Abstract: A processing system processes an I/O request and, upon interruption of the I/O request, identifies an owner of an active mount point or another entity, and then resumes processing the I/O request under the control of the identified owner. For instance, when an I/O request processed by an I/O system encounters an active mount point, the processing is interrupted as control is turned over to an active mount point driver. The active mount point driver assumes responsibility for processing the I/O request. In processing the I/O request, the active mount point driver decides what action should be taken to further processing of the I/O request. To further processing of the I/O request, the active mount point driver may utilize information from a variety of sources as well as make requests to other processes, drivers, systems, subsystems, devices, and so forth.

Abstract: A system and method for encryption and decryption of files. The system and method operate in conjunction with the file system to transparently encrypt and decrypt files in using a public key-private key pair encryption scheme. When a user puts a file in an encrypted directory or encrypts a file, all data writes to the disk for that file are encrypted with a random file encryption key generated from a random number and encrypted with the public key of a user and the public key of at least one recovery agent. The encrypted key information is stored with the file, whereby the user or a recovery agent can decrypt the file data using the private key thereof. When a proper private key is used, encrypted reads from the disk are decrypted transparently by the file system and returned to the user.

Abstract: A change journal for recording changes to files in a storage volume of a computer system keeps a record for each notable change to a file. Each record is given a unique update sequence number, which is a serial number of ever-increasing value assigned to each record. Each record includes one or more change reasons specifying what type of action occurred with respect to the associated file. The presence of a close file change reason in a record connotes that the record includes all the notable changes made to the file in a preceding file session, which is defined as the time occurring after the last time a close file change reason was entered in a change record, up to the time of the next succeeding close file change reason. For each file, an entry is made in the storage volume's master file table referencing the change record that currently includes the most up-to-date information on the status of the change reasons for the file.

Abstract: The present invention allows arbitrary actions to be performed when grafting the namespace of one device into the namespace of the same or another device. Grafting of the namespace of one device into the namespace of the same or another device creates a logical namespace that can be presented to the user to allow the user to access information in a logically consistent manner. Active mount points are created by adding an active mount point attribute to a file or directory. When an I/O request processed by an I/O system encounters an active mount point, it turns control for processing the active mount point over to an active mount point driver. The active mount point driver assumes responsibility for processing the I/O request. In processing the I/O request, the active mount point driver decides what action should be taken to further processing of the I/O request.

Abstract: In order to decrease the overall cost of storing large amounts of data, systems have been developed that use a hierarchy of storage devices from fast local disks to archival off-line storage. Such storage devices may be managed in a hierarchy where data that is accessed only infrequently can be moved to archival storage. The present invention relies on a tight integration of a hierarchical storage manager into the I/O system so that remotely stored attributes can be identified and tracked internally to the I/O system just like any other attributes. Implementations of the present invention may rely on a layered driver model where lower level drivers detect the existence of files with remotely stored attributes and then transfer control for processing I/O requests involving files with remotely stored attributes to higher level drivers. The higher level drivers then assume control to finish processing the I/O request.

Abstract: I/O systems of computers typically utilize multiple layered drivers to process I/O requests. I/O requests are passed from one driver to another in a defined sequence with each driver performing its processing in turn. The present invention provides a system and method for interrupting the normal sequence of processing and for allowing drivers that would not normally process an I/O request to intervene and assume control for processing the I/O request. The system and method provides a flexible and extensible way to define special types of files or directories that require special processing by a particular driver. The present invention adds a "reparse point" attribute to a file or directory. The reparse point attribute preferably contains a tag which identifies a particular driver as the owner of the reparse point and a data value which can be used by the owner driver to store any information necessary or useful in processing an I/O request.

Abstract: A computer system includes a compression engine for compressing a decompressed sequence of data to produce a compressed sequence of data. The compression engine encodes each piece of data in the decompressed sequence of data as either a portion of a copy token or as a literal token. Tokens are grouped together into groups of up to 8 tokens and a bitmap holding 8 bits is provided to identify the respective tokens as either copy tokens or literal tokens. The copy tokens encode sub-sequences of data that have previously occurred in the decompressed data sequence. Each copy token is of a like size but includes a variable-sized offset field for encoding an offset between a current occurrence of a sub-sequence of data and a previous occurrence of a sub-sequence of data. The offset field is variable-sized to encode the offset in a minimal number of bits. The computer system also includes a decompression engine for decompressing data sequences that have been compressed using the compression engine.

Abstract: A multiple file name referencing system stores multiple file names in a file. These multiple file names include an operating system formatted file name and an application formatted file name. When an operating system formatted file name is created or renamed, the multiple file name referencing system automatically generates an application formatted file name having a potentially different format from, but preserving the extension of, the operating system formatted name. The multiple file name referencing system similarly generates an operating system formatted name upon creation or renaming of an application formatted name. A B-tree is provided which contains an operating system entry for the operating system formatted name and an application entry for the application formatted name, each entry containing the address of the same file to which both names refer.