cgroup: introduce cgroup_taskset and use it in subsys->can_attach(), cancel_attach() and attach()

Currently, there's no way to pass multiple tasks to cgroup_subsys
methods necessitating the need for separate per-process and per-task
methods.  This patch introduces cgroup_taskset which can be used to
pass multiple tasks and their associated cgroups to cgroup_subsys
methods.

Three methods - can_attach(), cancel_attach() and attach() - are
converted to use cgroup_taskset.  This unifies passed parameters so
that all methods have access to all information.  Conversions in this
patchset are identical and don't introduce any behavior change.

-v2: documentation updated as per Paul Menage's suggestion.

Signed-off-by: Tejun Heo <tj@kernel.org>
Reviewed-by: KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com>
Reviewed-by: Frederic Weisbecker <fweisbec@gmail.com>
Acked-by: Paul Menage <paul@paulmenage.org>
Acked-by: Li Zefan <lizf@cn.fujitsu.com>
Cc: Balbir Singh <bsingharora@gmail.com>
Cc: Daisuke Nishimura <nishimura@mxp.nes.nec.co.jp>
Cc: KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com>
Cc: James Morris <jmorris@namei.org>
master
Tejun Heo 11 years ago
parent 134d33737f
commit 2f7ee5691e
  1. 31
      Documentation/cgroups/cgroups.txt
  2. 28
      include/linux/cgroup.h
  3. 99
      kernel/cgroup.c
  4. 2
      kernel/cgroup_freezer.c
  5. 18
      kernel/cpuset.c
  6. 16
      mm/memcontrol.c
  7. 7
      security/device_cgroup.c

@ -594,15 +594,25 @@ rmdir() will fail with it. From this behavior, pre_destroy() can be
called multiple times against a cgroup.
int can_attach(struct cgroup_subsys *ss, struct cgroup *cgrp,
struct task_struct *task)
struct cgroup_taskset *tset)
(cgroup_mutex held by caller)
Called prior to moving a task into a cgroup; if the subsystem
returns an error, this will abort the attach operation. If a NULL
task is passed, then a successful result indicates that *any*
unspecified task can be moved into the cgroup. Note that this isn't
called on a fork. If this method returns 0 (success) then this should
remain valid while the caller holds cgroup_mutex and it is ensured that either
Called prior to moving one or more tasks into a cgroup; if the
subsystem returns an error, this will abort the attach operation.
@tset contains the tasks to be attached and is guaranteed to have at
least one task in it.
If there are multiple tasks in the taskset, then:
- it's guaranteed that all are from the same thread group
- @tset contains all tasks from the thread group whether or not
they're switching cgroups
- the first task is the leader
Each @tset entry also contains the task's old cgroup and tasks which
aren't switching cgroup can be skipped easily using the
cgroup_taskset_for_each() iterator. Note that this isn't called on a
fork. If this method returns 0 (success) then this should remain valid
while the caller holds cgroup_mutex and it is ensured that either
attach() or cancel_attach() will be called in future.
int can_attach_task(struct cgroup *cgrp, struct task_struct *tsk);
@ -613,14 +623,14 @@ attached (possibly many when using cgroup_attach_proc). Called after
can_attach.
void cancel_attach(struct cgroup_subsys *ss, struct cgroup *cgrp,
struct task_struct *task, bool threadgroup)
struct cgroup_taskset *tset)
(cgroup_mutex held by caller)
Called when a task attach operation has failed after can_attach() has succeeded.
A subsystem whose can_attach() has some side-effects should provide this
function, so that the subsystem can implement a rollback. If not, not necessary.
This will be called only about subsystems whose can_attach() operation have
succeeded.
succeeded. The parameters are identical to can_attach().
void pre_attach(struct cgroup *cgrp);
(cgroup_mutex held by caller)
@ -629,11 +639,12 @@ For any non-per-thread attachment work that needs to happen before
attach_task. Needed by cpuset.
void attach(struct cgroup_subsys *ss, struct cgroup *cgrp,
struct cgroup *old_cgrp, struct task_struct *task)
struct cgroup_taskset *tset)
(cgroup_mutex held by caller)
Called after the task has been attached to the cgroup, to allow any
post-attachment activity that requires memory allocations or blocking.
The parameters are identical to can_attach().
void attach_task(struct cgroup *cgrp, struct task_struct *tsk);
(cgroup_mutex held by caller)

