Messages in this thread | ![/](/images/icornerl.gif) | | Date | Tue, 7 Nov 2023 09:03:53 +0800 | Subject | Re: [PATCH v2] kpageflags: respect folio head-page flag placement | From | Kefeng Wang <> |
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On 2023/10/31 12:34, Gregory Price wrote: > On Tue, Oct 31, 2023 at 09:13:44AM +0000, Matthew Wilcox wrote: >> On Mon, Oct 30, 2023 at 07:41:23PM -0400, Gregory Price wrote: >>> On Mon, Oct 30, 2023 at 11:22:18PM +0000, Matthew Wilcox wrote: >>>> On Mon, Oct 30, 2023 at 02:00:05PM -0400, Gregory Price wrote: >>>>> kpageflags reads page-flags directly from the page, even when the >>>>> respective flag is only updated on the headpage of a folio. >>>>> >>>>> Update bitchecks to use PAGEFLAG() interfaces to check folio for the >>>>> referenced, dirty, lru, active, and unevictable bits. >>>> >>>> But uptodate, writeback and reclaim (amongst others) are also defined >>>> only on the head page. >>>> >>> >>> Ah yes i was only looking at the things defined w/ PAGEFLAG defines in >>> page-flags.h. I'll give it full once over can collect them all, my bad. >>> >>> (also i forgot to update my commit message) >>> >>> Quick question here since i have your attention: any recommendation on >>> what to do for ONLY_HEAD flags? If the provided page is not the head, >>> should the flag report 0... or whatever the head says? >> >> Thinking about it some more, really almost all flags are per-folio, not >> per-page. The only exceptions are HWPoison and AnonExclusive. So >> probably the right way to do this is to make k = folio->flags, and >> then just change a few places rather than changing all the places that >> test 'k'. > > Funny enough that's what i originally did but was confident it was > correct so walked it back. I'll take another crack at it.
Hi Gregory, any update? I changed stable_page_flags[1] when try to remove page idle wrapper, Matthew pointed it will conflict with this, I could redo my patch based on your new version:)
[1]https://lore.kernel.org/linux-mm/20231103072906.2000381-5-wangkefeng.wang@huawei.com/
Thanks. > > ~Gregory >
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