Reapply "kernel: expose umount list to ioctl interface #2950"

This reverts commit 088996da9b.

kernel/kernel_umount.h

@@ -2,13 +2,24 @@
 #define __KSU_H_KERNEL_UMOUNT
 
 #include <linux/types.h>
+#include <linux/list.h>
+#include <linux/rwsem.h>
 
 void ksu_kernel_umount_init(void);
 void ksu_kernel_umount_exit(void);
 
-void try_umount(const char *mnt, bool check_mnt, int flags);
+void try_umount(const char *mnt, int flags);
 
 // Handler function to be called from setresuid hook
 int ksu_handle_umount(uid_t old_uid, uid_t new_uid);
 
-#endif
+// for the umount list
+struct mount_entry {
+    char *umountable;
+    unsigned int flags;
+    struct list_head list;
+};
+extern struct list_head mount_list;
+extern struct rw_semaphore mount_list_lock;
+
+#endif