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>

diff --git a/mm/frontswap.c b/mm/frontswap.c
index 89dc399..0547a35 100644 (file)
--- 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;
 }