*/
#include <linux/cgroup.h>
+#include <linux/cred.h>
#include <linux/ctype.h>
#include <linux/errno.h>
#include <linux/fs.h>
+#include <linux/init_task.h>
#include <linux/kernel.h>
#include <linux/list.h>
#include <linux/mm.h>
#include <linux/vmalloc.h> /* TODO: replace with more sophisticated array */
#include <linux/eventfd.h>
#include <linux/poll.h>
+#include <linux/flex_array.h> /* used in cgroup_attach_proc */
-#include <asm/atomic.h>
+#include <linux/atomic.h>
static DEFINE_MUTEX(cgroup_mutex);
};
/*
- * cgroup_event represents events which userspace want to recieve.
+ * cgroup_event represents events which userspace want to receive.
*/
struct cgroup_event {
/*
static DECLARE_WORK(release_agent_work, cgroup_release_agent);
static void check_for_release(struct cgroup *cgrp);
+/*
+ * A queue for waiters to do rmdir() cgroup. A tasks will sleep when
+ * cgroup->count == 0 && list_empty(&cgroup->children) && subsys has some
+ * reference to css->refcnt. In general, this refcnt is expected to goes down
+ * to zero, soon.
+ *
+ * CGRP_WAIT_ON_RMDIR flag is set under cgroup's inode->i_mutex;
+ */
+DECLARE_WAIT_QUEUE_HEAD(cgroup_rmdir_waitq);
+
+static void cgroup_wakeup_rmdir_waiter(struct cgroup *cgrp)
+{
+ if (unlikely(test_and_clear_bit(CGRP_WAIT_ON_RMDIR, &cgrp->flags)))
+ wake_up_all(&cgroup_rmdir_waitq);
+}
+
+void cgroup_exclude_rmdir(struct cgroup_subsys_state *css)
+{
+ css_get(css);
+}
+
+void cgroup_release_and_wakeup_rmdir(struct cgroup_subsys_state *css)
+{
+ cgroup_wakeup_rmdir_waiter(css->cgroup);
+ css_put(css);
+}
+
/* Link structure for associating css_set objects with cgroups */
struct cg_cgroup_link {
/*
return &css_set_table[index];
}
+static void free_css_set_work(struct work_struct *work)
+{
+ struct css_set *cg = container_of(work, struct css_set, work);
+ struct cg_cgroup_link *link;
+ struct cg_cgroup_link *saved_link;
+
+ write_lock(&css_set_lock);
+ list_for_each_entry_safe(link, saved_link, &cg->cg_links,
+ cg_link_list) {
+ struct cgroup *cgrp = link->cgrp;
+ list_del(&link->cg_link_list);
+ list_del(&link->cgrp_link_list);
+ if (atomic_dec_and_test(&cgrp->count)) {
+ check_for_release(cgrp);
+ cgroup_wakeup_rmdir_waiter(cgrp);
+ }
+ kfree(link);
+ }
+ write_unlock(&css_set_lock);
+
+ kfree(cg);
+}
+
static void free_css_set_rcu(struct rcu_head *obj)
{
struct css_set *cg = container_of(obj, struct css_set, rcu_head);
- kfree(cg);
+
+ INIT_WORK(&cg->work, free_css_set_work);
+ schedule_work(&cg->work);
}
/* We don't maintain the lists running through each css_set to its
* compiled into their kernel but not actually in use */
static int use_task_css_set_links __read_mostly;
-static void __put_css_set(struct css_set *cg, int taskexit)
+/*
+ * refcounted get/put for css_set objects
+ */
+static inline void get_css_set(struct css_set *cg)
+{
+ atomic_inc(&cg->refcount);
+}
+
+static void put_css_set(struct css_set *cg)
{
- struct cg_cgroup_link *link;
- struct cg_cgroup_link *saved_link;
/*
* Ensure that the refcount doesn't hit zero while any readers
* can see it. Similar to atomic_dec_and_lock(), but for an
return;
}
- /* This css_set is dead. unlink it and release cgroup refcounts */
hlist_del(&cg->hlist);
css_set_count--;
- list_for_each_entry_safe(link, saved_link, &cg->cg_links,
- cg_link_list) {
- struct cgroup *cgrp = link->cgrp;
- list_del(&link->cg_link_list);
- list_del(&link->cgrp_link_list);
- if (atomic_dec_and_test(&cgrp->count) &&
- notify_on_release(cgrp)) {
- if (taskexit)
- set_bit(CGRP_RELEASABLE, &cgrp->flags);
- check_for_release(cgrp);
- }
-
- kfree(link);
- }
-
write_unlock(&css_set_lock);
call_rcu(&cg->rcu_head, free_css_set_rcu);
}
-/*
- * refcounted get/put for css_set objects
- */
-static inline void get_css_set(struct css_set *cg)
-{
- atomic_inc(&cg->refcount);
-}
-
-static inline void put_css_set(struct css_set *cg)
-{
- __put_css_set(cg, 0);
-}
-
-static inline void put_css_set_taskexit(struct css_set *cg)
-{
- __put_css_set(cg, 1);
-}
-
/*
* compare_css_sets - helper function for find_existing_css_set().
