cgroup: cosmetic updates to rebind_subsystems()

* Use local variables @scgrp and @dcgrp for @src_root->cgrp and
  @dst_root->cgrp respectively.

* Use initializers to set @src_root and @css in the inner bind loop.

Signed-off-by: Tejun Heo <tj@kernel.org>
Cc: Li Zefan <lizefan@huawei.com>
Cc: Johannes Weiner <hannes@cmpxchg.org>

diff --git a/kernel/cgroup.c b/kernel/cgroup.c
index f09bab1cf27581592b292d5bf11870162f9138cb..a4ff4965e53b44404226eccb9e95f150402a6c09 100644 (file)
--- a/kernel/cgroup.c
+++ b/kernel/cgroup.c
@@ -1366,6 +1366,7 @@ err:
 static int rebind_subsystems(struct cgroup_root *dst_root,
                             unsigned long ss_mask)
 {
+       struct cgroup *dcgrp = &dst_root->cgrp;
        struct cgroup_subsys *ss;
        unsigned long tmp_ss_mask;
        int ssid, i, ret;
@@ -1387,7 +1388,7 @@ static int rebind_subsystems(struct cgroup_root *dst_root,
        if (dst_root == &cgrp_dfl_root)
                tmp_ss_mask &= ~cgrp_dfl_root_inhibit_ss_mask;
 
-       ret = cgroup_populate_dir(&dst_root->cgrp, tmp_ss_mask);
+       ret = cgroup_populate_dir(dcgrp, tmp_ss_mask);
        if (ret) {
                if (dst_root != &cgrp_dfl_root)
                        return ret;
@@ -1413,37 +1414,35 @@ static int rebind_subsystems(struct cgroup_root *dst_root,
                cgroup_clear_dir(&ss->root->cgrp, 1 << ssid);
 
        for_each_subsys_which(ss, ssid, &ss_mask) {
-               struct cgroup_root *src_root;
-               struct cgroup_subsys_state *css;
+               struct cgroup_root *src_root = ss->root;
+               struct cgroup *scgrp = &src_root->cgrp;
+               struct cgroup_subsys_state *css = cgroup_css(scgrp, ss);
                struct css_set *cset;
 
-               src_root = ss->root;
-               css = cgroup_css(&src_root->cgrp, ss);
-
-               WARN_ON(!css || cgroup_css(&dst_root->cgrp, ss));
+               WARN_ON(!css || cgroup_css(dcgrp, ss));
 
-               RCU_INIT_POINTER(src_root->cgrp.subsys[ssid], NULL);
-               rcu_assign_pointer(dst_root->cgrp.subsys[ssid], css);
+               RCU_INIT_POINTER(scgrp->subsys[ssid], NULL);
+               rcu_assign_pointer(dcgrp->subsys[ssid], css);
                ss->root = dst_root;
-               css->cgroup = &dst_root->cgrp;
+               css->cgroup = dcgrp;
 
                down_write(&css_set_rwsem);
                hash_for_each(css_set_table, i, cset, hlist)
                        list_move_tail(&cset->e_cset_node[ss->id],
-                                      &dst_root->cgrp.e_csets[ss->id]);
+                                      &dcgrp->e_csets[ss->id]);
                up_write(&css_set_rwsem);
 
                src_root->subsys_mask &= ~(1 << ssid);
-               src_root->cgrp.subtree_control &= ~(1 << ssid);
-               cgroup_refresh_child_subsys_mask(&src_root->cgrp);
+               scgrp->subtree_control &= ~(1 << ssid);
+               cgroup_refresh_child_subsys_mask(scgrp);
 
                /* default hierarchy doesn't enable controllers by default */
                dst_root->subsys_mask |= 1 << ssid;
                if (dst_root == &cgrp_dfl_root) {
                        static_branch_enable(cgroup_subsys_on_dfl_key[ssid]);
                } else {
-                       dst_root->cgrp.subtree_control |= 1 << ssid;
-                       cgroup_refresh_child_subsys_mask(&dst_root->cgrp);
+                       dcgrp->subtree_control |= 1 << ssid;
+                       cgroup_refresh_child_subsys_mask(dcgrp);
                        static_branch_disable(cgroup_subsys_on_dfl_key[ssid]);
                }
 
@@ -1451,7 +1450,7 @@ static int rebind_subsystems(struct cgroup_root *dst_root,
                        ss->bind(css);
        }
 
-       kernfs_activate(dst_root->cgrp.kn);
+       kernfs_activate(dcgrp->kn);
        return 0;
 }