diff options
Diffstat (limited to 'fs/namespace.c')
| -rw-r--r-- | fs/namespace.c | 22 |
1 files changed, 19 insertions, 3 deletions
diff --git a/fs/namespace.c b/fs/namespace.c index 1686b4442f1d..443b0fa564c4 100644 --- a/fs/namespace.c +++ b/fs/namespace.c @@ -658,9 +658,25 @@ static bool legitimize_mnt(struct vfsmount *bastard, unsigned seq) return false; } -/* - * find the first mount at @dentry on vfsmount @mnt. - * call under rcu_read_lock() +/** + * __lookup_mnt - find first child mount + * @mnt: parent mount + * @dentry: mountpoint + * + * If @mnt has a child mount @c mounted @dentry find and return it. + * + * Note that the child mount @c need not be unique. There are cases + * where shadow mounts are created. For example, during mount + * propagation when a source mount @mnt whose root got overmounted by a + * mount @o after path lookup but before @namespace_sem could be + * acquired gets copied and propagated. So @mnt gets copied including + * @o. When @mnt is propagated to a destination mount @d that already + * has another mount @n mounted at the same mountpoint then the source + * mount @mnt will be tucked beneath @n, i.e., @n will be mounted on + * @mnt and @mnt mounted on @d. Now both @n and @o are mounted at @mnt + * on @dentry. + * + * Return: The first child of @mnt mounted @dentry or NULL. */ struct mount *__lookup_mnt(struct vfsmount *mnt, struct dentry *dentry) { |