On Wed, Apr 18, 2012 at 05:52:38PM -0400, J. Bruce Fields wrote: > On Wed, Apr 18, 2012 at 12:44:24AM +0100, Al Viro wrote: > > On Tue, Apr 17, 2012 at 03:08:26PM -0700, Linus Torvalds wrote: > > > > Or I could increment that counter for all the conflicting operations and > > > > rely on it instead of the i_mutex. ?I was trying to avoid adding > > > > something like that (an inc, a dec, another error path) to every > > > > operation. ?And hoping to avoid adding another field to struct inode. > > > > Oh well. > > > > > > We could just say that we can do a double inode lock, but then > > > standardize on the order. And the only sane order is comparing inode > > > pointers, not inode numbers like ext4 apparently does. > > > > > > With a standard order, I don't think it would be at all wrong to just > > > take the inode lock on rename. > > > > In principle, yes, but have you tried to grep for i_mutex? Note that > > we have *another* place where multiple ->i_mutex might be held on > > non-directories (and unless I'm missing something, ext4 move_extent.c > > stuff doesn't play well with it): quota writes. Which can, AFAICS, > > happen while write(2) is holding ->i_mutex on a regular file. So > > it's not _that_ easy - we want something like "and quota file is goes > > last" > > So the idea would be to always take the i_mutex on non-quota files > before taking it on quota files? > > I tried pulling the ext4 thing into fs/inode.c, modifying the order to > do that, and then doing the rename change on top of that. Patches follow, with the ordering change at the end. And a documentation fix that I suppose could go in whenever. --b. -- To unsubscribe from this list: send the line "unsubscribe linux-fsdevel" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
