linux-kernel - Re: [PATCH] memory-failure: fix section mismatch

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Message-ID: <20180316230448.GA37438@google.com>
Date:   Fri, 16 Mar 2018 16:04:49 -0700
From:   Matthias Kaehlcke <mka@...omium.org>
To:     Nick Desaulniers <nick.desaulniers@...il.com>
Cc:     Andrew Morton <akpm@...ux-foundation.org>,
        Dan Williams <dan.j.williams@...el.com>,
        Michal Hocko <mhocko@...e.com>,
        "Kirill A. Shutemov" <kirill.shutemov@...ux.intel.com>,
        Jan Kara <jack@...e.cz>,
        Jérôme Glisse <jglisse@...hat.com>,
        Hugh Dickins <hughd@...gle.com>,
        Matthew Wilcox <willy@...radead.org>, linux-mm@...ck.org,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH] memory-failure: fix section mismatch

El Sat, Mar 03, 2018 at 11:16:11PM -0800 Nick Desaulniers ha dit:

> Clang complains when a variable is declared extern twice, but with two
> different sections. num_poisoned_pages is marked extern and __read_mostly
> in include/linux/swapops.h, but only extern in include/linux/mm.h. Some
> c source files must include both, and thus see the conflicting
> declarations.
> 
> Signed-off-by: Nick Desaulniers <nick.desaulniers@...il.com>
> ---
>  include/linux/mm.h | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
> 
> diff --git a/include/linux/mm.h b/include/linux/mm.h
> index ad06d42adb1a..bd4bd59f02c1 100644
> --- a/include/linux/mm.h
> +++ b/include/linux/mm.h
> @@ -2582,7 +2582,7 @@ extern int get_hwpoison_page(struct page *page);
>  extern int sysctl_memory_failure_early_kill;
>  extern int sysctl_memory_failure_recovery;
>  extern void shake_page(struct page *p, int access);
> -extern atomic_long_t num_poisoned_pages;
> +extern atomic_long_t num_poisoned_pages __read_mostly;
>  extern int soft_offline_page(struct page *page, int flags);

An equivalent patch was posted by Guenter Roeck and has been picked up
by Andrew: https://patchwork.kernel.org/patch/10243919/