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| author | Zefan Li <lizefan@huawei.com> | 2014-09-26 12:03:25 +0800 |
|---|---|---|
| committer | Tejun Heo <tj@kernel.org> | 2014-09-26 00:16:23 -0400 |
| commit | e756c7b698604f11a979f2781d06eb7b80aba363 (patch) | |
| tree | d9deebb021eb70e509f0c44b4094bc18509ea036 | |
| parent | 0c7bf3e8cab7900e17ce7f97104c39927d835469 (diff) | |
| download | linux-e756c7b698604f11a979f2781d06eb7b80aba363.tar.gz | |
Revert "cgroup: remove redundant variable in cgroup_mount()"
This reverts commit 0c7bf3e8cab7900e17ce7f97104c39927d835469. If there are child cgroups in the cgroupfs and then we umount it, the superblock will be destroyed but the cgroup_root will be kept around. When we mount it again, cgroup_mount() will find this cgroup_root and allocate a new sb for it. So with this commit we will be trapped in a dead loop in the case described above, because kernfs_pin_sb() keeps returning NULL. Currently I don't see how we can avoid using both pinned_sb and new_sb, so just revert it. Cc: Al Viro <viro@ZenIV.linux.org.uk> Reported-by: Andrey Wagin <avagin@gmail.com> Signed-off-by: Zefan Li <lizefan@huawei.com> Signed-off-by: Tejun Heo <tj@kernel.org>
| -rw-r--r-- | kernel/cgroup.c | 11 |
1 files changed, 7 insertions, 4 deletions
diff --git a/kernel/cgroup.c b/kernel/cgroup.c index 5eb20cd1709c..f873c4681316 100644 --- a/kernel/cgroup.c +++ b/kernel/cgroup.c @@ -1694,6 +1694,7 @@ static struct dentry *cgroup_mount(struct file_system_type *fs_type, struct dentry *dentry; int ret; int i; + bool new_sb; /* * The first time anyone tries to mount a cgroup, enable the list @@ -1784,7 +1785,7 @@ static struct dentry *cgroup_mount(struct file_system_type *fs_type, * path is super cold. Let's just sleep a bit and retry. */ pinned_sb = kernfs_pin_sb(root->kf_root, NULL); - if (IS_ERR_OR_NULL(pinned_sb) || + if (IS_ERR(pinned_sb) || !percpu_ref_tryget_live(&root->cgrp.self.refcnt)) { mutex_unlock(&cgroup_mutex); if (!IS_ERR_OR_NULL(pinned_sb)) @@ -1830,16 +1831,18 @@ out_free: return ERR_PTR(ret); dentry = kernfs_mount(fs_type, flags, root->kf_root, - CGROUP_SUPER_MAGIC, NULL); - if (IS_ERR(dentry) || pinned_sb) + CGROUP_SUPER_MAGIC, &new_sb); + if (IS_ERR(dentry) || !new_sb) cgroup_put(&root->cgrp); /* * If @pinned_sb, we're reusing an existing root and holding an * extra ref on its sb. Mount is complete. Put the extra ref. */ - if (pinned_sb) + if (pinned_sb) { + WARN_ON(new_sb); deactivate_super(pinned_sb); + } return dentry; } |