* @cg: candidate css_set being tested
* cgroup_attach_task(), which overwrites one tasks cgroup pointer with
* another. It does so using cgroup_mutex, however there are
* several performance critical places that need to reference
- * task->cgroup without the expense of grabbing a system global
+ * task->cgroups without the expense of grabbing a system global
* mutex. Therefore except as noted below, when dereferencing or, as
- * in cgroup_attach_task(), modifying a task'ss cgroup pointer we use
+ * in cgroup_attach_task(), modifying a task's cgroups pointer we use
* task_lock(), which acts on a spinlock (task->alloc_lock) already in
* the task_struct routinely used for such matters.
*
return ret;
}
-static void free_cgroup_rcu(struct rcu_head *obj)
-{
- struct cgroup *cgrp = container_of(obj, struct cgroup, rcu_head);
-
- kfree(cgrp);
-}
-
static void cgroup_diput(struct dentry *dentry, struct inode *inode)
{
/* is dentry a directory ? if so, kfree() associated cgroup */
*/
BUG_ON(!list_empty(&cgrp->pidlists));
- call_rcu(&cgrp->rcu_head, free_cgroup_rcu);
+ kfree_rcu(cgrp, rcu_head);
}
iput(inode);
}
remove_dir(dentry);
}
-/*
- * A queue for waiters to do rmdir() cgroup. A tasks will sleep when
- * cgroup->count == 0 && list_empty(&cgroup->children) && subsys has some
- * reference to css->refcnt. In general, this refcnt is expected to goes down
- * to zero, soon.
- *
- * CGRP_WAIT_ON_RMDIR flag is set under cgroup's inode->i_mutex;
- */
-DECLARE_WAIT_QUEUE_HEAD(cgroup_rmdir_waitq);
-
-static void cgroup_wakeup_rmdir_waiter(struct cgroup *cgrp)
-{
- if (unlikely(test_and_clear_bit(CGRP_WAIT_ON_RMDIR, &cgrp->flags)))
- wake_up_all(&cgroup_rmdir_waitq);
-}
-
-void cgroup_exclude_rmdir(struct cgroup_subsys_state *css)
-{
- css_get(css);
-}
-
-void cgroup_release_and_wakeup_rmdir(struct cgroup_subsys_state *css)
-{
- cgroup_wakeup_rmdir_waiter(css->cgroup);
- css_put(css);
-}
-
/*
* Call with cgroup_mutex held. Drops reference counts on modules, including
* any duplicate ones that parse_cgroupfs_options took. If this function
/*
* If the 'all' option was specified select all the subsystems,
- * otherwise 'all, 'none' and a subsystem name options were not
- * specified, let's default to 'all'
+ * otherwise if 'none', 'name=' and a subsystem name options
+ * were not specified, let's default to 'all'
*/
- if (all_ss || (!all_ss && !one_ss && !opts->none)) {
+ if (all_ss || (!one_ss && !opts->none && !opts->name)) {
for (i = 0; i < CGROUP_SUBSYS_COUNT; i++) {
struct cgroup_subsys *ss = subsys[i];
if (ss == NULL)
struct cgroup *root_cgrp = &root->top_cgroup;
struct inode *inode;
struct cgroupfs_root *existing_root;
+ const struct cred *cred;
int i;
BUG_ON(sb->s_root != NULL);
BUG_ON(!list_empty(&root_cgrp->children));
BUG_ON(root->number_of_cgroups != 1);
+ cred = override_creds(&init_cred);
cgroup_populate_dir(root_cgrp);
+ revert_creds(cred);
mutex_unlock(&cgroup_mutex);
mutex_unlock(&inode->i_mutex);
} else {
{
char *start;
struct dentry *dentry = rcu_dereference_check(cgrp->dentry,
- rcu_read_lock_held() ||
cgroup_lock_is_held());
if (!dentry || cgrp == dummytop) {
break;
dentry = rcu_dereference_check(cgrp->dentry,
- rcu_read_lock_held() ||
cgroup_lock_is_held());
if (!cgrp->parent)
continue;
}
EXPORT_SYMBOL_GPL(cgroup_path);
+/*
+ * cgroup_task_migrate - move a task from one cgroup to another.
