mm: frontswap: fix a wrong if condition in frontswap_shrink

pages_to_unuse is set to 0 to unuse all frontswap pages
But that doesn't happen since a wrong condition in frontswap_shrink
cancel it.

-v2: Add comment to explain return value of __frontswap_shrink,
as suggested by Dan Carpenter, thanks

Signed-off-by: Zhenzhong Duan <zhenzhong.duan@oracle.com>
Signed-off-by: Konrad Rzeszutek Wilk <konrad.wilk@oracle.com>

1 files changed, 7 insertions, 2 deletions

diff --git a/mm/frontswap.c b/mm/frontswap.c
index 89dc399d3328..0547a35f798b 100644
--- a/mm/frontswap.c
+++ b/mm/frontswap.c
@@ -263,6 +263,11 @@ static int __frontswap_unuse_pages(unsigned long total, unsigned long *unused,
         return ret;
 }
 
+/*
+ * Used to check if it's necessory and feasible to unuse pages.
+ * Return 1 when nothing to do, 0 when need to shink pages,
+ * error code when there is an error.
+ */
 static int __frontswap_shrink(unsigned long target_pages,
                                 unsigned long *pages_to_unuse,
                                 int *type)
@@ -275,7 +280,7 @@ static int __frontswap_shrink(unsigned long target_pages,
         if (total_pages <= target_pages) {
                 /* Nothing to do */
                 *pages_to_unuse = 0;
-                return 0;
+                return 1;
         }
         total_pages_to_unuse = total_pages - target_pages;
         return __frontswap_unuse_pages(total_pages_to_unuse, pages_to_unuse, type);
@@ -302,7 +307,7 @@ void frontswap_shrink(unsigned long target_pages)
         spin_lock(&swap_lock);
         ret = __frontswap_shrink(target_pages, &pages_to_unuse, &type);
         spin_unlock(&swap_lock);
-        if (ret == 0 && pages_to_unuse)
+        if (ret == 0)
                 try_to_unuse(type, true, pages_to_unuse);
         return;
 }