On Fri, Nov 11, 2016 at 1:56 AM, Amir Goldstein <amir73il@xxxxxxxxx> wrote: > On Mon, Nov 7, 2016 at 3:38 PM, Amir Goldstein <amir73il@xxxxxxxxx> wrote: >> On Mon, Nov 7, 2016 at 12:08 PM, Konstantin Khlebnikov <koct9i@xxxxxxxxx> wrote: >>> On Mon, Nov 7, 2016 at 1:04 PM, Miklos Szeredi <miklos@xxxxxxxxxx> wrote: >>>> On Mon, Nov 7, 2016 at 10:58 AM, Konstantin Khlebnikov <koct9i@xxxxxxxxx> 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. -- 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
