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-rw-r--r--kernel/cgroup.c62
1 files changed, 50 insertions, 12 deletions
diff --git a/kernel/cgroup.c b/kernel/cgroup.c
index e2769e13980c..6d870f2d1228 100644
--- a/kernel/cgroup.c
+++ b/kernel/cgroup.c
@@ -1646,7 +1646,9 @@ static inline struct cftype *__d_cft(struct dentry *dentry)
1646int cgroup_path(const struct cgroup *cgrp, char *buf, int buflen) 1646int cgroup_path(const struct cgroup *cgrp, char *buf, int buflen)
1647{ 1647{
1648 char *start; 1648 char *start;
1649 struct dentry *dentry = rcu_dereference(cgrp->dentry); 1649 struct dentry *dentry = rcu_dereference_check(cgrp->dentry,
1650 rcu_read_lock_held() ||
1651 cgroup_lock_is_held());
1650 1652
1651 if (!dentry || cgrp == dummytop) { 1653 if (!dentry || cgrp == dummytop) {
1652 /* 1654 /*
@@ -1662,13 +1664,17 @@ int cgroup_path(const struct cgroup *cgrp, char *buf, int buflen)
1662 *--start = '\0'; 1664 *--start = '\0';
1663 for (;;) { 1665 for (;;) {
1664 int len = dentry->d_name.len; 1666 int len = dentry->d_name.len;
1667
1665 if ((start -= len) < buf) 1668 if ((start -= len) < buf)
1666 return -ENAMETOOLONG; 1669 return -ENAMETOOLONG;
1667 memcpy(start, cgrp->dentry->d_name.name, len); 1670 memcpy(start, dentry->d_name.name, len);
1668 cgrp = cgrp->parent; 1671 cgrp = cgrp->parent;
1669 if (!cgrp) 1672 if (!cgrp)
1670 break; 1673 break;
1671 dentry = rcu_dereference(cgrp->dentry); 1674
1675 dentry = rcu_dereference_check(cgrp->dentry,
1676 rcu_read_lock_held() ||
1677 cgroup_lock_is_held());
1672 if (!cgrp->parent) 1678 if (!cgrp->parent)
1673 continue; 1679 continue;
1674 if (--start < buf) 1680 if (--start < buf)
@@ -4429,7 +4435,15 @@ __setup("cgroup_disable=", cgroup_disable);
4429 */ 4435 */
4430unsigned short css_id(struct cgroup_subsys_state *css) 4436unsigned short css_id(struct cgroup_subsys_state *css)
4431{ 4437{
4432 struct css_id *cssid = rcu_dereference(css->id); 4438 struct css_id *cssid;
4439
4440 /*
4441 * This css_id() can return correct value when somone has refcnt
4442 * on this or this is under rcu_read_lock(). Once css->id is allocated,
4443 * it's unchanged until freed.
4444 */
4445 cssid = rcu_dereference_check(css->id,
4446 rcu_read_lock_held() || atomic_read(&css->refcnt));
4433 4447
4434 if (cssid) 4448 if (cssid)
4435 return cssid->id; 4449 return cssid->id;
@@ -4439,7 +4453,10 @@ EXPORT_SYMBOL_GPL(css_id);
4439 4453
4440unsigned short css_depth(struct cgroup_subsys_state *css) 4454unsigned short css_depth(struct cgroup_subsys_state *css)
4441{ 4455{
4442 struct css_id *cssid = rcu_dereference(css->id); 4456 struct css_id *cssid;
4457
4458 cssid = rcu_dereference_check(css->id,
4459 rcu_read_lock_held() || atomic_read(&css->refcnt));
4443 4460
4444 if (cssid) 4461 if (cssid)
4445 return cssid->depth; 4462 return cssid->depth;
@@ -4447,15 +4464,36 @@ unsigned short css_depth(struct cgroup_subsys_state *css)
4447} 4464}
4448EXPORT_SYMBOL_GPL(css_depth); 4465EXPORT_SYMBOL_GPL(css_depth);
4449 4466
4467/**
4468 * css_is_ancestor - test "root" css is an ancestor of "child"
4469 * @child: the css to be tested.
4470 * @root: the css supporsed to be an ancestor of the child.
4471 *
4472 * Returns true if "root" is an ancestor of "child" in its hierarchy. Because
4473 * this function reads css->id, this use rcu_dereference() and rcu_read_lock().
4474 * But, considering usual usage, the csses should be valid objects after test.
4475 * Assuming that the caller will do some action to the child if this returns
4476 * returns true, the caller must take "child";s reference count.
4477 * If "child" is valid object and this returns true, "root" is valid, too.
4478 */
4479
4450bool css_is_ancestor(struct cgroup_subsys_state *child, 4480bool css_is_ancestor(struct cgroup_subsys_state *child,
4451 const struct cgroup_subsys_state *root) 4481 const struct cgroup_subsys_state *root)
4452{ 4482{
4453 struct css_id *child_id = rcu_dereference(child->id); 4483 struct css_id *child_id;
4454 struct css_id *root_id = rcu_dereference(root->id); 4484 struct css_id *root_id;
4485 bool ret = true;
4455 4486
4456 if (!child_id || !root_id || (child_id->depth < root_id->depth)) 4487 rcu_read_lock();
4457 return false; 4488 child_id = rcu_dereference(child->id);
4458 return child_id->stack[root_id->depth] == root_id->id; 4489 root_id = rcu_dereference(root->id);
4490 if (!child_id
4491 || !root_id
4492 || (child_id->depth < root_id->depth)
4493 || (child_id->stack[root_id->depth] != root_id->id))
4494 ret = false;
4495 rcu_read_unlock();
4496 return ret;
4459} 4497}
4460 4498
4461static void __free_css_id_cb(struct rcu_head *head) 4499static void __free_css_id_cb(struct rcu_head *head)
@@ -4555,13 +4593,13 @@ static int alloc_css_id(struct cgroup_subsys *ss, struct cgroup *parent,
4555{ 4593{
4556 int subsys_id, i, depth = 0; 4594 int subsys_id, i, depth = 0;
4557 struct cgroup_subsys_state *parent_css, *child_css; 4595 struct cgroup_subsys_state *parent_css, *child_css;
4558 struct css_id *child_id, *parent_id = NULL; 4596 struct css_id *child_id, *parent_id;
4559 4597
4560 subsys_id = ss->subsys_id; 4598 subsys_id = ss->subsys_id;
4561 parent_css = parent->subsys[subsys_id]; 4599 parent_css = parent->subsys[subsys_id];
4562 child_css = child->subsys[subsys_id]; 4600 child_css = child->subsys[subsys_id];
4563 depth = css_depth(parent_css) + 1;
4564 parent_id = parent_css->id; 4601 parent_id = parent_css->id;
4602 depth = parent_id->depth;
4565 4603
4566 child_id = get_new_cssid(ss, depth); 4604 child_id = get_new_cssid(ss, depth);
4567 if (IS_ERR(child_id)) 4605 if (IS_ERR(child_id))