Merge branch 'for-4.21' of git://git.kernel.org/pub/scm/linux/kernel/git/tj/cgroup

[linux-2.6-microblaze.git] / kernel / cgroup / cgroup.c

diff --git a/kernel/cgroup/cgroup.c b/kernel/cgroup/cgroup.c
index 879c9f1..f31bd61 100644 (file)
--- a/kernel/cgroup/cgroup.c
+++ b/kernel/cgroup/cgroup.c
@@ -494,7 +494,7 @@ static struct cgroup_subsys_state *cgroup_tryget_css(struct cgroup *cgrp,
 }
 
 /**
- * cgroup_e_css - obtain a cgroup's effective css for the specified subsystem
+ * cgroup_e_css_by_mask - obtain a cgroup's effective css for the specified ss
  * @cgrp: the cgroup of interest
  * @ss: the subsystem of interest (%NULL returns @cgrp->self)
  *
@@ -503,8 +503,8 @@ static struct cgroup_subsys_state *cgroup_tryget_css(struct cgroup *cgrp,
  * enabled.  If @ss is associated with the hierarchy @cgrp is on, this
  * function is guaranteed to return non-NULL css.
  */
-static struct cgroup_subsys_state *cgroup_e_css(struct cgroup *cgrp,
-                                               struct cgroup_subsys *ss)
+static struct cgroup_subsys_state *cgroup_e_css_by_mask(struct cgroup *cgrp,
+                                                       struct cgroup_subsys *ss)
 {
        lockdep_assert_held(&cgroup_mutex);
 
@@ -524,6 +524,35 @@ static struct cgroup_subsys_state *cgroup_e_css(struct cgroup *cgrp,
        return cgroup_css(cgrp, ss);
 }
 
+/**
+ * cgroup_e_css - obtain a cgroup's effective css for the specified subsystem
+ * @cgrp: the cgroup of interest
+ * @ss: the subsystem of interest
+ *
+ * Find and get the effective css of @cgrp for @ss.  The effective css is
+ * defined as the matching css of the nearest ancestor including self which
+ * has @ss enabled.  If @ss is not mounted on the hierarchy @cgrp is on,
+ * the root css is returned, so this function always returns a valid css.
+ *
+ * The returned css is not guaranteed to be online, and therefore it is the
+ * callers responsiblity to tryget a reference for it.
+ */
+struct cgroup_subsys_state *cgroup_e_css(struct cgroup *cgrp,
+                                        struct cgroup_subsys *ss)
+{
+       struct cgroup_subsys_state *css;
+
+       do {
+               css = cgroup_css(cgrp, ss);
+
+               if (css)
+                       return css;
+               cgrp = cgroup_parent(cgrp);
+       } while (cgrp);
+
+       return init_css_set.subsys[ss->id];
+}
+
 /**
  * cgroup_get_e_css - get a cgroup's effective css for the specified subsystem
  * @cgrp: the cgroup of interest
@@ -606,10 +635,11 @@ EXPORT_SYMBOL_GPL(of_css);
  *
  * Should be called under cgroup_[tree_]mutex.
  */
-#define for_each_e_css(css, ssid, cgrp)                                        \
-       for ((ssid) = 0; (ssid) < CGROUP_SUBSYS_COUNT; (ssid)++)        \
-               if (!((css) = cgroup_e_css(cgrp, cgroup_subsys[(ssid)]))) \
-                       ;                                               \
+#define for_each_e_css(css, ssid, cgrp)                                            \
+       for ((ssid) = 0; (ssid) < CGROUP_SUBSYS_COUNT; (ssid)++)            \
+               if (!((css) = cgroup_e_css_by_mask(cgrp,                    \
+                                                  cgroup_subsys[(ssid)]))) \
+                       ;                                                   \
                else
 
 /**
@@ -1008,7 +1038,7 @@ static struct css_set *find_existing_css_set(struct css_set *old_cset,
                         * @ss is in this hierarchy, so we want the
                         * effective css from @cgrp.
                         */
-                       template[i] = cgroup_e_css(cgrp, ss);
+                       template[i] = cgroup_e_css_by_mask(cgrp, ss);
                } else {
                        /*
                         * @ss is not in this hierarchy, so we don't want
@@ -3028,7 +3058,7 @@ static int cgroup_apply_control(struct cgroup *cgrp)
                return ret;
 
        /*
-        * At this point, cgroup_e_css() results reflect the new csses
+        * At this point, cgroup_e_css_by_mask() results reflect the new csses
         * making the following cgroup_update_dfl_csses() properly update
         * css associations of all tasks in the subtree.
         */
@@ -5353,7 +5383,7 @@ int __init cgroup_init(void)
        cgroup_rstat_boot();
 
        /*
-        * The latency of the synchronize_sched() is too high for cgroups,
+        * The latency of the synchronize_rcu() is too high for cgroups,
         * avoid it at the cost of forcing all readers into the slow path.
         */
        rcu_sync_enter_start(&cgroup_threadgroup_rwsem.rss);