diff --git a/include/linux/cgroup.h b/include/linux/cgroup.h
index 665fa70e4094166c76b85176f0fbb3f5f6fae7c5..20411d2876f8cb5b36c5b724135cdf4944400299 100644
--- a/include/linux/cgroup.h
+++ b/include/linux/cgroup.h
@@ -179,14 +179,11 @@ struct cgroup {
*/
struct list_head release_list;
- /* pids_mutex protects the fields below */
+ /* pids_mutex protects pids_list and cached pid arrays. */
struct rw_semaphore pids_mutex;
- /* Array of process ids in the cgroup */
- pid_t *tasks_pids;
- /* How many files are using the current tasks_pids array */
- int pids_use_count;
- /* Length of the current tasks_pids array */
- int pids_length;
+
+ /* Linked list of struct cgroup_pids */
+ struct list_head pids_list;
/* For RCU-protected deletion */
struct rcu_head rcu_head;
diff --git a/kernel/cgroup.c b/kernel/cgroup.c
index 3737a682cdf52229ee78efa5c637164ba60dcc28..250dac05680feb16bb2fb647750a267216a97ed4 100644
--- a/kernel/cgroup.c
+++ b/kernel/cgroup.c
@@ -47,6 +47,7 @@
#include <linux/hash.h>
#include <linux/namei.h>
#include <linux/smp_lock.h>
+#include <linux/pid_namespace.h>
#include <asm/atomic.h>
@@ -960,6 +961,7 @@ static void init_cgroup_housekeeping(struct cgroup *cgrp)
INIT_LIST_HEAD(&cgrp->children);
INIT_LIST_HEAD(&cgrp->css_sets);
INIT_LIST_HEAD(&cgrp->release_list);
+ INIT_LIST_HEAD(&cgrp->pids_list);
init_rwsem(&cgrp->pids_mutex);
}
static void init_cgroup_root(struct cgroupfs_root *root)
@@ -2201,12 +2203,30 @@ int cgroupstats_build(struct cgroupstats *stats, struct dentry *dentry)
return ret;
}
+/*
+ * Cache pids for all threads in the same pid namespace that are
+ * opening the same "tasks" file.
+ */
+struct cgroup_pids {
+ /* The node in cgrp->pids_list */
+ struct list_head list;
+ /* The cgroup those pids belong to */
+ struct cgroup *cgrp;
+ /* The namepsace those pids belong to */
+ struct pid_namespace *ns;
+ /* Array of process ids in the cgroup */
+ pid_t *tasks_pids;
+ /* How many files are using the this tasks_pids array */
+ int use_count;
+ /* Length of the current tasks_pids array */
+ int length;
+};
+
static int cmppid(const void *a, const void *b)
{
return *(pid_t *)a - *(pid_t *)b;
}
-
/*
* seq_file methods for the "tasks" file. The seq_file position is the
* next pid to display; the seq_file iterator is a pointer to the pid
@@ -2221,45 +2241,47 @@ static void *cgroup_tasks_start(struct seq_file *s, loff_t *pos)
* after a seek to the start). Use a binary-search to find the
* next pid to display, if any
*/
- struct cgroup *cgrp = s->private;
+ struct cgroup_pids *cp = s->private;
+ struct cgroup *cgrp = cp->cgrp;
int index = 0, pid = *pos;
int *iter;
down_read(&cgrp->pids_mutex);
if (pid) {
- int end = cgrp->pids_length;
+ int end = cp->length;
while (index < end) {
int mid = (index + end) / 2;
- if (cgrp->tasks_pids[mid] == pid) {
+ if (cp->tasks_pids[mid] == pid) {
index = mid;
break;
- } else if (cgrp->tasks_pids[mid] <= pid)
+ } else if (cp->tasks_pids[mid] <= pid)
index = mid + 1;
else
end = mid;
}
}
/* If we're off the end of the array, we're done */
- if (index >= cgrp->pids_length)
