On Fri, Nov 11, 2016 at 2:42 PM, Amir Goldstein <amir7...@gmail.com> wrote: > On Fri, Nov 11, 2016 at 12:06 PM, Miklos Szeredi <mik...@szeredi.hu> wrote: >> On Fri, Nov 11, 2016 at 10:46 AM, Konstantin Khlebnikov >> <koc...@gmail.com> wrote: >>> On Fri, Nov 11, 2016 at 1:56 AM, Amir Goldstein <amir7...@gmail.com> wrote: >>>> On Mon, Nov 7, 2016 at 3:38 PM, Amir Goldstein <amir7...@gmail.com> wrote: >>>>> On Mon, Nov 7, 2016 at 12:08 PM, Konstantin Khlebnikov <koc...@gmail.com> >>>>> wrote: >>>>>> On Mon, Nov 7, 2016 at 1:04 PM, Miklos Szeredi <mik...@szeredi.hu> wrote: >>>>>>> On Mon, Nov 7, 2016 at 10:58 AM, Konstantin Khlebnikov >>>>>>> <koc...@gmail.com> wrote: >>>>>>> >>>>>>>> I've stumbled on somehow related problem - concurrent copy-ups are >>>>>>>> strictly serialized by rename locks. >>>>>>>> Obviously, file copying could be done in parallel: locks are required >>>>>>>> only for final rename. >>>>>>>> Because of that overlay slower that aufs for some workloads. >>>>>>> >>>>>>> Easy to fix: for each copy up create a separate subdir of "work". >>>>>>> Then the contention is only for the time of creating the subdir, which >>>>>>> is very short. >>>>>> >>>>>> Yeah, but lock_rename() also takes per-sb s_vfs_rename_mutex (kludge by >>>>>> Al Viro) >>>>>> I think proper synchronization for concurrent copy-up (for example >>>>>> round flag on ovl_entry) and locking rename only for rename could be >>>>>> better. >>>>> >>>>> Removing s_vfs_rename_mutex from copy-up path is something I have been >>>>> pondering about. >>>>> Assuming that I understand Al's comment above vfs_rename() correctly, >>>>> the sole purpose of per-sb serialization is to prevent loop creations. >>>>> However, how can one create a loop by moving a non-directory? >>>>> So it looks like at least for the non-dir copy up case, a much finer >>>>> grained >>>>> lock is in order. >>>>> >>>> >>>> >>>> I posted patches to relax the s_vfs_rename_mutex for copy-up and >>>> whiteout in some use cases. >>>> >>>> Konstantin, >>>> >>>> It would be useful to know if those patches help with your use case. >>>> >>> >>> Well.. I think relaxing only s_vfs_rename_mutex wouldn't help much here. >>> Copying is still serialized by i_mutex on workdir? >>> Data copying should be done without rename locks at all. >> >> We do need something to prevent multiple copy-ups starting up in >> parallel on the same file, though. >> > > I guess an inode_lock on the copy-up victim should suffice?
Just to follow up on this hijacked thread. I posted patches to lock the overlay inode of copied up file and relaxed the lock_rename during data copy up. Amir.
