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[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-block@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 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 us-smtp-delivery-124.mimecast.com (us-smtp-delivery-124.mimecast.com [170.10.133.124]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.lore.kernel.org (Postfix) with ESMTPS id 46CB6C433EF for ; Wed, 9 Mar 2022 16:12:04 +0000 (UTC) Received: from mimecast-mx02.redhat.com (mimecast-mx02.redhat.com [66.187.233.88]) by relay.mimecast.com with ESMTP with STARTTLS (version=TLSv1.2, cipher=TLS_ECDHE_RSA_WITH_AES_256_GCM_SHA384) id us-mta-592-Em8SiVxYOVGFVJzCiT9iDA-1; Wed, 09 Mar 2022 11:12:01 -0500 X-MC-Unique: Em8SiVxYOVGFVJzCiT9iDA-1 Received: from smtp.corp.redhat.com (int-mx08.intmail.prod.int.rdu2.redhat.com [10.11.54.8]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by mimecast-mx02.redhat.com (Postfix) with ESMTPS id EF48318019EE; Wed, 9 Mar 2022 16:11:59 +0000 (UTC) Received: from mm-prod-listman-01.mail-001.prod.us-east-1.aws.redhat.com (mm-prod-listman-01.mail-001.prod.us-east-1.aws.redhat.com [10.30.29.100]) by smtp.corp.redhat.com (Postfix) with ESMTP id 67343C50941; Wed, 9 Mar 2022 16:11:58 +0000 (UTC) Received: from mm-prod-listman-01.mail-001.prod.us-east-1.aws.redhat.com (localhost [IPv6:::1]) by mm-prod-listman-01.mail-001.prod.us-east-1.aws.redhat.com (Postfix) with ESMTP id 66E8D195355C; Wed, 9 Mar 2022 16:11:55 +0000 (UTC) Received: from smtp.corp.redhat.com (int-mx07.intmail.prod.int.rdu2.redhat.com [10.11.54.7]) by mm-prod-listman-01.mail-001.prod.us-east-1.aws.redhat.com (Postfix) with ESMTP id 5FD0D194F4AE for ; Wed, 9 Mar 2022 15:50:00 +0000 (UTC) Received: by smtp.corp.redhat.com (Postfix) id 2A7D8141DC2A; Wed, 9 Mar 2022 15:50:00 +0000 (UTC) Received: from mimecast-mx02.redhat.com (mimecast01.extmail.prod.ext.rdu2.redhat.com [10.11.55.17]) by smtp.corp.redhat.com (Postfix) with ESMTPS id 26722141DC28 for ; Wed, 9 Mar 2022 15:50:00 +0000 (UTC) Received: from us-smtp-1.mimecast.com (us-smtp-delivery-1.mimecast.com [205.139.110.120]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by mimecast-mx02.redhat.com (Postfix) with ESMTPS id F28B385A5BC for ; Wed, 9 Mar 2022 15:49:59 +0000 (UTC) Received: from mail-ej1-f42.google.com (mail-ej1-f42.google.com [209.85.218.42]) by relay.mimecast.com with ESMTP with STARTTLS (version=TLSv1.2, cipher=TLS_ECDHE_RSA_WITH_AES_256_GCM_SHA384) id us-mta-600-nQjfPAzEOcC50f-iS5ZJkA-1; Wed, 09 Mar 2022 10:49:58 -0500 X-MC-Unique: nQjfPAzEOcC50f-iS5ZJkA-1 Received: by mail-ej1-f42.google.com with SMTP id bg10so6033121ejb.4 for ; Wed, 09 Mar 2022 07:49:57 -0800 (PST) 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=dUPPs2XuWq+pR3oYKMf9iF9zgWpT8FnaNo8yQWmblrIuGIbLpRK6t7UQHuJ2aNWSC/ TTrMhtsn9evTBaa4JBrelZeUJJap0CAzDJzz+cjrX7olmVtPOxQ3kaGRVBdEtMoHZoAf GiFa1ROpNzRD5rf86Q9nkuTXhfT6avomtXbA5yHD9e7yUIIt6kUzAWnxcSblWjpca7H9 6kgcKMa0N2iOJXeHnsSbHkU5/iOg/JmoZ7h/yHlqe7kE/gSGF4qzbvHLDE//+WDB7UHD aczGaNKEjPB/w9KslV+26ZSkOSjX+/BgfvcaXX4XT9XJB4rrbS/bWDtqbOBvs5gJvd/C qClQ== X-Gm-Message-State: AOAM5322Rhvsuk62V17RASh+1SYNX6wNRYXw+uw876HlE0I99fa3rG4+ YPrifz0/YUECbf/4nzXnZwmscw== 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 To: Mikulas Patocka References: <012723a9-2e9c-c638-4944-fa560e1b0df0@arrikto.com> <23895da7-bcec-d092-373a-c3d961ab5c48@arrikto.com> From: Nikos Tsironis In-Reply-To: X-Mimecast-Impersonation-Protect: Policy=CLT - Impersonation Protection Definition; Similar Internal Domain=false; Similar Monitored External Domain=false; Custom External Domain=false; Mimecast External Domain=false; Newly Observed Domain=false; Internal User Name=false; Custom Display Name List=false; Reply-to Address Mismatch=false; Targeted Threat Dictionary=false; Mimecast Threat Dictionary=false; Custom Threat Dictionary=false X-Scanned-By: MIMEDefang 2.85 on 10.11.54.7 Subject: Re: [dm-devel] [LSF/MM/BFP ATTEND] [LSF/MM/BFP TOPIC] Storage: Copy Offload X-BeenThere: dm-devel@redhat.com X-Mailman-Version: 2.1.29 Precedence: list List-Id: device-mapper development List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Cc: "djwong@kernel.org" , "linux-nvme@lists.infradead.org" , "clm@fb.com" , "dm-devel@redhat.com" , "osandov@fb.com" , "msnitzer@redhat.com >> msnitzer@redhat.com" , Bart Van Assche , "linux-scsi@vger.kernel.org" , Christoph Hellwig , "roland@purestorage.com" , "zach.brown@ni.com" , Chaitanya Kulkarni , "josef@toxicpanda.com" , "linux-block@vger.kernel.org" , "dsterba@suse.com" , "kbus @imap.gmail.com>> Keith Busch" , "Frederick.Knight@netapp.com" , Jens Axboe , "tytso@mit.edu" , "martin.petersen@oracle.com >> Martin K. Petersen" , "jack@suse.com" , linux-fsdevel , "lsf-pc@lists.linux-foundation.org" Errors-To: dm-devel-bounces@redhat.com Sender: "dm-devel" X-Scanned-By: MIMEDefang 2.85 on 10.11.54.8 Authentication-Results: relay.mimecast.com; auth=pass smtp.auth=CUSA124A263 smtp.mailfrom=dm-devel-bounces@redhat.com X-Mimecast-Spam-Score: 0 X-Mimecast-Originator: redhat.com Content-Language: en-US Content-Transfer-Encoding: 7bit Content-Type: text/plain; charset="us-ascii"; Format="flowed" 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 -- dm-devel mailing list dm-devel@redhat.com https://listman.redhat.com/mailman/listinfo/dm-devel