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Commit af351026 authored by Paul Menage's avatar Paul Menage Committed by Linus Torvalds
Browse files

cgroup files: turn attach_task_by_pid directly into a cgroup write handler 



This patch changes attach_task_by_pid() to take a u64 rather than a
string; as a result it can be called directly as a control groups
write_u64 handler, and cgroup_common_file_write() can be removed.

Signed-off-by: default avatarPaul Menage <menage@google.com>
Cc: Paul Jackson <pj@sgi.com>
Cc: Pavel Emelyanov <xemul@openvz.org>
Cc: Balbir Singh <balbir@in.ibm.com>
Cc: Serge Hallyn <serue@us.ibm.com>
Cc: KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com>
Signed-off-by: default avatarAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: default avatarLinus Torvalds <torvalds@linux-foundation.org>
parent 6379c106

kernel/cgroup.c

+14 −66
Original line number Diff line number Diff line
@@ -504,10 +504,6 @@ static struct css_set *find_css_set( 
 * knows that the cgroup won't be removed, as cgroup_rmdir()

 * needs that mutex.

 *

 * The cgroup_common_file_write handler for operations that modify

 * the cgroup hierarchy holds cgroup_mutex across the entire operation,

 * single threading all such cgroup modifications across the system.

 *

 * The fork and exit callbacks cgroup_fork() and cgroup_exit(), don't

 * (usually) take cgroup_mutex.  These are the two most performance

 * critical pieces of code here.  The exception occurs on cgroup_exit(),
@@ -1279,18 +1275,14 @@ int cgroup_attach_task(struct cgroup *cgrp, struct task_struct *tsk) 
}



/*

 * Attach task with pid 'pid' to cgroup 'cgrp'. Call with

 * cgroup_mutex, may take task_lock of task

 * Attach task with pid 'pid' to cgroup 'cgrp'. Call with cgroup_mutex

 * held. May take task_lock of task

 */

static int attach_task_by_pid(struct cgroup *cgrp, char *pidbuf)

static int attach_task_by_pid(struct cgroup *cgrp, u64 pid)

{

	pid_t pid;

	struct task_struct *tsk;

	int ret;



	if (sscanf(pidbuf, "%d", &pid) != 1)

		return -EIO;



	if (pid) {

		rcu_read_lock();

		tsk = find_task_by_vpid(pid);
@@ -1316,6 +1308,16 @@ static int attach_task_by_pid(struct cgroup *cgrp, char *pidbuf) 
	return ret;

}



static int cgroup_tasks_write(struct cgroup *cgrp, struct cftype *cft, u64 pid)

{

	int ret;

	if (!cgroup_lock_live_group(cgrp))

		return -ENODEV;

	ret = attach_task_by_pid(cgrp, pid);

	cgroup_unlock();

	return ret;

}



/* The various types of files and directories in a cgroup file system */

enum cgroup_filetype {

	FILE_ROOT,
@@ -1434,60 +1436,6 @@ static ssize_t cgroup_write_string(struct cgroup *cgrp, struct cftype *cft, 
	return retval;

}



static ssize_t cgroup_common_file_write(struct cgroup *cgrp,

					   struct cftype *cft,

					   struct file *file,

					   const char __user *userbuf,

					   size_t nbytes, loff_t *unused_ppos)

{

	enum cgroup_filetype type = cft->private;

	char *buffer;

	int retval = 0;



	if (nbytes >= PATH_MAX)

		return -E2BIG;



	/* +1 for nul-terminator */

	buffer = kmalloc(nbytes + 1, GFP_KERNEL);

	if (buffer == NULL)

		return -ENOMEM;



	if (copy_from_user(buffer, userbuf, nbytes)) {

		retval = -EFAULT;

		goto out1;

	}

	buffer[nbytes] = 0;	/* nul-terminate */

	strstrip(buffer);	/* strip -just- trailing whitespace */



	mutex_lock(&cgroup_mutex);



	/*

	 * This was already checked for in cgroup_file_write(), but

	 * check again now we're holding cgroup_mutex.

	 */

	if (cgroup_is_removed(cgrp)) {

		retval = -ENODEV;

		goto out2;

	}



	switch (type) {

	case FILE_TASKLIST:

		retval = attach_task_by_pid(cgrp, buffer);

		break;

	default:

		retval = -EINVAL;

		goto out2;

	}



	if (retval == 0)

		retval = nbytes;

out2:

	mutex_unlock(&cgroup_mutex);

out1:

	kfree(buffer);

	return retval;

}



static ssize_t cgroup_file_write(struct file *file, const char __user *buf,

						size_t nbytes, loff_t *ppos)

{
@@ -2265,7 +2213,7 @@ static struct cftype files[] = { 
		.name = "tasks",

		.open = cgroup_tasks_open,

		.read = cgroup_tasks_read,

		.write = cgroup_common_file_write,

		.write_u64 = cgroup_tasks_write,

		.release = cgroup_tasks_release,

		.private = FILE_TASKLIST,

	},