Browse Prior Art Database

Asynchronous Dirty Status During Background Directory Flush

IP.com Disclosure Number: IPCOM000102777D
Original Publication Date: 1990-Jan-01
Included in the Prior Art Database: 2005-Mar-17
Document File: 1 page(s) / 46K

Publishing Venue

IBM

Related People

Friedl, TJ: AUTHOR [+3]

Abstract

A method is described which keeps track of changes on a media. For file systems, data structures are read from a media and put into storage for processing. If they are altered, they are written back to the media. When data structures are altered asynchronously with a task responsible for updating these structures on the media, the described method ensures that alterations which occur while the update is in process are not lost. This method avoids overhead and complexity of locking, and it accurately records dirty/clean status at all times.

This text was extracted from an ASCII text file.
This is the abbreviated version, containing approximately 82% of the total text.

Asynchronous Dirty Status During Background Directory Flush

      A method is described which keeps track of changes on a media.
For file systems, data structures are read from a media and put into
storage for processing.  If they are altered, they are written back
to the media.  When data structures are altered asynchronously with a
task responsible for updating these structures on the media, the
described method ensures that alterations which occur while the
update is in process are not lost.  This method avoids overhead and
complexity of locking, and it accurately records dirty/clean status
at all times.

      Each data structure contains a dirty counter.  When the dirty
counter has a non-zero value, the associated element is considered
altered (dirty).  When the counter value is zero, the structure is
considered clean.  That is to say, the version of the element on the
media is identical to the element in memory.  Whenever an element is
altered, its dirty counter is incremented.  This forces a clean
element to a dirty state.

      When a device operation is scheduled, the value of the dirty
counter is captured and retained with the device request information.
Subsequent alteration of the element again increments the associated
dirty counter.  The state of the counter which was saved when the
device operation was scheduled remains unchanged.

      With a successful completion of a device operation, the saved
value of the dirty counter is subtr...