linux-kernel - Re: [PATCH 18/39] lmb: Add lmb_reserve_area_overlap

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Date:	Mon, 12 Apr 2010 21:44:56 -0700
From:	Yinghai <yinghai.lu@...cle.com>
To:	Benjamin Herrenschmidt <benh@...nel.crashing.org>
CC:	Ingo Molnar <mingo@...e.hu>, Thomas Gleixner <tglx@...utronix.de>,
	"H. Peter Anvin" <hpa@...or.com>,
	Andrew Morton <akpm@...ux-foundation.org>,
	David Miller <davem@...emloft.net>,
	Linus Torvalds <torvalds@...ux-foundation.org>,
	Johannes Weiner <hannes@...xchg.org>,
	linux-kernel@...r.kernel.org, linux-arch@...r.kernel.org
Subject: Re: [PATCH 18/39] lmb: Add lmb_reserve_area_overlap_ok()

On 04/12/2010 09:21 PM, Benjamin Herrenschmidt wrote:
> On Thu, 2010-04-08 at 23:03 -0700, Yinghai Lu wrote:
>> Some areas from firmware could be reserved several times from different callers.
>>
>> If these area are overlapped, We may have overlapped entries in lmb.reserved.
>>
>> Try to free the area at first, before rerserve them again.
>>
>> Signed-off-by: Yinghai Lu <yinghai@...nel.org>
>> ---
> 
>> +
>> +/*
>> + * Could be used to avoid having overlap entries in lmb.reserved.region.
>> + *  Don't need to use it with area that is from lmb_find_area()
>> + *  Only use it for the area that fw hidden area.
>> + */
>> +void __init lmb_reserve_area_overlap_ok(u64 start, u64 end, char *name)
>> +{
>> +	if (start == end)
>> +		return;
>> +
>> +	if (WARN_ONCE(start > end, "lmb_reserve_area_overlap_ok: wrong range [%#llx, %#llx]\n", start, end))
>> +		return;
>> +
>> +	/* Free that region at first */
>> +	lmb_free(start, end - start);
>> +	__lmb_reserve_area(start, end, name);
>>  }
> 
> That is going to only work with one overlap. IE. lmb_free() will not do
> very well unless it's a one and only match.
> 
> You should modify it to work in a loop.
that is only for some special cases about area that is reserved for fw region.

and even there is overlapped area, it the code still can go through when lmb_to_bootmem or create range list for slab.
because they are using range array subtract.

> 
> Besides, lmb_reserve_area_overlap_ok() sucks as a name :-)

any suggestion for better name?

YH
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