+ *
+ * 'guarantee' is set if the caller promises that a new css_set for the task
+ * will already exist. If not set, this function might sleep, and can fail with
+ * -ENOMEM. Otherwise, it can only fail with -ESRCH.
+ */
+static int cgroup_task_migrate(struct cgroup *cgrp, struct cgroup *oldcgrp,
+ struct task_struct *tsk, bool guarantee)
+{
+ struct css_set *oldcg;
+ struct css_set *newcg;
+
+ /*
+ * get old css_set. we need to take task_lock and refcount it, because
+ * an exiting task can change its css_set to init_css_set and drop its
+ * old one without taking cgroup_mutex.
+ */
+ task_lock(tsk);
+ oldcg = tsk->cgroups;
+ get_css_set(oldcg);
+ task_unlock(tsk);
+
+ /* locate or allocate a new css_set for this task. */
+ if (guarantee) {
+ /* we know the css_set we want already exists. */
+ struct cgroup_subsys_state *template[CGROUP_SUBSYS_COUNT];
+ read_lock(&css_set_lock);
+ newcg = find_existing_css_set(oldcg, cgrp, template);
+ BUG_ON(!newcg);
+ get_css_set(newcg);
+ read_unlock(&css_set_lock);
+ } else {
+ might_sleep();
+ /* find_css_set will give us newcg already referenced. */
+ newcg = find_css_set(oldcg, cgrp);
+ if (!newcg) {
+ put_css_set(oldcg);
+ return -ENOMEM;
+ }
+ }
+ put_css_set(oldcg);
+
+ /* if PF_EXITING is set, the tsk->cgroups pointer is no longer safe. */
+ task_lock(tsk);
+ if (tsk->flags & PF_EXITING) {
+ task_unlock(tsk);
+ put_css_set(newcg);
+ return -ESRCH;
+ }
+ rcu_assign_pointer(tsk->cgroups, newcg);
+ task_unlock(tsk);
+
+ /* Update the css_set linked lists if we're using them */
+ write_lock(&css_set_lock);
+ if (!list_empty(&tsk->cg_list))
+ list_move(&tsk->cg_list, &newcg->tasks);
+ write_unlock(&css_set_lock);
+
+ /*
+ * We just gained a reference on oldcg by taking it from the task. As
+ * trading it for newcg is protected by cgroup_mutex, we're safe to drop
+ * it here; it will be freed under RCU.
+ */
+ put_css_set(oldcg);
+
+ set_bit(CGRP_RELEASABLE, &oldcgrp->flags);
+ return 0;
+}
+
/**
* cgroup_attach_task - attach task 'tsk' to cgroup 'cgrp'
* @cgrp: the cgroup the task is attaching to
*/
int cgroup_attach_task(struct cgroup *cgrp, struct task_struct *tsk)
{
- int retval = 0;
+ int retval;
struct cgroup_subsys *ss, *failed_ss = NULL;
struct cgroup *oldcgrp;
- struct css_set *cg;
- struct css_set *newcg;
struct cgroupfs_root *root = cgrp->root;
+ struct css_set *cg;
/* Nothing to do if the task is already in that cgroup */
oldcgrp = task_cgroup_from_root(tsk, root);
for_each_subsys(root, ss) {
if (ss->can_attach) {
- retval = ss->can_attach(ss, cgrp, tsk, false);
+ retval = ss->can_attach(ss, cgrp, tsk);
if (retval) {
/*
* Remember on which subsystem the can_attach()
goto out;
}
}
+ if (ss->can_attach_task) {
+ retval = ss->can_attach_task(cgrp, tsk);
+ if (retval) {
+ failed_ss = ss;
+ goto out;
+ }
+ }
}
task_lock(tsk);
cg = tsk->cgroups;
get_css_set(cg);
task_unlock(tsk);
- /*
- * Locate or allocate a new css_set for this task,
- * based on its final set of cgroups
- */
- newcg = find_css_set(cg, cgrp);
- put_css_set(cg);
- if (!newcg) {
- retval = -ENOMEM;
- goto out;
- }
- task_lock(tsk);
- if (tsk->flags & PF_EXITING) {
- task_unlock(tsk);
- put_css_set(newcg);
- retval = -ESRCH;
+ retval = cgroup_task_migrate(cgrp, oldcgrp, tsk, false);
+ if (retval)
goto out;
- }
- rcu_assign_pointer(tsk->cgroups, newcg);
- task_unlock(tsk);
-
- /* Update the css_set linked lists if we're using them */
- write_lock(&css_set_lock);
- if (!list_empty(&tsk->cg_list))
- list_move(&tsk->cg_list, &newcg->tasks);
- write_unlock(&css_set_lock);
for_each_subsys(root, ss) {
+ if (ss->pre_attach)
+ ss->pre_attach(cgrp);
+ if (ss->attach_task)
+ ss->attach_task(cgrp, tsk);
if (ss->attach)
- ss->attach(ss, cgrp, oldcgrp, tsk, false);
+ ss->attach(ss, cgrp, oldcgrp, tsk);
}
- set_bit(CGRP_RELEASABLE, &oldcgrp->flags);
- synchronize_rcu();
+ set_bit(CGRP_RELEASABLE, &cgrp->flags);
+ /* put_css_set will not destroy cg until after an RCU grace period */
put_css_set(cg);
/*
*/
break;
if (ss->cancel_attach)
- ss->cancel_attach(ss, cgrp, tsk, false);
+ ss->cancel_attach(ss, cgrp, tsk);
}
}
return retval;
EXPORT_SYMBOL_GPL(cgroup_attach_task_all);
/*
- * Attach task with pid 'pid' to cgroup 'cgrp'. Call with cgroup_mutex
- * held. May take task_lock of task
+ * cgroup_attach_proc works in two stages, the first of which prefetches all
+ * new css_sets needed (to make sure we have enough memory before committing
+ * to the move) and stores them in a list of entries of the following type.
