mm/list_lru: introduce list_lru_shrink_walk_irq()

Provide list_lru_shrink_walk_irq() and let it behave like
list_lru_walk_one() except that it locks the spinlock with
spin_lock_irq().  This is used by scan_shadow_nodes() because its lock
nests within the i_pages lock which is acquired with IRQ.  This change
allows to use proper locking promitives instead hand crafted
lock_irq_disable() plus spin_lock().

There is no EXPORT_SYMBOL provided because the current user is in-kernel
only.

Add list_lru_shrink_walk_irq() which acquires the spinlock with the
proper locking primitives.

Link: http://lkml.kernel.org/r/20180716111921.5365-5-bigeasy@linutronix.de
Signed-off-by: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
Reviewed-by: Vladimir Davydov <vdavydov.dev@gmail.com>
Cc: Thomas Gleixner <tglx@linutronix.de>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

1 files changed, 2 insertions, 6 deletions

diff --git a/mm/workingset.c b/mm/workingset.c
index bc72ad029b3e..4516dd790129 100644
--- a/mm/workingset.c
+++ b/mm/workingset.c
@@ -483,13 +483,9 @@ out:
 static unsigned long scan_shadow_nodes(struct shrinker *shrinker,
                                        struct shrink_control *sc)
 {
-        unsigned long ret;
-
         /* list_lru lock nests inside the IRQ-safe i_pages lock */
-        local_irq_disable();
-        ret = list_lru_shrink_walk(&shadow_nodes, sc, shadow_lru_isolate, NULL);
-        local_irq_enable();
-        return ret;
+        return list_lru_shrink_walk_irq(&shadow_nodes, sc, shadow_lru_isolate,
+                                        NULL);
 }
 
 static struct shrinker workingset_shadow_shrinker = {