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Commit 47c59803 authored by Lai Jiangshan's avatar Lai Jiangshan Committed by Linus Torvalds
Browse files

devcgroup: remove spin_lock() 



Since we introduced rcu for read side, spin_lock is used only for update.
But we always hold cgroup_lock() when update, so spin_lock() is not need.

Additional cleanup:
1) include linux/rcupdate.h explicitly
2) remove unused variable cur_devcgroup in devcgroup_update_access()

Signed-off-by: default avatarLai Jiangshan <laijs@cn.fujitsu.com>
Acked-by: default avatar"Serge E. Hallyn" <serue@us.ibm.com>
Cc: Paul Menage <menage@google.com>
Cc: James Morris <jmorris@namei.org>
Signed-off-by: default avatarAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: default avatarLinus Torvalds <torvalds@linux-foundation.org>
parent c012a54a

security/device_cgroup.c

+5 −29
Original line number Diff line number Diff line 
/*

 * dev_cgroup.c - device cgroup subsystem

 * device_cgroup.c - device cgroup subsystem

 *

 * Copyright 2007 IBM Corp

 */
@@ -10,6 +10,7 @@ 
#include <linux/list.h>

#include <linux/uaccess.h>

#include <linux/seq_file.h>

#include <linux/rcupdate.h>



#define ACC_MKNOD 1

#define ACC_READ  2
@@ -22,18 +23,8 @@ 


/*

 * whitelist locking rules:

 * cgroup_lock() cannot be taken under dev_cgroup->lock.

 * dev_cgroup->lock can be taken with or without cgroup_lock().

 *

 * modifications always require cgroup_lock

 * modifications to a list which is visible require the

 *   dev_cgroup->lock *and* cgroup_lock()

 * walking the list requires dev_cgroup->lock or cgroup_lock().

 *

 * reasoning: dev_whitelist_copy() needs to kmalloc, so needs

 *   a mutex, which the cgroup_lock() is.  Since modifying

 *   a visible list requires both locks, either lock can be

 *   taken for walking the list.

 * hold cgroup_lock() for update/read.

 * hold rcu_read_lock() for read.

 */



struct dev_whitelist_item {
@@ -47,7 +38,6 @@ struct dev_whitelist_item { 
struct dev_cgroup {

	struct cgroup_subsys_state css;

	struct list_head whitelist;

	spinlock_t lock;

};



static inline struct dev_cgroup *css_to_devcgroup(struct cgroup_subsys_state *s)
@@ -103,7 +93,6 @@ free_and_exit: 
/* Stupid prototype - don't bother combining existing entries */

/*

 * called under cgroup_lock()

 * since the list is visible to other tasks, we need the spinlock also

 */

static int dev_whitelist_add(struct dev_cgroup *dev_cgroup,

			struct dev_whitelist_item *wh)
@@ -114,7 +103,6 @@ static int dev_whitelist_add(struct dev_cgroup *dev_cgroup, 
	if (!whcopy)

		return -ENOMEM;



	spin_lock(&dev_cgroup->lock);

	list_for_each_entry(walk, &dev_cgroup->whitelist, list) {

		if (walk->type != wh->type)

			continue;
@@ -130,7 +118,6 @@ static int dev_whitelist_add(struct dev_cgroup *dev_cgroup, 


	if (whcopy != NULL)

		list_add_tail_rcu(&whcopy->list, &dev_cgroup->whitelist);

	spin_unlock(&dev_cgroup->lock);

	return 0;

}
@@ -144,14 +131,12 @@ static void whitelist_item_free(struct rcu_head *rcu) 


/*

 * called under cgroup_lock()

 * since the list is visible to other tasks, we need the spinlock also

 */

static void dev_whitelist_rm(struct dev_cgroup *dev_cgroup,

			struct dev_whitelist_item *wh)

{

	struct dev_whitelist_item *walk, *tmp;



	spin_lock(&dev_cgroup->lock);

	list_for_each_entry_safe(walk, tmp, &dev_cgroup->whitelist, list) {

		if (walk->type == DEV_ALL)

			goto remove;
@@ -169,7 +154,6 @@ remove: 
			call_rcu(&walk->rcu, whitelist_item_free);

		}

	}

	spin_unlock(&dev_cgroup->lock);

}



/*
@@ -209,7 +193,6 @@ static struct cgroup_subsys_state *devcgroup_create(struct cgroup_subsys *ss, 
		}

	}



	spin_lock_init(&dev_cgroup->lock);

	return &dev_cgroup->css;

}
@@ -325,15 +308,11 @@ static int parent_has_perm(struct dev_cgroup *childcg, 
{

	struct cgroup *pcg = childcg->css.cgroup->parent;

	struct dev_cgroup *parent;

	int ret;



	if (!pcg)

		return 1;

	parent = cgroup_to_devcgroup(pcg);

	spin_lock(&parent->lock);

	ret = may_access_whitelist(parent, wh);

	spin_unlock(&parent->lock);

	return ret;

	return may_access_whitelist(parent, wh);

}



/*
@@ -352,7 +331,6 @@ static int parent_has_perm(struct dev_cgroup *childcg, 
static int devcgroup_update_access(struct dev_cgroup *devcgroup,

				   int filetype, const char *buffer)

{

	struct dev_cgroup *cur_devcgroup;

	const char *b;

	char *endp;

	int count;
@@ -361,8 +339,6 @@ static int devcgroup_update_access(struct dev_cgroup *devcgroup, 
	if (!capable(CAP_SYS_ADMIN))

		return -EPERM;



	cur_devcgroup = task_devcgroup(current);



	memset(&wh, 0, sizeof(wh));

	b = buffer;