On Fri 02-12-16 09:26:51, Miklos Szeredi wrote: > On Thu, Nov 10, 2016 at 8:46 PM, Jan Kara <jack@xxxxxxx> wrote: > > On Wed 09-11-16 20:26:16, Amir Goldstein wrote: > >> On Wed, Nov 9, 2016 at 1:10 PM, Jan Kara <jack@xxxxxxx> wrote: > > >> > And this does not work as well... Fanotify must notify groups by their > >> > priority so you cannot arbitrarily reorder ordering in which groups get > >> > notified. I'm currently pondering on using mark refcount to pin it when > >> > processing permission event but there are still some details to check. > >> > > >> > >> All right, mark refcount sound like the proper solution. > > > > Except it doesn't quite work. We can pin the current marks by a refcount > > but they can still be removed from the list so after we regain srcu lock, > > we are not sure their ->next pointers still point to still allocated marks > > :-| Sadly I realized this only after implementing all this. > > Hmm, how about this: when removing mark from inode, drop refcount. If > refcount is zero can remove from list. Otherwise mark the mark "dead" > and leave it on the list. > > And fsnotify can just skip dead marks. I had this idea as well and when trying to implement this, I've stumbled over some problems. I think the biggest problem was that destruction of a notification mark is relatively complex operation (doing iput() for example) and quite a few places dropping mark references are in a context where this can cause problems. Also I don't want to defer iput() to a workqueue as that will have unexpected consequences such as unlinked watched inode lingering in the system (possibly colliding with umount etc.). Honza -- Jan Kara <jack@xxxxxxxx> SUSE Labs, CR -- 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