+ * TODO: possible optimization: use css_set->rcu_head for chaining instead
+ */
+struct cg_list_entry {
+ struct css_set *cg;
+ struct list_head links;
+};
+
+static bool css_set_check_fetched(struct cgroup *cgrp,
+ struct task_struct *tsk, struct css_set *cg,
+ struct list_head *newcg_list)
+{
+ struct css_set *newcg;
+ struct cg_list_entry *cg_entry;
+ struct cgroup_subsys_state *template[CGROUP_SUBSYS_COUNT];
+
+ read_lock(&css_set_lock);
+ newcg = find_existing_css_set(cg, cgrp, template);
+ if (newcg)
+ get_css_set(newcg);
+ read_unlock(&css_set_lock);
+
+ /* doesn't exist at all? */
+ if (!newcg)
+ return false;
+ /* see if it's already in the list */
+ list_for_each_entry(cg_entry, newcg_list, links) {
+ if (cg_entry->cg == newcg) {
+ put_css_set(newcg);
+ return true;
+ }
+ }
+
+ /* not found */
+ put_css_set(newcg);
+ return false;
+}
+
+/*
+ * Find the new css_set and store it in the list in preparation for moving the
+ * given task to the given cgroup. Returns 0 or -ENOMEM.
*/
-static int attach_task_by_pid(struct cgroup *cgrp, u64 pid)
+static int css_set_prefetch(struct cgroup *cgrp, struct css_set *cg,
+ struct list_head *newcg_list)
+{
+ struct css_set *newcg;
+ struct cg_list_entry *cg_entry;
+
+ /* ensure a new css_set will exist for this thread */
+ newcg = find_css_set(cg, cgrp);
+ if (!newcg)
+ return -ENOMEM;
+ /* add it to the list */
+ cg_entry = kmalloc(sizeof(struct cg_list_entry), GFP_KERNEL);
+ if (!cg_entry) {
+ put_css_set(newcg);
+ return -ENOMEM;
+ }
+ cg_entry->cg = newcg;
+ list_add(&cg_entry->links, newcg_list);
+ return 0;
+}
+
+/**
+ * cgroup_attach_proc - attach all threads in a threadgroup to a cgroup
+ * @cgrp: the cgroup to attach to
+ * @leader: the threadgroup leader task_struct of the group to be attached
+ *
+ * Call holding cgroup_mutex and the threadgroup_fork_lock of the leader. Will
+ * take task_lock of each thread in leader's threadgroup individually in turn.
+ */
+int cgroup_attach_proc(struct cgroup *cgrp, struct task_struct *leader)
+{
+ int retval, i, group_size;
+ struct cgroup_subsys *ss, *failed_ss = NULL;
+ bool cancel_failed_ss = false;
+ /* guaranteed to be initialized later, but the compiler needs this */
+ struct cgroup *oldcgrp = NULL;
+ struct css_set *oldcg;
+ struct cgroupfs_root *root = cgrp->root;
+ /* threadgroup list cursor and array */
+ struct task_struct *tsk;
+ struct flex_array *group;
+ /*
+ * we need to make sure we have css_sets for all the tasks we're
+ * going to move -before- we actually start moving them, so that in
+ * case we get an ENOMEM we can bail out before making any changes.
+ */
+ struct list_head newcg_list;
+ struct cg_list_entry *cg_entry, *temp_nobe;
+
+ /*
+ * step 0: in order to do expensive, possibly blocking operations for
+ * every thread, we cannot iterate the thread group list, since it needs
+ * rcu or tasklist locked. instead, build an array of all threads in the
+ * group - threadgroup_fork_lock prevents new threads from appearing,
+ * and if threads exit, this will just be an over-estimate.