@ -456,6 +456,28 @@ int cgroup_is_descendant(const struct cgroup *cgrp, struct task_struct *task);
void cgroup_exclude_rmdir(struct cgroup_subsys_state *css);
void cgroup_release_and_wakeup_rmdir(struct cgroup_subsys_state *css);
/*
* Control Group taskset, used to pass around set of tasks to cgroup_subsys
* methods.
*/
struct cgroup_taskset;
struct task_struct *cgroup_taskset_first(struct cgroup_taskset *tset);
struct task_struct *cgroup_taskset_next(struct cgroup_taskset *tset);
struct cgroup *cgroup_taskset_cur_cgroup(struct cgroup_taskset *tset);
int cgroup_taskset_size(struct cgroup_taskset *tset);
/**
* cgroup_taskset_for_each - iterate cgroup_taskset
* @task: the loop cursor
* @skip_cgrp: skip if task's cgroup matches this, %NULL to iterate through all
* @tset: taskset to iterate
*/
#define cgroup_taskset_for_each(task, skip_cgrp, tset) \
for ((task) = cgroup_taskset_first((tset)); (task); \
(task) = cgroup_taskset_next((tset))) \
if (!(skip_cgrp) || \
cgroup_taskset_cur_cgroup((tset)) != (skip_cgrp))
/*
* Control Group subsystem type.
* See Documentation/cgroups/cgroups.txt for details
@ -467,14 +489,14 @@ struct cgroup_subsys {
int (*pre_destroy)(struct cgroup_subsys *ss, struct cgroup *cgrp);
void (*destroy)(struct cgroup_subsys *ss, struct cgroup *cgrp);
int (*can_attach)(struct cgroup_subsys *ss, struct cgroup *cgrp,
struct task_struct *tsk);
struct cgroup_taskset *tset);
int (*can_attach_task)(struct cgroup *cgrp, struct task_struct *tsk);
void (*cancel_attach)(struct cgroup_subsys *ss, struct cgroup *cgrp,
struct task_struct *tsk);
struct cgroup_taskset *tset);
void (*pre_attach)(struct cgroup *cgrp);
void (*attach_task)(struct cgroup *cgrp, struct task_struct *tsk);
void (*attach)(struct cgroup_subsys *ss, struct cgroup *cgrp,
struct cgroup *old_cgrp, struct task_struct *tsk);
struct cgroup_taskset *tset);
void (*fork)(struct cgroup_subsys *ss, struct task_struct *task);
void (*exit)(struct cgroup_subsys *ss, struct cgroup *cgrp,
struct cgroup *old_cgrp, struct task_struct *task);

