cgroups: introduce link_css_set() to remove duplicate code

Add a common function link_css_set() to link a css_set to a cgroup.

Signed-off-by: Li Zefan <lizf@cn.fujitsu.com>
Cc: Paul Menage <menage@google.com>
Cc: KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com>
Cc: Balbir Singh <balbir@in.ibm.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

1 files changed, 30 insertions, 38 deletions

diff --git a/kernel/cgroup.c b/kernel/cgroup.c
index abf7248f501a..4c475ce4e222 100644
--- a/kernel/cgroup.c
+++ b/kernel/cgroup.c
@@ -384,6 +384,25 @@ static int allocate_cg_links(int count, struct list_head *tmp)
         return 0;
 }
 
+/**
+ * link_css_set - a helper function to link a css_set to a cgroup
+ * @tmp_cg_links: cg_cgroup_link objects allocated by allocate_cg_links()
+ * @cg: the css_set to be linked
+ * @cgrp: the destination cgroup
+ */
+static void link_css_set(struct list_head *tmp_cg_links,
+                         struct css_set *cg, struct cgroup *cgrp)
+{
+        struct cg_cgroup_link *link;
+
+        BUG_ON(list_empty(tmp_cg_links));
+        link = list_first_entry(tmp_cg_links, struct cg_cgroup_link,
+                                cgrp_link_list);
+        link->cg = cg;
+        list_move(&link->cgrp_link_list, &cgrp->css_sets);
+        list_add(&link->cg_link_list, &cg->cg_links);
+}
+
 /*
  * find_css_set() takes an existing cgroup group and a
  * cgroup object, and returns a css_set object that's
@@ -399,7 +418,6 @@ static struct css_set *find_css_set(
         int i;
 
         struct list_head tmp_cg_links;
-        struct cg_cgroup_link *link;
 
         struct hlist_head *hhead;
 
@@ -444,26 +462,11 @@ static struct css_set *find_css_set(
                  * only do it for the first subsystem in each
                  * hierarchy
                  */
-                if (ss->root->subsys_list.next == &ss->sibling) {
-                        BUG_ON(list_empty(&tmp_cg_links));
-                        link = list_entry(tmp_cg_links.next,
-                                          struct cg_cgroup_link,
-                                          cgrp_link_list);
-                        list_del(&link->cgrp_link_list);
-                        list_add(&link->cgrp_link_list, &cgrp->css_sets);
-                        link->cg = res;
-                        list_add(&link->cg_link_list, &res->cg_links);
-                }
-        }
-        if (list_empty(&rootnode.subsys_list)) {
-                link = list_entry(tmp_cg_links.next,
-                                  struct cg_cgroup_link,
-                                  cgrp_link_list);
-                list_del(&link->cgrp_link_list);
-                list_add(&link->cgrp_link_list, &dummytop->css_sets);
-                link->cg = res;
-                list_add(&link->cg_link_list, &res->cg_links);
+                if (ss->root->subsys_list.next == &ss->sibling)
+                        link_css_set(&tmp_cg_links, res, cgrp);
         }
+        if (list_empty(&rootnode.subsys_list))
+                link_css_set(&tmp_cg_links, res, dummytop);
 
         BUG_ON(!list_empty(&tmp_cg_links));
 
@@ -988,7 +991,7 @@ static int cgroup_get_sb(struct file_system_type *fs_type,
                 root = NULL;
         } else {
                 /* New superblock */
-                struct cgroup *cgrp = &root->top_cgroup;
+                struct cgroup *root_cgrp = &root->top_cgroup;
                 struct inode *inode;
                 int i;
 
@@ -1029,7 +1032,7 @@ static int cgroup_get_sb(struct file_system_type *fs_type,
                 list_add(&root->root_list, &roots);
                 root_count++;
 
-                sb->s_root->d_fsdata = &root->top_cgroup;
+                sb->s_root->d_fsdata = root_cgrp;
                 root->top_cgroup.dentry = sb->s_root;
 
                 /* Link the top cgroup in this hierarchy into all
@@ -1040,29 +1043,18 @@ static int cgroup_get_sb(struct file_system_type *fs_type,
                         struct hlist_node *node;
                         struct css_set *cg;
 
-                        hlist_for_each_entry(cg, node, hhead, hlist) {
-                                struct cg_cgroup_link *link;
-
-                                BUG_ON(list_empty(&tmp_cg_links));
-                                link = list_entry(tmp_cg_links.next,
-                                                  struct cg_cgroup_link,
-                                                  cgrp_link_list);
-                                list_del(&link->cgrp_link_list);
-                                link->cg = cg;
-                                list_add(&link->cgrp_link_list,
-                                         &root->top_cgroup.css_sets);
-                                list_add(&link->cg_link_list, &cg->cg_links);
-                        }
+                        hlist_for_each_entry(cg, node, hhead, hlist)
+                                link_css_set(&tmp_cg_links, cg, root_cgrp);
                 }
                 write_unlock(&css_set_lock);
 
                 free_cg_links(&tmp_cg_links);
 
-                BUG_ON(!list_empty(&cgrp->sibling));
-                BUG_ON(!list_empty(&cgrp->children));
+                BUG_ON(!list_empty(&root_cgrp->sibling));
+                BUG_ON(!list_empty(&root_cgrp->children));
                 BUG_ON(root->number_of_cgroups != 1);
 
-                cgroup_populate_dir(cgrp);
+                cgroup_populate_dir(root_cgrp);
                 mutex_unlock(&inode->i_mutex);
                 mutex_unlock(&cgroup_mutex);
         }