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=-8.8 required=3.0 tests=BAYES_00, HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI,MENTIONS_GIT_HOSTING, SPF_HELO_NONE,SPF_PASS autolearn=unavailable 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 7611CC49EA4 for ; Wed, 23 Jun 2021 12:46:54 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 586DB61076 for ; Wed, 23 Jun 2021 12:46:54 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S230312AbhFWMtK (ORCPT ); Wed, 23 Jun 2021 08:49:10 -0400 Received: from mail-wr1-f44.google.com ([209.85.221.44]:46054 "EHLO mail-wr1-f44.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S230019AbhFWMtJ (ORCPT ); Wed, 23 Jun 2021 08:49:09 -0400 Received: by mail-wr1-f44.google.com with SMTP id j2so2480783wrs.12; Wed, 23 Jun 2021 05:46:51 -0700 (PDT) X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20161025; h=x-gm-message-state:message-id:subject:from:to:cc:date:in-reply-to :references:user-agent:mime-version; bh=XOmIPJRzFakO/w4XtkertpgFPMyFgjY86X1TO7dNDw0=; b=pL3LHzVCpLmFfrrj3Aeqvm/N6M24GFlC/mHho83Fpto3pl4/CYKNK4wrRWgRnM/UFF oQCuEv6rhoNlI9kuONdfEo/UEL0wt6KEBvfskhufBm6m1fZitL/eSgU/KhpMNphbW5Ra sehYr/MeyortaeQytuKrW6a45jvNC5zhTS8WebQ0Ix/oilXWsDrhgx4BKBMI4KdM7tNj gwhtf31ab6Jm5jaPMOkNzRgqkhXHxQ0xrE7vQA6Q3WzMJN5nMZqCL5hRnLdZ9EQspzsg k4vBrmLY5GyFMfDD58ToVxz/7HJRhOLYUcDCCPi5DZyqRQdDSLgA3nxQVhNU5RYS6rd3 ZsVQ== X-Gm-Message-State: AOAM530LN1Y6OIji1K3bi3LBIfRyZEEkdy6oPC/Uie7UF2nTozJ1SKKP /7kl7bgATUcOy27tUpWYSzU= X-Google-Smtp-Source: ABdhPJxx8aaV8qjN7hGJFoqGJB5GJgItepkdKJ0B8XDDzEJkL3WD1H4tDQdxmiclFkDQtwxCuXg02g== X-Received: by 2002:a05:6000:8b:: with SMTP id m11mr11075087wrx.22.1624452410585; Wed, 23 Jun 2021 05:46:50 -0700 (PDT) Received: from localhost ([137.220.125.106]) by smtp.gmail.com with ESMTPSA id x1sm2971082wrv.49.2021.06.23.05.46.49 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Wed, 23 Jun 2021 05:46:49 -0700 (PDT) Message-ID: Subject: Re: [PATCH v3 0/6] block: add a sequence number to disks From: Luca Boccassi To: Hannes Reinecke , Matteo Croce , linux-block@vger.kernel.org, linux-fsdevel@vger.kernel.org, Jens Axboe Cc: linux-kernel@vger.kernel.org, Lennart Poettering , Alexander Viro , Damien Le Moal , Tejun Heo , Javier =?ISO-8859-1?Q?Gonz=E1lez?= , Niklas Cassel , Johannes Thumshirn , Matthew Wilcox , Christoph Hellwig , JeffleXu Date: Wed, 23 Jun 2021 13:46:48 +0100 In-Reply-To: References: <20210623105858.6978-1-mcroce@linux.microsoft.com> Content-Type: multipart/signed; micalg="pgp-sha512"; protocol="application/pgp-signature"; boundary="=-siui0wSAomKlfQSo0RJc" User-Agent: Evolution 3.30.5-1.2 MIME-Version: 1.0 Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org --=-siui0wSAomKlfQSo0RJc Content-Type: text/plain; charset="UTF-8" Content-Transfer-Encoding: quoted-printable On Wed, 2021-06-23 at 14:03 +0200, Hannes Reinecke wrote: > On 6/23/21 12:58 PM, Matteo Croce wrote: > > From: Matteo Croce > >=20 > > With this series a monotonically increasing number is added to disks, > > precisely in the genhd struct, and it's exported in sysfs and uevent. > >=20 > > This helps the userspace correlate events for devices that reuse the > > same device, like loop. > >=20 > I'm failing to see the point here. > Apparently you are assuming that there is a userspace tool tracking=20 > events, and has a need to correlate events related to different=20 > instances of the disk. > But if you have an userspace application tracking events, why can't the= =20 > same application track the 'add' and 'remove' events to track the=20 > lifetime of the devices, and implement its own numbering based on that? >=20 > Why do we need to burden the kernel with this? >=20 > Cheers, >=20 > Hannes Hi, It is not an assumption, such tool does exist, and manually tracking does not work because of the impossibility of reliably correlating events to devices (we've tried, again and again and again), which is the purpose of this series - to solve this long standing issue, which has been causing problems both in testing and production for a long time now, despite our best efforts to add workaround after workaround. For more info please see the discussion on the v1: https://lore.kernel.org/linux-fsdevel/20210315201331.GA2577561@casper.infra= dead.org/t/#m5b03e48013de14b4a080c90afdc4a8b8c94c30d4 and the bug linked in the cover letter: https://github.com/systemd/systemd/issues/17469#issuecomment-762919781 --=20 Kind regards, Luca Boccassi --=-siui0wSAomKlfQSo0RJc Content-Type: application/pgp-signature; name="signature.asc" Content-Description: This is a digitally signed message part -----BEGIN PGP SIGNATURE----- iQIzBAABCgAdFiEErCSqx93EIPGOymuRKGv37813JB4FAmDTLTgACgkQKGv37813 JB6A6Q//Z3SDBBRi6Ukl05ygOgOcNyIVCHNpxCzx+wViA4Q7RUCXnc7Q+oQwaib4 sz7IGa0rauYCgdr1y1PF5VAqqqxZpB7iWt+qDekOY5E0q+GQfjAuKJclS/C1J4JT pXhvELaWFISS+OhS1HhETcEzxXBQ9htOUjKMeilFKPetv5NPZTbvITK5vtIu+Toh +wT1OW0WU2OE1oIALmTgouqHyrhPjgVPS1oL32E7yYmsuTbbN4GrJP57NkLKx5xZ oF718/1sgwXeGMuk53GQ1ntjGfze4E4eBPJxuVXsJpSLOSiW0gSAK65ZcGP03C4G m6bcMWFxLCSlWpZ+diGgJgJuygvglv0sU2WVY+S0gifrZXSwm/Op8N38XorZFQ/L 5dYO+DkbyhSul1rPfG2W7OW7YYze/Xg+Gl1qqoy/vcc4Zfl0uJyxRuPHtsXd0AQs kpu4jtuY5BUmoM+SoULx9Bm+DpvgNbgR6kOLHBWrBvt87rppJlReFhBS0jTG85H4 uwl8EzLCNePGRij/UzmLjTdblJSxiOlpws55A1GgGELp2sjMlyXmo5TkS97F7I70 mK/LjFaiK3mSoE9Yl6xoj2b4PSf67PNDxCl7DGsLGkXk13NePGLcfynO8LkXUZwH Eas6LnpxQeuovYdmxx0ZHYJ3LoLPGwAWRdprWvcPu87hOTIs+Do= =z3th -----END PGP SIGNATURE----- --=-siui0wSAomKlfQSo0RJc--