+ */
+ group_size = get_nr_threads(leader);
+ /* flex_array supports very large thread-groups better than kmalloc. */
+ group = flex_array_alloc(sizeof(struct task_struct *), group_size,
+ GFP_KERNEL);
+ if (!group)
+ return -ENOMEM;
+ /* pre-allocate to guarantee space while iterating in rcu read-side. */
+ retval = flex_array_prealloc(group, 0, group_size - 1, GFP_KERNEL);
+ if (retval)
+ goto out_free_group_list;
+
+ /* prevent changes to the threadgroup list while we take a snapshot. */
+ rcu_read_lock();
+ if (!thread_group_leader(leader)) {
+ /*
+ * a race with de_thread from another thread's exec() may strip
+ * us of our leadership, making while_each_thread unsafe to use
+ * on this task. if this happens, there is no choice but to
+ * throw this task away and try again (from cgroup_procs_write);
+ * this is "double-double-toil-and-trouble-check locking".
+ */
+ rcu_read_unlock();
+ retval = -EAGAIN;
+ goto out_free_group_list;
+ }
+ /* take a reference on each task in the group to go in the array. */
+ tsk = leader;
+ i = 0;
+ do {
+ /* as per above, nr_threads may decrease, but not increase. */
+ BUG_ON(i >= group_size);
+ get_task_struct(tsk);
+ /*
+ * saying GFP_ATOMIC has no effect here because we did prealloc
+ * earlier, but it's good form to communicate our expectations.
+ */
+ retval = flex_array_put_ptr(group, i, tsk, GFP_ATOMIC);
+ BUG_ON(retval != 0);
+ i++;
+ } while_each_thread(leader, tsk);
+ /* remember the number of threads in the array for later. */
+ group_size = i;
+ rcu_read_unlock();
+
+ /*
+ * step 1: check that we can legitimately attach to the cgroup.
+ */
+ for_each_subsys(root, ss) {
+ if (ss->can_attach) {
+ retval = ss->can_attach(ss, cgrp, leader);
+ if (retval) {
+ failed_ss = ss;
+ goto out_cancel_attach;
+ }
+ }
+ /* a callback to be run on every thread in the threadgroup. */
+ if (ss->can_attach_task) {
+ /* run on each task in the threadgroup. */
+ for (i = 0; i < group_size; i++) {
+ tsk = flex_array_get_ptr(group, i);
+ retval = ss->can_attach_task(cgrp, tsk);
+ if (retval) {
+ failed_ss = ss;
+ cancel_failed_ss = true;
+ goto out_cancel_attach;
+ }
+ }
+ }
+ }
+
+ /*
+ * step 2: make sure css_sets exist for all threads to be migrated.
+ * we use find_css_set, which allocates a new one if necessary.
+ */
+ INIT_LIST_HEAD(&newcg_list);
+ for (i = 0; i < group_size; i++) {
+ tsk = flex_array_get_ptr(group, i);
+ /* nothing to do if this task is already in the cgroup */
+ oldcgrp = task_cgroup_from_root(tsk, root);
+ if (cgrp == oldcgrp)
+ continue;
+ /* get old css_set pointer */
+ task_lock(tsk);
+ oldcg = tsk->cgroups;
+ get_css_set(oldcg);
+ task_unlock(tsk);
+ /* see if the new one for us is already in the list? */
+ if (css_set_check_fetched(cgrp, tsk, oldcg, &newcg_list)) {
+ /* was already there, nothing to do. */
+ put_css_set(oldcg);
+ } else {
+ /* we don't already have it. get new one. */
+ retval = css_set_prefetch(cgrp, oldcg, &newcg_list);
+ put_css_set(oldcg);
+ if (retval)
+ goto out_list_teardown;
+ }
+ }
+
+ /*
+ * step 3: now that we're guaranteed success wrt the css_sets, proceed
+ * to move all tasks to the new cgroup, calling ss->attach_task for each
+ * one along the way. there are no failure cases after here, so this is
+ * the commit point.
+ */
+ for_each_subsys(root, ss) {
+ if (ss->pre_attach)
+ ss->pre_attach(cgrp);
+ }
+ for (i = 0; i < group_size; i++) {
+ tsk = flex_array_get_ptr(group, i);
+ /* leave current thread as it is if it's already there */
+ oldcgrp = task_cgroup_from_root(tsk, root);
+ if (cgrp == oldcgrp)
+ continue;
+ /* attach each task to each subsystem */
+ for_each_subsys(root, ss) {
+ if (ss->attach_task)
+ ss->attach_task(cgrp, tsk);
+ }
+ /* if the thread is PF_EXITING, it can just get skipped. */
+ retval = cgroup_task_migrate(cgrp, oldcgrp, tsk, true);
+ BUG_ON(retval != 0 && retval != -ESRCH);
+ }
+ /* nothing is sensitive to fork() after this point. */
+
+ /*
+ * step 4: do expensive, non-thread-specific subsystem callbacks.
