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>

diff --git a/include/linux/list_lru.h b/include/linux/list_lru.h
index d9c16f2f2f00b69fc9edd0387f225a51dbabe16b..aa5efd9351ebd80a5db735184be7eb34993a174b 100644 (file)
--- a/include/linux/list_lru.h
+++ b/include/linux/list_lru.h
@@ -166,6 +166,23 @@ unsigned long list_lru_walk_one(struct list_lru *lru,
                                int nid, struct mem_cgroup *memcg,
                                list_lru_walk_cb isolate, void *cb_arg,
                                unsigned long *nr_to_walk);
+/**
+ * list_lru_walk_one_irq: walk a list_lru, isolating and disposing freeable items.
+ * @lru: the lru pointer.
+ * @nid: the node id to scan from.
+ * @memcg: the cgroup to scan from.
+ * @isolate: callback function that is resposible for deciding what to do with
+ *  the item currently being scanned
+ * @cb_arg: opaque type that will be passed to @isolate
+ * @nr_to_walk: how many items to scan.
+ *
+ * Same as @list_lru_walk_one except that the spinlock is acquired with
+ * spin_lock_irq().
+ */
+unsigned long list_lru_walk_one_irq(struct list_lru *lru,
+                                   int nid, struct mem_cgroup *memcg,
+                                   list_lru_walk_cb isolate, void *cb_arg,
+                                   unsigned long *nr_to_walk);
 unsigned long list_lru_walk_node(struct list_lru *lru, int nid,
                                 list_lru_walk_cb isolate, void *cb_arg,
                                 unsigned long *nr_to_walk);
@@ -178,6 +195,14 @@ list_lru_shrink_walk(struct list_lru *lru, struct shrink_control *sc,
                                 &sc->nr_to_scan);
 }
 
+static inline unsigned long
+list_lru_shrink_walk_irq(struct list_lru *lru, struct shrink_control *sc,
+                        list_lru_walk_cb isolate, void *cb_arg)
+{
+       return list_lru_walk_one_irq(lru, sc->nid, sc->memcg, isolate, cb_arg,
+                                    &sc->nr_to_scan);
+}
+
 static inline unsigned long
 list_lru_walk(struct list_lru *lru, list_lru_walk_cb isolate,
              void *cb_arg, unsigned long nr_to_walk)

diff --git a/mm/list_lru.c b/mm/list_lru.c
index f5c6a2d1ea6646b154b9d7c2143034af76f68c39..5b30625fd3651a51deab140c3412897a51624f4f 100644 (file)
--- a/mm/list_lru.c
+++ b/mm/list_lru.c
@@ -282,6 +282,21 @@ list_lru_walk_one(struct list_lru *lru, int nid, struct mem_cgroup *memcg,
 }
 EXPORT_SYMBOL_GPL(list_lru_walk_one);
 
+unsigned long
+list_lru_walk_one_irq(struct list_lru *lru, int nid, struct mem_cgroup *memcg,
+                     list_lru_walk_cb isolate, void *cb_arg,
+                     unsigned long *nr_to_walk)
+{
+       struct list_lru_node *nlru = &lru->node[nid];
+       unsigned long ret;
+
+       spin_lock_irq(&nlru->lock);
+       ret = __list_lru_walk_one(nlru, memcg_cache_id(memcg), isolate, cb_arg,
+                                 nr_to_walk);
+       spin_unlock_irq(&nlru->lock);
+       return ret;
+}
+
 unsigned long list_lru_walk_node(struct list_lru *lru, int nid,
                                 list_lru_walk_cb isolate, void *cb_arg,
                                 unsigned long *nr_to_walk)

diff --git a/mm/workingset.c b/mm/workingset.c
index bc72ad029b3e7109840dae005e29cd9422e77d55..4516dd790129131d4d989d2967bf59c3645e51d4 100644 (file)
--- 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 = {