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Commit acbef755 authored by Tejun Heo's avatar Tejun Heo
Browse files

cgroup: convert "tasks" and "cgroup.procs" handle to use cftype->write() 



cgroup_tasks_write() and cgroup_procs_write() are currently using
cftype->write_u64().  This patch converts them to use cftype->write()
instead.  This allows access to the associated kernfs_open_file which
will be necessary to implement the planned kernfs active protection
manipulation for these files.

This shifts buffer parsing to attach_task_by_pid() and makes it return
@nbytes on success.  Let's rename it to __cgroup_procs_write() to
clearly indicate that this is a write handler implementation.

This patch doesn't introduce any visible behavior changes.

Signed-off-by: default avatarTejun Heo <tj@kernel.org>
Acked-by: default avatarLi Zefan <lizefan@huawei.com>
parent 6770c64e

kernel/cgroup.c

+16 −10
Original line number Diff line number Diff line
@@ -2232,12 +2232,18 @@ static int cgroup_attach_task(struct cgroup *dst_cgrp, 
 * function to attach either it or all tasks in its threadgroup. Will lock

 * cgroup_mutex and threadgroup.

 */

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

static ssize_t __cgroup_procs_write(struct kernfs_open_file *of, char *buf,

				    size_t nbytes, loff_t off, bool threadgroup)

{

	struct task_struct *tsk;

	const struct cred *cred = current_cred(), *tcred;

	struct cgroup *cgrp = of_css(of)->cgroup;

	pid_t pid;

	int ret;



	if (kstrtoint(strstrip(buf), 0, &pid) || pid < 0)

		return -EINVAL;



	if (!cgroup_lock_live_group(cgrp))

		return -ENODEV;
@@ -2305,7 +2311,7 @@ static int attach_task_by_pid(struct cgroup *cgrp, u64 pid, bool threadgroup) 
	put_task_struct(tsk);

out_unlock_cgroup:

	mutex_unlock(&cgroup_mutex);

	return ret;

	return ret ?: nbytes;

}



/**
@@ -2339,16 +2345,16 @@ int cgroup_attach_task_all(struct task_struct *from, struct task_struct *tsk) 
}

EXPORT_SYMBOL_GPL(cgroup_attach_task_all);



static int cgroup_tasks_write(struct cgroup_subsys_state *css,

			      struct cftype *cft, u64 pid)

static ssize_t cgroup_tasks_write(struct kernfs_open_file *of,

				  char *buf, size_t nbytes, loff_t off)

{

	return attach_task_by_pid(css->cgroup, pid, false);

	return __cgroup_procs_write(of, buf, nbytes, off, false);

}



static int cgroup_procs_write(struct cgroup_subsys_state *css,

			      struct cftype *cft, u64 tgid)

static ssize_t cgroup_procs_write(struct kernfs_open_file *of,

				  char *buf, size_t nbytes, loff_t off)

{

	return attach_task_by_pid(css->cgroup, tgid, true);

	return __cgroup_procs_write(of, buf, nbytes, off, true);

}



static ssize_t cgroup_release_agent_write(struct kernfs_open_file *of,
@@ -3953,7 +3959,7 @@ static struct cftype cgroup_base_files[] = { 
		.seq_stop = cgroup_pidlist_stop,

		.seq_show = cgroup_pidlist_show,

		.private = CGROUP_FILE_PROCS,

		.write_u64 = cgroup_procs_write,

		.write = cgroup_procs_write,

		.mode = S_IRUGO | S_IWUSR,

	},

	{
@@ -4002,7 +4008,7 @@ static struct cftype cgroup_base_files[] = { 
		.seq_stop = cgroup_pidlist_stop,

		.seq_show = cgroup_pidlist_show,

		.private = CGROUP_FILE_TASKS,

		.write_u64 = cgroup_tasks_write,

		.write = cgroup_tasks_write,

		.mode = S_IRUGO | S_IWUSR,

	},

	{