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Wed, 01 May 2024 00:05:16 +0200 Message-ID: <4a83b326-9cde-45f5-8a53-da7b62c45619@gmx.com> Date: Wed, 1 May 2024 07:35:09 +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> 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: <20240430105938.GM2585@suse.cz> Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: quoted-printable X-Provags-ID: V03:K1:onvKilrUGkh4ee8cC4x0xpIBTVpU0ldxuI/EdzqMRlrVy+25b23 FPyPTRy8sFWgUDl+uYBgvD1WBGZNQizHS06IzxWyO8xV3Wm5RMR6fbcwgplTcMzucJCCjUX P0ilvdd+zMpAzq0M5+dBx8IdlSE5+kIeYZ6WgxXDhnyO0jl5rvT88iusUDn7H6UgF89iisj Jj/UCX9a+kDEL3gDH3o5Q== X-Spam-Flag: NO UI-OutboundReport: notjunk:1;M01:P0:leGS3NUYC+4=;wGtKLpUWmA8YT1wUXO2K6bYzfV2 gkxs9NBq6UgW6Fw2fVx81/HjBt/liauFznZyzjTSq7iDQ7Fv14z2I8LKUkc9vkKj00JYeLnyK Qo/ScQGe1xZfw4ck7wy6DwKTUzFn9XvJIwluKiVywoVYjipcIJhtAGDMD9v/4rAeYv+3RjenN 5wElikiDHZHyzp4e+oiINw3P6n+nshrlDmNZLO9MC2v8YG1uUChLYE5VB4X0IMYnEg79zpP1T 81m9iCKSeBycgrA80wKg0Un6EKbMne9gY0LviH6v01gG4IIQjZwqnt+outuSdIFDuvASVC8Xs M5Gm8/y0bgzo28tcOy4lprrYNuVcodnQBsAGM6e71kSxHIjH0CGAN9YBd65+3LxfhOGMMg0Ew l9gWvau2CZj4tSXJyH4s9YbaaDQxquNehnQrBY3y/COk/ZHaIIjKXFbaKhAibL8+GOKTqeIs2 2IT0mSEzKSUIsIGbY0PoMgIMzn+lv7qp4oW/u28Hv0lKzcobEsHcHzVGkiLAzA/rZRfEt6P5j dsezishTGGu1k6vv9zdEd64qG+3LCEfX/vyGrutRsQ6/0QWAWpbZyBeY/ZHk8X+K/YHvPNTfr vkiBEKhbwvvqF5lMys2hx7IVrFwHvdEob+DzHLs3Ipapn37YPORNSZHPpkuOkh9ZhH9bqGrxF /I1mRCNhuAKddtvZyJrY6XtwGDilNrFN1fedt+nQlIwGuvflL+mDySkmksxd/f0uIErNGC9cJ HnUWbf9HHfNxNRwY82vhBD1PJnPL4Y3tBgbyBsfpY0bkDD0IbAwag6RLeLEtGdviQscIg2ofu bzZwJKFc51PFk10oxCTqV4OVt0aV2m1zN3iqyq9X0hksA= =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 it >>>> 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 f= ull >>>> scan? >>> >>> The stale qgroups have been out for a long time so removing them after >>> 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 example >> 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. The new bit would be something like BTRFS_QGROUP_AUTO_REMOVAL, with that set, btrfs would auto remove any stale qgroups (for regular qgroups though= ). Without that, it would be as usual (no auto removal). Since this doesn't cause any on-disk change, it does not needs compat-ro nor incompat. Thanks, Qu