cgroup_housekeeping(struct cgroup *cgrp)
                 INIT_LIST_HEAD(&cgrp->e_csets[ssid]);
 
         init_waitqueue_head(&cgrp->offline_waitq);
+        INIT_WORK(&cgrp->release_agent_work, cgroup_release_agent);
 }
 
 static void init_cgroup_root(struct cgroup_root *root,
@@ -2052,8 +2025,7 @@ static void cgroup_task_migrate(struct cgroup *old_cgrp,
          * task. As trading it for new_cset is protected by cgroup_mutex,
          * we're safe to drop it here; it will be freed under RCU.
          */
-        set_bit(CGRP_RELEASABLE, &old_cgrp->flags);
-        put_css_set_locked(old_cset, false);
+        put_css_set_locked(old_cset);
 }
 
 /**
@@ -2074,7 +2046,7 @@ static void cgroup_migrate_finish(struct list_head *preloaded_csets)
                 cset->mg_src_cgrp = NULL;
                 cset->mg_dst_cset = NULL;
                 list_del_init(&cset->mg_preload_node);
-                put_css_set_locked(cset, false);
+                put_css_set_locked(cset);
         }
         up_write(&css_set_rwsem);
 }
@@ -2168,8 +2140,8 @@ static int cgroup_migrate_prepare_dst(struct cgroup *dst_cgrp,
                 if (src_cset == dst_cset) {
                         src_cset->mg_src_cgrp = NULL;
                         list_del_init(&src_cset->mg_preload_node);
-                        put_css_set(src_cset, false);
-                        put_css_set(dst_cset, false);
+                        put_css_set(src_cset);
+                        put_css_set(dst_cset);
                         continue;
                 }
 
@@ -2178,7 +2150,7 @@ static int cgroup_migrate_prepare_dst(struct cgroup *dst_cgrp,
                 if (list_empty(&dst_cset->mg_preload_node))
                         list_add(&dst_cset->mg_preload_node, &csets);
                 else
-                        put_css_set(dst_cset, false);
+                        put_css_set(dst_cset);
         }
 
         list_splice_tail(&csets, preloaded_csets);
@@ -4173,7 +4145,6 @@ static u64 cgroup_read_notify_on_release(struct cgroup_subsys_state *css,
 static int cgroup_write_notify_on_release(struct cgroup_subsys_state *css,
                                           struct cftype *cft, u64 val)
 {
-        clear_bit(CGRP_RELEASABLE, &css->cgroup->flags);
         if (val)
                 set_bit(CGRP_NOTIFY_ON_RELEASE, &css->cgroup->flags);
         else
@@ -4351,6 +4322,7 @@ static void css_free_work_fn(struct work_struct *work)
                 /* cgroup free path */
                 atomic_dec(&cgrp->root->nr_cgrps);
                 cgroup_pidlist_destroy_all(cgrp);
+                cancel_work_sync(&cgrp->release_agent_work);
 
                 if (cgroup_parent(cgrp)) {
                         /*
@@ -4813,19 +4785,12 @@ static int cgroup_destroy_locked(struct cgroup *cgrp)
         for_each_css(css, ssid, cgrp)
                 kill_css(css);
 
-        /* CSS_ONLINE is clear, remove from ->release_list for the last time */
-        raw_spin_lock(&release_list_lock);
-        if (!list_empty(&cgrp->release_list))
-                list_del_init(&cgrp->release_list);
-        raw_spin_unlock(&release_list_lock);
-
         /*
          * Remove @cgrp directory along with the base files.  @cgrp has an
          * extra ref on its kn.
          */
         kernfs_remove(cgrp->kn);
 
-        set_bit(CGRP_RELEASABLE, &cgroup_parent(cgrp)->flags);
         check_for_release(cgroup_parent(cgrp));
 
