thp: ksm: free swap when swapcache page is replaced

When a swapcache page is replaced by a ksm page, it's best to free that
swap immediately.

Reported-by: Andrea Arcangeli <aarcange@redhat.com>
Signed-off-by: Hugh Dickins <hughd@google.com>
Signed-off-by: Andrea Arcangeli <aarcange@redhat.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

diff --git a/mm/ksm.c b/mm/ksm.c
index 43bc893..b5b907c 100644 (file)
--- a/mm/ksm.c
+++ b/mm/ksm.c
@@ -800,6 +800,8 @@ static int replace_page(struct vm_area_struct *vma, struct page *page,
        set_pte_at_notify(mm, addr, ptep, mk_pte(kpage, vma->vm_page_prot));
 
        page_remove_rmap(page);
+       if (!page_mapped(page))
+               try_to_free_swap(page);
        put_page(page);
 
        pte_unmap_unlock(ptep, ptl);