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Date:   Tue, 06 Nov 2012 02:30:07 -0500
From:   Rik van Riel <riel@redhat.com>
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To:     David Miller <davem@davemloft.net>
CC:     walken@google.com, akpm@linux-foundation.org, hughd@google.com,
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Subject: Re: [PATCH 15/16] mm: use vm_unmapped_area() on sparc32 architecture
References: <1352155633-8648-1-git-send-email-walken@google.com> <1352155633-8648-16-git-send-email-walken@google.com> <20121105.202501.1246122770431623794.davem@davemloft.net>
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On 11/05/2012 08:25 PM, David Miller wrote:
> From: Michel Lespinasse <walken@google.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@google.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?
>

That would be this part:

+found:
+	/* We found a suitable gap. Clip it with the original low_limit. */
+	if (gap_start < info->low_limit)
+		gap_start = info->low_limit;
+
+	/* Adjust gap address to the desired alignment */
+	gap_start += (info->align_offset - gap_start) & info->align_mask;
+
+	VM_BUG_ON(gap_start + info->length > info->high_limit);
+	VM_BUG_ON(gap_start + info->length > gap_end);
+	return gap_start;
+}