@ -1757,11 +1757,85 @@ int cgroup_path(const struct cgroup *cgrp, char *buf, int buflen)
}
EXPORT_SYMBOL_GPL(cgroup_path);
/*
* Control Group taskset
*/
struct task_and_cgroup {
struct task_struct *task;
struct cgroup *cgrp;
};
struct cgroup_taskset {
struct task_and_cgroup single;
struct flex_array *tc_array;
int tc_array_len;
int idx;
struct cgroup *cur_cgrp;
};
/**
* cgroup_taskset_first - reset taskset and return the first task
* @tset: taskset of interest
*
* @tset iteration is initialized and the first task is returned.
*/
struct task_struct *cgroup_taskset_first(struct cgroup_taskset *tset)
{
if (tset->tc_array) {
tset->idx = 0;
return cgroup_taskset_next(tset);
} else {
tset->cur_cgrp = tset->single.cgrp;
return tset->single.task;
}
}
EXPORT_SYMBOL_GPL(cgroup_taskset_first);
/**
* cgroup_taskset_next - iterate to the next task in taskset
* @tset: taskset of interest
*
* Return the next task in @tset. Iteration must have been initialized
* with cgroup_taskset_first().
*/
struct task_struct *cgroup_taskset_next(struct cgroup_taskset *tset)
{
struct task_and_cgroup *tc;
if (!tset->tc_array || tset->idx >= tset->tc_array_len)
return NULL;
tc = flex_array_get(tset->tc_array, tset->idx++);
tset->cur_cgrp = tc->cgrp;
return tc->task;
}
EXPORT_SYMBOL_GPL(cgroup_taskset_next);
/**
* cgroup_taskset_cur_cgroup - return the matching cgroup for the current task
* @tset: taskset of interest
*
* Return the cgroup for the current (last returned) task of @tset. This
* function must be preceded by either cgroup_taskset_first() or
* cgroup_taskset_next().
*/
struct cgroup *cgroup_taskset_cur_cgroup(struct cgroup_taskset *tset)
{
return tset->cur_cgrp;
}
EXPORT_SYMBOL_GPL(cgroup_taskset_cur_cgroup);
/**
* cgroup_taskset_size - return the number of tasks in taskset
* @tset: taskset of interest
*/
int cgroup_taskset_size(struct cgroup_taskset *tset)
{
return tset->tc_array ? tset->tc_array_len : 1;
}
EXPORT_SYMBOL_GPL(cgroup_taskset_size);
/*
* cgroup_task_migrate - move a task from one cgroup to another.
*
@ -1842,6 +1916,7 @@ int cgroup_attach_task(struct cgroup *cgrp, struct task_struct *tsk)
struct cgroup_subsys *ss, *failed_ss = NULL;
struct cgroup *oldcgrp;
struct cgroupfs_root *root = cgrp->root;
struct cgroup_taskset tset = { };
/* @tsk either already exited or can't exit until the end */
if (tsk->flags & PF_EXITING)
@ -1852,9 +1927,12 @@ int cgroup_attach_task(struct cgroup *cgrp, struct task_struct *tsk)
if (cgrp == oldcgrp)
return 0;
tset.single.task = tsk;
tset.single.cgrp = oldcgrp;
for_each_subsys(root, ss) {
if (ss->can_attach) {
retval = ss->can_attach(ss, cgrp, tsk);
retval = ss->can_attach(ss, cgrp, &tset);
if (retval) {
/*
* Remember on which subsystem the can_attach()
@ -1885,7 +1963,7 @@ int cgroup_attach_task(struct cgroup *cgrp, struct task_struct *tsk)
if (ss->attach_task)
ss->attach_task(cgrp, tsk);
if (ss->attach)
ss->attach(ss, cgrp, oldcgrp, tsk);
ss->attach(ss, cgrp, &tset);
}
synchronize_rcu();
@ -1907,7 +1985,7 @@ out:
*/
break;
if (ss->cancel_attach)
ss->cancel_attach(ss, cgrp, tsk);
ss->cancel_attach(ss, cgrp, &tset);
}
}
return retval;
@ -2023,6 +2101,7 @@ int cgroup_attach_proc(struct cgroup *cgrp, struct task_struct *leader)
struct task_struct *tsk;
struct task_and_cgroup *tc;
struct flex_array *group;
struct cgroup_taskset tset = { };
/*
* we need to make sure we have css_sets for all the tasks we're
* going to move -before- we actually start moving them, so that in
@ -2089,6 +2168,8 @@ int cgroup_attach_proc(struct cgroup *cgrp, struct task_struct *leader)
} while_each_thread(leader, tsk);
/* remember the number of threads in the array for later. */
group_size = i;
tset.tc_array = group;
tset.tc_array_len = group_size;
read_unlock(&tasklist_lock);
/* methods shouldn't be called if no task is actually migrating */
@ -2101,7 +2182,7 @@ int cgroup_attach_proc(struct cgroup *cgrp, struct task_struct *leader)
*/
for_each_subsys(root, ss) {
if (ss->can_attach) {
retval = ss->can_attach(ss, cgrp, leader);
retval = ss->can_attach(ss, cgrp, &tset);
if (retval) {
failed_ss = ss;
goto out_cancel_attach;
@ -2183,10 +2264,8 @@ int cgroup_attach_proc(struct cgroup *cgrp, struct task_struct *leader)
* being moved, this call will need to be reworked to communicate that.
*/
for_each_subsys(root, ss) {
if (ss->attach) {
tc = flex_array_get(group, 0);
ss->attach(ss, cgrp, tc->cgrp, tc->task);
}
if (ss->attach)
ss->attach(ss, cgrp, &tset);
}
/*
@ -2208,11 +2287,11 @@ out_cancel_attach:
for_each_subsys(root, ss) {
if (ss == failed_ss) {
if (cancel_failed_ss && ss->cancel_attach)
ss->cancel_attach(ss, cgrp, leader);
ss->cancel_attach(ss, cgrp, &tset);
break;
}
if (ss->cancel_attach)
ss->cancel_attach(ss, cgrp, leader);
ss->cancel_attach(ss, cgrp, &tset);
}
}
out_put_tasks:

@ -159,7 +159,7 @@ static void freezer_destroy(struct cgroup_subsys *ss,
*/
static int freezer_can_attach(struct cgroup_subsys *ss,
struct cgroup *new_cgroup,
struct task_struct *task)
struct cgroup_taskset *tset)
{
struct freezer *freezer;

