Browse Prior Art Database

Use of HOLD Tokens to Prevent Deallocation of Resources for Active, Deleted Files

IP.com Disclosure Number: IPCOM000116379D
Original Publication Date: 1995-Sep-01
Included in the Prior Art Database: 2005-Mar-30
Document File: 2 page(s) / 61K

Publishing Venue

IBM

Related People

Mohindra, A: AUTHOR [+2]

Abstract

Disclosed is a technique for keeping file resources in a cluster file system from being deallocated at the file server, if that file is referenced by a process from any node in the cluster. The scheme uses HOLD tokens to achieve this behavior.

This text was extracted from an ASCII text file.
This is the abbreviated version, containing approximately 52% of the total text.

Use of HOLD Tokens to Prevent Deallocation of Resources for Active,
Deleted Files

      Disclosed is a technique for keeping file resources in a
cluster file system from being deallocated at the file server, if
that file is referenced by a process from any node in the cluster.
The scheme uses HOLD tokens to achieve this behavior.

      HOLD tokens are granted to client nodes whenever a reference to
a file is created.  These references are generated when a file name
is "looked up", that is when the kernel system code walks through the
file system tree, and locates the file.  Many of the file system
interfaces (such as open()) take a file name as an argument, and each
will generate a reference to the named file as a side effect of their
operation.  If there are references to a file, the unlink() system
call should not deallocate the file's resources.  Rather, the
resources should persist at the server until all references from any
node in the cluster have been released.

      The scheme uses a distributed protocol to guarantee that file
resources in a cluster file system are not released prematurely.
When a reference to a file is made from a given client node in the
cluster, a token for that file is granted by the server node to the
client node for that file.  This token is said to be a HOLD token and
it is in a shared state.  The server node maintains information about
all outstanding HOLD tokens that it has granted.  The server node may
grant HOLD tokens to multiple client nodes for the same file.  As
file system operations on the client node complete, file references
will be released, h...