Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1755426AbcKKJqe (ORCPT ); Fri, 11 Nov 2016 04:46:34 -0500 Received: from mail-lf0-f66.google.com ([209.85.215.66]:33411 "EHLO mail-lf0-f66.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1754579AbcKKJqb (ORCPT ); Fri, 11 Nov 2016 04:46:31 -0500 MIME-Version: 1.0 In-Reply-To: References: <1477380887-21333-1-git-send-email-mszeredi@redhat.com> <1477380887-21333-4-git-send-email-mszeredi@redhat.com> <20161025115748.ydhkkp5cfcdnjzwn@home.ouaza.com> From: Konstantin Khlebnikov Date: Fri, 11 Nov 2016 12:46:28 +0300 Message-ID: Subject: Re: [PATCH 3/3] ovl: redirect on rename-dir To: Amir Goldstein Cc: Miklos Szeredi , Raphael Hertzog , Miklos Szeredi , "linux-unionfs@vger.kernel.org" , Guillem Jover , linux-fsdevel , Linux Kernel Mailing List Content-Type: text/plain; charset=UTF-8 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1899 Lines: 42 On Fri, Nov 11, 2016 at 1:56 AM, Amir Goldstein wrote: > On Mon, Nov 7, 2016 at 3:38 PM, Amir Goldstein wrote: >> On Mon, Nov 7, 2016 at 12:08 PM, Konstantin Khlebnikov wrote: >>> On Mon, Nov 7, 2016 at 1:04 PM, Miklos Szeredi wrote: >>>> On Mon, Nov 7, 2016 at 10:58 AM, Konstantin Khlebnikov 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.