+ if (index >= cp->length)
return NULL;
/* Update the abstract position to be the actual pid that we found */
- iter = cgrp->tasks_pids + index;
+ iter = cp->tasks_pids + index;
*pos = *iter;
return iter;
}
static void cgroup_tasks_stop(struct seq_file *s, void *v)
{
- struct cgroup *cgrp = s->private;
+ struct cgroup_pids *cp = s->private;
+ struct cgroup *cgrp = cp->cgrp;
up_read(&cgrp->pids_mutex);
}
static void *cgroup_tasks_next(struct seq_file *s, void *v, loff_t *pos)
{
- struct cgroup *cgrp = s->private;
+ struct cgroup_pids *cp = s->private;
int *p = v;
- int *end = cgrp->tasks_pids + cgrp->pids_length;
+ int *end = cp->tasks_pids + cp->length;
/*
* Advance to the next pid in the array. If this goes off the
@@ -2286,26 +2308,33 @@ static struct seq_operations cgroup_tasks_seq_operations = {
.show = cgroup_tasks_show,
};
-static void release_cgroup_pid_array(struct cgroup *cgrp)
+static void release_cgroup_pid_array(struct cgroup_pids *cp)
{
+ struct cgroup *cgrp = cp->cgrp;
+
down_write(&cgrp->pids_mutex);
- BUG_ON(!cgrp->pids_use_count);
- if (!--cgrp->pids_use_count) {
- kfree(cgrp->tasks_pids);
- cgrp->tasks_pids = NULL;
- cgrp->pids_length = 0;
+ BUG_ON(!cp->use_count);
+ if (!--cp->use_count) {
+ list_del(&cp->list);
+ put_pid_ns(cp->ns);
+ kfree(cp->tasks_pids);
+ kfree(cp);
}
up_write(&cgrp->pids_mutex);
}
static int cgroup_tasks_release(struct inode *inode, struct file *file)
{
- struct cgroup *cgrp = __d_cgrp(file->f_dentry->d_parent);
+ struct seq_file *seq;
+ struct cgroup_pids *cp;
if (!(file->f_mode & FMODE_READ))
return 0;
- release_cgroup_pid_array(cgrp);
+ seq = file->private_data;
+ cp = seq->private;
+
+ release_cgroup_pid_array(cp);
return seq_release(inode, file);
}
@@ -2324,6 +2353,8 @@ static struct file_operations cgroup_tasks_operations = {
static int cgroup_tasks_open(struct inode *unused, struct file *file)
{
struct cgroup *cgrp = __d_cgrp(file->f_dentry->d_parent);
+ struct pid_namespace *ns = current->nsproxy->pid_ns;
+ struct cgroup_pids *cp;
pid_t *pidarray;
int npids;
int retval;
@@ -2350,20 +2381,37 @@ static int cgroup_tasks_open(struct inode *unused, struct file *file)
* array if necessary
*/
down_write(&cgrp->pids_mutex);
- kfree(cgrp->tasks_pids);
- cgrp->tasks_pids = pidarray;
- cgrp->pids_length = npids;
- cgrp->pids_use_count++;
+
+ list_for_each_entry(cp, &cgrp->pids_list, list) {
+ if (ns == cp->ns)
+ goto found;
+ }
+
+ cp = kzalloc(sizeof(*cp), GFP_KERNEL);
+ if (!cp) {
+ up_write(&cgrp->pids_mutex);
+ kfree(pidarray);
+ return -ENOMEM;
+ }
+ cp->cgrp = cgrp;
+ cp->ns = ns;
+ get_pid_ns(ns);
+ list_add(&cp->list, &cgrp->pids_list);
+found:
+ kfree(cp->tasks_pids);
+ cp->tasks_pids = pidarray;
+ cp->length = npids;
+ cp->use_count++;
up_write(&cgrp->pids_mutex);
file->f_op = &cgroup_tasks_operations;
retval = seq_open(file, &cgroup_tasks_seq_operations);
if (retval) {
- release_cgroup_pid_array(cgrp);
+ release_cgroup_pid_array(cp);
return retval;
}
- ((struct seq_file *)file->private_data)->private = cgrp;
+ ((struct seq_file *)file->private_data)->private = cp;
return 0;
}