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authorPaul Menage <menage@google.com>2007-10-19 02:39:34 -0400
committerLinus Torvalds <torvalds@woody.linux-foundation.org>2007-10-19 14:53:36 -0400
commit697f41610863c9264a7ae26dac9a387c9dda8c84 (patch)
tree9d4321f93abe36920a8e9d5239d120803f6cabbc /kernel
parentb4f48b6363c81ca743ef46943ef23fd72e60f679 (diff)
Task Control Groups: add cgroup_clone() interface
Add support for cgroup_clone(), a way to create new cgroups intended to be used for systems such as namespace unsharing. A new subsystem callback, post_clone(), is added to allow subsystems to automatically configure cloned cgroups. Signed-off-by: Paul Menage <menage@google.com> Cc: Serge E. Hallyn <serue@us.ibm.com> Cc: "Eric W. Biederman" <ebiederm@xmission.com> Cc: Dave Hansen <haveblue@us.ibm.com> Cc: Balbir Singh <balbir@in.ibm.com> Cc: Paul Jackson <pj@sgi.com> Cc: Kirill Korotaev <dev@openvz.org> Cc: Herbert Poetzl <herbert@13thfloor.at> Cc: Srivatsa Vaddagiri <vatsa@in.ibm.com> Cc: Cedric Le Goater <clg@fr.ibm.com> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Diffstat (limited to 'kernel')
-rw-r--r--kernel/cgroup.c135
1 files changed, 135 insertions, 0 deletions
diff --git a/kernel/cgroup.c b/kernel/cgroup.c
index 7bb520aaf0a3..cc68fe68a60e 100644
--- a/kernel/cgroup.c
+++ b/kernel/cgroup.c
@@ -1708,3 +1708,138 @@ void cgroup_exit(struct task_struct *tsk, int run_callbacks)
1708 tsk->cgroups = init_task.cgroups; 1708 tsk->cgroups = init_task.cgroups;
1709 task_unlock(tsk); 1709 task_unlock(tsk);
1710} 1710}
1711
1712/**
1713 * cgroup_clone - duplicate the current cgroup in the hierarchy
1714 * that the given subsystem is attached to, and move this task into
1715 * the new child
1716 */
1717int cgroup_clone(struct task_struct *tsk, struct cgroup_subsys *subsys)
1718{
1719 struct dentry *dentry;
1720 int ret = 0;
1721 char nodename[MAX_CGROUP_TYPE_NAMELEN];
1722 struct cgroup *parent, *child;
1723 struct inode *inode;
1724 struct css_set *cg;
1725 struct cgroupfs_root *root;
1726 struct cgroup_subsys *ss;
1727
1728 /* We shouldn't be called by an unregistered subsystem */
1729 BUG_ON(!subsys->active);
1730
1731 /* First figure out what hierarchy and cgroup we're dealing
1732 * with, and pin them so we can drop cgroup_mutex */
1733 mutex_lock(&cgroup_mutex);
1734 again:
1735 root = subsys->root;
1736 if (root == &rootnode) {
1737 printk(KERN_INFO
1738 "Not cloning cgroup for unused subsystem %s\n",
1739 subsys->name);
1740 mutex_unlock(&cgroup_mutex);
1741 return 0;
1742 }
1743 cg = &tsk->cgroups;
1744 parent = task_cgroup(tsk, subsys->subsys_id);
1745
1746 snprintf(nodename, MAX_CGROUP_TYPE_NAMELEN, "node_%d", tsk->pid);
1747
1748 /* Pin the hierarchy */
1749 atomic_inc(&parent->root->sb->s_active);
1750
1751 mutex_unlock(&cgroup_mutex);
1752
1753 /* Now do the VFS work to create a cgroup */
1754 inode = parent->dentry->d_inode;
1755
1756 /* Hold the parent directory mutex across this operation to
1757 * stop anyone else deleting the new cgroup */
1758 mutex_lock(&inode->i_mutex);
1759 dentry = lookup_one_len(nodename, parent->dentry, strlen(nodename));
1760 if (IS_ERR(dentry)) {
1761 printk(KERN_INFO
1762 "Couldn't allocate dentry for %s: %ld\n", nodename,
1763 PTR_ERR(dentry));
1764 ret = PTR_ERR(dentry);
1765 goto out_release;
1766 }
1767
1768 /* Create the cgroup directory, which also creates the cgroup */
1769 ret = vfs_mkdir(inode, dentry, S_IFDIR | 0755);
1770 child = __d_cont(dentry);
1771 dput(dentry);
1772 if (ret) {
1773 printk(KERN_INFO
1774 "Failed to create cgroup %s: %d\n", nodename,
1775 ret);
1776 goto out_release;
1777 }
1778
1779 if (!child) {
1780 printk(KERN_INFO
1781 "Couldn't find new cgroup %s\n", nodename);
1782 ret = -ENOMEM;
1783 goto out_release;
1784 }
1785
1786 /* The cgroup now exists. Retake cgroup_mutex and check
1787 * that we're still in the same state that we thought we
1788 * were. */
1789 mutex_lock(&cgroup_mutex);
1790 if ((root != subsys->root) ||
1791 (parent != task_cgroup(tsk, subsys->subsys_id))) {
1792 /* Aargh, we raced ... */
1793 mutex_unlock(&inode->i_mutex);
1794
1795 deactivate_super(parent->root->sb);
1796 /* The cgroup is still accessible in the VFS, but
1797 * we're not going to try to rmdir() it at this
1798 * point. */
1799 printk(KERN_INFO
1800 "Race in cgroup_clone() - leaking cgroup %s\n",
1801 nodename);
1802 goto again;
1803 }
1804
1805 /* do any required auto-setup */
1806 for_each_subsys(root, ss) {
1807 if (ss->post_clone)
1808 ss->post_clone(ss, child);
1809 }
1810
1811 /* All seems fine. Finish by moving the task into the new cgroup */
1812 ret = attach_task(child, tsk);
1813 mutex_unlock(&cgroup_mutex);
1814
1815 out_release:
1816 mutex_unlock(&inode->i_mutex);
1817 deactivate_super(parent->root->sb);
1818 return ret;
1819}
1820
1821/*
1822 * See if "cont" is a descendant of the current task's cgroup in
1823 * the appropriate hierarchy
1824 *
1825 * If we are sending in dummytop, then presumably we are creating
1826 * the top cgroup in the subsystem.
1827 *
1828 * Called only by the ns (nsproxy) cgroup.
1829 */
1830int cgroup_is_descendant(const struct cgroup *cont)
1831{
1832 int ret;
1833 struct cgroup *target;
1834 int subsys_id;
1835
1836 if (cont == dummytop)
1837 return 1;
1838
1839 get_first_subsys(cont, NULL, &subsys_id);
1840 target = task_cgroup(current, subsys_id);
1841 while (cont != target && cont!= cont->top_cgroup)
1842 cont = cont->parent;
1843 ret = (cont == target);
1844 return ret;
1845}