linux-kernel - [PATCH v2 4/5] mm/memory_hotplug: Make sure the pfn is aligned to the order when onlining

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Date:   Wed, 14 Aug 2019 17:41:08 +0200
From:   David Hildenbrand <david@...hat.com>
To:     linux-kernel@...r.kernel.org
Cc:     linux-mm@...ck.org, David Hildenbrand <david@...hat.com>,
        Arun KS <arunks@...eaurora.org>,
        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 4/5] mm/memory_hotplug: Make sure the pfn is aligned to the order when onlining

Commit a9cd410a3d29 ("mm/page_alloc.c: memory hotplug: free pages as higher
order") assumed that any PFN we get via memory resources is aligned to
to MAX_ORDER - 1, I am not convinced that is always true. Let's play safe,
check the alignment and fallback to single pages.

Cc: Arun KS <arunks@...eaurora.org>
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 | 3 +++
 1 file changed, 3 insertions(+)

diff --git a/mm/memory_hotplug.c b/mm/memory_hotplug.c
index 63b1775f7cf8..f245fb50ba7f 100644
--- a/mm/memory_hotplug.c
+++ b/mm/memory_hotplug.c
@@ -646,6 +646,9 @@ static int online_pages_range(unsigned long start_pfn, unsigned long nr_pages,
 	 */
 	for (pfn = start_pfn; pfn < end_pfn; pfn += 1ul << order) {
 		order = min(MAX_ORDER - 1, get_order(PFN_PHYS(end_pfn - pfn)));
+		/* __free_pages_core() wants pfns to be aligned to the order */
+		if (unlikely(!IS_ALIGNED(pfn, 1ul << order)))
+			order = 0;
 		(*online_page_callback)(pfn_to_page(pfn), order);
 	}
 
-- 
2.21.0