linux-kernel - Re: [PATCH RESEND 2/3] x86, mm: Update min_pfn_mapped in add_pfn_range

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Date:	Mon, 2 Sep 2013 19:48:12 -0700
From:	Yinghai Lu <yinghai@...nel.org>
To:	Tang Chen <tangchen@...fujitsu.com>
Cc:	Ingo Molnar <mingo@...hat.com>, "H. Peter Anvin" <hpa@...or.com>,
	Pekka Enberg <penberg@...nel.org>,
	Jacob Shin <jacob.shin@....com>,
	Thomas Gleixner <tglx@...utronix.de>,
	Len Brown <lenb@...nel.org>, "Rafael J. Wysocki" <rjw@...k.pl>,
	Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
	ACPI Devel Maling List <linux-acpi@...r.kernel.org>,
	"the arch/x86 maintainers" <x86@...nel.org>
Subject: Re: [PATCH RESEND 2/3] x86, mm: Update min_pfn_mapped in add_pfn_range_mapped().

On Mon, Sep 2, 2013 at 6:06 PM, Tang Chen <tangchen@...fujitsu.com> wrote:
> Hi Yinghai,
>
> On 09/03/2013 02:41 AM, Yinghai Lu wrote:

> How about change the "for (from low to high)" in init_range_memory_mapping()
> to
> "for_rev(from high to low)" ?
> Then we can update min_pfn_mapped in add_pfn_range_mapped().
>
> And also, the outer loop is from high to low, we can change the inner loop
> to be from high
> to low too.

No. there is other reason for doing local from low to high.

kernel_physical_mapping_init() could clear some mapping near the end
of PUG/PMD entries but not the head.

>
> I think updating min_pfn_mapped in init_mem_mapping() is less readable. And
> min_pfn_mapped
> and max_pfn_mapped should be updated together.

min_pfn_mapped is early local variable to control allocation in alloc_low_pages.
put it in init_mem_mapping is more readable.

Yinghai
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