Methods for maintaining data and attribute coherency in instances of sharable files

A method for sharing a file managed by a file system, the method comprising:

• associating a file consistency protocol with an operating system (O/S), the file consistency protocol maintaining file consistency between instances of the file associated with the file system using a set of file consistency protocol bits;
• checking each instance of the file for an exclusive bit setting of true;
• failing an opening of another instance of the file if the exclusive bit of at least one instance of the file was determined to be set to true;
• opening another instance of the file in a shared mode by setting a shared bit in the set of file consistency protocol bits associated with the another instance of the file if the exclusive bit of each instance of the file was determined to be set to false;
• setting a shared bit in the set of file consistency protocol bits associated with each instance of the file;
• modifying contents of one instance of the file;
• setting a modified bit in the set of file consistency protocol bits associated with the one instance of the file, the modified bit being indicative of the modified contents;
• and
• setting an invalid bit in the set of file consistency protocol bits associated with each instance of the file other than the one instance of the file, the invalid bit being indicative of the modified contents of the one instance of the file.

A method for sharing a file, the method comprising:

• checking for open instances of the file;
• determining whether an open instance of the file has an exclusive bit of a first bitmap set to true;
• opening another instance of the file with a shared bit of a second bitmap of the another instance set to true if the open instance of the file does not have an exclusive bit of the first bitmap set to true;
• setting a shared bit in the first bitmap to true;
• maintaining the shared bit of the first bitmap and second bitmap set to true so long as the open instance of the file and the another instance of the file is open;
• modifying contents of the another instance of the file;
• setting a modified bit in the second bitmap to true;
• and
• setting an invalid bit in the first bitmap of the open instance of the file to true;
• wherein the invalid bit indicates that the contents of the open instance of the file are not consistent with the contents of the another instance of the file due to the modifying.