linux-kernel - Re: [PATCH v1 1/6] mm: Section numbers use the type "unsigned long"

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Message-ID: <e07449fa-251f-51c7-9ee2-202635c4aef7@redhat.com>
Date:   Fri, 14 Jun 2019 21:34:59 +0200
From:   David Hildenbrand <david@...hat.com>
To:     Andrew Morton <akpm@...ux-foundation.org>
Cc:     linux-kernel@...r.kernel.org,
        Dan Williams <dan.j.williams@...el.com>,
        linuxppc-dev@...ts.ozlabs.org, linux-acpi@...r.kernel.org,
        linux-mm@...ck.org,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        "Rafael J. Wysocki" <rafael@...nel.org>,
        Vlastimil Babka <vbabka@...e.cz>,
        Michal Hocko <mhocko@...e.com>,
        Mel Gorman <mgorman@...hsingularity.net>,
        Wei Yang <richard.weiyang@...il.com>,
        Johannes Weiner <hannes@...xchg.org>,
        Arun KS <arunks@...eaurora.org>,
        Pavel Tatashin <pasha.tatashin@...cle.com>,
        Oscar Salvador <osalvador@...e.de>,
        Stephen Rothwell <sfr@...b.auug.org.au>,
        Mike Rapoport <rppt@...ux.vnet.ibm.com>,
        Baoquan He <bhe@...hat.com>
Subject: Re: [PATCH v1 1/6] mm: Section numbers use the type "unsigned long"

On 14.06.19 21:00, Andrew Morton wrote:
> On Fri, 14 Jun 2019 12:01:09 +0200 David Hildenbrand <david@...hat.com> wrote:
> 
>> We are using a mixture of "int" and "unsigned long". Let's make this
>> consistent by using "unsigned long" everywhere. We'll do the same with
>> memory block ids next.
>>
>> ...
>>
>> -	int i, ret, section_count = 0;
>> +	unsigned long i;
>>
>> ...
>>
>> -	unsigned int i;
>> +	unsigned long i;
> 
> Maybe I did too much fortran back in the day, but I think the
> expectation is that a variable called "i" has type "int".
> 
> This?

t460s: ~/git/linux memory_block_devices2 $ git grep "unsigned long i;" |
wc -l
245
t460s: ~/git/linux memory_block_devices2 $ git grep "int i;" | wc -l
26827

Yes ;)

While it makes sense for the second and third occurrence, I think for
the first one it could be confusing (it's not actually a section number
but a counter for sections_per_block).

I see just now that we can avoid converting the first occurrence
completely. So maybe we should drop changing removable_show() from this
patch.

Cheers!

> 
> 
> 
> s/unsigned long i/unsigned long section_nr/
> 
> --- a/drivers/base/memory.c~mm-section-numbers-use-the-type-unsigned-long-fix
> +++ a/drivers/base/memory.c
> @@ -131,17 +131,17 @@ static ssize_t phys_index_show(struct de
>  static ssize_t removable_show(struct device *dev, struct device_attribute *attr,
>  			      char *buf)
>  {
> -	unsigned long i, pfn;
> +	unsigned long section_nr, pfn;
>  	int ret = 1;
>  	struct memory_block *mem = to_memory_block(dev);
>  
>  	if (mem->state != MEM_ONLINE)
>  		goto out;
>  
> -	for (i = 0; i < sections_per_block; i++) {
> -		if (!present_section_nr(mem->start_section_nr + i))
> +	for (section_nr = 0; section_nr < sections_per_block; section_nr++) {
> +		if (!present_section_nr(mem->start_section_nr + section_nr))
>  			continue;
> -		pfn = section_nr_to_pfn(mem->start_section_nr + i);
> +		pfn = section_nr_to_pfn(mem->start_section_nr + section_nr);
>  		ret &= is_mem_section_removable(pfn, PAGES_PER_SECTION);
>  	}
>  
> @@ -695,12 +695,12 @@ static int add_memory_block(unsigned lon
>  {
>  	int ret, section_count = 0;
>  	struct memory_block *mem;
> -	unsigned long i;
> +	unsigned long section_nr;
>  
> -	for (i = base_section_nr;
> -	     i < base_section_nr + sections_per_block;
> -	     i++)
> -		if (present_section_nr(i))
> +	for (section_nr = base_section_nr;
> +	     section_nr < base_section_nr + sections_per_block;
> +	     section_nr++)
> +		if (present_section_nr(section_nr))
>  			section_count++;
>  
>  	if (section_count == 0)
> @@ -823,7 +823,7 @@ static const struct attribute_group *mem
>   */
>  int __init memory_dev_init(void)
>  {
> -	unsigned long i;
> +	unsigned long section_nr;
>  	int ret;
>  	int err;
>  	unsigned long block_sz;
> @@ -840,9 +840,9 @@ int __init memory_dev_init(void)
>  	 * during boot and have been initialized
>  	 */
>  	mutex_lock(&mem_sysfs_mutex);
> -	for (i = 0; i <= __highest_present_section_nr;
> -		i += sections_per_block) {
> -		err = add_memory_block(i);
> +	for (section_nr = 0; section_nr <= __highest_present_section_nr;
> +		section_nr += sections_per_block) {
> +		err = add_memory_block(section_nr);
>  		if (!ret)
>  			ret = err;
>  	}
> _
> 


-- 

Thanks,

David / dhildenb