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. Thanks, Amir.
