From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id BE877C433F5 for ; Wed, 9 Mar 2022 15:50:00 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S234039AbiCIPu6 (ORCPT ); Wed, 9 Mar 2022 10:50:58 -0500 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:32962 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S234041AbiCIPu5 (ORCPT ); Wed, 9 Mar 2022 10:50:57 -0500 Received: from mail-ej1-x62d.google.com (mail-ej1-x62d.google.com [IPv6:2a00:1450:4864:20::62d]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id E3A0D1342DC for ; Wed, 9 Mar 2022 07:49:57 -0800 (PST) Received: by mail-ej1-x62d.google.com with SMTP id r13so6021338ejd.5 for ; Wed, 09 Mar 2022 07:49:57 -0800 (PST) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=arrikto-com.20210112.gappssmtp.com; s=20210112; h=message-id:date:mime-version:user-agent:subject:content-language:to :cc:references:from:in-reply-to:content-transfer-encoding; bh=xrbpP/Yfwao8lnj7LaSM/uRQpgaSVRznTS0TTH/HjZY=; b=s3xFNi6w/peDGqcEmc0BfMkPZn7cwxFxTcYpMhZo8mLd849lJJCJPAfTNkd3VaRKMn 8D/pjSsda3jU/kUBKgqXjBLnK+pfqfXsEJb+MLwdZg9xmpkHQylcEcckW1X1Ej7wxleM Ocg1MWV+93+ARFiP/QbJy1epHrG9KrAALd91YORM/vgENm4v3zou2T2CrXDJY1TL81SQ LAlXStVVmvhEUfG4kfQ4LJnb3TkAtXzEhDl4vxr5+owgko1gg5gks3ZdBIr/A+yDY/gM RO33ihV+A5M7uWuDaf1/mtjmApBj24Up9s8gK/ksaVxOtT85uLj8B9Ov6cycxj929zDc Fr+w== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20210112; h=x-gm-message-state:message-id:date:mime-version:user-agent:subject :content-language:to:cc:references:from:in-reply-to :content-transfer-encoding; bh=xrbpP/Yfwao8lnj7LaSM/uRQpgaSVRznTS0TTH/HjZY=; b=iXSA7TdxC2qyX8Mcfe8Zm6oEViiZ35DlfTlvh7RnOeoYWVDoxl74V0Rj8TphHLE4vD B+gd6XDIFBZflmHy+6x7pItBKAUuXC3HDFz73kTXqkLZ7NOpTpa4BSf2mUQZdJxDVxc3 CnzRH4uwXKl8OvJTAPnoA22VQku03kdaBwnUmP/2L21GLUe6zmVrQCvttt0dGhVyz+Qn CBWjLWDGcqGxpOHAewrwgvAYECjjmz+RsXjzHCVkbUbnSdfL8djQKWyVql8ZWJOwNXIw utH0P76UlOSSYkdM919FZtnf0u3wDIkB2MhrlrkvAId2KR9FtS90xHbNLpZwWqvdkoO8 drYQ== X-Gm-Message-State: AOAM532Tefo61ZZh92HV8nN4EyprCg139UV3qDn3icTsNQnp7X4atkya RseJLDWLQ/WsgMfTnUzaLXBicA== X-Google-Smtp-Source: ABdhPJxZ5pBljQ9c4cS3Z9+taf/t5M3OBOhL/UO8YvG/idZkX4Ez6hrxTSX+wbR+RbFNFZdxzRpO9g== X-Received: by 2002:a17:907:7f2a:b0:6d6:df12:7f57 with SMTP id qf42-20020a1709077f2a00b006d6df127f57mr390349ejc.122.1646840996396; Wed, 09 Mar 2022 07:49:56 -0800 (PST) Received: from [172.16.10.50] (213.16.174.189.dsl.dyn.forthnet.gr. [213.16.174.189]) by smtp.gmail.com with ESMTPSA id h8-20020a50ed88000000b004160630c980sm960188edr.62.2022.03.09.07.49.53 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Wed, 09 Mar 2022 07:49:55 -0800 (PST) Message-ID: <2015a35a-915c-351f-81cf-bd7dfe4502a1@arrikto.com> Date: Wed, 9 Mar 2022 17:49:52 +0200 MIME-Version: 1.0 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:91.0) Gecko/20100101 Thunderbird/91.6.1 Subject: Re: [LSF/MM/BFP ATTEND] [LSF/MM/BFP TOPIC] Storage: Copy Offload Content-Language: en-US To: Mikulas Patocka Cc: Chaitanya Kulkarni , "linux-block@vger.kernel.org" , "linux-scsi@vger.kernel.org" , "dm-devel@redhat.com" , "linux-nvme@lists.infradead.org" , linux-fsdevel , Jens Axboe , "msnitzer@redhat.com >> msnitzer@redhat.com" , Bart Van Assche , "martin.petersen@oracle.com >> Martin K. Petersen" , "roland@purestorage.com" , Hannes Reinecke , "kbus @imap.gmail.com>> Keith Busch" , Christoph Hellwig , "Frederick.Knight@netapp.com" , "zach.brown@ni.com" , "osandov@fb.com" , "lsf-pc@lists.linux-foundation.org" , "djwong@kernel.org" , "josef@toxicpanda.com" , "clm@fb.com" , "dsterba@suse.com" , "tytso@mit.edu" , "jack@suse.com" References: <012723a9-2e9c-c638-4944-fa560e1b0df0@arrikto.com> <23895da7-bcec-d092-373a-c3d961ab5c48@arrikto.com> From: Nikos Tsironis In-Reply-To: Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 7bit Precedence: bulk List-ID: X-Mailing-List: linux-scsi@vger.kernel.org On 3/9/22 10:51, Mikulas Patocka wrote: > > Hi > > Note that you must submit kcopyd callbacks from a single thread, otherwise > there's a race condition in snapshot. > Hi, Thanks for the feedback. Yes, I'm aware of that. > The snapshot code doesn't take locks in the copy_callback and it expects > that the callbacks are serialized. > > Maybe, adding the locks to copy_callback would solve it. > That's what I did. I used a lock to ensure that kcopyd callbacks are serialized for persistent snapshots. For transient snapshots we can lift this limitation, and complete pending exceptions out-of-oder and in "parallel", i.e., without explicitly serializing kcopyd callbacks. The locks in pending_complete() are enough in this case. Nikos