[PATCH 26/29] mm: shrinker: make count and scan in shrinker debugfs lockless

[Qi Zheng]

Like global and memcg slab shrink, also make count and scan
operations in memory shrinker debugfs lockless.

The debugfs_remove_recursive() will wait for debugfs_file_put()
to return, so there is no need to call rcu_read_lock() before
calling shrinker_try_get().

Signed-off-by: Qi Zheng <zhengqi.arch@xxxxxxxxxxxxx>
---
 mm/shrinker_debug.c | 12 ++++++------
 1 file changed, 6 insertions(+), 6 deletions(-)

diff --git a/mm/shrinker_debug.c b/mm/shrinker_debug.c
index 3ab53fad8876..c18fa9b6b7f0 100644
--- a/mm/shrinker_debug.c
+++ b/mm/shrinker_debug.c
@@ -55,8 +55,8 @@ static int shrinker_debugfs_count_show(struct seq_file *m, void *v)
 	if (!count_per_node)
 		return -ENOMEM;
 
-	ret = down_read_killable(&shrinker_rwsem);
-	if (ret) {
+	ret = shrinker_try_get(shrinker);
+	if (!ret) {
 		kfree(count_per_node);
 		return ret;
 	}
@@ -92,7 +92,7 @@ static int shrinker_debugfs_count_show(struct seq_file *m, void *v)
 	} while ((memcg = mem_cgroup_iter(NULL, memcg, NULL)) != NULL);
 
 	rcu_read_unlock();
-	up_read(&shrinker_rwsem);
+	shrinker_put(shrinker);
 
 	kfree(count_per_node);
 	return ret;
@@ -146,8 +146,8 @@ static ssize_t shrinker_debugfs_scan_write(struct file *file,
 		return -EINVAL;
 	}
 
-	ret = down_read_killable(&shrinker_rwsem);
-	if (ret) {
+	ret = shrinker_try_get(shrinker);
+	if (!ret) {
 		mem_cgroup_put(memcg);
 		return ret;
 	}
@@ -159,7 +159,7 @@ static ssize_t shrinker_debugfs_scan_write(struct file *file,
 
 	shrinker->scan_objects(shrinker, &sc);
 
-	up_read(&shrinker_rwsem);
+	shrinker_put(shrinker);
 	mem_cgroup_put(memcg);
 
 	return size;
-- 
2.30.2