On Fri, Dec 2, 2016 at 11:48 AM, Jan Kara <jack@xxxxxxx> wrote: > 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.). Okay, but all we need from the deleted mark is the ->next pointer, no? So everything else related to destruction can be done. Thanks, Miklos -- 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
