Revert "cgroup: remove redundant variable in cgroup_mount()"
This reverts commit 0c7bf3e8ca
.
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>
This commit is contained in:
Родитель
0c7bf3e8ca
Коммит
e756c7b698
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@ -1694,6 +1694,7 @@ static struct dentry *cgroup_mount(struct file_system_type *fs_type,
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struct dentry *dentry;
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int ret;
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int i;
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bool new_sb;
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/*
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* The first time anyone tries to mount a cgroup, enable the list
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@ -1784,7 +1785,7 @@ static struct dentry *cgroup_mount(struct file_system_type *fs_type,
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* path is super cold. Let's just sleep a bit and retry.
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*/
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pinned_sb = kernfs_pin_sb(root->kf_root, NULL);
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if (IS_ERR_OR_NULL(pinned_sb) ||
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if (IS_ERR(pinned_sb) ||
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!percpu_ref_tryget_live(&root->cgrp.self.refcnt)) {
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mutex_unlock(&cgroup_mutex);
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if (!IS_ERR_OR_NULL(pinned_sb))
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@ -1830,16 +1831,18 @@ out_free:
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return ERR_PTR(ret);
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dentry = kernfs_mount(fs_type, flags, root->kf_root,
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CGROUP_SUPER_MAGIC, NULL);
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if (IS_ERR(dentry) || pinned_sb)
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CGROUP_SUPER_MAGIC, &new_sb);
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if (IS_ERR(dentry) || !new_sb)
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cgroup_put(&root->cgrp);
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/*
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* If @pinned_sb, we're reusing an existing root and holding an
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* extra ref on its sb. Mount is complete. Put the extra ref.
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*/
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if (pinned_sb)
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if (pinned_sb) {
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WARN_ON(new_sb);
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deactivate_super(pinned_sb);
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}
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return dentry;
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}
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