J. Bruce Fields wrote: > On Mon, Sep 17, 2007 at 10:37:56AM +0400, Pavel Emelyanov wrote: >> J. Bruce Fields wrote: >>> Is there a small chance that a lock may be applied after this check: >>> >>>> + mandatory = (inode->i_flock && MANDATORY_LOCK(inode)); >>>> + >>> but early enough that someone can still block on the lock while the file >>> is still marked for mandatory locking? (And is the inode->i_flock check >>> there really necessary?) >> There is, but as you have noticed: > > OK, but why not just remove the inode->i_flock check there? I can't see > how it helps anyway. > >>> Well, there are probably worse races in the mandatory locking code. >> ...there are. The inode->i_lock is protected with lock_kernel() only >> and is not in sync with any other checks for inodes. This is sad :( >> but a good locking for locks is to be done... > > I would also prefer a locking scheme that didn't rely on the BKL. That > said, except for this race:
I would as well :) But I don't know the locking code good enough to start fixing. Besides, even if I send a patch series that handles this, I don't think that anyone will accept it, due to "this changes too much code", "can you prove you fixed all the places" and so on... >>> (For example, my impression is that a mandatory lock can be applied just >>> after the locks_mandatory_area() checks but before the io actually >>> completes.) > > ... I'm not aware of other races in the existing file-locking code. It > sounds like you might be. Could you give specific examples? Well, there's a long standing BUG in leases code - when we made all the checks in inserting lease, we call the locks_alloc_lock() and may fall asleep. Bu after the wakeup nobody re-checks for the things to change. I suspect there are other bad places. > --b. > - To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to [EMAIL PROTECTED] More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
