lkml.org 
[lkml]   [2014]   [Jan]   [28]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
Patch in this message
/
From
Subject[PATCH 5/8] cgroup: make cgroup hold onto its kernfs_node
Date
cgroup currently releases its kernfs_node when it gets removed.  While
not buggy, this makes cgroup->kn access rules complicated than
necessary and leads to things like get/put protection around
kernfs_remove() in cgroup_destroy_locked(). In addition, we want to
use kernfs_name/path() and friends but also want to be able to
determine a cgroup's name between removal and release.

This patch makes cgroup hold onto its kernfs_node until freed so that
cgroup->kn is always accessible.

Signed-off-by: Tejun Heo <tj@kernel.org>
---
kernel/cgroup.c | 16 +++++++++-------
1 file changed, 9 insertions(+), 7 deletions(-)

diff --git a/kernel/cgroup.c b/kernel/cgroup.c
index 5d015c1..3e4df3c 100644
--- a/kernel/cgroup.c
+++ b/kernel/cgroup.c
@@ -957,6 +957,8 @@ static void cgroup_free_fn(struct work_struct *work)

cgroup_pidlist_destroy_all(cgrp);

+ kernfs_put(cgrp->kn);
+
kfree(rcu_dereference_raw(cgrp->name));
kfree(cgrp);
}
@@ -3768,6 +3770,12 @@ static long cgroup_create(struct cgroup *parent, const char *name_str,
}
cgrp->kn = kn;

+ /*
+ * This extra ref will be put in cgroup_free_fn() and guarantees
+ * that @cgrp->kn is always accessible.
+ */
+ kernfs_get(kn);
+
cgrp->serial_nr = cgroup_serial_nr_next++;

/* allocation complete, commit to creation */
@@ -3948,7 +3956,6 @@ static int cgroup_destroy_locked(struct cgroup *cgrp)
{
struct cgroup *child;
struct cgroup_subsys_state *css;
- struct kernfs_node *kn;
bool empty;
int ssid;

@@ -4026,13 +4033,8 @@ static int cgroup_destroy_locked(struct cgroup *cgrp)
* cgrp->kn->priv backpointer, which should be cleared after all
* files under it have been removed.
*/
- kn = cgrp->kn;
- kernfs_get(kn);
-
- kernfs_remove(cgrp->kn);
-
+ kernfs_remove(cgrp->kn); /* @cgrp has an extra ref on its kn */
RCU_INIT_POINTER(cgrp->kn->priv, NULL);
- kernfs_put(kn);

mutex_lock(&cgroup_mutex);

--
1.8.5.3


\
 
 \ /
  Last update: 2014-01-29 01:41    [W:0.069 / U:0.888 seconds]
©2003-2020 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site