mandatory locks and LOCK_MAND
Hi,
I'm trying to get mandatory file locking to work. I don't want to use the mount option plus permission bits hack.
The only helpful document I could find (besides mandatory.txt in the kernel sources) was http://infradead.org/~willy/locking_manifesto.html
which describes "share modes":
"* Share modes. These are whole-file mandatory locks. No other process may open a file which would conflict with the Share Mode on the file. Use flock() with the %LOCK_MAND flag to set a Share Mode."
However, this doesn't work for me (kernel 2.4.17). /proc/locks shows the lock:
1: FLOCK MSNFS NONE 17653 03:05:44 0 EOF dfb6b458 c02eb928dfb6bb30 000000
00 dfb6b464
but it doesn't seem to be enforced anywhere. other processes can still open(2), read(2), write(2). I've skimmed fs/locks.c and for locks_may_read() it says:
"*
N.B. this function is only ever called
* from knfsd and ownership of locks is never checked."
It seems to me, LOCK_MAND is not intended to be used outside the kernel. is this correct, or am I doing something wrong?
on the other hand, leases work as described.
regards
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