Re: Does mandatory locking need to be set when the file is locked?

[Matthew Wilcox <willy@debian.org>]

On Mon, Dec 15, 2003 at 07:57:57AM +0600, Joseph D. Wagner wrote:
> I'm writing a program that changes the permissions on a file to enable 
> mandatory locking, does its thing to the file, and then resets the 
> permissions.
> 
> Do do the mandatory locking permissions have to be set before the lock is 
> set? Or will the kernel dynamically recognize the change on the fly so that 
> an active lock becomes mandatory?

Please, don't use mandatory locking.  It's racy (by design), buggy
(by design) and adds code to the fast path.

-- 
"Next the statesmen will invent cheap lies, putting the blame upon 
the nation that is attacked, and every man will be glad of those
conscience-soothing falsities, and will diligently study them, and refuse
to examine any refutations of them; and thus he will by and by convince 
himself that the war is just, and will thank God for the better sleep 
he enjoys after this process of grotesque self-deception." -- Mark Twain