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cgroup: simplify cgroup_load_subsys() failure path 

Now that cgroup_unload_subsys() can tell whether the root css is
online or not, we can safely call cgroup_unload_subsys() after idr
init failure in cgroup_load_subsys().

Replace the manual unrolling and invoke cgroup_unload_subsys() on
failure.  This drops cgroup_mutex inbetween but should be safe as the
subsystem will fail try_module_get() and thus can't be mounted
inbetween.  As this means that cgroup_unload_subsys() can be called
before css_sets are rehashed, remove BUG_ON() on %NULL
css_set->subsys[] from cgroup_unload_subsys().

Signed-off-by: Tejun Heo <tj@kernel.org>
Acked-by: Li Zefan <lizefan@huawei.com>
This commit is contained in:
Tejun Heo 2012-11-19 08:13:37 -08:00
parent a31f2d3ff7
commit d19e19de48
1 changed files with 10 additions and 11 deletions
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21
kernel/cgroup.c
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@ -4400,8 +4400,8 @@ static void __init cgroup_init_subsys(struct cgroup_subsys *ss)
*/
int __init_or_module cgroup_load_subsys(struct cgroup_subsys *ss)
{
int i;
struct cgroup_subsys_state *css;
int i, ret;
/* check name and function validity */
if (ss->name == NULL || strlen(ss->name) > MAX_CGROUP_TYPE_NAMELEN ||
@ -4452,15 +4452,9 @@ int __init_or_module cgroup_load_subsys(struct cgroup_subsys *ss)
init_cgroup_css(css, ss, dummytop);
/* init_idr must be after init_cgroup_css because it sets css->id. */
if (ss->use_id) {
int ret = cgroup_init_idr(ss, css);
if (ret) {
ss->destroy(dummytop);
dummytop->subsys[ss->subsys_id] = NULL;
subsys[ss->subsys_id] = NULL;
list_del_init(&ss->sibling);
mutex_unlock(&cgroup_mutex);
return ret;
}
ret = cgroup_init_idr(ss, css);
if (ret)
goto err_unload;
}
/*
@ -4498,6 +4492,12 @@ int __init_or_module cgroup_load_subsys(struct cgroup_subsys *ss)
/* success! */
mutex_unlock(&cgroup_mutex);
return 0;
err_unload:
mutex_unlock(&cgroup_mutex);
/* @ss can't be mounted here as try_module_get() would fail */
cgroup_unload_subsys(ss);
return ret;
}
EXPORT_SYMBOL_GPL(cgroup_load_subsys);
@ -4548,7 +4548,6 @@ void cgroup_unload_subsys(struct cgroup_subsys *ss)
struct css_set *cg = link->cg;
hlist_del(&cg->hlist);
BUG_ON(!cg->subsys[ss->subsys_id]);
cg->subsys[ss->subsys_id] = NULL;
hhead = css_set_hash(cg->subsys);
hlist_add_head(&cg->hlist, hhead);