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-rw-r--r--mm/swapfile.c15
1 files changed, 11 insertions, 4 deletions
diff --git a/mm/swapfile.c b/mm/swapfile.c
index 214e90b9494..bfd4ee59cb8 100644
--- a/mm/swapfile.c
+++ b/mm/swapfile.c
@@ -326,17 +326,24 @@ static inline int page_swapcount(struct page *page)
}
/*
- * We can use this swap cache entry directly
- * if there are no other references to it.
+ * We can write to an anon page without COW if there are no other references
+ * to it. And as a side-effect, free up its swap: because the old content
+ * on disk will never be read, and seeking back there to write new content
+ * later would only waste time away from clustering.
*/
-int can_share_swap_page(struct page *page)
+int reuse_swap_page(struct page *page)
{
int count;
VM_BUG_ON(!PageLocked(page));
count = page_mapcount(page);
- if (count <= 1 && PageSwapCache(page))
+ if (count <= 1 && PageSwapCache(page)) {
count += page_swapcount(page);
+ if (count == 1 && !PageWriteback(page)) {
+ delete_from_swap_cache(page);
+ SetPageDirty(page);
+ }
+ }
return count == 1;
}