[PLUG] file locking

steve steve at lonetwin.net
Thu Jul 23 19:31:09 IST 2009

Aditya Godbole wrote:
> On Wed, Jul 22, 2009 at 11:41 AM, Shridhar
> Daithankar<ghodechhap at ghodechhap.net> wrote:
>> If it is application specific, e.g. word or excel, then they do locking
>> already(but opening a word/excel file on a share could have performance
>> problems).
>> Recently OOo has implemented their own locking scheme that works  on all the
>> platforms. If it is your own application, then you could take this route too.
> 1. It is not application specific
> 2. It is not my own application
> 3. I don't give a damn about performance
> I can't understand why people cannot see beyond their own assumptions!
> I think I have already made my requirements very clear. If an inode
> (file) has already been opened, all other simultaneous open requests
> on that inode should fail, irrespective of the application trying to
> open it.
> If anyone has an answer to the above question, please reply. Otherwise
> please, please do not reply.
People have already answered your question but you are unwilling to accept the 
answer they provide.

The answer once again is "No, you can't". The reason is not because locking is 
unnecessary or too complicated or (as someone suggested -- weaker permissions 
model -- whatever /that/ is supposed to mean). It is simply because mandatory 
locking is something that needs to be supported not only by the OS but also by 
the filesystem. For instance in your case, even if linux's OS locks were in 
place, the windows OS running on the system which provides the SMB shares along 
with any other OS accessing such shares would have to recognize and honor these 
locks. Although, doing this or achieving the same effect is still possible, but 
not without special mount options (as someone else pointed out) or other 
non-userspace alternatives.

- steve

why procrastinate when you can perendinate ?
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