2 files changed, 31 insertions, 75 deletions

diff --git a/include/linux/cgroup.h b/include/linux/cgroup.h
index 90bba9e6228..c833d6f2367 100644
--- a/include/linux/cgroup.h
+++ b/include/linux/cgroup.h
@@ -179,11 +179,14 @@ struct cgroup {
 	 */
 	struct list_head release_list;
 
-	/* pids_mutex protects pids_list and cached pid arrays. */
+	/* pids_mutex protects the fields below */
 	struct rw_semaphore pids_mutex;
-
-	/* Linked list of struct cgroup_pids */
-	struct list_head pids_list;
+	/* 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;
 
 	/* For RCU-protected deletion */
 	struct rcu_head rcu_head;
diff --git a/kernel/cgroup.c b/kernel/cgroup.c
index 14efffed72c..22db0a7cf1f 100644
--- a/kernel/cgroup.c
+++ b/kernel/cgroup.c
@@ -1121,7 +1121,6 @@ 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);
 }
 
@@ -2431,30 +2430,12 @@ err:
 	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
@@ -2469,47 +2450,45 @@ 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_pids *cp = s->private;
-	struct cgroup *cgrp = cp->cgrp;
+	struct cgroup *cgrp = s->private;
 	int index = 0, pid = *pos;
 	int *iter;
 
 	down_read(&cgrp->pids_mutex);
 	if (pid) {
-		int end = cp->length;
+		int end = cgrp->pids_length;
 
 		while (index < end) {
 			int mid = (index + end) / 2;
-			if (cp->tasks_pids[mid] == pid) {
+			if (cgrp->tasks_pids[mid] == pid) {
 				index = mid;
 				break;
-			} else if (cp->tasks_pids[mid] <= pid)
+			} else if (cgrp->tasks_pids[mid] <= pid)
 				index = mid + 1;
 			else
 				end = mid;
 		}
 	}
 	/* If we're off the end of the array, we're done */
-	if (index >= cp->length)
+	if (index >= cgrp->pids_length)
 		return NULL;
 	/* Update the abstract position to be the actual pid that we found */
-	iter = cp->tasks_pids + index;
+	iter = cgrp->tasks_pids + index;
 	*pos = *iter;
 	return iter;
 }
 
 static void cgroup_tasks_stop(struct seq_file *s, void *v)
 {
-	struct cgroup_pids *cp = s->private;
-	struct cgroup *cgrp = cp->cgrp;
+	struct cgroup *cgrp = s->private;
 	up_read(&cgrp->pids_mutex);
 }
 
 static void *cgroup_tasks_next(struct seq_file *s, void *v, loff_t *pos)
 {
-	struct cgroup_pids *cp = s->private;
+	struct cgroup *cgrp = s->private;
 	int *p = v;
-	int *end = cp->tasks_pids + cp->length;
+	int *end = cgrp->tasks_pids + cgrp->pids_length;
 
 	/*
 	 * Advance to the next pid in the array. If this goes off the
@@ -2536,33 +2515,26 @@ static const struct seq_operations cgroup_tasks_seq_operations = {
 	.show = cgroup_tasks_show,
 };
 
-static void release_cgroup_pid_array(struct cgroup_pids *cp)
+static void release_cgroup_pid_array(struct cgroup *cgrp)
 {
-	struct cgroup *cgrp = cp->cgrp;
-
 	down_write(&cgrp->pids_mutex);
-	BUG_ON(!cp->use_count);
-	if (!--cp->use_count) {
-		list_del(&cp->list);
-		put_pid_ns(cp->ns);
-		kfree(cp->tasks_pids);
-		kfree(cp);
+	BUG_ON(!cgrp->pids_use_count);
+	if (!--cgrp->pids_use_count) {
+		kfree(cgrp->tasks_pids);
+		cgrp->tasks_pids = NULL;
+		cgrp->pids_length = 0;
 	}
 	up_write(&cgrp->pids_mutex);
 }
 
 static int cgroup_tasks_release(struct inode *inode, struct file *file)
 {
-	struct seq_file *seq;
-	struct cgroup_pids *cp;
+	struct cgroup *cgrp = __d_cgrp(file->f_dentry->d_parent);
 
 	if (!(file->f_mode & FMODE_READ))
 		return 0;
 
-	seq = file->private_data;
-	cp = seq->private;
-
-	release_cgroup_pid_array(cp);
+	release_cgroup_pid_array(cgrp);
 	return seq_release(inode, file);
 }
 
@@ -2581,8 +2553,6 @@ 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;
@@ -2609,37 +2579,20 @@ static int cgroup_tasks_open(struct inode *unused, struct file *file)
 	 * array if necessary
 	 */
 	down_write(&cgrp->pids_mutex);
-
-	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++;
+	kfree(cgrp->tasks_pids);
+	cgrp->tasks_pids = pidarray;
+	cgrp->pids_length = npids;
+	cgrp->pids_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(cp);
+		release_cgroup_pid_array(cgrp);
 		return retval;
 	}
-	((struct seq_file *)file->private_data)->private = cp;
+	((struct seq_file *)file->private_data)->private = cgrp;
 	return 0;
 }