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Commit 31583bb0 authored by Michael S. Tsirkin's avatar Michael S. Tsirkin Committed by Linus Torvalds
Browse files

cgroups: fix API thinko 



Add cgroup_attach_task_all()

The existing cgroup_attach_task_current_cg() API is called by a thread to
attach another thread to all of its cgroups; this is unsuitable for cases
where a privileged task wants to attach itself to the cgroups of a less
privileged one, since the call must be made from the context of the target
task.

This patch adds a more generic cgroup_attach_task_all() API that allows
both the source task and to-be-moved task to be specified.
cgroup_attach_task_current_cg() becomes a specialization of the more
generic new function.

[menage@google.com: rewrote changelog]
[akpm@linux-foundation.org: address reviewer comments]
Signed-off-by: default avatarMichael S. Tsirkin <mst@redhat.com>
Tested-by: default avatarAlex Williamson <alex.williamson@redhat.com>
Acked-by: default avatarPaul Menage <menage@google.com>
Cc: Li Zefan <lizf@cn.fujitsu.com>
Cc: Ben Blum <bblum@google.com>
Cc: Sridhar Samudrala <sri@us.ibm.com>
Signed-off-by: default avatarAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: default avatarLinus Torvalds <torvalds@linux-foundation.org>
parent ed430fec

include/linux/cgroup.h

+11 −1
Original line number Diff line number Diff line
@@ -578,7 +578,12 @@ struct task_struct *cgroup_iter_next(struct cgroup *cgrp, 
void cgroup_iter_end(struct cgroup *cgrp, struct cgroup_iter *it);

int cgroup_scan_tasks(struct cgroup_scanner *scan);

int cgroup_attach_task(struct cgroup *, struct task_struct *);

int cgroup_attach_task_current_cg(struct task_struct *);

int cgroup_attach_task_all(struct task_struct *from, struct task_struct *);



static inline int cgroup_attach_task_current_cg(struct task_struct *tsk)

{

	return cgroup_attach_task_all(current, tsk);

}



/*

 * CSS ID is ID for cgroup_subsys_state structs under subsys. This only works
@@ -636,6 +641,11 @@ static inline int cgroupstats_build(struct cgroupstats *stats, 
}



/* No cgroups - nothing to do */

static inline int cgroup_attach_task_all(struct task_struct *from,

					 struct task_struct *t)

{

	return 0;

}

static inline int cgroup_attach_task_current_cg(struct task_struct *t)

{

	return 0;

kernel/cgroup.c

+7 −6
Original line number Diff line number Diff line
@@ -1791,19 +1791,20 @@ int cgroup_attach_task(struct cgroup *cgrp, struct task_struct *tsk) 
}



/**

 * cgroup_attach_task_current_cg - attach task 'tsk' to current task's cgroup

 * cgroup_attach_task_all - attach task 'tsk' to all cgroups of task 'from'

 * @from: attach to all cgroups of a given task

 * @tsk: the task to be attached

 */

int cgroup_attach_task_current_cg(struct task_struct *tsk)

int cgroup_attach_task_all(struct task_struct *from, struct task_struct *tsk)

{

	struct cgroupfs_root *root;

	struct cgroup *cur_cg;

	int retval = 0;



	cgroup_lock();

	for_each_active_root(root) {

		cur_cg = task_cgroup_from_root(current, root);

		retval = cgroup_attach_task(cur_cg, tsk);

		struct cgroup *from_cg = task_cgroup_from_root(from, root);



		retval = cgroup_attach_task(from_cg, tsk);

		if (retval)

			break;

	}
@@ -1811,7 +1812,7 @@ int cgroup_attach_task_current_cg(struct task_struct *tsk) 


	return retval;

}

EXPORT_SYMBOL_GPL(cgroup_attach_task_current_cg);

EXPORT_SYMBOL_GPL(cgroup_attach_task_all);



/*

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