Abstract: A method and system for updating a filter's data after the filter's metadata file is restored. The filter maintains an open handle to the metadata until the filter receives a request to have the metadata restored. The filter then closes the open handle and allows the metadata to be restored. After the metadata is restored, data associated with the filter is rebuilt based on the restored metadata.

Abstract: A method and system for computing disk space used by a directory and its descendants that may proceed while input and output are occurring that involve the directory and any of its descendants. A calculation of the total amount of disk space consumed by a set of objects is commenced. While performing the calculation, changes to the objects are monitored. If a change to one or more of the objects affects the disk space consumed by the objects, the calculation is changed so that the total reflects the change to the one or more objects.

Abstract: Described is a mechanism comprising a data screening filter and user mode service that applies (enforces) policies regarding allowing or blocking file content of a directory, based on matching the filename against patterns associated with that directory. An administrator configures a screening policy, such as the types of files to allow in a particular directory and the types of files to block. File groups of member patterns and non-member exclusion patterns are defined and selectively collected in directory screening objects (DSOs). A directory screening object (DSO) is associated with a directory. When an I/O create request specifying a filename and a target directory is received, the filename is evaluated against the member/non-member patterns in the file groups referenced by the DSO for that directory to make for an allow or block policy decision. If not matched, DSOs on parent directories are evaluated upwards seeking a policy decision.

Abstract: Method and system for maintaining namespace consistency between selected objects maintained by a file system and a filter associated therewith. Metadata regarding selected objects of a file system is maintained by a filter while the filter is attached to the file system and persisted in non-volatile storage. The namespace of the file system may be changed while the filter is unattached from the file system. Afterwards, when the filter is attached to the file system, the namespace of the filter is synchronized with the namespace of the file system for the selected objects.

Abstract: Method and system for establishing and maintaining quotas. An auto quota is defined and applied to a directory. Input and output is monitored to detect a successful operation that involves a subdirectory of the directory. A determination is made as to whether to apply a quota associated with the auto quota to the subdirectory. If the determination is that the quota is to be applied to the subdirectory, it is automatically applied.

Abstract: A method and system for maintaining namespace consistency between selected objects maintained by a file system and a filter associated therewith. A filter monitors selected types of requests (or operations associated therewith) and determines whether the object is within a namespace associated with the filter. The namespace associated with the filter is updated based on a change to the object.

Abstract: A model in which filter drivers are managed to receive callbacks for I/O requests in which the filter drivers have registered an interest. Per-volume instances of filter drivers register with a filter manager for pre-callbacks (for I/O to the file system) and post-callbacks (for I/O from the file system), and identify which I/O requests (e.g., create, read, write) they are registering to receive callbacks. The filter manager orders the instances for callbacks. When an I/O request is received, the filter manager converts the I/O request to callback data and calls the interested filters in the callback order, whereby the filter instances can process the I/O data. As the request returns from the file system, filters desiring post callbacks are called in the reverse order. Efficient context management for the filters and other functions, such as non-reentrant file I/O, are also provided by the model.

Abstract: The invention provides a system and method for dynamically unloading file system filters in a stacked-call-back model where filters are stacked one on top of the other to form a filter stack. A filter manager keeps track of the progress of each I/O operation and calls each filter in turn with the filter returning after it has completed processing the given operation. The filter manager dynamically unloads a filter (or an instance of a filter) that is positioned at any position in the filter stack in a reasonable amount of time while I/O operations are actively being processed. The filter/filter instance can be unloaded with outstanding I/O operations on the filter either hosted by the filter or pended by other filters. I/O operations are canceled, completed or drained in order to unload the filter or filter instance. A filter may veto the unloading of the filter.

Abstract: A model in which filter drivers are managed to receive callbacks for I/O requests in which the filter drivers have registered an interest. Per-volume instances of filter drivers register with a filter manager for pre-callbacks (for I/O to the file system) and post-callbacks (for I/O from the file system), and identify which I/O requests (e.g., create, read, write) they are registering to receive callbacks. The filter manager orders the instances for callbacks. When an I/O request is received, the filter manager converts the I/O request to callback data and calls the interested filters in the callback order, whereby the filter instances can process the I/O data. As the request returns from the file system, filters desiring post callbacks are called in the reverse order. Efficient context management for the filters and other functions, such as non-reentrant file I/O, are also provided by the model.

Abstract: A method and system for ordering software modules in a guaranteed order for execution. Unique values are statically assigned to software modules (e.g., filter drivers) when fully developed. Each module's assigned value determines its relative position to other modules in a stack or other arrangement, fixing the execution order for any set of filter drivers. Static values may comprise floating-point numbers, whereby each new software module may be assigned a number that enables positioning it between any two existing software modules. For example, filter drivers may be generally classified and assigned values in a range according to type. Drivers of the same type may be ordered within their general range to guarantee one possible ordering. A filter manager architecture is described, in which filter drivers register with a manager for relevant file system I/O operations. The manager calls appropriately registered filter drivers in an order based on their assigned numbers.