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

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Date:	Mon, 27 Sep 2010 16:55:07 -0700
From:	Dave Hansen <dave@...ux.vnet.ibm.com>
To:	Nathan Fontenot <nfont@...tin.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 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.

-- Dave

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