Patent ID: 7702662

Claim:
A computer implemented method for managing a file system, the computer implemented method comprising: responsive to a user selecting an image of the file system to perform a rollback operation, searching for each data block in the file system that is owned by the image; determining that a data block owned by the image is marked in a first map and a second map; responsive to determining that the data block owned by the image is marked in the first map and the second map, marking the data block in a third map; responsive to determining that the data block owned by the image is marked in the third map, allocating a new data block in the file system; and copying data from the data block owned by the image to the new data block in the file system prior to performing the rollback operation to avoid a collision that causes data corruption; wherein the first map is a snapshot owned data block bitmap, the second map is a copy on delete data block bitmap, and the third map is a collision bitmap; and wherein the collision bitmap identifies impending collisions in the file system prior to performance of the rollback operation.