+ * TODO: if ever a subsystem needs to know the oldcgrp for each task
+ * being moved, this call will need to be reworked to communicate that.
+ */
+ for_each_subsys(root, ss) {
+ if (ss->attach)
+ ss->attach(ss, cgrp, oldcgrp, leader);
+ }
+
+ /*
+ * step 5: success! and cleanup
+ */
+ synchronize_rcu();
+ cgroup_wakeup_rmdir_waiter(cgrp);
+ retval = 0;
+out_list_teardown:
+ /* clean up the list of prefetched css_sets. */
+ list_for_each_entry_safe(cg_entry, temp_nobe, &newcg_list, links) {
+ list_del(&cg_entry->links);
+ put_css_set(cg_entry->cg);
+ kfree(cg_entry);
+ }
+out_cancel_attach:
+ /* same deal as in cgroup_attach_task */
+ if (retval) {
+ for_each_subsys(root, ss) {
+ if (ss == failed_ss) {
+ if (cancel_failed_ss && ss->cancel_attach)
+ ss->cancel_attach(ss, cgrp, leader);
+ break;
+ }
+ if (ss->cancel_attach)
+ ss->cancel_attach(ss, cgrp, leader);
+ }
+ }
+ /* clean up the array of referenced threads in the group. */
+ for (i = 0; i < group_size; i++) {
+ tsk = flex_array_get_ptr(group, i);
+ put_task_struct(tsk);
+ }
+out_free_group_list:
+ flex_array_free(group);
+ return retval;
+}
+
+static int cgroup_allow_attach(struct cgroup *cgrp, struct task_struct *tsk)
+{
+ struct cgroup_subsys *ss;
+ int ret;
+
+ for_each_subsys(cgrp->root, ss) {
+ if (ss->allow_attach) {
+ ret = ss->allow_attach(cgrp, tsk);
+ if (ret)
+ return ret;
+ } else {
+ return -EACCES;
+ }
+ }
+
+ return 0;
+}
+
+/*
+ * Find the task_struct of the task to attach by vpid and pass it along to the
+ * function to attach either it or all tasks in its threadgroup. Will take
+ * cgroup_mutex; may take task_lock of task.
+ */
+static int attach_task_by_pid(struct cgroup *cgrp, u64 pid, bool threadgroup)
{
struct task_struct *tsk;
const struct cred *cred = current_cred(), *tcred;
int ret;
+ if (!cgroup_lock_live_group(cgrp))
+ return -ENODEV;
+
if (pid) {
rcu_read_lock();
tsk = find_task_by_vpid(pid);
- if (!tsk || tsk->flags & PF_EXITING) {
+ if (!tsk) {
rcu_read_unlock();
+ cgroup_unlock();
+ return -ESRCH;
+ }
+ if (threadgroup) {
+ /*
+ * RCU protects this access, since tsk was found in the
+ * tid map. a race with de_thread may cause group_leader
+ * to stop being the leader, but cgroup_attach_proc will
+ * detect it later.
+ */
+ tsk = tsk->group_leader;
+ } else if (tsk->flags & PF_EXITING) {
+ /* optimization for the single-task-only case */
+ rcu_read_unlock();
+ cgroup_unlock();
return -ESRCH;
}
+ /*
+ * even if we're attaching all tasks in the thread group, we
+ * only need to check permissions on one of them.
+ */
tcred = __task_cred(tsk);
if (cred->euid &&
cred->euid != tcred->uid &&
cred->euid != tcred->suid) {
- rcu_read_unlock();
- return -EACCES;
+ /*
+ * if the default permission check fails, give each
+ * cgroup a chance to extend the permission check
+ */
+ ret = cgroup_allow_attach(cgrp, tsk);
+ if (ret) {
+ rcu_read_unlock();
+ cgroup_unlock();
+ return ret;
+ }
}
get_task_struct(tsk);
rcu_read_unlock();
} else {
- tsk = current;
+ if (threadgroup)
+ tsk = current->group_leader;
+ else
+ tsk = current;
get_task_struct(tsk);
}
- ret = cgroup_attach_task(cgrp, tsk);
+ if (threadgroup) {
+ threadgroup_fork_write_lock(tsk);
+ ret = cgroup_attach_proc(cgrp, tsk);
+ threadgroup_fork_write_unlock(tsk);
+ } else {
+ ret = cgroup_attach_task(cgrp, tsk);
+ }
put_task_struct(tsk);
+ cgroup_unlock();
return ret;
}
static int cgroup_tasks_write(struct cgroup *cgrp, struct cftype *cft, u64 pid)
+{
+ return attach_task_by_pid(cgrp, pid, false);
+}
+
+static int cgroup_procs_write(struct cgroup *cgrp, struct cftype *cft, u64 tgid)
{
int ret;
- if (!cgroup_lock_live_group(cgrp))
- return -ENODEV;
- ret = attach_task_by_pid(cgrp, pid);
- cgroup_unlock();
+ do {
+ /*
+ * attach_proc fails with -EAGAIN if threadgroup leadership
+ * changes in the middle of the operation, in which case we need
+ * to find the task_struct for the new leader and start over.
