diff mbox series

[v2,02/47] mm: shrinker: remove redundant shrinker_rwsem in debugfs operations

Message ID 20230724094354.90817-3-zhengqi.arch@bytedance.com (mailing list archive)
State Not Applicable, archived
Delegated to: Mike Snitzer
Headers show
Series use refcount+RCU method to implement lockless slab shrink | expand

Commit Message

Qi Zheng July 24, 2023, 9:43 a.m. UTC 
The debugfs_remove_recursive() will wait for debugfs_file_put() to return,
so the shrinker will not be freed when doing debugfs operations (such as
shrinker_debugfs_count_show() and shrinker_debugfs_scan_write()), so there
is no need to hold shrinker_rwsem during debugfs operations.

Signed-off-by: Qi Zheng <zhengqi.arch@bytedance.com>
---
 mm/shrinker_debug.c | 14 --------------
 1 file changed, 14 deletions(-)

Comments

Muchun Song July 25, 2023, 3:17 a.m. UTC | #1 
> On Jul 24, 2023, at 17:43, Qi Zheng <zhengqi.arch@bytedance.com> wrote:
> 
> The debugfs_remove_recursive() will wait for debugfs_file_put() to return,
> so the shrinker will not be freed when doing debugfs operations (such as
> shrinker_debugfs_count_show() and shrinker_debugfs_scan_write()), so there
> is no need to hold shrinker_rwsem during debugfs operations.
> 
> Signed-off-by: Qi Zheng <zhengqi.arch@bytedance.com>

Reviewed-by: Muchun Song <songmuchun@bytedance.com>

Thanks.


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diff mbox series

Patch

diff --git a/mm/shrinker_debug.c b/mm/shrinker_debug.c
index 3ab53fad8876..f1becfd45853 100644
--- a/mm/shrinker_debug.c
+++ b/mm/shrinker_debug.c
@@ -55,11 +55,6 @@  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) {
-		kfree(count_per_node);
-		return ret;
-	}
 	rcu_read_lock();
 
 	memcg_aware = shrinker->flags & SHRINKER_MEMCG_AWARE;
@@ -92,7 +87,6 @@  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);
 
 	kfree(count_per_node);
 	return ret;
@@ -117,7 +111,6 @@  static ssize_t shrinker_debugfs_scan_write(struct file *file,
 	struct mem_cgroup *memcg = NULL;
 	int nid;
 	char kbuf[72];
-	ssize_t ret;
 
 	read_len = size < (sizeof(kbuf) - 1) ? size : (sizeof(kbuf) - 1);
 	if (copy_from_user(kbuf, buf, read_len))
@@ -146,12 +139,6 @@  static ssize_t shrinker_debugfs_scan_write(struct file *file,
 		return -EINVAL;
 	}
 
-	ret = down_read_killable(&shrinker_rwsem);
-	if (ret) {
-		mem_cgroup_put(memcg);
-		return ret;
-	}
-
 	sc.nid = nid;
 	sc.memcg = memcg;
 	sc.nr_to_scan = nr_to_scan;
@@ -159,7 +146,6 @@  static ssize_t shrinker_debugfs_scan_write(struct file *file,
 
 	shrinker->scan_objects(shrinker, &sc);
 
-	up_read(&shrinker_rwsem);
 	mem_cgroup_put(memcg);
 
 	return size;