On Sun, Apr 15, 2018 at 01:51:07AM +0100, Al Viro wrote: > On Sat, Apr 14, 2018 at 02:47:21PM -0700, Linus Torvalds wrote: > > On Sat, Apr 14, 2018 at 1:58 PM, Al Viro <viro@xxxxxxxxxxxxxxxxxx> wrote: > > > > > > That breaks d_invalidate(), unfortunately. Look at the termination > > > conditions in the loop there... > > > > Ugh. I was going to say "but that doesn't even use select_collect()", > > but yeah, detach_and_collect() calls it. > > > > It would be easy enough to just change the > > > > if (!list_empty(&data.select.dispose)) > > > > there to > > > > if (!list_empty(&data.select.found)) > > > > too. > > You would have to do the same in check_and_drop() as well, > and that brings back d_invalidate()/d_invalidate() livelock > we used to have. See 81be24d263db... > > I'm trying to put something together, but the damn thing is > full of potential livelocks, unfortunately ;-/ Will send > a followup once I have something resembling a sane solution... I really wonder if we should just do the following in d_invalidate(): * grab ->d_lock on victim, check if it's unhashed, unlock and bugger off if it is. Otherwise, unhash and unlock. >From that point on any d_set_mounted() in the subtree will fail. * shrink_dcache_parent() to reduce the subtree size. * go through the (hopefully shrunk) subtree, picking mountpoints. detach_mounts() for each of them. * shrink_dcache_parent() if any points had been encountered, to kick the now-unpinned stuff. As a side benefit, we could probably be gentler on rename_lock in d_set_mounted() after that change...
