linux-kernel - [PATCH v2 3/5] mm/memory_hotplug: Simplify online_pages

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Date:   Wed, 14 Aug 2019 17:41:07 +0200
From:   David Hildenbrand <david@...hat.com>
To:     linux-kernel@...r.kernel.org
Cc:     linux-mm@...ck.org, David Hildenbrand <david@...hat.com>,
        Andrew Morton <akpm@...ux-foundation.org>,
        Oscar Salvador <osalvador@...e.de>,
        Michal Hocko <mhocko@...e.com>,
        Pavel Tatashin <pasha.tatashin@...een.com>,
        Dan Williams <dan.j.williams@...el.com>
Subject: [PATCH v2 3/5] mm/memory_hotplug: Simplify online_pages_range()

online_pages always corresponds to nr_pages. Simplify the code, getting
rid of online_pages_blocks(). Add some comments.

Cc: Andrew Morton <akpm@...ux-foundation.org>
Cc: Oscar Salvador <osalvador@...e.de>
Cc: Michal Hocko <mhocko@...e.com>
Cc: Pavel Tatashin <pasha.tatashin@...een.com>
Cc: Dan Williams <dan.j.williams@...el.com>
Signed-off-by: David Hildenbrand <david@...hat.com>
---
 mm/memory_hotplug.c | 36 ++++++++++++++++--------------------
 1 file changed, 16 insertions(+), 20 deletions(-)

diff --git a/mm/memory_hotplug.c b/mm/memory_hotplug.c
index 10ad970f3f14..63b1775f7cf8 100644
--- a/mm/memory_hotplug.c
+++ b/mm/memory_hotplug.c
@@ -632,31 +632,27 @@ static void generic_online_page(struct page *page, unsigned int order)
 #endif
 }
 
-static int online_pages_blocks(unsigned long start, unsigned long nr_pages)
-{
-	unsigned long end = start + nr_pages;
-	int order, onlined_pages = 0;
-
-	while (start < end) {
-		order = min(MAX_ORDER - 1,
-			get_order(PFN_PHYS(end) - PFN_PHYS(start)));
-		(*online_page_callback)(pfn_to_page(start), order);
-
-		onlined_pages += (1UL << order);
-		start += (1UL << order);
-	}
-	return onlined_pages;
-}
-
 static int online_pages_range(unsigned long start_pfn, unsigned long nr_pages,
 			void *arg)
 {
-	unsigned long onlined_pages = *(unsigned long *)arg;
+	const unsigned long end_pfn = start_pfn + nr_pages;
+	unsigned long pfn;
+	int order;
+
+	/*
+	 * Online the pages. The callback might decide to keep some pages
+	 * PG_reserved (to add them to the buddy later), but we still account
+	 * them as being online/belonging to this zone ("present").
+	 */
+	for (pfn = start_pfn; pfn < end_pfn; pfn += 1ul << order) {
+		order = min(MAX_ORDER - 1, get_order(PFN_PHYS(end_pfn - pfn)));
+		(*online_page_callback)(pfn_to_page(pfn), order);
+	}
 
-	onlined_pages += online_pages_blocks(start_pfn, nr_pages);
-	online_mem_sections(start_pfn, start_pfn + nr_pages);
+	/* mark all involved sections as online */
+	online_mem_sections(start_pfn, end_pfn);
 
-	*(unsigned long *)arg = onlined_pages;
+	*(unsigned long *)arg += nr_pages;
 	return 0;
 }
 
-- 
2.21.0