linux-kernel - Re: [PATCH, RFD]: Unbreak no-mmu mmap

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Message-ID: <4681FAC2.2030800@snapgear.com>
Date:	Wed, 27 Jun 2007 15:50:58 +1000
From:	Greg Ungerer <gerg@...pgear.com>
To:	bryan.wu@...log.com
CC:	Paul Mundt <lethal@...ux-sh.org>,
	Bernd Schmidt <bernds_cb1@...nline.de>,
	Robin Getz <rgetz@...ckfin.uclinux.org>,
	Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
	David Howells <dhowells@...hat.com>,
	Andrew Morton <akpm@...ux-foundation.org>
Subject: Re: [PATCH, RFD]: Unbreak no-mmu mmap


Bryan Wu wrote:
> On Wed, 2007-06-20 at 12:00 +0900, Paul Mundt wrote:
>> On Fri, Jun 08, 2007 at 03:53:49PM +0200, Bernd Schmidt wrote:
>>> diff --git a/mm/nommu.c b/mm/nommu.c
>>> index 2b16b00..7480a95 100644
>>> --- a/mm/nommu.c
>>> +++ b/mm/nommu.c
>> [snip]
>>> +	/*
>>> +	 * Must always set the VM_SPLIT_PAGES flag for single-page allocations,
>>> +	 * to avoid trying to get the order of the compound page later on.
>>> +	 */
>>> +	if (len == PAGE_SIZE)
>>> +		vma->vm_flags |= VM_SPLIT_PAGES;
>>> +	else if (flags & MAP_SPLIT_PAGES
>> And now you've just broken every non-blackfin nommu platform, as you've
>> only defined MAP_SPLIT_PAGES in asm-blackfin/mman.h.
>>
>>> +#ifdef CONFIG_NP2
>>> +	    || len < total_len
>>> +#endif
>> And what is this? It only shows up in the blackfin defconfig. This is not
>> the place to be putting board-specific hacks.
> 
> Yes, it is our own NP2 memory allocator option. I think Bernd will fix
> it.

Theres no reason you can't add the MAP_SPLIT_PAGES define in
all the necessary places too.


>> On Tue, Jun 19, 2007 at 07:26:19PM -0400, Robin Getz wrote:
>>> I'm assuming that since no one had any large objections, that this is OK, and 
>>> we should send to Andrew to live in -mm for awhile?
>>>
>> No real objections to the approach, but it would be nice if these sorts
>> of things were test compiled for at least one platform that isn't yours,
>> so the obviously broken stuff is fixed before it's posted and someone
>> else has to find out about it later.
> 
> Exactly, Could please do some simple test on your SH-NOMMU platform? And
> we are waiting for some feedback from other nommu arch maintainers.
> 
> David and Grep could you please help on this? Maybe Robin got some m68k
> nommu by hand which can be used for testing, I only have Blackfin, -:))

I have compiled the patch on m68knommu (after adding a MAP_SPLIT_PAGES
define). And it seems to work ok with simple testing.

I don't have a problem with the change, though please do add that
MAP_SPLIT_PAGES define in the appropriate mman.h includes. And like Paul
said there is no place for CONFIG_NP2 in it currently. Please take
that out.

Regards
Greg




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Greg Ungerer  --  Chief Software Dude       EMAIL:     gerg@...pgear.com
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