linux-kernel - Re: [PATCH V2 1/2] mm/memblock.c: trivial code refine in memblock_is_region

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Date:   Wed, 21 Dec 2016 13:15:31 +0000
From:   Wei Yang <richard.weiyang@...il.com>
To:     Michal Hocko <mhocko@...nel.org>
Cc:     Wei Yang <richard.weiyang@...il.com>, trivial@...nel.org,
        akpm@...ux-foundation.org, linux-mm@...ck.org,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH V2 1/2] mm/memblock.c: trivial code refine in
 memblock_is_region_memory()

On Wed, Dec 21, 2016 at 01:48:17PM +0100, Michal Hocko wrote:
>On Wed 21-12-16 12:43:20, Wei Yang wrote:
>> On Wed, Dec 21, 2016 at 08:48:09AM +0100, Michal Hocko wrote:
>> >On Tue 20-12-16 16:35:40, Wei Yang wrote:
>> >> On Mon, Dec 19, 2016 at 04:15:14PM +0100, Michal Hocko wrote:
>> >> >On Sun 18-12-16 14:47:49, Wei Yang wrote:
>> >> >> The base address is already guaranteed to be in the region by
>> >> >> memblock_search().
>> >> >
>> >> 
>> >> Hi, Michal
>> >> 
>> >> Nice to receive your comment.
>> >> 
>> >> >First of all the way how the check is removed is the worst possible...
>> >> >Apart from that it is really not clear to me why checking the base
>> >> >is not needed. You are mentioning memblock_search but what about other
>> >> >callers? adjust_range_page_size_mask e.g...
>> >> >
>> >> 
>> >> Hmm... the memblock_search() is called by memblock_is_region_memory(). Maybe I
>> >> paste the whole function here would clarify the change.
>> >> 
>> >> int __init_memblock memblock_is_region_memory(phys_addr_t base, phys_addr_t size)
>> >> {
>> >> 	int idx = memblock_search(&memblock.memory, base);
>> >> 	phys_addr_t end = base + memblock_cap_size(base, &size);
>> >> 
>> >> 	if (idx == -1)
>> >> 		return 0;
>> >> 	return memblock.memory.regions[idx].base <= base &&
>> >> 		(memblock.memory.regions[idx].base +
>> >> 		 memblock.memory.regions[idx].size) >= end;
>> >> }
>> >
>> >Ohh, my bad. I thought that memblock_search is calling
>> >memblock_is_region_memory. I didn't notice this is other way around.
>> >Then I agree that the check for the base is not needed and can be
>> >removed.
>> 
>> Thanks~ 
>> 
>> I would feel honored if you would like to add Acked-by :-)
>
>My Nack to the original patch still holds. If you want to remove the
>check then remove it rather than comment it out.

Got it, will send a new version.

>-- 
>Michal Hocko
>SUSE Labs

-- 
Wei Yang
Help you, Help me