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 X-Spam-Level: X-Spam-Status: No, score=-2.8 required=3.0 tests=BAYES_00,DKIM_SIGNED, DKIM_VALID,DKIM_VALID_AU,FREEMAIL_FORGED_FROMDOMAIN,FREEMAIL_FROM, HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS autolearn=no autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id 8DE12C48BCF for ; Wed, 9 Jun 2021 09:04:44 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 7844B61181 for ; Wed, 9 Jun 2021 09:04:44 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S237634AbhFIJGh (ORCPT ); Wed, 9 Jun 2021 05:06:37 -0400 Received: from mail-pj1-f54.google.com ([209.85.216.54]:53038 "EHLO mail-pj1-f54.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S237085AbhFIJGh (ORCPT ); Wed, 9 Jun 2021 05:06:37 -0400 Received: by mail-pj1-f54.google.com with SMTP id h16so975392pjv.2; Wed, 09 Jun 2021 02:04:27 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=20161025; h=mime-version:subject:from:in-reply-to:date:cc :content-transfer-encoding:message-id:references:to; bh=p509XquklGPlHgIgLviWSLP6RC8IGBzAqX0rlKOEPB0=; b=arQmByQXbbDKQBLqyclwq5I0Fm2ow+XetxFCyzjadndLtrmHo+Lf/AWvEu7/LACjJS 2KcfUQCQRXfyX1u4c4CdC/v+L3WM6A7wTdCzA0Ih7/UKkJGcWZ2IGxum+H0y1euuO80P sh1jo528WfjWEfVXbJJ9mkUuIScDKOK0ArRP9uque7qjTXfDHE+1wyBaJz92PyLTtGq/ Q/5RMnTncYG6Zwu55T5JUmuHQlY7x5qgUQyBDLomrrfhGBZgZ2+Euz38KsHm82KZGeMQ mUnV0Fa9d65Dk5dO9vHjlHEItRx+k1WkD+bu7GSupweYzRgJNbY/3vkr7dBn8m1uE5ep FC1Q== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20161025; h=x-gm-message-state:mime-version:subject:from:in-reply-to:date:cc :content-transfer-encoding:message-id:references:to; bh=p509XquklGPlHgIgLviWSLP6RC8IGBzAqX0rlKOEPB0=; b=VMtLDqPC9kZIucM10Gu58q4Gg3NTPw/N1mgnjBuZdlEcvbFqXTj+TiTkuEUl5MgbEu L3+OUwSrkQiQER71LwBL7ifWPvf6ZemMMhy+ZkeC6kBpVLP+aHSFtt9/1BlRmtop8/qR vfaijGRvVTBDwbLfALCAzu1Hq7JRcJ578vvOwQa/ZqJdOQGWc8pU5QtZtX53oj/Cr/vS gprXlP80S0Zty8c5xY5fZ+Eb4NG4++scZh3eUF1yehrbUXmn3lG4Sv2r2x0AUWePFgC4 vge1CeLTNtjm3GppanAymCiN+wCDOQJ3cHbigpuFyYnEe1Z2ZWE5mB7+CW4UXGvqLJtD ouQA== X-Gm-Message-State: AOAM531XeMvF1iTZJ0W4XpswD9NmPPHcKAmdODnv2b7JZYocWdwHGKI6 zpiwMn5sXWGHDjwXjQL0EmM= X-Google-Smtp-Source: ABdhPJwnJjEeG/UnQ9HkZG2AGk2j8LX0p5mr5IbXIQAQlGbykdC126JUSdkQ3T1basqET5VuuDBk3Q== X-Received: by 2002:a17:902:8484:b029:101:7016:fb7b with SMTP id c4-20020a1709028484b02901017016fb7bmr4015286plo.23.1623229407608; Wed, 09 Jun 2021 02:03:27 -0700 (PDT) Received: from [10.7.3.1] ([133.130.111.179]) by smtp.gmail.com with ESMTPSA id s3sm14846565pgs.62.2021.06.09.02.03.24 (version=TLS1_2 cipher=ECDHE-ECDSA-AES128-GCM-SHA256 bits=128/128); Wed, 09 Jun 2021 02:03:27 -0700 (PDT) Content-Type: text/plain; charset=utf-8 Mime-Version: 1.0 (Mac OS X Mail 13.4 \(3608.120.23.2.6\)) Subject: Re: [Bug Report] Discard bios cannot be correctly merged in blk-mq From: Wang Shanker In-Reply-To: Date: Wed, 9 Jun 2021 17:03:22 +0800 Cc: Ming Lei , linux-block@vger.kernel.org, linux-raid@vger.kernel.org Content-Transfer-Encoding: quoted-printable Message-Id: References: <85F98DA6-FB28-4C1F-A47D-C410A7C22A3D@gmail.com> <1C6DB607-B7BE-4257-8384-427BB490C9C0@gmail.com> To: Xiao Ni X-Mailer: Apple Mail (2.3608.120.23.2.6) Precedence: bulk List-ID: X-Mailing-List: linux-block@vger.kernel.org > 2021=E5=B9=B406=E6=9C=8809=E6=97=A5 16:44=EF=BC=8CXiao Ni = =E5=86=99=E9=81=93=EF=BC=9A >=20 > Hi all >=20 > Thanks for reporting about this. I did a test in my environment. > time blkdiscard /dev/nvme5n1 (477GB) > real 0m0.398s > time blkdiscard /dev/md0 > real 9m16.569s >=20 > I'm not familiar with the block layer codes. I'll try to understand > the codes related with discard request and > try to fix this problem. >=20 > I have a question for raid5 discard, it needs to consider more than > raid0 and raid10. For example, there is a raid5 with 3 disks. > D11 D21 P1 (stripe size is 4KB) > D12 D22 P2 > D13 D23 P3 > D14 D24 P4 > ... (chunk size is 512KB) > If there is a discard request on D13 and D14, and there is no discard > request on D23 D24. It can't send > discard request to D13 and D14, right? P3 =3D D23 xor D13. If we = discard > D13 and disk2 is broken, it can't > get the right data from D13 and P3. The discard request on D13 can > write 0 to the discard region, right? Yes. It can be seen at the beginning of make_discard_request(), where the requested range being discarded is aligned to ``stripe_sectors",=20 which should be chunk_sectors * nr_data_disks. Cheers, Miao Wang