From: Thomas Gleixner <tglx@linutronix.de>
To: Linus Torvalds <torvalds@linux-foundation.org>
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Subject: Re: [patch V3 22/37] highmem: High implementation details and document API
Date: Tue, 03 Nov 2020 20:00:20 +0100 [thread overview]
Message-ID: <87y2ji1d17.fsf@nanos.tec.linutronix.de> (raw)
In-Reply-To: <CAHk-=wg2D_yjgKYkXCybD3uf0dtwYh6HxZ9BQJfV5t+EBqLGQQ@mail.gmail.com>
On Tue, Nov 03 2020 at 09:48, Linus Torvalds wrote:
> I have no complaints about the patch, but it strikes me that if people
> want to actually have much better debug coverage, this is where it
> should be (I like the "every other address" thing too, don't get me
> wrong).
>
> In particular, instead of these PageHighMem(page) tests, I think
> something like this would be better:
>
> #ifdef CONFIG_DEBUG_HIGHMEM
> #define page_use_kmap(page) ((page),1)
> #else
> #define page_use_kmap(page) PageHighMem(page)
> #endif
>
> adn then replace those "if (!PageHighMem(page))" tests with "if
> (!page_use_kmap())" instead.
>
> IOW, in debug mode, it would _always_ remap the page, whether it's
> highmem or not. That would really stress the highmem code and find any
> fragilities.
Yes, that makes a lot of sense. We just have to avoid that for the
architectures with aliasing issues.
> Anyway, this is all sepatrate from the series, which still looks fine
> to me. Just a reaction to seeing the patch, and Thomas' earlier
> mention that the highmem debugging doesn't actually do much.
Right, forcing it for both kmap and kmap_local is straight forward. I'll
cook a patch on top for that.
Thanks,
tglx
next prev parent reply other threads:[~2020-11-03 19:00 UTC|newest]
Thread overview: 69+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-11-03 9:27 [patch V3 00/37] mm/highmem: Preemptible variant of kmap_atomic & friends Thomas Gleixner
2020-11-03 9:27 ` [patch V3 01/37] mm/highmem: Un-EXPORT __kmap_atomic_idx() Thomas Gleixner
2020-11-06 23:27 ` [tip: core/mm] " tip-bot2 for Thomas Gleixner
2020-11-03 9:27 ` [patch V3 02/37] highmem: Remove unused functions Thomas Gleixner
2020-11-06 23:27 ` [tip: core/mm] " tip-bot2 for Thomas Gleixner
2020-11-03 9:27 ` [patch V3 03/37] fs: Remove asm/kmap_types.h includes Thomas Gleixner
2020-11-03 11:12 ` David Sterba
2020-11-06 23:27 ` [tip: core/mm] " tip-bot2 for Thomas Gleixner
2020-11-03 9:27 ` [patch V3 04/37] sh/highmem: Remove all traces of unused cruft Thomas Gleixner
2020-11-06 23:27 ` [tip: core/mm] " tip-bot2 for Thomas Gleixner
2020-11-03 9:27 ` [patch V3 05/37] asm-generic: Provide kmap_size.h Thomas Gleixner
2020-11-03 12:25 ` Arnd Bergmann
2020-11-06 23:27 ` [tip: core/mm] " tip-bot2 for Thomas Gleixner
2020-11-03 9:27 ` [patch V3 06/37] highmem: Provide generic variant of kmap_atomic* Thomas Gleixner
2020-11-06 23:27 ` [tip: core/mm] " tip-bot2 for Thomas Gleixner
2020-11-03 9:27 ` [patch V3 07/37] highmem: Make DEBUG_HIGHMEM functional Thomas Gleixner
2020-11-06 23:27 ` [tip: core/mm] " tip-bot2 for Thomas Gleixner
2020-11-03 9:27 ` [patch V3 08/37] x86/mm/highmem: Use generic kmap atomic implementation Thomas Gleixner
2020-11-06 23:27 ` [tip: core/mm] " tip-bot2 for Thomas Gleixner
2020-11-03 9:27 ` [patch V3 09/37] arc/mm/highmem: " Thomas Gleixner
2020-11-06 23:27 ` [tip: core/mm] " tip-bot2 for Thomas Gleixner
2020-11-03 9:27 ` [patch V3 10/37] ARM: highmem: Switch to generic kmap atomic Thomas Gleixner
2020-11-06 23:27 ` [tip: core/mm] " tip-bot2 for Thomas Gleixner