+ */
+ ret = attach_task_by_pid(cgrp, tgid, true);
+ } while (ret == -EAGAIN);
return ret;
}
}
/* the process need read permission on control file */
- ret = file_permission(cfile, MAY_READ);
+ /* AV: shouldn't we check that it's been opened for read instead? */
+ ret = inode_permission(cfile->f_path.dentry->d_inode, MAY_READ);
if (ret < 0)
goto fail;
{
.name = CGROUP_FILE_GENERIC_PREFIX "procs",
.open = cgroup_procs_open,
- /* .write_u64 = cgroup_procs_write, TODO */
+ .write_u64 = cgroup_procs_write,
.release = cgroup_pidlist_release,
- .mode = S_IRUGO,
+ .mode = S_IRUGO | S_IWUSR,
},
{
.name = "notify_on_release",
if (err < 0)
goto err_remove;
+ set_bit(CGRP_RELEASABLE, &parent->flags);
+
/* The cgroup directory was pre-locked for us */
BUG_ON(!mutex_is_locked(&cgrp->dentry->d_inode->i_mutex));
return !failed;
}
+/* checks if all of the css_sets attached to a cgroup have a refcount of 0.
+ * Must be called with css_set_lock held */
+static int cgroup_css_sets_empty(struct cgroup *cgrp)
+{
+ struct cg_cgroup_link *link;
+
+ list_for_each_entry(link, &cgrp->css_sets, cgrp_link_list) {
+ struct css_set *cg = link->cg;
+ if (atomic_read(&cg->refcount) > 0)
+ return 0;
+ }
+
+ return 1;
+}
+
static int cgroup_rmdir(struct inode *unused_dir, struct dentry *dentry)
{
struct cgroup *cgrp = dentry->d_fsdata;
/* the vfs holds both inode->i_mutex already */
again:
mutex_lock(&cgroup_mutex);
- if (atomic_read(&cgrp->count) != 0) {
+ if (!cgroup_css_sets_empty(cgrp)) {
mutex_unlock(&cgroup_mutex);
return -EBUSY;
}
mutex_lock(&cgroup_mutex);
parent = cgrp->parent;
- if (atomic_read(&cgrp->count) || !list_empty(&cgrp->children)) {
+ if (!cgroup_css_sets_empty(cgrp) || !list_empty(&cgrp->children)) {
clear_bit(CGRP_WAIT_ON_RMDIR, &cgrp->flags);
mutex_unlock(&cgroup_mutex);
return -EBUSY;
cgroup_d_remove_dir(d);
dput(d);
- set_bit(CGRP_RELEASABLE, &parent->flags);
check_for_release(parent);
/*
task_unlock(tsk);
if (cg)
- put_css_set_taskexit(cg);
-}
-
-/**
- * cgroup_clone - clone the cgroup the given subsystem is attached to
- * @tsk: the task to be moved
- * @subsys: the given subsystem
- * @nodename: the name for the new cgroup
- *
- * Duplicate the current cgroup in the hierarchy that the given
- * subsystem is attached to, and move this task into the new
- * child.
