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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: Michael S. Tsirkin <mst@redhat.com>
Tested-by: Alex Williamson <alex.williamson@redhat.com>
Acked-by: Paul 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: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
This commit is contained in:
Michael S. Tsirkin 2010-09-09 16:37:37 -07:00 committed by Linus Torvalds
parent ed430fec75
commit 31583bb0cf
2 changed files with 18 additions and 7 deletions
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12
include/linux/cgroup.h
View File

@ -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;

13
kernel/cgroup.c
View File

@ -1791,19 +1791,20 @@ out:
}
/**
* 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