[PATCH] mm/page_owner.c Clean up init_pages_in_zone()

[PATCH] mm/page_owner.c Clean up init_pages_in_zone()

[Oscar Salvador]

This patch removes two redundant assignments in init_pages_in_zone function

Signed-off-by: Oscar Salvador <osalvador@techadventures.net>
---
 mm/page_owner.c | 9 ++-------
 1 file changed, 2 insertions(+), 7 deletions(-)

diff --git a/mm/page_owner.c b/mm/page_owner.c
index 8602fb41b293..7d20c6cc98e0 100644
--- a/mm/page_owner.c
+++ b/mm/page_owner.c
@@ -528,14 +528,11 @@ read_page_owner(struct file *file, char __user *buf, size_t count, loff_t *ppos)
 
 static void init_pages_in_zone(pg_data_t *pgdat, struct zone *zone)
 {
-	struct page *page;
-	struct page_ext *page_ext;
 	unsigned long pfn = zone->zone_start_pfn, block_end_pfn;
 	unsigned long end_pfn = pfn + zone->spanned_pages;
 	unsigned long count = 0;
 
 	/* Scan block by block. First and last block may be incomplete */
-	pfn = zone->zone_start_pfn;
 
 	/*
 	 * Walk the zone in pageblock_nr_pages steps. If a page block spans
@@ -551,13 +548,11 @@ static void init_pages_in_zone(pg_data_t *pgdat, struct zone *zone)
 		block_end_pfn = ALIGN(pfn + 1, pageblock_nr_pages);
 		block_end_pfn = min(block_end_pfn, end_pfn);
 
-		page = pfn_to_page(pfn);
-
 		for (; pfn < block_end_pfn; pfn++) {
 			if (!pfn_valid_within(pfn))
 				continue;
 
-			page = pfn_to_page(pfn);
+			struct page *page = pfn_to_page(pfn);
 
 			if (page_zone(page) != zone)
 				continue;
@@ -580,7 +575,7 @@ static void init_pages_in_zone(pg_data_t *pgdat, struct zone *zone)
 			if (PageReserved(page))
 				continue;
 
-			page_ext = lookup_page_ext(page);
+			struct page_ext *page_ext = lookup_page_ext(page);
 			if (unlikely(!page_ext))
 				continue;
 
-- 
2.13.5

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Re: [PATCH] mm/page_owner.c Clean up init_pages_in_zone()

[Michal Hocko]

On Tue 09-01-18 14:33:03, Oscar Salvador wrote:
[...]
> @@ -551,13 +548,11 @@ static void init_pages_in_zone(pg_data_t *pgdat, struct zone *zone)
>  		block_end_pfn = ALIGN(pfn + 1, pageblock_nr_pages);
>  		block_end_pfn = min(block_end_pfn, end_pfn);
>  
> -		page = pfn_to_page(pfn);
> -
>  		for (; pfn < block_end_pfn; pfn++) {
>  			if (!pfn_valid_within(pfn))
>  				continue;
>  
> -			page = pfn_to_page(pfn);
> +			struct page *page = pfn_to_page(pfn);
>  
>  			if (page_zone(page) != zone)
>  				continue;
> @@ -580,7 +575,7 @@ static void init_pages_in_zone(pg_data_t *pgdat, struct zone *zone)
>  			if (PageReserved(page))
>  				continue;
>  
> -			page_ext = lookup_page_ext(page);
> +			struct page_ext *page_ext = lookup_page_ext(page);
>  			if (unlikely(!page_ext))
>  				continue;

we do not interleave declarations with the code in the kernel. You can
move those from the function scope to the loop scope and remove the
pointless pfn and page initialization outside of the loop.
-- 
Michal Hocko
SUSE Labs

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Re: [PATCH] mm/page_owner.c Clean up init_pages_in_zone()

[Oscar Salvador]

On Tue, Jan 09, 2018 at 06:18:20PM +0100, Michal Hocko wrote:
> On Tue 09-01-18 14:33:03, Oscar Salvador wrote:
> [...]
> > @@ -551,13 +548,11 @@ static void init_pages_in_zone(pg_data_t *pgdat, struct zone *zone)
> >  		block_end_pfn = ALIGN(pfn + 1, pageblock_nr_pages);
> >  		block_end_pfn = min(block_end_pfn, end_pfn);
> >  
> > -		page = pfn_to_page(pfn);
> > -
> >  		for (; pfn < block_end_pfn; pfn++) {
> >  			if (!pfn_valid_within(pfn))
> >  				continue;
> >  
> > -			page = pfn_to_page(pfn);
> > +			struct page *page = pfn_to_page(pfn);
> >  
> >  			if (page_zone(page) != zone)
> >  				continue;
> > @@ -580,7 +575,7 @@ static void init_pages_in_zone(pg_data_t *pgdat, struct zone *zone)
> >  			if (PageReserved(page))
> >  				continue;
> >  
> > -			page_ext = lookup_page_ext(page);
> > +			struct page_ext *page_ext = lookup_page_ext(page);
> >  			if (unlikely(!page_ext))
> >  				continue;
> 
> we do not interleave declarations with the code in the kernel. You can
> move those from the function scope to the loop scope and remove the
> pointless pfn and page initialization outside of the loop.

I will send a v2 fixing this.

Thanks!

Oscar Salvador

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