linux-kernel - Re: [PATCH 4/8] v2 Allow memory block to span multiple memory sections

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Date:	Tue, 28 Sep 2010 13:06:26 -0500
From:	Nathan Fontenot <nfont@...tin.ibm.com>
To:	Dave Hansen <dave@...ux.vnet.ibm.com>
CC:	linux-kernel@...r.kernel.org, linux-mm@...ck.org,
	linuxppc-dev@...abs.org, Greg KH <greg@...ah.com>,
	KAMEZAWA Hiroyuki <kamezawa.hiroyu@...fujitsu.com>
Subject: Re: [PATCH 4/8] v2 Allow memory block to span multiple memory sections

On 09/27/2010 06:55 PM, Dave Hansen wrote:
> On Mon, 2010-09-27 at 14:25 -0500, Nathan Fontenot wrote:
>> +static inline int base_memory_block_id(int section_nr)
>> +{
>> +       return section_nr / sections_per_block;
>> +}
> ...
>> -       mutex_lock(&mem_sysfs_mutex);
>> -
>> -       mem->phys_index = __section_nr(section);
>> +       scn_nr = __section_nr(section);
>> +       mem->phys_index = base_memory_block_id(scn_nr) * sections_per_block; 
> 
> I'm really regretting giving this variable such a horrid name.  I suck.
> 
> I think this is correct now:
> 
> 	mem->phys_index = base_memory_block_id(scn_nr) * sections_per_block;
> 	mem->phys_index = section_nr / sections_per_block * sections_per_block;
> 	mem->phys_index = section_nr
> 
> Since it gets exported to userspace this way:
> 
>> +static ssize_t show_mem_start_phys_index(struct sys_device *dev,
>>                         struct sysdev_attribute *attr, char *buf)
>>  {
>>         struct memory_block *mem =
>>                 container_of(dev, struct memory_block, sysdev);
>> -       return sprintf(buf, "%08lx\n", mem->phys_index / sections_per_block);
>> +       unsigned long phys_index;
>> +
>> +       phys_index = mem->start_phys_index / sections_per_block;
>> +       return sprintf(buf, "%08lx\n", phys_index);
>> +}
> 
> The only other thing I'd say is that we need to put phys_index out of
> its misery and call it what it is now: a section number.  I think it's
> OK to call them "start/end_section_nr", at least inside the kernel.  I
> intentionally used "phys_index" terminology in sysfs so that we _could_
> eventually do this stuff and break the relationship between sections and
> the sysfs dirs, but I think keeping the terminology around inside the
> kernel is confusing now.

Yes, it took me a couple o looks to get the phys_index <-> section number
correlation.  I think changing the kernel names to start/end_section_number
is a good idea.

-Nathan

> 
> -- Dave
> 

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