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cgroup: make cgroup[_taskset]_migrate() take cgroup_root instead of cgroup

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On the default hierarchy, a migration can be multi-source and/or
multi-destination.  cgroup_taskest_migrate() used to incorrectly
assume single destination cgroup but the bug has been fixed by
1f7dd3e5a6 ("cgroup: fix handling of multi-destination migration
from subtree_control enabling").

Since the commit, @dst_cgrp to cgroup[_taskset]_migrate() is only used
to determine which subsystems are affected or which cgroup_root the
migration is taking place in.  As such, @dst_cgrp is misleading.  This
patch replaces @dst_cgrp with @root.

Signed-off-by: Tejun Heo <tj@kernel.org>
This commit is contained in:
Tejun Heo 2016-03-08 11:51:26 -05:00
parent 6c694c8825
commit 37ff9f8f47
1 changed files with 35 additions and 35 deletions
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70
kernel/cgroup.c
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@ -2355,38 +2355,38 @@ struct task_struct *cgroup_taskset_next(struct cgroup_taskset *tset,
}
/**
* cgroup_taskset_migrate - migrate a taskset to a cgroup
* cgroup_taskset_migrate - migrate a taskset
* @tset: taget taskset
* @dst_cgrp: destination cgroup
* @root: cgroup root the migration is taking place on
*
* Migrate tasks in @tset to @dst_cgrp. This function fails iff one of the
* ->can_attach callbacks fails and guarantees that either all or none of
* the tasks in @tset are migrated. @tset is consumed regardless of
* success.
* Migrate tasks in @tset as setup by migration preparation functions.
* This function fails iff one of the ->can_attach callbacks fails and
* guarantees that either all or none of the tasks in @tset are migrated.
* @tset is consumed regardless of success.
*/
static int cgroup_taskset_migrate(struct cgroup_taskset *tset,
struct cgroup *dst_cgrp)
struct cgroup_root *root)
{
struct cgroup_subsys_state *css, *failed_css = NULL;
struct cgroup_subsys *ss;
struct task_struct *task, *tmp_task;
struct css_set *cset, *tmp_cset;
int i, ret;
int ssid, failed_ssid, ret;
/* methods shouldn't be called if no task is actually migrating */
if (list_empty(&tset->src_csets))
return 0;
/* check that we can legitimately attach to the cgroup */
for_each_e_css(css, i, dst_cgrp) {
if (css->ss->can_attach) {
tset->ssid = i;
ret = css->ss->can_attach(tset);
do_each_subsys_mask(ss, ssid, root->subsys_mask) {
if (ss->can_attach) {
tset->ssid = ssid;
ret = ss->can_attach(tset);
if (ret) {
failed_css = css;
failed_ssid = ssid;
goto out_cancel_attach;
}
}
}
} while_each_subsys_mask();
/*
* Now that we're guaranteed success, proceed to move all tasks to
@ -2413,25 +2413,25 @@ static int cgroup_taskset_migrate(struct cgroup_taskset *tset,
*/
tset->csets = &tset->dst_csets;
for_each_e_css(css, i, dst_cgrp) {
if (css->ss->attach) {
tset->ssid = i;
css->ss->attach(tset);
do_each_subsys_mask(ss, ssid, root->subsys_mask) {
if (ss->attach) {
tset->ssid = ssid;
ss->attach(tset);
}
}
} while_each_subsys_mask();
ret = 0;
goto out_release_tset;
out_cancel_attach:
for_each_e_css(css, i, dst_cgrp) {
if (css == failed_css)
do_each_subsys_mask(ss, ssid, root->subsys_mask) {
if (ssid == failed_ssid)
break;
if (css->ss->cancel_attach) {
tset->ssid = i;
css->ss->cancel_attach(tset);
if (ss->cancel_attach) {
tset->ssid = ssid;
ss->cancel_attach(tset);
}
}
} while_each_subsys_mask();
out_release_tset:
spin_lock_bh(&css_set_lock);
list_splice_init(&tset->dst_csets, &tset->src_csets);
@ -2586,11 +2586,11 @@ err:
* cgroup_migrate - migrate a process or task to a cgroup
* @leader: the leader of the process or the task to migrate
* @threadgroup: whether @leader points to the whole process or a single task
* @cgrp: the destination cgroup
* @root: cgroup root migration is taking place on
*
* Migrate a process or task denoted by @leader to @cgrp. If migrating a
* process, the caller must be holding cgroup_threadgroup_rwsem. The
* caller is also responsible for invoking cgroup_migrate_add_src() and
* Migrate a process or task denoted by @leader. If migrating a process,
* the caller must be holding cgroup_threadgroup_rwsem. The caller is also
* responsible for invoking cgroup_migrate_add_src() and
* cgroup_migrate_prepare_dst() on the targets before invoking this
* function and following up with cgroup_migrate_finish().
*
@ -2601,7 +2601,7 @@ err:
* actually starting migrating.
*/
static int cgroup_migrate(struct task_struct *leader, bool threadgroup,
struct cgroup *cgrp)
struct cgroup_root *root)
{
struct cgroup_taskset tset = CGROUP_TASKSET_INIT(tset);
struct task_struct *task;
@ -2622,7 +2622,7 @@ static int cgroup_migrate(struct task_struct *leader, bool threadgroup,
rcu_read_unlock();
spin_unlock_bh(&css_set_lock);
return cgroup_taskset_migrate(&tset, cgrp);
return cgroup_taskset_migrate(&tset, root);
}
/**
@ -2659,7 +2659,7 @@ static int cgroup_attach_task(struct cgroup *dst_cgrp,
/* prepare dst csets and commit */
ret = cgroup_migrate_prepare_dst(dst_cgrp, &preloaded_csets);
if (!ret)
ret = cgroup_migrate(leader, threadgroup, dst_cgrp);
ret = cgroup_migrate(leader, threadgroup, dst_cgrp->root);
cgroup_migrate_finish(&preloaded_csets);
return ret;
@ -2934,7 +2934,7 @@ static int cgroup_update_dfl_csses(struct cgroup *cgrp)
}
spin_unlock_bh(&css_set_lock);
ret = cgroup_taskset_migrate(&tset, cgrp);
ret = cgroup_taskset_migrate(&tset, cgrp->root);
out_finish:
cgroup_migrate_finish(&preloaded_csets);
percpu_up_write(&cgroup_threadgroup_rwsem);
@ -4172,7 +4172,7 @@ int cgroup_transfer_tasks(struct cgroup *to, struct cgroup *from)
css_task_iter_end(&it);
if (task) {
ret = cgroup_migrate(task, false, to);
ret = cgroup_migrate(task, false, to->root);
put_task_struct(task);
}
} while (task && !ret);