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charset=us-ascii Content-Disposition: inline Hello. On Sun, Dec 11, 2022 at 05:20:57PM -0500, Waiman Long wrote: > Before commit 3b8cc6298724 ("blk-cgroup: Optimize blkcg_rstat_flush()"), > blkg's stats is only flushed if they are online. I'm not sure I follow -- css_release_work_fn/cgroup_rstat_flush may be called on an offlined blkcg (offlined!=released). There's no invariant ensuring offlined blkcg won't be flushed. (There is only current situation when there is no reader of io data that'd need them flushed [1].) > In addition, the stat flushing of blkgs in blkcg_rstat_flush() > includes propagating the rstat data to its parent. However, if a blkg > has been destroyed (offline), the validity of its parent may be > questionable. Parents won't be freed (neither offlined) before children (see css_killed_work_fn). It should be regularly OK to pass data into a parent of an offlined blkcg. > For safety, revert back to the old behavior by ignoring offline > blkg's. I don't know if this is a good reasoning. If you argue that offlined children needn't be taken into parent's account, then I think it's more efficient to exclude the offlined blkcgs from update. (With the caveat I have in [1].) Regards, Michal [1] https://lore.kernel.org/r/YqEfNgUc8jxlAq8D@blackbook/ --11Y7aswkeuHtSBEs Content-Type: application/pgp-signature; name="signature.asc" Content-Description: Digital signature -----BEGIN PGP SIGNATURE----- iHUEARYIAB0WIQTrXXag4J0QvXXBmkMkDQmsBEOquQUCY5clxQAKCRAkDQmsBEOq uSetAQCmnfBYSQWk5l/gfz/eBj+JLLtB5FF0vKwMUp7t6s2hdQEA/iF6GKtaE8D3 6UdBR14daTYUWeIsw+Jji88gMzQy9gY= =kEQi -----END PGP SIGNATURE----- --11Y7aswkeuHtSBEs--