cgroup: initialize cgrp->dentry before css_alloc()

With this change, we're guaranteed that cgroup_path() won't see NULL
cgrp->dentry, and thus we can remove the NULL check in it.

(Well, it's not strictly true, because dummptop.dentry is always NULL
 but we already handle that separately.)

Signed-off-by: Li Zefan <lizefan@huawei.com>
Signed-off-by: Tejun Heo <tj@kernel.org>

1 files changed, 4 insertions, 3 deletions

diff --git a/kernel/cgroup.c b/kernel/cgroup.c
index 8da9048078c5..a04932281bc9 100644
--- a/kernel/cgroup.c
+++ b/kernel/cgroup.c
@@ -1767,7 +1767,7 @@ int cgroup_path(const struct cgroup *cgrp, char *buf, int buflen)
         rcu_lockdep_assert(rcu_read_lock_held() || cgroup_lock_is_held(),
                            "cgroup_path() called without proper locking");
 
-        if (!dentry || cgrp == dummytop) {
+        if (cgrp == dummytop) {
                 /*
                  * Inactive subsystems have no dentry for their root
                  * cgroup
@@ -4153,6 +4153,9 @@ static long cgroup_create(struct cgroup *parent, struct dentry *dentry,
 
         init_cgroup_housekeeping(cgrp);
 
+        dentry->d_fsdata = cgrp;
+        cgrp->dentry = dentry;
+
         cgrp->parent = parent;
         cgrp->root = parent->root;
         cgrp->top_cgroup = parent->top_cgroup;
@@ -4190,8 +4193,6 @@ static long cgroup_create(struct cgroup *parent, struct dentry *dentry,
         lockdep_assert_held(&dentry->d_inode->i_mutex);
 
         /* allocation complete, commit to creation */
-        dentry->d_fsdata = cgrp;
-        cgrp->dentry = dentry;
         list_add_tail(&cgrp->allcg_node, &root->allcg_list);
         list_add_tail_rcu(&cgrp->sibling, &cgrp->parent->children);
         root->number_of_cgroups++;