linux-kernel - Re: [PATCH 15/16] mm: use vm_unmapped

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Message-ID: <CANN689Gt2mG8xfkVkFtOHDFxkoZZAL-p-8yMSw=qvy5zaGs1ag@mail.gmail.com>
Date:	Mon, 5 Nov 2012 19:13:19 -0800
From:	Michel Lespinasse <walken@...gle.com>
To:	David Miller <davem@...emloft.net>
Cc:	akpm@...ux-foundation.org, riel@...hat.com, hughd@...gle.com,
	linux-kernel@...r.kernel.org, linux@....linux.org.uk,
	ralf@...ux-mips.org, lethal@...ux-sh.org, cmetcalf@...era.com,
	x86@...nel.org, wli@...omorphy.com, linux-mm@...ck.org,
	linux-arm-kernel@...ts.infradead.org, linux-mips@...ux-mips.org,
	linux-sh@...r.kernel.org, sparclinux@...r.kernel.org
Subject: Re: [PATCH 15/16] mm: use vm_unmapped_area() on sparc32 architecture

On Mon, Nov 5, 2012 at 5:25 PM, David Miller <davem@...emloft.net> wrote:
> From: Michel Lespinasse <walken@...gle.com>
> Date: Mon,  5 Nov 2012 14:47:12 -0800
>
>> Update the sparc32 arch_get_unmapped_area function to make use of
>> vm_unmapped_area() instead of implementing a brute force search.
>>
>> Signed-off-by: Michel Lespinasse <walken@...gle.com>
>
> Hmmm...
>
>> -     if (flags & MAP_SHARED)
>> -             addr = COLOUR_ALIGN(addr);
>> -     else
>> -             addr = PAGE_ALIGN(addr);
>
> What part of vm_unmapped_area() is going to duplicate this special
> aligning logic we need on sparc?

The idea there is that you can specify the desired alignment mask and
offset using info.align_mask and info.align_offset.

Now, I just noticed that the old code actually always uses an
alignment offset of 0 instead of basing it on pgoff. I'm not sure why
that is, but it looks like this may be an issue ?

-- 
Michel "Walken" Lespinasse
A program is never fully debugged until the last user dies.
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