On 3/7/23 07:56, Qi Zheng wrote:
> Like global and memcg slab shrink, also use SRCU to
> make count and scan operations in memory shrinker
> debugfs lockless.
>
> Signed-off-by: Qi Zheng <zhengqi.arch@xxxxxxxxxxxxx>
Acked-by: Vlastimil Babka <vbabka@xxxxxxx>
> ---
> mm/shrinker_debug.c | 24 +++++++-----------------
> 1 file changed, 7 insertions(+), 17 deletions(-)
>
> diff --git a/mm/shrinker_debug.c b/mm/shrinker_debug.c
> index 39c3491e28a3..6aa7a7ec69da 100644
> --- a/mm/shrinker_debug.c
> +++ b/mm/shrinker_debug.c
> @@ -9,6 +9,7 @@
> /* defined in vmscan.c */
> extern struct rw_semaphore shrinker_rwsem;
> extern struct list_head shrinker_list;
> +extern struct srcu_struct shrinker_srcu;
>
> static DEFINE_IDA(shrinker_debugfs_ida);
> static struct dentry *shrinker_debugfs_root;
> @@ -49,18 +50,13 @@ static int shrinker_debugfs_count_show(struct seq_file *m, void *v)
> struct mem_cgroup *memcg;
> unsigned long total;
> bool memcg_aware;
> - int ret, nid;
> + int ret = 0, nid, srcu_idx;
>
> count_per_node = kcalloc(nr_node_ids, sizeof(unsigned long), GFP_KERNEL);
> if (!count_per_node)
> return -ENOMEM;
>
> - ret = down_read_killable(&shrinker_rwsem);
> - if (ret) {
> - kfree(count_per_node);
> - return ret;
> - }
> - rcu_read_lock();
> + srcu_idx = srcu_read_lock(&shrinker_srcu);
>
> memcg_aware = shrinker->flags & SHRINKER_MEMCG_AWARE;
>
> @@ -91,8 +87,7 @@ 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);
> + srcu_read_unlock(&shrinker_srcu, srcu_idx);
>
> kfree(count_per_node);
> return ret;
> @@ -115,9 +110,8 @@ static ssize_t shrinker_debugfs_scan_write(struct file *file,
> .gfp_mask = GFP_KERNEL,
> };
> struct mem_cgroup *memcg = NULL;
> - int nid;
> + int nid, srcu_idx;
> char kbuf[72];
> - ssize_t ret;
>
> read_len = size < (sizeof(kbuf) - 1) ? size : (sizeof(kbuf) - 1);
> if (copy_from_user(kbuf, buf, read_len))
> @@ -146,11 +140,7 @@ 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;
> - }
> + srcu_idx = srcu_read_lock(&shrinker_srcu);
>
> sc.nid = nid;
> sc.memcg = memcg;
> @@ -159,7 +149,7 @@ static ssize_t shrinker_debugfs_scan_write(struct file *file,
>
> shrinker->scan_objects(shrinker, &sc);
>
> - up_read(&shrinker_rwsem);
> + srcu_read_unlock(&shrinker_srcu, srcu_idx);
> mem_cgroup_put(memcg);
>
> return size;
