Hi Sergey,
On 2023/6/23 13:25, Sergey Senozhatsky wrote:
On (23/06/22 16:53), Qi Zheng wrote:
+/*
+ * Remove one
+ */
+void unregister_shrinker(struct shrinker *shrinker)
+{
+ struct dentry *debugfs_entry;
+ int debugfs_id;
+
+ if (!(shrinker->flags & SHRINKER_REGISTERED))
+ return;
+
+ shrinker_put(shrinker);
+ wait_for_completion(&shrinker->completion_wait);
+
+ mutex_lock(&shrinker_mutex);
+ list_del_rcu(&shrinker->list);
Should this function wait for RCU grace period(s) before it goes
touching shrinker fields?
Why? We will free this shrinker instance by rcu after executing
unregister_shrinker(). So it is safe to touch shrinker fields here.
+ shrinker->flags &= ~SHRINKER_REGISTERED;
+ if (shrinker->flags & SHRINKER_MEMCG_AWARE)
+ unregister_memcg_shrinker(shrinker);
+ debugfs_entry = shrinker_debugfs_detach(shrinker, &debugfs_id);
+ mutex_unlock(&shrinker_mutex);
+
+ shrinker_debugfs_remove(debugfs_entry, debugfs_id);
+
+ kfree(shrinker->nr_deferred);
+ shrinker->nr_deferred = NULL;
+}
+EXPORT_SYMBOL(unregister_shrinker);
[..]
+void shrinker_free(struct shrinker *shrinker)
+{
+ kfree(shrinker);
+}
+EXPORT_SYMBOL(shrinker_free);
+
+void unregister_and_free_shrinker(struct shrinker *shrinker)
+{
+ unregister_shrinker(shrinker);
+ kfree_rcu(shrinker, rcu);
+}
Seems like this
unregister_shrinker();
shrinker_free();
is not exact equivalent of this
unregister_and_free_shrinker();
Yes, my original intention is that shrinker_free() is only used to
handle the case where register_shrinker() returns failure.
I will implement the method suggested by Dave in 02/29. Those APIs are
more concise and will bring more benefits. :)
Thanks,
Qi
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