         /* put the base reference */
@@ -4842,13 +4807,10 @@ static int cgroup_rmdir(struct kernfs_node *kn)
         cgrp = cgroup_kn_lock_live(kn);
         if (!cgrp)
                 return 0;
-        cgroup_get(cgrp);       /* for @kn->priv clearing */
 
         ret = cgroup_destroy_locked(cgrp);
 
         cgroup_kn_unlock(kn);
-
-        cgroup_put(cgrp);
         return ret;
 }
 
@@ -5052,12 +5014,9 @@ core_initcall(cgroup_wq_init);
  *  - Print task's cgroup paths into seq_file, one line for each hierarchy
  *  - Used for /proc/<pid>/cgroup.
  */
-
-/* TODO: Use a proper seq_file iterator */
-int proc_cgroup_show(struct seq_file *m, void *v)
+int proc_cgroup_show(struct seq_file *m, struct pid_namespace *ns,
+                     struct pid *pid, struct task_struct *tsk)
 {
-        struct pid *pid;
-        struct task_struct *tsk;
         char *buf, *path;
         int retval;
         struct cgroup_root *root;
@@ -5067,14 +5026,6 @@ int proc_cgroup_show(struct seq_file *m, void *v)
         if (!buf)
                 goto out;
 
-        retval = -ESRCH;
-        pid = m->private;
-        tsk = get_pid_task(pid, PIDTYPE_PID);
-        if (!tsk)
-                goto out_free;
-
-        retval = 0;
-
         mutex_lock(&cgroup_mutex);
         down_read(&css_set_rwsem);
 
@@ -5104,11 +5055,10 @@ int proc_cgroup_show(struct seq_file *m, void *v)
                 seq_putc(m, '\n');
         }
 
+        retval = 0;
 out_unlock:
         up_read(&css_set_rwsem);
         mutex_unlock(&cgroup_mutex);
-        put_task_struct(tsk);
-out_free:
         kfree(buf);
 out:
         return retval;
@@ -5179,7 +5129,7 @@ void cgroup_post_fork(struct task_struct *child)
         int i;
 
         /*
-         * This may race against cgroup_enable_task_cg_links().  As that
+         * This may race against cgroup_enable_task_cg_lists().  As that
          * function sets use_task_css_set_links before grabbing
          * tasklist_lock and we just went through tasklist_lock to add
          * @child, it's guaranteed that either we see the set
@@ -5194,7 +5144,7 @@ void cgroup_post_fork(struct task_struct *child)
          * when implementing operations which need to migrate all tasks of
          * a cgroup to another.
          *
-         * Note that if we lose to cgroup_enable_task_cg_links(), @child
+         * Note that if we lose to cgroup_enable_task_cg_lists(), @child
          * will remain in init_css_set.  This is safe because all tasks are
          * in the init_css_set before cg_links is enabled and there's no
          * operation which transfers all tasks out of init_css_set.
@@ -5278,30 +5228,14 @@ void cgroup_exit(struct task_struct *tsk)
         }
 
         if (put_cset)
-                put_css_set(cset, true);
+                put_css_set(cset);
 }
 
 static void check_for_release(struct cgroup *cgrp)
 {
-        if (cgroup_is_releasable(cgrp) && list_empty(&cgrp->cset_links) &&
-            !css_has_online_children(&cgrp->self)) {
-                /*
-                 * Control Group is currently removeable. If it's not
-                 * already queued for a userspace notification, queue
-                 * it now
-                 */
-                int need_schedule_work = 0;
-
-                raw_spin_lock(&release_list_lock);
-                if (!cgroup_is_dead(cgrp) &&
-                    list_empty(&cgrp->release_list)) {
-                        list_add(&cgrp->release_list, &release_list);
-                        need_schedule_work = 1;
-                }
-                raw_spin_unlock(&release_list_lock);
-                if (need_schedule_work)
-                        schedule_work(&release_agent_work);
-        }
+        if (notify_on_release(cgrp) && !cgroup_has_tasks(cgrp) &&
+            !css_has_online_children(&cgrp->self) && !cgroup_is_dead(cgrp))
+                schedule_work(&cgrp->release_agent_work);
 }
 
