Now that gigantic pages are dynamically allocatable, care must be taken
to ensure that p->first_page is valid before setting PageTail.
If this isn't done, then it is possible to race and have compound_head()
return NULL.
Signed-off-by: David Rientjes <rientjes@xxxxxxxxxx>
---
mm/hugetlb.c | 4 +++-
1 file changed, 3 insertions(+), 1 deletion(-)
diff --git a/mm/hugetlb.c b/mm/hugetlb.c
--- a/mm/hugetlb.c
+++ b/mm/hugetlb.c
@@ -917,7 +917,6 @@ static void prep_compound_gigantic_page(struct page *page, unsigned long order)
__SetPageHead(page);
__ClearPageReserved(page);
for (i = 1; i < nr_pages; i++, p = mem_map_next(p, page, i)) {
- __SetPageTail(p);
/*
* For gigantic hugepages allocated through bootmem at
* boot, it's safer to be consistent with the not-gigantic
@@ -933,6 +932,9 @@ static void prep_compound_gigantic_page(struct page *page, unsigned long order)
__ClearPageReserved(p);
set_page_count(p, 0);
p->first_page = page;
+ /* Make sure p->first_page is always valid for PageTail() */
+ smp_wmb();
+ __SetPageTail(p);
}
}
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