static struct mount *last_dest, *first_source, *last_source, *dest_master;
static struct hlist_head *list;
-static inline bool peers(struct mount *m1, struct mount *m2)
+static inline bool peers(const struct mount *m1, const struct mount *m2)
{
return m1->mnt_group_id == m2->mnt_group_id && m1->mnt_group_id;
}
return mnt_get_count(mnt) > count;
}
+/**
+ * propagation_would_overmount - check whether propagation from @from
+ * would overmount @to
+ * @from: shared mount
+ * @to: mount to check
+ * @mp: future mountpoint of @to on @from
+ *
+ * If @from propagates mounts to @to, @from and @to must either be peers
+ * or one of the masters in the hierarchy of masters of @to must be a
+ * peer of @from.
+ *
+ * If the root of the @to mount is equal to the future mountpoint @mp of
+ * the @to mount on @from then @to will be overmounted by whatever is
+ * propagated to it.
+ *
+ * Context: This function expects namespace_lock() to be held and that
+ * @mp is stable.
+ * Return: If @from overmounts @to, true is returned, false if not.
+ */
+bool propagation_would_overmount(const struct mount *from,
+ const struct mount *to,
+ const struct mountpoint *mp)
+{
+ if (!IS_MNT_SHARED(from))
+ return false;
+
+ if (IS_MNT_NEW(to))
+ return false;
+
+ if (to->mnt.mnt_root != mp->m_dentry)
+ return false;
+
+ for (const struct mount *m = to; m; m = m->mnt_master) {
+ if (peers(from, m))
+ return true;
+ }
+
+ return false;
+}
+
/*
* check if the mount 'mnt' can be unmounted successfully.
* @mnt: the mount to be checked for unmount