Merge branch 'for-3.6' of git://git.kernel.org/pub/scm/linux/kernel/git/tj/cgroup

Pull cgroup changes from Tejun Heo: "Nothing too interesting. A minor bug fix and some cleanups." * 'for-3.6' of git://git.kernel.org/pub/scm/linux/kernel/git/tj/cgroup: cgroup: Update remount documentation cgroup: cgroup_rm_files() was calling simple_unlink() with the wrong inode cgroup: Remove populate() documentation cgroup: remove hierarchy_mutex

Merge branch 'for-3.6' of git://git.kernel.org/pub/scm/linux/kernel/git/tj/cgroup
Pull cgroup changes from Tejun Heo: "Nothing too interesting. A minor bug fix and some cleanups." * 'for-3.6' of git://git.kernel.org/pub/scm/linux/kernel/git/tj/cgroup: cgroup: Update remount documentation cgroup: cgroup_rm_files() was calling simple_unlink() with the wrong inode cgroup: Remove populate() documentation cgroup: remove hierarchy_mutex
Linus Torvalds
2 parents a08489c569 9a8054aa5d
Showing 3 changed files Side-by-side Diff
Documentation/cgroups/cgroups.txt
include/linux/cgroup.h
kernel/cgroup.c
@@ -370,16 +370,13 @@
 subsystems, type:
 # mount -t cgroup -o cpuset,memory hier1 /sys/fs/cgroup/rg1
  
-To change the set of subsystems bound to a mounted hierarchy, just
-remount with different options:
-# mount -o remount,cpuset,blkio hier1 /sys/fs/cgroup/rg1
+While remounting cgroups is currently supported, it is not recommend
+to use it. Remounting allows changing bound subsystems and
+release_agent. Rebinding is hardly useful as it only works when the
+hierarchy is empty and release_agent itself should be replaced with
+conventional fsnotify. The support for remounting will be removed in
+the future.
  
-Now memory is removed from the hierarchy and blkio is added.
-
-Note this will add blkio to the hierarchy but won't remove memory or
-cpuset, because the new options are appended to the old ones:
-# mount -o remount,blkio /sys/fs/cgroup/rg1
-
 To Specify a hierarchy's release_agent:
 # mount -t cgroup -o cpuset,release_agent="/sbin/cpuset_release_agent" \
   xxx /sys/fs/cgroup/rg1
@@ -637,16 +634,6 @@
  
 Called during task exit.
  
-int populate(struct cgroup *cgrp)
-(cgroup_mutex held by caller)
-
-Called after creation of a cgroup to allow a subsystem to populate
-the cgroup directory with file entries.  The subsystem should make
-calls to cgroup_add_file() with objects of type cftype (see
-include/linux/cgroup.h for details).  Note that although this
-method can return an error code, the error code is currently not
-always handled well.
-
 void post_clone(struct cgroup *cgrp)
 (cgroup_mutex held by caller)
  
@@ -656,7 +643,7 @@
 up.
  
 void bind(struct cgroup *root)
-(cgroup_mutex and ss->hierarchy_mutex held by caller)
+(cgroup_mutex held by caller)
  
 Called when a cgroup subsystem is rebound to a different hierarchy
 and root cgroup. Currently this will only involve movement between
@@ -500,21 +500,8 @@
 	const char *name;
  
 	/*
-	 * Protects sibling/children links of cgroups in this
-	 * hierarchy, plus protects which hierarchy (or none) the
-	 * subsystem is a part of (i.e. root/sibling).  To avoid
-	 * potential deadlocks, the following operations should not be
-	 * undertaken while holding any hierarchy_mutex:
-	 *
-	 * - allocating memory
-	 * - initiating hotplug events
-	 */
-	struct mutex hierarchy_mutex;
-	struct lock_class_key subsys_key;
-
-	/*
 	 * Link to parent, and list entry in parent's children.
-	 * Protected by this->hierarchy_mutex and cgroup_lock()
+	 * Protected by cgroup_lock()
 	 */
 	struct cgroupfs_root *root;
 	struct list_head sibling;
@@ -602,7 +589,7 @@
  * the lifetime of cgroup_subsys_state is subsys's matter.
  *
  * Looking up and scanning function should be called under rcu_read_lock().
- * Taking cgroup_mutex()/hierarchy_mutex() is not necessary for following calls.
+ * Taking cgroup_mutex is not necessary for following calls.
  * But the css returned by this routine can be "not populated yet" or "being
  * destroyed". The caller should check css and cgroup's status.
  */
@@ -954,7 +954,7 @@
  
 		dget(d);
 		d_delete(d);
-		simple_unlink(d->d_inode, d);
+		simple_unlink(cgrp->dentry->d_inode, d);
 		list_del_init(&cfe->node);
 		dput(d);
  
