linux-kernel - [PATCH v2 04/10] mm/page_alloc: simplify __offline_isolated

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Date:   Wed, 19 Aug 2020 19:59:51 +0200
From:   David Hildenbrand <david@...hat.com>
To:     linux-kernel@...r.kernel.org
Cc:     linux-mm@...ck.org, David Hildenbrand <david@...hat.com>,
        Michal Hocko <mhocko@...e.com>,
        Andrew Morton <akpm@...ux-foundation.org>,
        Wei Yang <richard.weiyang@...ux.alibaba.com>,
        Baoquan He <bhe@...hat.com>,
        Pankaj Gupta <pankaj.gupta.linux@...il.com>,
        Oscar Salvador <osalvador@...e.de>
Subject: [PATCH v2 04/10] mm/page_alloc: simplify __offline_isolated_pages()

offline_pages() is the only user. __offline_isolated_pages() never gets
called with ranges that contain memory holes and we no longer care about
the return value. Drop the return value handling and all pfn_valid()
checks.

Update the documentation.

Acked-by: Michal Hocko <mhocko@...e.com>
Cc: Andrew Morton <akpm@...ux-foundation.org>
Cc: Michal Hocko <mhocko@...e.com>
Cc: Wei Yang <richard.weiyang@...ux.alibaba.com>
Cc: Baoquan He <bhe@...hat.com>
Cc: Pankaj Gupta <pankaj.gupta.linux@...il.com>
Cc: Oscar Salvador <osalvador@...e.de>
Signed-off-by: David Hildenbrand <david@...hat.com>
---
 include/linux/memory_hotplug.h |  4 ++--
 mm/page_alloc.c                | 27 ++++-----------------------
 2 files changed, 6 insertions(+), 25 deletions(-)

diff --git a/include/linux/memory_hotplug.h b/include/linux/memory_hotplug.h
index 375515803cd83..0b461691d1a49 100644
--- a/include/linux/memory_hotplug.h
+++ b/include/linux/memory_hotplug.h
@@ -103,8 +103,8 @@ extern int online_pages(unsigned long pfn, unsigned long nr_pages,
 			int online_type, int nid);
 extern struct zone *test_pages_in_a_zone(unsigned long start_pfn,
 					 unsigned long end_pfn);
-extern unsigned long __offline_isolated_pages(unsigned long start_pfn,
-						unsigned long end_pfn);
+extern void __offline_isolated_pages(unsigned long start_pfn,
+				     unsigned long end_pfn);
 
 typedef void (*online_page_callback_t)(struct page *page, unsigned int order);
 
diff --git a/mm/page_alloc.c b/mm/page_alloc.c
index cf0b25161feae..03f585f95dc60 100644
--- a/mm/page_alloc.c
+++ b/mm/page_alloc.c
@@ -8692,35 +8692,21 @@ void zone_pcp_reset(struct zone *zone)
 
 #ifdef CONFIG_MEMORY_HOTREMOVE
 /*
- * All pages in the range must be in a single zone and isolated
- * before calling this.
+ * All pages in the range must be in a single zone, must not contain holes,
+ * must span full sections, and must be isolated before calling this function.
  */
-unsigned long
-__offline_isolated_pages(unsigned long start_pfn, unsigned long end_pfn)
+void __offline_isolated_pages(unsigned long start_pfn, unsigned long end_pfn)
 {
+	unsigned long pfn = start_pfn;
 	struct page *page;
 	struct zone *zone;
 	unsigned int order;
-	unsigned long pfn;
 	unsigned long flags;
-	unsigned long offlined_pages = 0;
-
-	/* find the first valid pfn */
-	for (pfn = start_pfn; pfn < end_pfn; pfn++)
-		if (pfn_valid(pfn))
-			break;
-	if (pfn == end_pfn)
-		return offlined_pages;
 
 	offline_mem_sections(pfn, end_pfn);
 	zone = page_zone(pfn_to_page(pfn));
 	spin_lock_irqsave(&zone->lock, flags);
-	pfn = start_pfn;
 	while (pfn < end_pfn) {
-		if (!pfn_valid(pfn)) {
-			pfn++;
-			continue;
-		}
 		page = pfn_to_page(pfn);
 		/*
 		 * The HWPoisoned page may be not in buddy system, and
@@ -8728,7 +8714,6 @@ __offline_isolated_pages(unsigned long start_pfn, unsigned long end_pfn)
 		 */
 		if (unlikely(!PageBuddy(page) && PageHWPoison(page))) {
 			pfn++;
-			offlined_pages++;
 			continue;
 		}
 		/*
@@ -8739,20 +8724,16 @@ __offline_isolated_pages(unsigned long start_pfn, unsigned long end_pfn)
 			BUG_ON(page_count(page));
 			BUG_ON(PageBuddy(page));
 			pfn++;
-			offlined_pages++;
 			continue;
 		}
 
 		BUG_ON(page_count(page));
 		BUG_ON(!PageBuddy(page));
 		order = page_order(page);
-		offlined_pages += 1 << order;
 		del_page_from_free_list(page, zone, order);
 		pfn += (1 << order);
 	}
 	spin_unlock_irqrestore(&zone->lock, flags);
-
-	return offlined_pages;
 }
 #endif
 
-- 
2.26.2