Merge tag 'pinctrl-v4.20-1' of git://git.kernel.org/pub/scm/linux/kernel/git/linusw...

[sfrench/cifs-2.6.git] / kernel / cgroup / cgroup.c

diff --git a/kernel/cgroup/cgroup.c b/kernel/cgroup/cgroup.c
index 4a3dae2a8283041b46d2c9ff981a51a7d5c2563e..4c1cf0969a80e9c63d111ab60e23b180f402cde0 100644 (file)
--- a/kernel/cgroup/cgroup.c
+++ b/kernel/cgroup/cgroup.c
@@ -492,7 +492,7 @@ 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)
  *
@@ -501,8 +501,8 @@ 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);
 
@@ -522,6 +522,35 @@ 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
@@ -604,10 +633,11 @@ 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
 
 /**
@@ -1006,7 +1036,7 @@ 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
@@ -3023,7 +3053,7 @@ 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.
         */