  
  
  
@@ -1068,28 +1068,24 @@
 			BUG_ON(cgrp->subsys[i]);
 			BUG_ON(!dummytop->subsys[i]);
 			BUG_ON(dummytop->subsys[i]->cgroup != dummytop);
-			mutex_lock(&ss->hierarchy_mutex);
 			cgrp->subsys[i] = dummytop->subsys[i];
 			cgrp->subsys[i]->cgroup = cgrp;
 			list_move(&ss->sibling, &root->subsys_list);
 			ss->root = root;
 			if (ss->bind)
 				ss->bind(cgrp);
-			mutex_unlock(&ss->hierarchy_mutex);
 			/* refcount was already taken, and we're keeping it */
 		} else if (bit & removed_bits) {
 			/* We're removing this subsystem */
 			BUG_ON(ss == NULL);
 			BUG_ON(cgrp->subsys[i] != dummytop->subsys[i]);
 			BUG_ON(cgrp->subsys[i]->cgroup != cgrp);
-			mutex_lock(&ss->hierarchy_mutex);
 			if (ss->bind)
 				ss->bind(dummytop);
 			dummytop->subsys[i]->cgroup = dummytop;
 			cgrp->subsys[i] = NULL;
 			subsys[i]->root = &rootnode;
 			list_move(&ss->sibling, &rootnode.subsys_list);
-			mutex_unlock(&ss->hierarchy_mutex);
 			/* subsystem is now free - drop reference on module */
 			module_put(ss->module);
 		} else if (bit & final_bits) {
@@ -3915,37 +3911,6 @@
 		set_bit(CSS_CLEAR_CSS_REFS, &css->flags);
 }
  
-static void cgroup_lock_hierarchy(struct cgroupfs_root *root)
-{
-	/* We need to take each hierarchy_mutex in a consistent order */
-	int i;
-
-	/*
-	 * No worry about a race with rebind_subsystems that might mess up the
-	 * locking order, since both parties are under cgroup_mutex.
-	 */
-	for (i = 0; i < CGROUP_SUBSYS_COUNT; i++) {
-		struct cgroup_subsys *ss = subsys[i];
-		if (ss == NULL)
-			continue;
-		if (ss->root == root)
-			mutex_lock(&ss->hierarchy_mutex);
-	}
-}
-
-static void cgroup_unlock_hierarchy(struct cgroupfs_root *root)
-{
-	int i;
-
-	for (i = 0; i < CGROUP_SUBSYS_COUNT; i++) {
-		struct cgroup_subsys *ss = subsys[i];
-		if (ss == NULL)
-			continue;
-		if (ss->root == root)
-			mutex_unlock(&ss->hierarchy_mutex);
-	}
-}
-
 /*
  * cgroup_create - create a cgroup
  * @parent: cgroup that will be parent of the new cgroup
  
@@ -4006,9 +3971,7 @@
 			ss->post_clone(cgrp);
 	}
  
-	cgroup_lock_hierarchy(root);
 	list_add(&cgrp->sibling, &cgrp->parent->children);
-	cgroup_unlock_hierarchy(root);
 	root->number_of_cgroups++;
  
 	err = cgroup_create_dir(cgrp, dentry, mode);
  
@@ -4035,9 +3998,7 @@
  
  err_remove:
  
-	cgroup_lock_hierarchy(root);
 	list_del(&cgrp->sibling);
-	cgroup_unlock_hierarchy(root);
 	root->number_of_cgroups--;
  
  err_destroy:
  
@@ -4245,10 +4206,8 @@
 		list_del_init(&cgrp->release_list);
 	raw_spin_unlock(&release_list_lock);
  
-	cgroup_lock_hierarchy(cgrp->root);
 	/* delete this cgroup from parent->children */
 	list_del_init(&cgrp->sibling);
-	cgroup_unlock_hierarchy(cgrp->root);
  
 	list_del_init(&cgrp->allcg_node);
  
@@ -4322,8 +4281,6 @@
 	 * need to invoke fork callbacks here. */
 	BUG_ON(!list_empty(&init_task.tasks));
  
-	mutex_init(&ss->hierarchy_mutex);
-	lockdep_set_class(&ss->hierarchy_mutex, &ss->subsys_key);
 	ss->active = 1;
  
 	/* this function shouldn't be used with modular subsystems, since they
@@ -4450,8 +4407,6 @@
 	}
 	write_unlock(&css_set_lock);
  
-	mutex_init(&ss->hierarchy_mutex);
-	lockdep_set_class(&ss->hierarchy_mutex, &ss->subsys_key);
 	ss->active = 1;
  
