From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from mout.gmx.net (mout.gmx.net [212.227.17.22]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id DBFD3181313 for ; Thu, 2 May 2024 21:27:16 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=212.227.17.22 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1714685239; cv=none; b=Kpq5XYDPHdnohweoCSmjcxmIecsiOGm28HmHOOltTvywGJL80ZAe0KsPhLxPlrs23ZM+IU45ppNO4AgJw0Tm3z6c7GPMO31EWp3caVXsyPR6VTUVSte+aygPpQegj5D9cWqRV1D4nzQBhuyx1mNC1L5V1ueObM4lCHdKjLwgmX0= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1714685239; c=relaxed/simple; bh=bxk8dXlxuZiRI7FHKtSd5kS+6GVFc1KACiTW4X+ZM8Y=; h=Message-ID:Date:MIME-Version:Subject:To:Cc:References:From: In-Reply-To:Content-Type; b=Gc07gCXRrUv7E3J2tO/96gNm4r25C21mFo6M6peQ9/BkYN+mfz044N4b61/xHxvgvvBPnR2kZDPqo1ckWdiRGrKXWSJ1lpXrg++IylxaQEZDhYBi/QxjFIYBl7DdNNVZfnLPDVXAQ1NAd5/i08krjbwaU9ZYmbHzPt9tjttSv0E= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dmarc=pass (p=quarantine dis=none) header.from=gmx.com; spf=pass smtp.mailfrom=gmx.com; dkim=pass (2048-bit key) header.d=gmx.com header.i=quwenruo.btrfs@gmx.com header.b=fXnienSo; arc=none smtp.client-ip=212.227.17.22 Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=quarantine dis=none) header.from=gmx.com Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=gmx.com Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=gmx.com header.i=quwenruo.btrfs@gmx.com header.b="fXnienSo" DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmx.com; s=s31663417; t=1714685230; x=1715290030; i=quwenruo.btrfs@gmx.com; bh=IT8ivJLXYilJdothllFHsf6vNZrQxE8FoHix2ibJ7qs=; h=X-UI-Sender-Class:Message-ID:Date:MIME-Version:Subject:To:Cc: References:From:In-Reply-To:Content-Type: Content-Transfer-Encoding:cc:content-transfer-encoding: content-type:date:from:message-id:mime-version:reply-to:subject: to; b=fXnienSorOdhZc1YW/aarb85L2ElvM1DYno6EZd7zBO+0mFJHlLBQYASOdetAQdr 771whuW6+0r3BMqil3fonGYF9gpM3/oVynlQCJe1owtLcvgn+EoQdyoTOlEL5/jvW EA/koRW6Jn1VbpPH4M6XtsfP0DXSFy6mNTDnr+Qv0FhK3mP+A9EQtL0D2msoowqU+ QgktzMEXphs2sa3dvgGfOCLX3tX5N92ZgGIP4kqIPDaOxkGchPFXmPpDxijC3Qfoq DvwbJ/A90XHcqGWDcj6Z3CodskBRkxPLquFBGIKlfWGqNmN0W2WRri2wjbaPir0DM nXtVME80rj17GRcBIQ== X-UI-Sender-Class: 724b4f7f-cbec-4199-ad4e-598c01a50d3a Received: from [172.16.0.219] ([159.196.52.54]) by mail.gmx.net (mrgmx105 [212.227.17.174]) with ESMTPSA (Nemesis) id 1M2wKq-1s3kPp2JO0-003LQy; Thu, 02 May 2024 23:27:10 +0200 Message-ID: Date: Fri, 3 May 2024 06:57:03 +0930 Precedence: bulk X-Mailing-List: linux-btrfs@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH v2 2/2] btrfs: automatically remove the subvolume qgroup To: dsterba@suse.cz Cc: Boris Burkov , Qu Wenruo , linux-btrfs@vger.kernel.org References: <07e54de6747a5bf1e6a422cba80cbb06ba832cf4.1713519718.git.wqu@suse.com> <20240424124156.GO3492@twin.jikos.cz> <598907d6-77e0-4134-b709-51106dcfb2f8@gmx.com> <20240425123450.GP3492@twin.jikos.cz> <9df817bc-f3a8-4096-aabc-12044447a900@gmx.com> <20240429131333.GC21573@zen.localdomain> <20240429163136.GG2585@suse.cz> <20240430105938.GM2585@suse.cz> <4a83b326-9cde-45f5-8a53-da7b62c45619@gmx.com> <20240502150056.GR2585@twin.jikos.cz> Content-Language: en-US From: Qu Wenruo Autocrypt: addr=quwenruo.btrfs@gmx.com; keydata= xsBNBFnVga8BCACyhFP3ExcTIuB73jDIBA/vSoYcTyysFQzPvez64TUSCv1SgXEByR7fju3o 8RfaWuHCnkkea5luuTZMqfgTXrun2dqNVYDNOV6RIVrc4YuG20yhC1epnV55fJCThqij0MRL 1NxPKXIlEdHvN0Kov3CtWA+R1iNN0RCeVun7rmOrrjBK573aWC5sgP7YsBOLK79H3tmUtz6b 9Imuj0ZyEsa76Xg9PX9Hn2myKj1hfWGS+5og9Va4hrwQC8ipjXik6NKR5GDV+hOZkktU81G5 gkQtGB9jOAYRs86QG/b7PtIlbd3+pppT0gaS+wvwMs8cuNG+Pu6KO1oC4jgdseFLu7NpABEB AAHNIlF1IFdlbnJ1byA8cXV3ZW5ydW8uYnRyZnNAZ214LmNvbT7CwJQEEwEIAD4CGwMFCwkI BwIGFQgJCgsCBBYCAwECHgECF4AWIQQt33LlpaVbqJ2qQuHCPZHzoSX+qAUCY00iVQUJDToH pgAKCRDCPZHzoSX+qNKACACkjDLzCvcFuDlgqCiS4ajHAo6twGra3uGgY2klo3S4JespWifr BLPPak74oOShqNZ8yWzB1Bkz1u93Ifx3c3H0r2vLWrImoP5eQdymVqMWmDAq+sV1Koyt8gXQ XPD2jQCrfR9nUuV1F3Z4Lgo+6I5LjuXBVEayFdz/VYK63+YLEAlSowCF72Lkz06TmaI0XMyj jgRNGM2MRgfxbprCcsgUypaDfmhY2nrhIzPUICURfp9t/65+/PLlV4nYs+DtSwPyNjkPX72+ LdyIdY+BqS8cZbPG5spCyJIlZonADojLDYQq4QnufARU51zyVjzTXMg5gAttDZwTH+8LbNI4 mm2YzsBNBFnVga8BCACqU+th4Esy/c8BnvliFAjAfpzhI1wH76FD1MJPmAhA3DnX5JDORcga CbPEwhLj1xlwTgpeT+QfDmGJ5B5BlrrQFZVE1fChEjiJvyiSAO4yQPkrPVYTI7Xj34FnscPj /IrRUUka68MlHxPtFnAHr25VIuOS41lmYKYNwPNLRz9Ik6DmeTG3WJO2BQRNvXA0pXrJH1fN GSsRb+pKEKHKtL1803x71zQxCwLh+zLP1iXHVM5j8gX9zqupigQR/Cel2XPS44zWcDW8r7B0 q1eW4Jrv0x19p4P923voqn+joIAostyNTUjCeSrUdKth9jcdlam9X2DziA/DHDFfS5eq4fEv ABEBAAHCwHwEGAEIACYCGwwWIQQt33LlpaVbqJ2qQuHCPZHzoSX+qAUCY00ibgUJDToHvwAK CRDCPZHzoSX+qK6vB/9yyZlsS+ijtsvwYDjGA2WhVhN07Xa5SBBvGCAycyGGzSMkOJcOtUUf tD+ADyrLbLuVSfRN1ke738UojphwkSFj4t9scG5A+U8GgOZtrlYOsY2+cG3R5vjoXUgXMP37 INfWh0KbJodf0G48xouesn08cbfUdlphSMXujCA8y5TcNyRuNv2q5Nizl8sKhUZzh4BascoK DChBuznBsucCTAGrwPgG4/ul6HnWE8DipMKvkV9ob1xJS2W4WJRPp6QdVrBWJ9cCdtpR6GbL iQi22uZXoSPv/0oUrGU+U5X4IvdnvT+8viPzszL5wXswJZfqfy8tmHM85yjObVdIG6AlnrrD In-Reply-To: <20240502150056.GR2585@twin.jikos.cz> Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: quoted-printable X-Provags-ID: V03:K1:lgTLiv8enJDncnEGwQ/g0bKUT9qrnpUR3aqgkHH1l65Z8zoV8n7 /jEOmJ7awW9r0H1uowF9SQu+LbHTiIPXE7w/RJ+k5RPotfcHdVe3UW17SA1+0oq4KRfj0MH CNZIAMU3bVnHxgLE5+wCY84++EaZQryW3xJqk3kWeAXXw6qw2moTVjNdg2dyOOa2+fS8K+t MdFWKKTz+ESCmlgCZmU9w== X-Spam-Flag: NO UI-OutboundReport: notjunk:1;M01:P0:oHXl1UR/xLA=;P5i9C/thIrGcIuuCiQHc+EPvXCT OjJffW/zXuziyZjCKF/y/qZLmTBXnnAVs5bM/GUmgvlGxQ3v88/bgzNewRXs8I+q5crjjKcNc me/wamQb6dKx/ECoeg3pF7QHxmqmpqNYk/7sUuaENi3GvAphADiwKIn9cSRBXFXZfW0jbb0oh zww4xM6xpafy1cUXEtjKr5S46TR7AoDccqo6KyiiOgJOqT8GhQbRy7HeVY5ErV4++h2pyYiNe On/4TnDJqh72mx/G8ZxEi+ly0DiJIjscUOTEQV3HXpo5kmKMNB0LGcsC+go/9JquI3JauX1rW q0Wo9ppdj32Cs879iRKT4YrwPf4DmrGwOUqUT5FbrS0NEDf1fWvzQN5uS7O2LIf5AZPlxbyY1 31s2UOChWa0B3mYPgHmilH/kDTsjYOCvm0d51rt1OEgXm7zX6wM1b20XBu4Ra50QTk96jvRvT dw62a2GZy5aJDkH+Ay15NduLIKRZvr6cRl3Mm/n7MGzryYeO+ONYFNkt7hi5yLFPc7NN9w5D2 