get_huge_page_tail()->compound_head() looks confusing. Every caller
must check PageTail(page), otherwise atomic_inc(&page->_mapcount) is
simply wrong if this page is compound-trans-head.
Signed-off-by: Oleg Nesterov <o...@redhat.com>
---
include/linux/mm.h | 7 +++----
1 files changed, 3 insertions(+), 4 deletions(-)
diff --git a/include/linux/mm.h b/include/linux/mm.h
index 13bae9e..13495bd 100644
--- a/include/linux/mm.h
+++ b/include/linux/mm.h
@@ -431,13 +431,12 @@ static inline bool compound_tail_refcounted(struct page
*page)
static inline void get_huge_page_tail(struct page *page)
{
/*
- * __split_huge_page_refcount() cannot run
- * from under us.
- * In turn no need of compound_trans_head here.
+ * __split_huge_page_refcount() cannot run from under us.
*/
+ VM_BUG_ON(!PageTail(page));
VM_BUG_ON(page_mapcount(page) < 0);
VM_BUG_ON(atomic_read(&page->_count) != 0);
- if (compound_tail_refcounted(compound_head(page)))
+ if (compound_tail_refcounted(page->first_page))
atomic_inc(&page->_mapcount);
}
--
1.5.5.1
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