Handling renames in an overlay optimizer

One or more computer storage media storing computer executable instructions which when executed by one or more processors implement a method for preventing a failure of a rename operation, the method comprising:

• receiving, by a write filter via a post operation callback function, a first I/O operation that opened or created a file;
• determining an identifier of the first I/O operation and a volume on which the file was opened or created;
• storing an entry in a data structure that associates the identifier of the first I/O operation and the volume;
• receiving, by the write filter via a pre operation callback function, a second I/O operation;
• determining an identifier of the second I/O operation;
• searching the data structure using the identifier of the second I/O operation;
• upon determining that the identifier of the second I/O operation matches the identifier of the first I/O operation stored in the entry, obtaining the volume defined in the entry as a source volume for the second I/O operation;
• determining that the source volume for the second I/O operation is a volume on which the write filter implements an overlay cache, the volume being separate from a protected volume;
• and
• redirecting the second I/O operation to the volume rather than allowing the second I/O operation to be directed to the protected volume.

A method, implemented in a system that includes a write filter that implements an overlay for protecting contents of a protected volume and an overlay-optimizing write filter that implements an overlay cache on a separate volume from the protected volume, for preventing a rename operation from failing, the method comprising:

• receiving, by the overlay-optimizing write filter, an IRP_MJ_CREATE operation;
• determining that the IRP_MJ_CREATE operation includes the SL_OPEN_TARGET_DIRECTORY flag;
• obtaining a process identifier associated with the IRP_MJ_CREATE operation;
• using the process identifier to search a data structure containing entries that each maps a process identifier to a volume;
• determining that the process identifier associated with the IRP_MJ_CREATE operation matches an entry in the data structure;
• determining that the volume defined in the matching entry is the separate volume on which the overlay cache is implemented;
• and
• redirecting the IRP_MJ_CREATE operation to the separate volume.