[PATCH 05/11] mm: frontswap: split frontswap_shrink further to eliminate locking games

Sasha Levin
2012-06-06T10:54:31Z

Split frontswap_shrink to eliminate the locking issues in the original code.

Signed-off-by: Sasha Levin <levinsasha928@gmail.com>
---
mm/frontswap.c | 36 +++++++++++++++++++++---------------
1 files changed, 21 insertions(+), 15 deletions(-)

diff --git a/mm/frontswap.c b/mm/frontswap.c
index a9b76cb..618ef91 100644
--- a/mm/frontswap.c
+++ b/mm/frontswap.c
@@ -244,6 +244,24 @@ static int __frontswap_unuse_pages(unsigned long total, unsigned long *unused,
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;
+
+ lockdep_assert_held(&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
@@ -254,10 +272,8 @@ static int __frontswap_unuse_pages(unsigned long total, unsigned long *unused,
*/
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
@@ -265,20 +281,10 @@ void frontswap_shrink(unsigned long target_pages)
* 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);
--
1.7.8.6