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cgroup: reserve ID 0 for dummy_root and 1 for unified hierarchy

PATCH In review Tejun Heo 2 participants 3 messages Jun 22, 2013 – Jun 25, 2013 1 message not in the archive cgroup

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Tejun Heo

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#0 lore raw

PATCH 1/1 cgroup: reserve ID 0 for dummy_root and 1 for unified hierarchy

Before 1a57423166 ("cgroup: make hierarchy_id use cyclic idr"), hierarchy IDs were allocated from 0. As the dummy hierarchy was always the one first initialized, it got assigned 0 and all other hierarchies from 1. The patch accidentally changed the minimum useable ID to 2.

Let's restore ID 0 for dummy_root and while at it reserve 1 for unified hierarchy.

Signed-off-by Tejun Heo <[email protected]>
Cc [email protected]
---
 kernel/cgroup.c |   10 ++++++----
 1 file changed, 6 insertions(+), 4 deletions(-)
kernel/cgroup.c +6 -4
@@ -1421,14 +1421,15 @@ static void init_cgroup_root(struct cgro
 	init_cgroup_housekeeping(cgrp);
 }
 
-static int cgroup_init_root_id(struct cgroupfs_root *root)
+static int cgroup_init_root_id(struct cgroupfs_root *root, int start, int end)
 {
 	int id;
 
 	lockdep_assert_held(&cgroup_mutex);
 	lockdep_assert_held(&cgroup_root_mutex);
 
-	id = idr_alloc_cyclic(&cgroup_hierarchy_idr, root, 2, 0, GFP_KERNEL);
+	id = idr_alloc_cyclic(&cgroup_hierarchy_idr, root, start, end,
+			      GFP_KERNEL);
 	if (id < 0)
 		return id;
 

@@ -1631,7 +1632,8 @@ static struct dentry *cgroup_mount(struc
 		if (ret)
 			goto unlock_drop;
 
-		ret = cgroup_init_root_id(root);
+		/* ID 0 is reserved for dummy root, 1 for unified hierarchy */
+		ret = cgroup_init_root_id(root, 2, 0);
 		if (ret)
 			goto unlock_drop;
 

@@ -4899,7 +4901,7 @@ int __init cgroup_init(void)
 	mutex_lock(&cgroup_mutex);
 	mutex_lock(&cgroup_root_mutex);
 
-	BUG_ON(cgroup_init_root_id(&cgroup_dummy_root));
+	BUG_ON(cgroup_init_root_id(&cgroup_dummy_root, 0, 1));
 
 	mutex_unlock(&cgroup_root_mutex);
 	mutex_unlock(&cgroup_mutex);

A message that is not in the archive (sent off-list or not yet received): 20130622163041.GA15261-Gd/HAXX7CRxy/[email protected]

Acked-by
#2 lore raw
Quoted 6 lines · Tejun Heo

Before 1a57423166 ("cgroup: make hierarchy_id use cyclic idr"), hierarchy IDs were allocated from 0. As the dummy hierarchy was always the one first initialized, it got assigned 0 and all other hierarchies from 1. The patch accidentally changed the minimum useable ID to 2.

Quoted 9 lines

Let's restore ID 0 for dummy_root and while at it reserve 1 for unified hierarchy.

Signed-off-by Tejun Heo <[email protected]>
Cc [email protected]
---
 kernel/cgroup.c |   10 ++++++----
 1 file changed, 6 insertions(+), 4 deletions(-)
Acked-by Li Zefan <[email protected]>
author Applied
#3 lore raw
In reply to a message not in the archive
Quoted 11 lines · Tejun Heo

Before 1a57423166 ("cgroup: make hierarchy_id use cyclic idr"), hierarchy IDs were allocated from 0. As the dummy hierarchy was always the one first initialized, it got assigned 0 and all other hierarchies from 1. The patch accidentally changed the minimum useable ID to 2.

Let's restore ID 0 for dummy_root and while at it reserve 1 for unified hierarchy.

Signed-off-by Tejun Heo <[email protected]>
Cc [email protected]

Applied to cgroup/for-3.11.

Thanks.

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