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Thu, 25 Apr 2024 00:19:19 +0200 Message-ID: <598907d6-77e0-4134-b709-51106dcfb2f8@gmx.com> Date: Thu, 25 Apr 2024 07:49:12 +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, Qu Wenruo Cc: linux-btrfs@vger.kernel.org, boris@bur.io References: <07e54de6747a5bf1e6a422cba80cbb06ba832cf4.1713519718.git.wqu@suse.com> <20240424124156.GO3492@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: <20240424124156.GO3492@twin.jikos.cz> Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: quoted-printable X-Provags-ID: V03:K1:LMVIdDq0Nqc66wwoHv+9oEK2KubLjxZM4neBwC0KFZom2A/fWuu XQE1bnCWUPSTAWF8JWdGVCjlwKsw/BJkR5Asnn6qQxEatqr+o+ZIOf9w0Hh/xIh45DX2VGi Kvzyoy2CLwQeiEr+W24VsAU+0jK0rCV3gKQ58ZYy7cUavim/bWkyAuVWxyLdEUtBi8QAFcZ HUI9sCSCqBa71puLjX7Gg== X-Spam-Flag: NO UI-OutboundReport: notjunk:1;M01:P0:PZ+UTUQVChs=;kWVE8b8E3qi0BqXUCmqYfNYeKac wuPvqMj12lq3pME3lyK8+8TPSzKpfiZwmlUCG9vjA8Ef5KHCKF6eECwRRE4xQKmGXBfzbjOXo BBn9cdWc5e/i7K13di8K2zaUerQdBy4geMRxAMPA6WXzovObVUOrnhZZgTUt4rWNGgUBDOzC1 qlPloqohe12fwyGp2OUbuL8GN4tUWt4KWQwJGfBFMqzrXQ5Th6YCFlByIH6luMYhdWuQF0iW9 Mk+syhxirGeXtt6qHn3hw8mHCDAQBrd6rj5Y9Nj+j0YxhCBE8EEITxWJso3TUe5FlncbEy01T ovFF4XLQ4RYdraeHetO7TeArkfetCIntWygrIYp+2J3hFSwCPVs0E2MqHnCH42cr04sd3hJT/ 1CLnsjnZ8mY8YBD/Wp8BEOgnAuYAtwXojMVcLgZAAmPA1QWu+6pffp2lsRlEZoWdAbRFKL9bX Shoc6rodmR79UUBA0gPrmyhSElY8XFTeZ2X3AOrBI6Zc8gxzG3+H81ScFqBP/QzeCFf1l8ntQ jb0pE/pkvNY2luZlh+LAKtjt0Y+kEdViKAPK83BZ0ELdiN0bmmpRimFIDW6pET4cJ2c3fEfCv +3uwBmVh8ZKaAM3Oe8wM7j5zX2D8Rz/IcyxlQ33fmt9p4MHgDzalPQ7AkEA5/hvtzMfXME6i2 /+wjbUIToAP9UTeenQjG3nxgh6bTjhb0zqGbExAd7O8w9IcAebOyl1oYJdlfgvJR9CO8U7xOJ 0+Ly9IgNeUjcgwO+EmvVgxOcKNtNIdUgHdOlsNG/CINLqfKYAxgsuSyhpPSRrUBi0YUAVOtPJ OP/suOGKUNB1wVhVcwDrswcoj01nU62MY12XQ6GCiNYCM= =E5=9C=A8 2024/4/24 22:11, David Sterba =E5=86=99=E9=81=93: > On Fri, Apr 19, 2024 at 07:16:53PM +0930, Qu Wenruo wrote: >> Currently if we fully removed a subvolume (not only unlinked, but fully >> dropped its root item), its qgroup would not be removed. >> >> Thus we have "btrfs qgroup clear-stale" to handle such 0 level qgroups. > > There's also an option 'btrfs subvolume delete --delete-qgroup' that > does that and is going to be default in 6.9. With this kernel change it > would break the behaviour of the --no-delete-qgroup, which is there for > the case something depends on that. For now I'd rather postpone > changing the kernel behaviour. > A quick glance of the --delete-qgroup shows it won't work as expected at all. Firstly, the qgroup delete requires the qgroup numbers to be 0. Meanwhile qgroup numbers can only be 0 after 1) the full subvolume has been dropped 2) a transaction is committed to reflect the qgroup numbers. Both situation is only handled in my patchset, thus this means for a lot of cases it won't work at all. Furthermore, there is the drop_subtree_threshold thing, which can mark qgroup inconsistent and skip accounting, making the target subvolume's qgroup numbers never fall back to 0 (until next rescan). So I'm afraid the --delete-qgroup won't work until the 1/2 patch get merged (allowing deleting qgroups as long as the target subvolume is gone)= . Thanks, Qu