[not found] ` <CGME20201112081036eucas1p14e135a370d3bccab311727fd2e89f4df@eucas1p1.samsung.com>
2020-11-12 8:10 ` [patch V3 10/37] " Marek Szyprowski
2020-11-12 11:03 ` Thomas Gleixner
2020-11-12 11:07 ` Sebastian Andrzej Siewior
2020-11-03 9:27 ` [patch V3 11/37] csky/mm/highmem: " Thomas Gleixner
2020-11-06 23:27 ` [tip: core/mm] " tip-bot2 for Thomas Gleixner
2020-11-03 9:27 ` [patch V3 12/37] microblaze/mm/highmem: " Thomas Gleixner
2020-11-06 23:27 ` [tip: core/mm] " tip-bot2 for Thomas Gleixner
2020-11-03 9:27 ` [patch V3 13/37] mips/mm/highmem: " Thomas Gleixner
2020-11-06 23:27 ` [tip: core/mm] " tip-bot2 for Thomas Gleixner
2020-11-03 9:27 ` [patch V3 14/37] nds32/mm/highmem: " Thomas Gleixner
2020-11-06 23:27 ` [tip: core/mm] " tip-bot2 for Thomas Gleixner
2020-11-03 9:27 ` [patch V3 15/37] powerpc/mm/highmem: " Thomas Gleixner
2020-11-06 23:27 ` [tip: core/mm] " tip-bot2 for Thomas Gleixner
2020-11-03 9:27 ` [patch V3 16/37] sparc/mm/highmem: " Thomas Gleixner
2020-11-06 23:27 ` [tip: core/mm] " tip-bot2 for Thomas Gleixner
2020-11-03 9:27 ` [patch V3 17/37] xtensa/mm/highmem: " Thomas Gleixner
2020-11-06 23:27 ` [tip: core/mm] " tip-bot2 for Thomas Gleixner
2020-11-03 9:27 ` [patch V3 18/37] highmem: Get rid of kmap_types.h Thomas Gleixner
2020-11-06 23:27 ` [tip: core/mm] " tip-bot2 for Thomas Gleixner
2020-11-03 9:27 ` [patch V3 19/37] mm/highmem: Remove the old kmap_atomic cruft Thomas Gleixner
2020-11-06 23:27 ` [tip: core/mm] " tip-bot2 for Thomas Gleixner
2020-11-03 9:27 ` [patch V3 20/37] io-mapping: Cleanup atomic iomap Thomas Gleixner
2020-11-06 23:27 ` [tip: core/mm] " tip-bot2 for Thomas Gleixner
2020-11-03 9:27 ` [patch V3 21/37] Documentation/io-mapping: Remove outdated blurb Thomas Gleixner
2020-11-06 23:27 ` [tip: core/mm] " tip-bot2 for Thomas Gleixner
2020-11-03 9:27 ` [patch V3 22/37] highmem: High implementation details and document API Thomas Gleixner
2020-11-03 17:48 ` Linus Torvalds
2020-11-03 19:00 ` Thomas Gleixner [this message]
2020-11-06 23:27 ` [tip: core/mm] " tip-bot2 for Thomas Gleixner
2020-11-03 9:27 ` [patch V3 23/37] sched: Make migrate_disable/enable() independent of RT Thomas Gleixner
2020-11-03 9:27 ` [patch V3 24/37] sched: highmem: Store local kmaps in task struct Thomas Gleixner
2020-11-03 13:49 ` Thomas Gleixner
2020-11-03 13:51 ` [patch V4 " Thomas Gleixner
2020-11-03 9:27 ` [patch V3 25/37] mm/highmem: Provide kmap_local* Thomas Gleixner
2020-11-03 9:27 ` [patch V3 26/37] io-mapping: Provide iomap_local variant Thomas Gleixner
2020-11-03 9:27 ` [patch V3 27/37] x86/crashdump/32: Simplify copy_oldmem_page() Thomas Gleixner
2020-11-03 9:27 ` [patch V3 28/37] mips/crashdump: " Thomas Gleixner
2020-11-03 9:27 ` [patch V3 29/37] ARM: mm: Replace kmap_atomic_pfn() Thomas Gleixner
2020-11-03 9:27 ` [patch V3 30/37] highmem: Remove kmap_atomic_pfn() Thomas Gleixner
2020-11-03 9:27 ` [patch V3 31/37] drm/ttm: Replace kmap_atomic() usage Thomas Gleixner
2020-11-03 9:27 ` [patch V3 32/37] drm/vmgfx: Replace kmap_atomic() Thomas Gleixner
2020-11-03 9:27 ` [patch V3 33/37] highmem: Remove kmap_atomic_prot() Thomas Gleixner
2020-11-03 9:27 ` [patch V3 34/37] drm/qxl: Replace io_mapping_map_atomic_wc() Thomas Gleixner
2020-11-03 9:27 ` [patch V3 35/37] drm/nouveau/device: " Thomas Gleixner
2020-11-03 9:27 ` [patch V3 36/37] drm/i915: " Thomas Gleixner
2020-11-03 9:27 ` [patch V3 37/37] io-mapping: Remove io_mapping_map_atomic_wc() Thomas Gleixner
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