 	/* success! */
...	...	@@ -370,16 +370,13 @@
370	370	subsystems, type:
371	371	# mount -t cgroup -o cpuset,memory hier1 /sys/fs/cgroup/rg1
372	372
373		-To change the set of subsystems bound to a mounted hierarchy, just
374		-remount with different options:
375		-# mount -o remount,cpuset,blkio hier1 /sys/fs/cgroup/rg1
	373	+While remounting cgroups is currently supported, it is not recommend
	374	+to use it. Remounting allows changing bound subsystems and
	375	+release_agent. Rebinding is hardly useful as it only works when the
	376	+hierarchy is empty and release_agent itself should be replaced with
	377	+conventional fsnotify. The support for remounting will be removed in
	378	+the future.
376	379
377		-Now memory is removed from the hierarchy and blkio is added.
378		-
379		-Note this will add blkio to the hierarchy but won't remove memory or
380		-cpuset, because the new options are appended to the old ones:
381		-# mount -o remount,blkio /sys/fs/cgroup/rg1
382		-
383	380	To Specify a hierarchy's release_agent:
384	381	# mount -t cgroup -o cpuset,release_agent="/sbin/cpuset_release_agent" \
385	382	xxx /sys/fs/cgroup/rg1
...	...	@@ -637,16 +634,6 @@
637	634
638	635	Called during task exit.
639	636
640		-int populate(struct cgroup *cgrp)
641		-(cgroup_mutex held by caller)
642		-
643		-Called after creation of a cgroup to allow a subsystem to populate
644		-the cgroup directory with file entries. The subsystem should make
645		-calls to cgroup_add_file() with objects of type cftype (see
646		-include/linux/cgroup.h for details). Note that although this
647		-method can return an error code, the error code is currently not
648		-always handled well.
649		-
650	637	void post_clone(struct cgroup *cgrp)
651	638	(cgroup_mutex held by caller)
652	639
...	...	@@ -656,7 +643,7 @@
656	643	up.
657	644
658	645	void bind(struct cgroup *root)
659		-(cgroup_mutex and ss->hierarchy_mutex held by caller)
	646	+(cgroup_mutex held by caller)
660	647
661	648	Called when a cgroup subsystem is rebound to a different hierarchy
662	649	and root cgroup. Currently this will only involve movement between
...	...	@@ -500,21 +500,8 @@
500	500	const char *name;
501	501
502	502	/*
503		- * Protects sibling/children links of cgroups in this
504		- * hierarchy, plus protects which hierarchy (or none) the
505		- * subsystem is a part of (i.e. root/sibling). To avoid
506		- * potential deadlocks, the following operations should not be
507		- * undertaken while holding any hierarchy_mutex:
508		- *
509		- * - allocating memory
510		- * - initiating hotplug events
511		- */
512		- struct mutex hierarchy_mutex;
513		- struct lock_class_key subsys_key;
514		-
515		- /*
516	503	* Link to parent, and list entry in parent's children.
517		- * Protected by this->hierarchy_mutex and cgroup_lock()
	504	+ * Protected by cgroup_lock()
518	505	*/
519	506	struct cgroupfs_root *root;
520	507	struct list_head sibling;
...	...	@@ -602,7 +589,7 @@
602	589	* the lifetime of cgroup_subsys_state is subsys's matter.
603	590	*
604	591	* Looking up and scanning function should be called under rcu_read_lock().
605		- * Taking cgroup_mutex()/hierarchy_mutex() is not necessary for following calls.
	592	+ * Taking cgroup_mutex is not necessary for following calls.
606	593	* But the css returned by this routine can be "not populated yet" or "being
607	594	* destroyed". The caller should check css and cgroup's status.
608	595	*/
...	...	@@ -954,7 +954,7 @@
954	954
955	955	dget(d);
956	956	d_delete(d);
957		- simple_unlink(d->d_inode, d);
	957	+ simple_unlink(cgrp->dentry->d_inode, d);
958	958	list_del_init(&cfe->node);
959	959	dput(d);
960	960
961	961
962	962
963	963
...	...	@@ -1068,28 +1068,24 @@
1068	1068	BUG_ON(cgrp->subsys[i]);
1069	1069	BUG_ON(!dummytop->subsys[i]);
1070	1070	BUG_ON(dummytop->subsys[i]->cgroup != dummytop);
