cgroup: add cgroup->id
With the introduction of generic cgroup hierarchy iterators, css_id is
being phased out. It was unnecessarily complex, id'ing the wrong
thing (cgroups need IDs, not CSSes) and has other oddities like not
being available at ->css_alloc().
This patch adds cgroup->id, which is a simple per-hierarchy
ida-allocated ID which is assigned before ->css_alloc() and released
after ->css_free().
Signed-off-by: Tejun Heo <tj@kernel.org>
Acked-by: Li Zefan <lizefan@huawei.com>
Acked-by: Neil Horman <nhorman@tuxdriver.com>
diff --git a/kernel/cgroup.c b/kernel/cgroup.c
index 96719f7..6db0141 100644
--- a/kernel/cgroup.c
+++ b/kernel/cgroup.c
@@ -138,6 +138,9 @@
/* Hierarchy-specific flags */
unsigned long flags;
+ /* IDs for cgroups in this hierarchy */
+ struct ida cgroup_ida;
+
/* The path to use for release notifications. */
char release_agent_path[PATH_MAX];
@@ -890,6 +893,7 @@
simple_xattrs_free(&cgrp->xattrs);
+ ida_simple_remove(&cgrp->root->cgroup_ida, cgrp->id);
kfree_rcu(cgrp, rcu_head);
} else {
struct cfent *cfe = __d_cfe(dentry);
@@ -1465,6 +1469,7 @@
root->subsys_mask = opts->subsys_mask;
root->flags = opts->flags;
+ ida_init(&root->cgroup_ida);
if (opts->release_agent)
strcpy(root->release_agent_path, opts->release_agent);
if (opts->name)
@@ -1483,6 +1488,7 @@
spin_lock(&hierarchy_id_lock);
ida_remove(&hierarchy_ida, root->hierarchy_id);
spin_unlock(&hierarchy_id_lock);
+ ida_destroy(&root->cgroup_ida);
kfree(root);
}
@@ -4093,10 +4099,15 @@
struct cgroup_subsys *ss;
struct super_block *sb = root->sb;
+ /* allocate the cgroup and its ID, 0 is reserved for the root */
cgrp = kzalloc(sizeof(*cgrp), GFP_KERNEL);
if (!cgrp)
return -ENOMEM;
+ cgrp->id = ida_simple_get(&root->cgroup_ida, 1, 0, GFP_KERNEL);
+ if (cgrp->id < 0)
+ goto err_free_cgrp;
+
/*
* Only live parents can have children. Note that the liveliness
* check isn't strictly necessary because cgroup_mkdir() and
@@ -4106,7 +4117,7 @@
*/
if (!cgroup_lock_live_group(parent)) {
err = -ENODEV;
- goto err_free_cgrp;
+ goto err_free_id;
}
/* Grab a reference on the superblock so the hierarchy doesn't
@@ -4198,6 +4209,8 @@
mutex_unlock(&cgroup_mutex);
/* Release the reference count that we took on the superblock */
deactivate_super(sb);
+err_free_id:
+ ida_simple_remove(&root->cgroup_ida, cgrp->id);
err_free_cgrp:
kfree(cgrp);
return err;
