J. Bruce Fields wrote: > On Thu, Sep 13, 2007 at 06:30:43PM +0400, Pavel Emelyanov wrote: >> When the process is blocked on mandatory lock and someone changes >> the inode's permissions, so that the lock is no longer mandatory, >> nobody wakes up the blocked process, but probably should. > > I suppose so. Does anyone actually use mandatory locking?
:) Good question. > Would it be worth adding a > > if (MANDATORY_LOCK(inode)) > return; > > to the beginning of locks_wakeup_mandatory() to avoid walking the list > of locks in that case? Perhaps setattr is rare enough that this just > isn't worth caring about. > > 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: > 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... > (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.) > > --b. Thanks, Pavel - 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/
