linux-kernel - Re: [PATCH] [v2] mm: make arch_has_descending_max_zone

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Date:   Tue, 18 Apr 2023 14:36:42 +0200 (CEST)
From:   Geert Uytterhoeven <geert@...ux-m68k.org>
To:     Arnd Bergmann <arnd@...nel.org>
cc:     Andrew Morton <akpm@...ux-foundation.org>,
        Arnd Bergmann <arnd@...db.de>, llvm@...ts.linux.dev,
        Vineet Gupta <vgupta@...nel.org>,
        Mike Rapoport <rppt@...nel.org>,
        Nathan Chancellor <nathan@...nel.org>,
        Nick Desaulniers <ndesaulniers@...gle.com>,
        Tom Rix <trix@...hat.com>,
        David Hildenbrand <david@...hat.com>,
        "Liam R. Howlett" <Liam.Howlett@...cle.com>,
        "Matthew Wilcox (Oracle)" <willy@...radead.org>,
        Suren Baghdasaryan <surenb@...gle.com>,
        Naoya Horiguchi <naoya.horiguchi@....com>,
        linux-snps-arc@...ts.infradead.org, linux-kernel@...r.kernel.org,
        linux-mm@...ck.org, Biju Das <biju.das.jz@...renesas.com>,
        linux-renesas-soc@...r.kernel.org
Subject: Re: [PATCH] [v2] mm: make arch_has_descending_max_zone_pfns()
 static

 	Hi Arnd,

On Sat, 15 Apr 2023, Arnd Bergmann wrote:
> From: Arnd Bergmann <arnd@...db.de>
>
> clang produces a build failure on x86 for some randconfig builds
> after a change that moves around code to mm/mm_init.c:
>
> Cannot find symbol for section 2: .text.
> mm/mm_init.o: failed
>
> I have not been able to figure out why this happens, but the __weak
> annotation on arch_has_descending_max_zone_pfns() is the trigger here.
>
> Removing the weak function in favor of an open-coded Kconfig option
> check avoids the problem and becomes clearer as well as better to
> optimize by the compiler.
>
> Fixes: 9420f89db2dd ("mm: move most of core MM initialization to mm/mm_init.c")
> Cc: llvm@...ts.linux.dev
> Signed-off-by: Arnd Bergmann <arnd@...db.de>
> ---
> v2: fix logic bug reported-by: kernel test robot <oliver.sang@...el.com>,
> see https://lore.kernel.org/oe-lkp/202304151422.5e4d380b-oliver.sang@intel.com

Thanks, reverting commit 413d478d3b366d09 ("mm: make
arch_has_descending_max_zone_pfns() static") in next-20230417 and
applying your v2 makes Salvator-XS regain its DMA memory zone.

Tested-by: Geert Uytterhoeven <geert+renesas@...der.be>

Gr{oetje,eeting}s,

 						Geert

--
Geert Uytterhoeven -- There's lots of Linux beyond ia32 -- geert@...ux-m68k.org

In personal conversations with technical people, I call myself a hacker. But
when I'm talking to journalists I just say "programmer" or something like that.
 							    -- Linus Torvalds