On 08/13, Jan Kara wrote: > > On Thu 13-08-15 15:36:16, Oleg Nesterov wrote: > > On 08/13, Jan Kara wrote: > > > > > > Looking into this again, it would seem somewhat cleaner to me to move the > > > destruction to deactivate_locked_super() instead. > > > > Heh ;) You know, I was looking at deactivate_locked_super(). However, I > > simply do not understand this code enough, I failed to verify it would > > be safe to destroy s_writers there. > > Yes, it will be safe. After ->kill_sb() callback the filesystem is dead. > There can be someone still holding reference to superblock but these are > just users inspecting the structure definitely not caring about freeze > protection. OK, thanks. > > And. Please note destroy_super() in alloc_super() error path, so this > > needs a bit more changes in any case. > > Yes. But you can sleep in alloc_super() so that would be easy enough. Yes, yes, I didn't mean this is a problem. > > Can't we live with this hack for now? To remind, it will be reverted > > (at least partially) in any case. Yes, yes, it is very ugly and the > > changelog documents this fact. But it looks simple and safe. To me > > it would be better to make the conversion first, then cleanup this > > horror after another discussion. > > All I care about is that long-term, all handling from destroy_super() that > needs to sleep ends up in one place. So if you promise you'll make this > happen I can live with the workqueue solution for now I certainly promise I will try to do something in any case ;) But let me repeat another reason why I think we should do this later. The necessary changes depend on other work-in-progress rcu_sync changes in percpu_rw_semaphore. Now that you confirm that we should not worry about sb_writers after deactivate_locked_super(), the cleanup looks even simpler than I thought initially: 1. We do not even need to destroy the counters in deactivate_locked_super(). It should only stop the (potentially) pending rcu-callback(s). 2. Just revert this patch altogether. > (but you have to > convince also Al as a maintainer ;). Perhaps he won't notice how ugly this change is? If you won't tell him. Oleg. -- 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