 /*
@@ -5329,52 +5263,39 @@ static void check_for_release(struct cgroup *cgrp)
  */
 static void cgroup_release_agent(struct work_struct *work)
 {
-        BUG_ON(work != &release_agent_work);
+        struct cgroup *cgrp =
+                container_of(work, struct cgroup, release_agent_work);
+        char *pathbuf = NULL, *agentbuf = NULL, *path;
+        char *argv[3], *envp[3];
+
         mutex_lock(&cgroup_mutex);
-        raw_spin_lock(&release_list_lock);
-        while (!list_empty(&release_list)) {
-                char *argv[3], *envp[3];
-                int i;
-                char *pathbuf = NULL, *agentbuf = NULL, *path;
-                struct cgroup *cgrp = list_entry(release_list.next,
-                                                    struct cgroup,
-                                                    release_list);
-                list_del_init(&cgrp->release_list);
-                raw_spin_unlock(&release_list_lock);
-                pathbuf = kmalloc(PATH_MAX, GFP_KERNEL);
-                if (!pathbuf)
-                        goto continue_free;
-                path = cgroup_path(cgrp, pathbuf, PATH_MAX);
-                if (!path)
-                        goto continue_free;
-                agentbuf = kstrdup(cgrp->root->release_agent_path, GFP_KERNEL);
-                if (!agentbuf)
-                        goto continue_free;
-
-                i = 0;
-                argv[i++] = agentbuf;
-                argv[i++] = path;
-                argv[i] = NULL;
-
-                i = 0;
-                /* minimal command environment */
-                envp[i++] = "HOME=/";
-                envp[i++] = "PATH=/sbin:/bin:/usr/sbin:/usr/bin";
-                envp[i] = NULL;
-
-                /* Drop the lock while we invoke the usermode helper,
-                 * since the exec could involve hitting disk and hence
-                 * be a slow process */
-                mutex_unlock(&cgroup_mutex);
-                call_usermodehelper(argv[0], argv, envp, UMH_WAIT_EXEC);
-                mutex_lock(&cgroup_mutex);
- continue_free:
-                kfree(pathbuf);
-                kfree(agentbuf);
-                raw_spin_lock(&release_list_lock);
-        }
-        raw_spin_unlock(&release_list_lock);
+
+        pathbuf = kmalloc(PATH_MAX, GFP_KERNEL);
+        agentbuf = kstrdup(cgrp->root->release_agent_path, GFP_KERNEL);
+        if (!pathbuf || !agentbuf)
+                goto out;
+
+        path = cgroup_path(cgrp, pathbuf, PATH_MAX);
+        if (!path)
+                goto out;
+
+        argv[0] = agentbuf;
+        argv[1] = path;
+        argv[2] = NULL;
+
+        /* minimal command environment */
+        envp[0] = "HOME=/";
+        envp[1] = "PATH=/sbin:/bin:/usr/sbin:/usr/bin";
+        envp[2] = NULL;
+
+        mutex_unlock(&cgroup_mutex);
+        call_usermodehelper(argv[0], argv, envp, UMH_WAIT_EXEC);
+        goto out_free;
+out:
         mutex_unlock(&cgroup_mutex);
+out_free:
+        kfree(agentbuf);
+        kfree(pathbuf);
 }
 
 static int __init cgroup_disable(char *str)
@@ -5562,7 +5483,8 @@ static int cgroup_css_links_read(struct seq_file *seq, void *v)
 
 static u64 releasable_read(struct cgroup_subsys_state *css, struct cftype *cft)
 {
-        return test_bit(CGRP_RELEASABLE, &css->cgroup->flags);
+        return (!cgroup_has_tasks(css->cgroup) &&
+                !css_has_online_children(&css->cgroup->self));
 }
 
 static struct cftype debug_files[] =  {