linux-kernel - Re: [PATCH 14/17] mm: Make hibernate handle unmapped pages

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Date:   Thu, 17 Jan 2019 10:39:50 +0100
From:   Pavel Machek <pavel@....cz>
To:     Rick Edgecombe <rick.p.edgecombe@...el.com>
Cc:     Andy Lutomirski <luto@...nel.org>, Ingo Molnar <mingo@...hat.com>,
        linux-kernel@...r.kernel.org, x86@...nel.org, hpa@...or.com,
        Thomas Gleixner <tglx@...utronix.de>,
        Borislav Petkov <bp@...en8.de>,
        Nadav Amit <nadav.amit@...il.com>,
        Dave Hansen <dave.hansen@...ux.intel.com>,
        Peter Zijlstra <peterz@...radead.org>, linux_dti@...oud.com,
        linux-integrity@...r.kernel.org,
        linux-security-module@...r.kernel.org, akpm@...ux-foundation.org,
        kernel-hardening@...ts.openwall.com, linux-mm@...ck.org,
        will.deacon@....com, ard.biesheuvel@...aro.org,
        kristen@...ux.intel.com, deneen.t.dock@...el.com,
        "Rafael J. Wysocki" <rjw@...ysocki.net>
Subject: Re: [PATCH 14/17] mm: Make hibernate handle unmapped pages

Hi!

> For architectures with CONFIG_ARCH_HAS_SET_ALIAS, pages can be unmapped
> briefly on the directmap, even when CONFIG_DEBUG_PAGEALLOC is not configured.
> So this changes kernel_map_pages and kernel_page_present to be defined when
> CONFIG_ARCH_HAS_SET_ALIAS is defined as well. It also changes places
> (page_alloc.c) where those functions are assumed to only be implemented when
> CONFIG_DEBUG_PAGEALLOC is defined.

Which architectures are that?

Should this be merged to the patch where HAS_SET_ALIAS is introduced? We
don't want broken hibernation in between....


> -#ifdef CONFIG_DEBUG_PAGEALLOC
>  extern bool _debug_pagealloc_enabled;
> -extern void __kernel_map_pages(struct page *page, int numpages, int enable);
>  
>  static inline bool debug_pagealloc_enabled(void)
>  {
> -	return _debug_pagealloc_enabled;
> +	return IS_ENABLED(CONFIG_DEBUG_PAGEALLOC) && _debug_pagealloc_enabled;
>  }

This will break build AFAICT. _debug_pagealloc_enabled variable does
not exist in !CONFIG_DEBUG_PAGEALLOC case.

									Pavel

-- 
(english) http://www.livejournal.com/~pavelmachek
(cesky, pictures) http://atrey.karlin.mff.cuni.cz/~pavel/picture/horses/blog.html

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