Technologies are described for implementing locks to control I/O operations in a storage system. The lock implementations can have reduced resource requirements for memory and processing. Through the utilization of the technologies and concepts presented herein, an I/O process preparing to acquire a write lock can advertise its need for the lock for a pre-determined time before the lock is granted. The time period for advertisement can be specified so that all I/O operations that were initiated before the advertisement are guaranteed to have completed by the time the advertisement period is over. As such, a lock controller may only need to track outstanding I/Os that begin once the advertisement starts. This can reduce the typical requirement to maintain and process a lock structure for every unit of storage in the system at all times.