y9k/ABUGf9qYhKI929VzfF12++iJ9MvNhZfcJU3l6CwMJ+hXs4Dqo+pwgty+8FzHbq6m6WhHY oeKZbva4BqEPh1vkb2KwWjHC1u9ufdQLOMU1W9xTfM2j4Rq+G3mOFEecxUSQ/KyqlYxF5m67F hwN/UxIoyMCggGwH2q2W4N7UrtmejeWW6ggOQAM7LFkaoHnNOBhlD54XkVSSj/smQeI54C+Uq CiiPYO8/gVjCaYIG6TbdcLeRHaYGlhIKaqegKJDPbbPYNInR1D3NGq1qr6v2nENWpHhabXwq9 ngTtalHDBGucNT9RM5bPT9TXl84JYf4y1r9XVA7fOSRL4= =E5=9C=A8 2024/5/3 00:30, David Sterba =E5=86=99=E9=81=93: > On Wed, May 01, 2024 at 07:35:09AM +0930, Qu Wenruo wrote: >> >> >> =E5=9C=A8 2024/4/30 20:29, David Sterba =E5=86=99=E9=81=93: >>> On Tue, Apr 30, 2024 at 07:35:11AM +0930, Qu Wenruo wrote: >>>> >>>> >>>> =E5=9C=A8 2024/4/30 02:01, David Sterba =E5=86=99=E9=81=93: >>>>> On Mon, Apr 29, 2024 at 06:13:33AM -0700, Boris Burkov wrote: >>>>>> I support the auto deletion in the kernel as you propose, I think i= t >>>>>> just makes sense. Who wants stale, empty qgroups around that aren't >>>>>> attached to any subvol? I suppose that with the drop_thresh thing, = it is >>>>>> possible some parent qgroup still reflects the usage until the next= full >>>>>> scan? >>>>> >>>>> The stale qgroups have been out for a long time so removing them aft= er >>>>> subvolume deletion is changing default behaviour, this always breaks >>>>> somebody's scripts or tools. >>>> >>>> If needed I can introduce a compat bit (the first one), to tell the >>>> behavior difference. >>>> >>>> And if we go the compat bit way, I believe it can be the first exampl= e >>>> on how to do a kernel behavior change correctly without breaking any >>>> user space assumption. >>> >>> I don't see how a compat bit would work here, we use them for feature >>> compatibility and for general access to data (full or read-only). What >>> we do with individual behavioral changes are sysfs files. They're >>> detectable by scripts and can be also used for configuration. In this >>> case enabling/disabling autoclean of the qgroups. >> >> I mean the compat bit, which is fully empty now. > > Which compat bit and in which structure? What I mean is the super block > incompat/compat bits but what you described below does not match it. Superblock compat bit exactly. I didn't see why my following description doesn't match it. We have 3 compat bits: - incompat Huge on-disk format change that older kernel can not understand and affects older kernels' ability to read files. This is the most abused bits from the past. A lot of features like skinny metadata should go compat_ro. - compat_ro On-disk format changes, but older kernels should still be able to read the fs/csum tree etc. - compat Not utilized for now. Older kernel can still do everything without any problem. Thus this should be the best candidate for runtime behavior changes that doesn't affect on-disk format at all. Thanks, Qu > >> The new bit would be something like BTRFS_QGROUP_AUTO_REMOVAL, with tha= t >> set, btrfs would auto remove any stale qgroups (for regular qgroups tho= ugh). >> >> Without that, it would be as usual (no auto removal).