mm: frontswap: split frontswap_shrink further to simplify locking
Split frontswap_shrink to simplify the locking in the original code.
Also, assert that the function that was split still runs under the
swap spinlock.
Signed-off-by: Sasha Levin <levinsasha928@gmail.com>
Signed-off-by: Konrad Rzeszutek Wilk <konrad.wilk@oracle.com>
diff --git a/mm/frontswap.c b/mm/frontswap.c
index faa43b7..e6353d9 100644
--- a/mm/frontswap.c
+++ b/mm/frontswap.c
@@ -265,6 +265,24 @@
return ret;
}
+static int __frontswap_shrink(unsigned long target_pages,
+ unsigned long *pages_to_unuse,
+ int *type)
+{
+ unsigned long total_pages = 0, total_pages_to_unuse;
+
+ assert_spin_locked(&swap_lock);
+
+ total_pages = __frontswap_curr_pages();
+ if (total_pages <= target_pages) {
+ /* Nothing to do */
+ *pages_to_unuse = 0;
+ return 0;
+ }
+ total_pages_to_unuse = total_pages - target_pages;
+ return __frontswap_unuse_pages(total_pages_to_unuse, pages_to_unuse, type);
+}
+
/*
* Frontswap, like a true swap device, may unnecessarily retain pages
* under certain circumstances; "shrink" frontswap is essentially a
@@ -275,10 +293,8 @@
*/
void frontswap_shrink(unsigned long target_pages)
{
- unsigned long total_pages = 0, total_pages_to_unuse;
unsigned long pages_to_unuse = 0;
int type, ret;
- bool locked = false;
/*
* we don't want to hold swap_lock while doing a very
@@ -286,20 +302,10 @@
* so restart scan from swap_list.head each time
*/
spin_lock(&swap_lock);
- locked = true;
- total_pages = __frontswap_curr_pages();
- if (total_pages <= target_pages)
- goto out;
- total_pages_to_unuse = total_pages - target_pages;
- ret = __frontswap_unuse_pages(total_pages_to_unuse, &pages_to_unuse, &type);
- if (ret < 0)
- goto out;
- locked = false;
+ ret = __frontswap_shrink(target_pages, &pages_to_unuse, &type);
spin_unlock(&swap_lock);
- try_to_unuse(type, true, pages_to_unuse);
-out:
- if (locked)
- spin_unlock(&swap_lock);
+ if (ret == 0 && pages_to_unuse)
+ try_to_unuse(type, true, pages_to_unuse);
return;
}
EXPORT_SYMBOL(frontswap_shrink);
