Microsoft Technology Licensing, LLC

Scott M Cutshall

William J Bolosky

Gilad Odinak

John R Douceur

Richard P Draves

Nathan P Myhrvold

Richard F Rashid

Brian J Smith

David Allen Goebel

Michael A Schmidt

Jonathan G Thomason

A method and system for backing up and restoring single instance store (SIS) files comprising links to common store files. A dynamic link library (DLL) including an interface enables a backup/restore application to properly backup and restore SIS-enabled volumes including SIS links and their corresponding store files. For each link to be backed up, the DLL tracks whether its corresponding common store file has already been identified for backing up to the backup application, such that it is identified only once, whereby only one copy of a common store file is backed up per volume, regardless of the number of additional links pointing thereto. For each link to be restored, the DLL tracks whether its corresponding common store file has already been identified for restoring to the restore application, or is already present on the volume, whereby a common store file for a link file is only restored to a volume only once and if not already present on that volume.

Method and system for backing up and restoring files stored in a single instance store

A method and system for storing the data of files having duplicate content, by maintaining a single instance of the data, and providing logically separate links to the single instance. Files of duplicate content have their data stored in a common store file by a single instance store (SIS) facility, which also converts the original file or files to links to that common store file and creates additional links thereto as needed. The SIS facility may reside above a file system as a filter driver. File system requests directed to the link file (e.g., open, write, read, close and delete) reach the SIS filter, which then transparently handles each request as if the link file was a normal file. To preserve logical separation, writes to a SIS link file are to the link file, and the written portion recorded as dirty. The SIS filter intercepts SIS read requests, and reads clean portions from the common store file and any dirty portions from the link file. When the link file is closed, the common store file also may be closed, and, if the link file has been written, the non-dirtied portions of the link file are filled in with clean data from the common store file, and the link file reconverted to a normal file. Security is provided to prevent unauthorized access to the common store files, as is a volume check facility that repairs any inconsistencies in SIS metadata.

Single instance store for file systems

A method and system that operates as a background process automatically identify and merge duplicate files into a single instance files, wherein the duplicate files become independent links to the single instance files. A groveler maintains a database of information about the files on a volume, including a file size and checksum (signature) based on the file contents. The groveler periodically acts in the background to scan the USN log, a log that dynamically records file system activity. New or modified files detected in the USN log are queued as work items, each work item representing a file. The volume may be scanned to add work items to the queue, which takes place initially or when there is a potential problem with the USN log. The groveler periodically removes items from the queue, calculates the signature of the corresponding file contents, and uses the signature and file size to query the database for matching files. The groveler then compares any matching files with the file corresponding to the work item for an exact duplicate, and if found, calls a single instance store facility to merge the files and create independent links to those files.

Method and system for automatically merging files into a single instance store

A computer system has a microprocessor that can execute in a non-privileged user mode and a privileged kernel mode. A user virtual address space is used when the microprocessor is in the user mode, and a kernel virtual address space is used when the microprocessor is in the kernel mode. Each of the address spaces has the same range of virtual addresses that is designated for shared components. The user virtual address space is mapped to an offset position within the kernel address space. When a user process calls a kernel function with a pointer argument, the pointer is biased before being dereferenced to account for the offset of the user address space within the kernel address space. This allows for sharing of position-dependent code, while still allowing the kernel to access the entire user address space.

Sharing executable modules between user and kernel threads

A method and system for protecting shared code and data, in particular, shared system code and data, in a multitasking operating system are provided. The operating system includes a cooperative subsystem and a preemptive subsystem. The cooperative subsystem includes shared system code and data. The method and system include a synchronization mechanism for controlling access to the shared system code and data by threads. Ownership of the synchronization mechanism must be requested and obtained before a cooperatively scheduled thread can execute in the cooperative subsystem. Additionally, ownership of the synchronization mechanism must be requested and obtained before a preemptively scheduled thread can execute the shared system code in the cooperative subsystem. If the synchronization mechanism is already owned, the requesting thread is blocked until ownership is released. Otherwise, the requesting thread is granted ownership. Since no other thread can obtain ownership of the synchronization mechanism while one thread owns the synchronization mechanism, the shared system code and data in the cooperative subsystem is protected.

Method and system for protecting shared code and data in a multitasking

The invention described herein works in conjunction with a processor having an address translation cache that is updated by referencing a page table directory and a plurality of associated page tables referenced by the page table directory. The page table directory and a single page table are configured to generate a memory fault whenever the processor attempts to update its address translation cache. In response to such a memory fault, a memory fault handler temporarily loads a single page table entry with the needed address translation. In addition, the memory fault handler initializes the page table directory so that it references the single page table entry that has been loaded. Control is then returned from the memory fault handler, and the processor obtains the address translation. In response to a subsequent memory fault, the memory fault handler invalidates the previously loaded entry, and loads whatever address translation is currently needed by the processor. The address translations are cached in the processor's translation lookaside buffer.

System and method for minimizing page tables in virtual memory systems

The invention includes a computer system having a processor that executes program instructions in privileged and non-privileged execution modes. A user stack is used when the processor is executing in the non-privileged execution mode. A kernel memory stack is used when the processor is executing in the privileged execution mode. The kernel memory stack can grow and shrink dynamically as it is used by its associated thread, through the use of allocate-on-demand memory. A stack overflow handler is executed from within the kernel to resolve allocate-on-demand faults. The stack handler uses only fixed-size memory stacks.

Growing community of inventors

Carnation, WA, United States of America

Scott M Cutshall