- */
-int cgroup_clone(struct task_struct *tsk, struct cgroup_subsys *subsys,
- char *nodename)
-{
- struct dentry *dentry;
- int ret = 0;
- struct cgroup *parent, *child;
- struct inode *inode;
- struct css_set *cg;
- struct cgroupfs_root *root;
- struct cgroup_subsys *ss;
-
- /* We shouldn't be called by an unregistered subsystem */
- BUG_ON(!subsys->active);
-
- /* First figure out what hierarchy and cgroup we're dealing
- * with, and pin them so we can drop cgroup_mutex */
- mutex_lock(&cgroup_mutex);
- again:
- root = subsys->root;
- if (root == &rootnode) {
- mutex_unlock(&cgroup_mutex);
- return 0;
- }
-
- /* Pin the hierarchy */
- if (!atomic_inc_not_zero(&root->sb->s_active)) {
- /* We race with the final deactivate_super() */
- mutex_unlock(&cgroup_mutex);
- return 0;
- }
-
- /* Keep the cgroup alive */
- task_lock(tsk);
- parent = task_cgroup(tsk, subsys->subsys_id);
- cg = tsk->cgroups;
- get_css_set(cg);
- task_unlock(tsk);
-
- mutex_unlock(&cgroup_mutex);
-
- /* Now do the VFS work to create a cgroup */
- inode = parent->dentry->d_inode;
-
- /* Hold the parent directory mutex across this operation to
- * stop anyone else deleting the new cgroup */
- mutex_lock(&inode->i_mutex);
- dentry = lookup_one_len(nodename, parent->dentry, strlen(nodename));
- if (IS_ERR(dentry)) {
- printk(KERN_INFO
- "cgroup: Couldn't allocate dentry for %s: %ld\n", nodename,
- PTR_ERR(dentry));
- ret = PTR_ERR(dentry);
- goto out_release;
- }
-
- /* Create the cgroup directory, which also creates the cgroup */
- ret = vfs_mkdir(inode, dentry, 0755);
- child = __d_cgrp(dentry);
- dput(dentry);
- if (ret) {
- printk(KERN_INFO
- "Failed to create cgroup %s: %d\n", nodename,
- ret);
- goto out_release;
- }
-
- /* The cgroup now exists. Retake cgroup_mutex and check
- * that we're still in the same state that we thought we
- * were. */
- mutex_lock(&cgroup_mutex);
- if ((root != subsys->root) ||
- (parent != task_cgroup(tsk, subsys->subsys_id))) {
- /* Aargh, we raced ... */
- mutex_unlock(&inode->i_mutex);
put_css_set(cg);
-
- deactivate_super(root->sb);
- /* The cgroup is still accessible in the VFS, but
- * we're not going to try to rmdir() it at this
- * point. */
- printk(KERN_INFO
- "Race in cgroup_clone() - leaking cgroup %s\n",
- nodename);
- goto again;
- }
-
- /* do any required auto-setup */
- for_each_subsys(root, ss) {
- if (ss->post_clone)
- ss->post_clone(ss, child);
- }
-
- /* All seems fine. Finish by moving the task into the new cgroup */
- ret = cgroup_attach_task(child, tsk);
- mutex_unlock(&cgroup_mutex);
-
- out_release:
- mutex_unlock(&inode->i_mutex);
-
- mutex_lock(&cgroup_mutex);
- put_css_set(cg);
- mutex_unlock(&cgroup_mutex);
- deactivate_super(root->sb);
- return ret;
}
/**
}
}
+/* Caller must verify that the css is not for root cgroup */
+void __css_get(struct cgroup_subsys_state *css, int count)
+{
+ atomic_add(count, &css->refcnt);
+ set_bit(CGRP_RELEASABLE, &css->cgroup->flags);
+}
+EXPORT_SYMBOL_GPL(__css_get);
+
/* Caller must verify that the css is not for root cgroup */
void __css_put(struct cgroup_subsys_state *css, int count)
{
rcu_read_lock();
val = atomic_sub_return(count, &css->refcnt);
if (val == 1) {
- if (notify_on_release(cgrp)) {
- set_bit(CGRP_RELEASABLE, &cgrp->flags);
- check_for_release(cgrp);
- }
+ check_for_release(cgrp);
cgroup_wakeup_rmdir_waiter(cgrp);
}
rcu_read_unlock();
* on this or this is under rcu_read_lock(). Once css->id is allocated,
* it's unchanged until freed.
*/
- cssid = rcu_dereference_check(css->id,
- rcu_read_lock_held() || atomic_read(&css->refcnt));
+ cssid = rcu_dereference_check(css->id, atomic_read(&css->refcnt));
if (cssid)
return cssid->id;
{
struct css_id *cssid;
- cssid = rcu_dereference_check(css->id,
- rcu_read_lock_held() || atomic_read(&css->refcnt));
+ cssid = rcu_dereference_check(css->id, atomic_read(&css->refcnt));
if (cssid)
return cssid->depth;
return ret;
}
-static void __free_css_id_cb(struct rcu_head *head)
-{
- struct css_id *id;
-
- id = container_of(head, struct css_id, rcu_head);
- kfree(id);
-}
-
void free_css_id(struct cgroup_subsys *ss, struct cgroup_subsys_state *css)
{
struct css_id *id = css->id;
spin_lock(&ss->id_lock);
idr_remove(&ss->idr, id->id);
spin_unlock(&ss->id_lock);
- call_rcu(&id->rcu_head, __free_css_id_cb);
+ kfree_rcu(id, rcu_head);
}
EXPORT_SYMBOL_GPL(free_css_id);
Code Review / linux-2.6.git / blobdiff