1071		- mutex_lock(&ss->hierarchy_mutex);
1072	1071	cgrp->subsys[i] = dummytop->subsys[i];
1073	1072	cgrp->subsys[i]->cgroup = cgrp;
1074	1073	list_move(&ss->sibling, &root->subsys_list);
1075	1074	ss->root = root;
1076	1075	if (ss->bind)
1077	1076	ss->bind(cgrp);
1078		- mutex_unlock(&ss->hierarchy_mutex);
1079	1077	/* refcount was already taken, and we're keeping it */
1080	1078	} else if (bit & removed_bits) {
1081	1079	/* We're removing this subsystem */
1082	1080	BUG_ON(ss == NULL);
1083	1081	BUG_ON(cgrp->subsys[i] != dummytop->subsys[i]);
1084	1082	BUG_ON(cgrp->subsys[i]->cgroup != cgrp);
1085		- mutex_lock(&ss->hierarchy_mutex);
1086	1083	if (ss->bind)
1087	1084	ss->bind(dummytop);
1088	1085	dummytop->subsys[i]->cgroup = dummytop;
1089	1086	cgrp->subsys[i] = NULL;
1090	1087	subsys[i]->root = &rootnode;
1091	1088	list_move(&ss->sibling, &rootnode.subsys_list);
1092		- mutex_unlock(&ss->hierarchy_mutex);
1093	1089	/* subsystem is now free - drop reference on module */
1094	1090	module_put(ss->module);
1095	1091	} else if (bit & final_bits) {
...	...	@@ -3915,37 +3911,6 @@
3915	3911	set_bit(CSS_CLEAR_CSS_REFS, &css->flags);
3916	3912	}
3917	3913
3918		-static void cgroup_lock_hierarchy(struct cgroupfs_root *root)
3919		-{
3920		- /* We need to take each hierarchy_mutex in a consistent order */
3921		- int i;
3922		-
3923		- /*
3924		- * No worry about a race with rebind_subsystems that might mess up the
3925		- * locking order, since both parties are under cgroup_mutex.
3926		- */
3927		- for (i = 0; i < CGROUP_SUBSYS_COUNT; i++) {
3928		- struct cgroup_subsys *ss = subsys[i];
3929		- if (ss == NULL)
3930		- continue;
3931		- if (ss->root == root)
3932		- mutex_lock(&ss->hierarchy_mutex);
3933		- }
3934		-}
3935		-
3936		-static void cgroup_unlock_hierarchy(struct cgroupfs_root *root)
3937		-{
3938		- int i;
3939		-
3940		- for (i = 0; i < CGROUP_SUBSYS_COUNT; i++) {
3941		- struct cgroup_subsys *ss = subsys[i];
3942		- if (ss == NULL)
3943		- continue;
3944		- if (ss->root == root)
3945		- mutex_unlock(&ss->hierarchy_mutex);
3946		- }
3947		-}
3948		-
3949	3914	/*
3950	3915	* cgroup_create - create a cgroup
3951	3916	* @parent: cgroup that will be parent of the new cgroup
3952	3917
...	...	@@ -4006,9 +3971,7 @@
4006	3971	ss->post_clone(cgrp);
4007	3972	}
4008	3973
4009		- cgroup_lock_hierarchy(root);
4010	3974	list_add(&cgrp->sibling, &cgrp->parent->children);
4011		- cgroup_unlock_hierarchy(root);
4012	3975	root->number_of_cgroups++;
4013	3976
4014	3977	err = cgroup_create_dir(cgrp, dentry, mode);
4015	3978
...	...	@@ -4035,9 +3998,7 @@
4035	3998
4036	3999	err_remove:
4037	4000
4038		- cgroup_lock_hierarchy(root);
4039	4001	list_del(&cgrp->sibling);
4040		- cgroup_unlock_hierarchy(root);
4041	4002	root->number_of_cgroups--;
4042	4003
4043	4004	err_destroy:
4044	4005
...	...	@@ -4245,10 +4206,8 @@
4245	4206	list_del_init(&cgrp->release_list);
4246	4207	raw_spin_unlock(&release_list_lock);
4247	4208
4248		- cgroup_lock_hierarchy(cgrp->root);
4249	4209	/* delete this cgroup from parent->children */
4250	4210	list_del_init(&cgrp->sibling);
4251		- cgroup_unlock_hierarchy(cgrp->root);
4252	4211
4253	4212	list_del_init(&cgrp->allcg_node);
4254	4213
...	...	@@ -4322,8 +4281,6 @@
4322	4281	* need to invoke fork callbacks here. */
4323	4282	BUG_ON(!list_empty(&init_task.tasks));
4324	4283
4325		- mutex_init(&ss->hierarchy_mutex);
4326		- lockdep_set_class(&ss->hierarchy_mutex, &ss->subsys_key);
4327	4284	ss->active = 1;
4328	4285
4329	4286	/* this function shouldn't be used with modular subsystems, since they
...	...	@@ -4450,8 +4407,6 @@
4450	4407	}
4451	4408	write_unlock(&css_set_lock);
4452	4409
4453		- mutex_init(&ss->hierarchy_mutex);
4454		- lockdep_set_class(&ss->hierarchy_mutex, &ss->subsys_key);
4455	4410	ss->active = 1;
4456	4411
4457	4412	/* success! */