@ -1371,10 +1371,10 @@ static int fmeter_getrate(struct fmeter *fmp)
}
/* Called by cgroups to determine if a cpuset is usable; cgroup_mutex held */
static int cpuset_can_attach(struct cgroup_subsys *ss, struct cgroup *cont,
struct task_struct *tsk)
static int cpuset_can_attach(struct cgroup_subsys *ss, struct cgroup *cgrp,
struct cgroup_taskset *tset)
{
struct cpuset *cs = cgroup_cs(cont);
struct cpuset *cs = cgroup_cs(cgrp);
if (cpumask_empty(cs->cpus_allowed) || nodes_empty(cs->mems_allowed))
return -ENOSPC;
@ -1387,7 +1387,7 @@ static int cpuset_can_attach(struct cgroup_subsys *ss, struct cgroup *cont,
* set_cpus_allowed_ptr() on all attached tasks before cpus_allowed may
* be changed.
*/
if (tsk->flags & PF_THREAD_BOUND)
if (cgroup_taskset_first(tset)->flags & PF_THREAD_BOUND)
return -EINVAL;
return 0;
@ -1437,12 +1437,14 @@ static void cpuset_attach_task(struct cgroup *cont, struct task_struct *tsk)
cpuset_update_task_spread_flag(cs, tsk);
}
static void cpuset_attach(struct cgroup_subsys *ss, struct cgroup *cont,
struct cgroup *oldcont, struct task_struct *tsk)
static void cpuset_attach(struct cgroup_subsys *ss, struct cgroup *cgrp,
struct cgroup_taskset *tset)
{
struct mm_struct *mm;
struct cpuset *cs = cgroup_cs(cont);
struct cpuset *oldcs = cgroup_cs(oldcont);
struct task_struct *tsk = cgroup_taskset_first(tset);
struct cgroup *oldcgrp = cgroup_taskset_cur_cgroup(tset);
struct cpuset *cs = cgroup_cs(cgrp);
struct cpuset *oldcs = cgroup_cs(oldcgrp);
/*
* Change mm, possibly for multiple threads in a threadgroup. This is

@ -5298,8 +5298,9 @@ static void mem_cgroup_clear_mc(void)
static int mem_cgroup_can_attach(struct cgroup_subsys *ss,
struct cgroup *cgroup,
struct task_struct *p)
struct cgroup_taskset *tset)
{
struct task_struct *p = cgroup_taskset_first(tset);
int ret = 0;
struct mem_cgroup *memcg = mem_cgroup_from_cont(cgroup);
@ -5337,7 +5338,7 @@ static int mem_cgroup_can_attach(struct cgroup_subsys *ss,
static void mem_cgroup_cancel_attach(struct cgroup_subsys *ss,
struct cgroup *cgroup,
struct task_struct *p)
struct cgroup_taskset *tset)
{
mem_cgroup_clear_mc();
}
@ -5454,9 +5455,9 @@ retry:
static void mem_cgroup_move_task(struct cgroup_subsys *ss,
struct cgroup *cont,
struct cgroup *old_cont,
struct task_struct *p)
struct cgroup_taskset *tset)
{
struct task_struct *p = cgroup_taskset_first(tset);
struct mm_struct *mm = get_task_mm(p);
if (mm) {
@ -5471,19 +5472,18 @@ static void mem_cgroup_move_task(struct cgroup_subsys *ss,
#else /* !CONFIG_MMU */
static int mem_cgroup_can_attach(struct cgroup_subsys *ss,
struct cgroup *cgroup,
struct task_struct *p)
struct cgroup_taskset *tset)
{
return 0;
}
static void mem_cgroup_cancel_attach(struct cgroup_subsys *ss,
struct cgroup *cgroup,
struct task_struct *p)
struct cgroup_taskset *tset)
{
}
static void mem_cgroup_move_task(struct cgroup_subsys *ss,
struct cgroup *cont,
struct cgroup *old_cont,
struct task_struct *p)
struct cgroup_taskset *tset)
{
}
#endif

@ -62,11 +62,12 @@ static inline struct dev_cgroup *task_devcgroup(struct task_struct *task)
struct cgroup_subsys devices_subsys;
static int devcgroup_can_attach(struct cgroup_subsys *ss,
struct cgroup *new_cgroup, struct task_struct *task)
struct cgroup *new_cgrp, struct cgroup_taskset *set)
{
if (current != task && !capable(CAP_SYS_ADMIN))
return -EPERM;
struct task_struct *task = cgroup_taskset_first(set);
if (current != task && !capable(CAP_SYS_ADMIN))
return -EPERM;
return 0;
}

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