On Thu, Aug 17, 2023 at 09:53:43PM +0100, Matthew Wilcox wrote: > On Thu, Aug 17, 2023 at 02:50:21PM +0200, Jan Kara wrote: > > > +/** > > > + * super_wait - wait for superblock to become ready > > > + * @sb: superblock to wait for > > > + * @excl: whether exclusive access is required > > > + * > > > + * If the superblock has neither passed through vfs_get_tree() or > > > + * generic_shutdown_super() yet wait for it to happen. Either superblock > > > + * creation will succeed and SB_BORN is set by vfs_get_tree() or we're > > > + * woken and we'll see SB_DYING. > > > + * > > > + * The caller must have acquired a temporary reference on @sb->s_count. > > > + * > > > + * Return: true if SB_BORN was set, false if SB_DYING was set. > > > > The comment should mention that this acquires s_umount and returns with it > > held. Also the name is a bit too generic for my taste and not expressing > > the fact this is in fact a lock operation. Maybe something like > > super_lock_wait_born()? > > Isn't this actually the normal function we want people to call? So maybe > this function should be called super_lock() and the functions in the > last patch get called __super_lock() for raw access to the lock. I think that's a good point. I've renamed them accordingly. > > I'm also a little wary that this isn't _killable. Are we guaranteed > that a superblock will transition to BORN or DYING within a limited > time? Yes, it should. If this would be an issue it's something we should have seen already. Random example being s_umount being held over a filesytem's fill_super() method all while concurrent iterators are sleeping on s_umount unconditionally. It is ofc always possible for us to make this killable in the future should it become an issue.
