linux-kernel - Re: [PATCH] mm,memory_hotplug: Fix scan_movable

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Date:   Mon, 28 Jan 2019 14:53:09 -0800
From:   Andrew Morton <akpm@...ux-foundation.org>
To:     Oscar Salvador <osalvador@...e.de>
Cc:     David Hildenbrand <david@...hat.com>, linux-mm@...ck.org,
        linux-kernel@...r.kernel.org, mhocko@...e.com
Subject: Re: [PATCH] mm,memory_hotplug: Fix scan_movable_pages for gigantic
 hugepages

On Fri, 25 Jan 2019 08:58:33 +0100 Oscar Salvador <osalvador@...e.de> wrote:

> On Wed, Jan 23, 2019 at 11:33:56AM +0100, David Hildenbrand wrote:
> > If you use {} for the else case, please also do so for the if case.
> 
> Diff on top:
> 
> diff --git a/mm/memory_hotplug.c b/mm/memory_hotplug.c
> index 25aee4f04a72..d5810e522b72 100644
> --- a/mm/memory_hotplug.c
> +++ b/mm/memory_hotplug.c
> @@ -1338,9 +1338,9 @@ static unsigned long scan_movable_pages(unsigned long start, unsigned long end)
>  				struct page *head = compound_head(page);
>  
>  				if (hugepage_migration_supported(page_hstate(head)) &&
> -				    page_huge_active(head))
> +				    page_huge_active(head)) {
>  					return pfn;
> -				else {
> +				} else {
>  					unsigned long skip;
>  
>  					skip = (1 << compound_order(head)) - (page - head);
> 

The indenting is getting a bit deep also, so how about this?

static unsigned long scan_movable_pages(unsigned long start, unsigned long end)
{
	unsigned long pfn;

	for (pfn = start; pfn < end; pfn++) {
		struct page *page, *head;
	
		if (!pfn_valid(pfn))
			continue;
		page = pfn_to_page(pfn);
		if (PageLRU(page))
			return pfn;
		if (__PageMovable(page))
			return pfn;

		if (!PageHuge(page))
			continue;
		head = compound_head(page);
		if (hugepage_migration_supported(page_hstate(head)) &&
		    page_huge_active(head)) {
			return pfn;
		} else {
			unsigned long skip;

			skip = (1 << compound_order(head)) - (page - head);
			pfn += skip - 1;
		}
	}
	return 0;
}


From: Andrew Morton <akpm@...ux-foundation.org>
Subject: mmmemory_hotplug-fix-scan_movable_pages-for-gigantic-hugepages-fix

fix brace layout, per David.  Also reduce indentation

Cc: Anthony Yznaga <anthony.yznaga@...cle.com>
Cc: David Hildenbrand <david@...hat.com>
Cc: Michal Hocko <mhocko@...e.com>
Cc: Oscar Salvador <osalvador@...e.de>
Signed-off-by: Andrew Morton <akpm@...ux-foundation.org>
---

 mm/memory_hotplug.c |   38 ++++++++++++++++++++------------------
 1 file changed, 20 insertions(+), 18 deletions(-)

--- a/mm/memory_hotplug.c~mmmemory_hotplug-fix-scan_movable_pages-for-gigantic-hugepages-fix
+++ a/mm/memory_hotplug.c
@@ -1305,27 +1305,29 @@ int test_pages_in_a_zone(unsigned long s
 static unsigned long scan_movable_pages(unsigned long start, unsigned long end)
 {
 	unsigned long pfn;
-	struct page *page;
+
 	for (pfn = start; pfn < end; pfn++) {
-		if (pfn_valid(pfn)) {
-			page = pfn_to_page(pfn);
-			if (PageLRU(page))
-				return pfn;
-			if (__PageMovable(page))
-				return pfn;
-			if (PageHuge(page)) {
-				struct page *head = compound_head(page);
+		struct page *page, *head;
+	
+		if (!pfn_valid(pfn))
+			continue;
+		page = pfn_to_page(pfn);
+		if (PageLRU(page))
+			return pfn;
+		if (__PageMovable(page))
+			return pfn;
 
-				if (hugepage_migration_supported(page_hstate(head)) &&
-				    page_huge_active(head))
-					return pfn;
-				else {
-					unsigned long skip;
+		if (!PageHuge(page))
+			continue;
+		head = compound_head(page);
+		if (hugepage_migration_supported(page_hstate(head)) &&
+		    page_huge_active(head)) {
+			return pfn;
+		} else {
+			unsigned long skip;
 
-					skip = (1 << compound_order(head)) - (page - head);
-					pfn += skip - 1;
-				}
-			}
+			skip = (1 << compound_order(head)) - (page - head);
+			pfn += skip - 1;
 		}
 	}
 	return 0;
_