linux-kernel - Re: [PATCH 2/3] x86/mm: Simplify for-loop in free_init

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Message-ID: <CAOJsxLEU=Ls1XtS0nndmJrvAObHuaasHBu8=7iFbjYVBX8g=Ng@mail.gmail.com>
Date:	Sat, 14 Jul 2012 23:48:16 +0300
From:	Pekka Enberg <penberg@...nel.org>
To:	Joe Perches <joe@...ches.com>
Cc:	Yinghai Lu <yinghai@...nel.org>, mingo@...nel.org,
	linux-kernel@...r.kernel.org, x86@...nel.org,
	Tejun Heo <tj@...nel.org>
Subject: Re: [PATCH 2/3] x86/mm: Simplify for-loop in free_init_pages()

On Sat, Jul 14, 2012 at 11:43 PM, Joe Perches <joe@...ches.com> wrote:
> On Sat, 2012-07-14 at 13:36 -0700, Yinghai Lu wrote:
>> On Sat, Jul 14, 2012 at 6:41 AM, Pekka Enberg <penberg@...nel.org> wrote:
>> > As a cleanup, move initial "addr" assignment to the for-loop construct
>> > in free_init_pages().
>
> Not really a good idea.

Of course it's a good idea. The current code flow makes no sense.

>> > diff --git a/arch/x86/mm/init.c b/arch/x86/mm/init.c
> []
>> > @@ -349,8 +349,6 @@ void free_init_pages(char *what, unsigned long begin, unsigned long end)
>> >         if (begin >= end)
>> >                 return;
>> >
>> > -       addr = begin;
>> > -
>> >         /*
>> >          * If debugging page accesses then do not free this memory but
>> >          * mark them not present - any buggy init-section access will
>> > @@ -371,7 +369,7 @@ void free_init_pages(char *what, unsigned long begin, unsigned long end)
>> >
>> >         printk(KERN_INFO "Freeing %s: %luk freed\n", what, (end - begin) >> 10);
>> >
>> > -       for (; addr < end; addr += PAGE_SIZE) {
>> > +       for (addr = begin; addr < end; addr += PAGE_SIZE) {
>> >                 ClearPageReserved(virt_to_page(addr));
>> >                 init_page_count(virt_to_page(addr));
>> >                 memset((void *)addr, POISON_FREE_INITMEM, PAGE_SIZE);
>> > --
>
> Now there's an unused variable warning when CONFIG_DEBUG_PAGEALLOC

Sure, that needs fixing. It'd probably be simplest to introduce a
__free_init_pages() helper.
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