Add the new helper, __put_nontail_page(page), which simply does
compound/single put depending on PageHead(). put_compound_page()
can use it 3 times, probably it can have other users.
Signed-off-by: Oleg Nesterov <o...@redhat.com>
---
mm/swap.c | 60 ++++++++++++++++++++++++++----------------------------------
1 files changed, 26 insertions(+), 34 deletions(-)
diff --git a/mm/swap.c b/mm/swap.c
index 0040d9c..f83de1f 100644
--- a/mm/swap.c
+++ b/mm/swap.c
@@ -79,21 +79,26 @@ static void __put_compound_page(struct page *page)
(*dtor)(page);
}
+static void __put_nontail_page(struct page *page)
+{
+ if (put_page_testzero(page)) {
+ /*
+ * By the time all refcounts have been released
+ * split_huge_page cannot run anymore from under us.
+ */
+ if (PageHead(page))
+ __put_compound_page(page);
+ else
+ __put_single_page(page);
+ }
+}
+
static void put_compound_page(struct page *page)
{
struct page *page_head;
if (likely(!PageTail(page))) {
- if (put_page_testzero(page)) {
- /*
- * By the time all refcounts have been released
- * split_huge_page cannot run anymore from under us.
- */
- if (PageHead(page))
- __put_compound_page(page);
- else
- __put_single_page(page);
- }
+ __put_nontail_page(page);
return;
}
@@ -176,24 +181,16 @@ static void put_compound_page(struct page *page)
if (unlikely(!PageTail(page))) {
/* __split_huge_page_refcount run before us */
compound_unlock_irqrestore(page_head, flags);
- if (put_page_testzero(page_head)) {
- /*
- * The head page may have been freed
- * and reallocated as a compound page
- * of smaller order and then freed
- * again. All we know is that it
- * cannot have become: a THP page, a
- * compound page of higher order, a
- * tail page. That is because we
- * still hold the refcount of the
- * split THP tail and page_head was
- * the THP head before the split.
- */
- if (PageHead(page_head))
- __put_compound_page(page_head);
- else
- __put_single_page(page_head);
- }
+ /*
+ * The head page may have been freed and reallocated
+ * as a compound page of smaller order and then freed
+ * again. All we know is that it cannot have become:
+ * a THP page, a compound page of higher order, a tail
+ * page. That is because we still hold the refcount of
+ * the split THP tail and page_head was the THP head
+ * before the split.
+ */
+ __put_nontail_page(page_head);
out_put_single:
if (put_page_testzero(page))
__put_single_page(page);
@@ -215,12 +212,7 @@ out_put_single:
VM_BUG_ON(atomic_read(&page->_count) != 0);
compound_unlock_irqrestore(page_head, flags);
- if (put_page_testzero(page_head)) {
- if (PageHead(page_head))
- __put_compound_page(page_head);
- else
- __put_single_page(page_head);
- }
+ __put_nontail_page(page_head);
} else {
/* page_head is a dangling pointer */
VM_BUG_ON(PageTail(page));
--
1.5.5.1
--
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