Abstract: A computer implemented method, data processing system, and computer usable code are provided for mapping between a file system and a log. Opaque data is generated that identifies a location of the file system and a location of the log. The file system and the log are accessed using this opaque data. An opaque identifier is associated with the opaque data, which is then sent to the file system and the log. When a log access request, which includes the opaque identifier, is received from the file system, the location of the log is identified using the opaque identifier and the file system is directed to the location of the log. When a logredo request, which includes the opaque identifier, is received from the log, the file system location is identified using the opaque identifier and the log is directed to the location of the file system.

Abstract: Computer implemented method, system and computer program product for shrinking a file system in a data processing system. A computer implemented method for shrinking a file system in a data processing system includes designating an amount by which a file system comprised of a plurality of contiguous blocks is to be shrunk, and removing at least one contiguous intermediate block of the plurality of contiguous blocks from the file system to shrink the file system by the designated amount.

Abstract: A system and method for dynamically altering a Virtual Memory Manager (VMM) Sequential-Access Read Ahead settings based upon current system memory conditions is provided. Normal VMM operations are performed using the Sequential-Access Read Ahead values set by the user. When low memory is detected, the system either turns off Sequential-Access Read Ahead operations or decreases the maximum page ahead (maxpgahead) value based upon whether the amount of free space is simply low or has reached a critically low level. The altered VMM Sequential-Access Read Ahead state remains in effect until enough free space is available so that normal VMM Sequential-Access Read Ahead operations can be performed (at which point the altered Sequential-Access Read Ahead values are reset to their original levels).

Abstract: A system and method for dynamically altering a Virtual Memory Manager (VMM) Sequential-Access Read Ahead settings based upon current system memory conditions is provided. Normal VMM operations are performed using the Sequential-Access Read Ahead values set by the user. When low memory is detected, the system either turns off Sequential-Access Read Ahead operations or decreases the maximum page ahead (maxpgahead) value based upon whether the amount of free space is simply low or has reached a critically low level. The altered VMM Sequential-Access Read Ahead state remains in effect until enough free space is available so that normal VMM Sequential-Access Read Ahead operations can be performed (at which point the altered Sequential-Access Read Ahead values are reset to their original levels).

Abstract: A filesystem operation binds “undo” information to given filesystem resources, in order for the filesystem operation to reverse or rollback changes made to the resources, and thereby return a filesystem affected by a failed or incomplete operation from an inconsistent state to a previous, consistent state. Changes can be undone, to return the filesystem to a consistent state, as long as any further changes can also be undone successfully. Latter changes can be undone by making sure that no operation is fully successful until the preceding operations that changed the same metadata are successful. In an error path, the operation can go through every resource modified to determine if other threads have modified data beyond the initial modification. A failing thread can notify later threads that an operation has failed and all changes are to be undone. Each thread can then run through and undo all pertinent metadata changes that were made.

Abstract: Rather than unmounting a corrupt filesystem while doing recovery, the filesystem remains mounted but I/Os to the corrupt area are blocked while a repair process is called to repair the corruption. Threads attempting to access the filesystem go into a waiting state until the corruption is fixed, then are restarted at a stable point in their execution.

Abstract: A method and apparatus for ensuring valid journaled file system metadata during a backup operation are provided. With the method and apparatus, mechanisms are provided for suspending write I/O operations to storage devices during a point-in-time backup operation. Once the point-in-time backup operation is completed, the suspended write I/O operations are released and may then be processed by the storage system. In one exemplary embodiment, when a point-in-time operation is initiated, a point-in-time backup flag is set in a logical volume manager. In response to receiving a write I/O operation, the logical volume manager checks the status of the point-in-time backup flag to determine if a point-in-time backup operation is currently being performed. If the flag is not set, then the write I/O operation is logged and performed in a normal manner. If the flag is set, then the write I/O operation is stored in a hold queue of the logical volume manager.