linux-kernel - [PATCH 1/6] cgroup: initialize cgrp->dentry before css

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Message-ID: <50F7B040.2020906@huawei.com>
Date:	Thu, 17 Jan 2013 16:03:12 +0800
From:	Li Zefan <lizefan@...wei.com>
To:	Tejun Heo <tj@...nel.org>
CC:	Peter Zijlstra <peterz@...radead.org>,
	Ingo Molnar <mingo@...nel.org>,
	LKML <linux-kernel@...r.kernel.org>,
	Cgroups <cgroups@...r.kernel.org>
Subject: [PATCH 1/6] cgroup: initialize cgrp->dentry before css_alloc()

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

(Well, it's not true, because dummptop.dentry is always NULL)

Signed-off-by: Li Zefan <lizefan@...wei.com>
---
 kernel/cgroup.c | 7 ++++---
 1 file changed, 4 insertions(+), 3 deletions(-)

diff --git a/kernel/cgroup.c b/kernel/cgroup.c
index a893985..23a0ce1 100644
--- a/kernel/cgroup.c
+++ b/kernel/cgroup.c
@@ -1764,7 +1764,7 @@ 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
@@ -4150,6 +4150,9 @@ 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;
@@ -4187,8 +4190,6 @@ 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++;
-- 
1.8.0.2

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