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From: Oscar Salvador <osalvador@suse.de>
To: akpm@linux-foundation.org
Cc: mhocko@suse.com, david@redhat.com, anthony.yznaga@oracle.com,
	linux-mm@kvack.org, linux-kernel@vger.kernel.org,
	Oscar Salvador <osalvador@suse.de>
Subject: [PATCH] mm,memory_hotplug: Explicitly pass the head to isolate_huge_page
Date: Fri,  8 Feb 2019 10:06:04 +0100
Message-ID: <20190208090604.975-1-osalvador@suse.de> (raw)

isolate_huge_page() expects we pass the head of hugetlb page to it:

bool isolate_huge_page(...)
{
	...
	VM_BUG_ON_PAGE(!PageHead(page), page);
	...
}

While I really cannot think of any situation where we end up with a
non-head page between hands in do_migrate_range(), let us make sure
the code is as sane as possible by explicitly passing the Head.
Since we already got the pointer, it does not take us extra effort.

Signed-off-by: Oscar Salvador <osalvador@suse.de>
---
 mm/memory_hotplug.c | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/mm/memory_hotplug.c b/mm/memory_hotplug.c
index 656ff386ac15..d5f7afda67db 100644
--- a/mm/memory_hotplug.c
+++ b/mm/memory_hotplug.c
@@ -1378,12 +1378,12 @@ do_migrate_range(unsigned long start_pfn, unsigned long end_pfn)
 
 		if (PageHuge(page)) {
 			struct page *head = compound_head(page);
-			pfn = page_to_pfn(head) + (1<<compound_order(head)) - 1;
 			if (compound_order(head) > PFN_SECTION_SHIFT) {
 				ret = -EBUSY;
 				break;
 			}
-			isolate_huge_page(page, &source);
+			pfn = page_to_pfn(head) + (1<<compound_order(head)) - 1;
+			isolate_huge_page(head, &source);
 			continue;
 		} else if (PageTransHuge(page))
 			pfn = page_to_pfn(compound_head(page))
-- 
2.13.7


             reply index

Thread overview: 9+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2019-02-08  9:06 Oscar Salvador [this message]
2019-02-11  8:58 ` David Hildenbrand
2019-02-12  8:33 ` Michal Hocko
2019-02-12 13:45   ` Oscar Salvador
2019-02-12 14:40     ` Michal Hocko
2019-02-13  0:13       ` Mike Kravetz
2019-02-13  8:13         ` Oscar Salvador
2019-02-13 12:33           ` Michal Hocko
2019-02-13 15:15             ` Oscar Salvador

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