* Paul Menage <[email protected]> wrote:
> cgroup: Fix root_count when mount fails due to busy subsystem
>
> root_count was being incremented in cgroup_get_sb() after all error
> checking was complete, but decremented in cgroup_kill_sb(), which can be
> called on a superblock that we gave up on due to an error. This patch
> changes cgroup_kill_sb() to only decrement root_count if the root was
> previously linked into the list of roots.
i'm wondering, what happens in the buggy case: does cgroup_kill_sb() get
called twice (if yes, why?), or do we call cgroup_kill_sb() on a not yet
added sb and hence root_count has not been elevated yet? (if yes, which
codepath does this?)
The error handling in cgroup_get_sb() definitely seems a bit twisted -
find below a few error path and other cleanups.
Thanks,
Ingo
diff --git a/kernel/cgroup.c b/kernel/cgroup.c
index c298310..28d1b67 100644
--- a/kernel/cgroup.c
+++ b/kernel/cgroup.c
@@ -1025,18 +1026,12 @@ static int cgroup_get_sb(struct file_system_type
*fs_type,
* have some link structures left over
*/
ret = allocate_cg_links(css_set_count, &tmp_cg_links);
- if (ret) {
- mutex_unlock(&cgroup_mutex);
- mutex_unlock(&inode->i_mutex);
- goto drop_new_super;
- }
+ if (ret)
+ goto drop_new_super_unlock;
ret = rebind_subsystems(root, root->subsys_bits);
- if (ret == -EBUSY) {
- mutex_unlock(&cgroup_mutex);
- mutex_unlock(&inode->i_mutex);
+ if (ret == -EBUSY)
goto free_cg_links;
- }
/* EBUSY should be the only error here */
BUG_ON(ret);
@@ -1075,18 +1070,24 @@ static int cgroup_get_sb(struct file_system_type
*fs_type,
free_cg_links:
free_cg_links(&tmp_cg_links);
+
+ drop_new_super_unlock:
+ mutex_unlock(&cgroup_mutex);
+ mutex_unlock(&inode->i_mutex);
drop_new_super:
up_write(&sb->s_umount);
deactivate_super(sb);
+
return ret;
}
-static void cgroup_kill_sb(struct super_block *sb) {
+static void cgroup_kill_sb(struct super_block *sb)
+{
struct cgroupfs_root *root = sb->s_fs_info;
struct cgroup *cgrp = &root->top_cgroup;
- int ret;
- struct cg_cgroup_link *link;
struct cg_cgroup_link *saved_link;
+ struct cg_cgroup_link *link;
+ int ret;
BUG_ON(!root);
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