ksmbd: Implements sess->rpc_handle_list as xarray

For some ops on rpc handle:
1. ksmbd_session_rpc_method(), possibly on high frequency.
2. ksmbd_session_rpc_close().

id is used as indexing key to lookup channel, in that case,
linear search based on list may suffer a bit for performance.

Implements sess->rpc_handle_list as xarray.

Signed-off-by: Dawei Li <set_pte_at@outlook.com>
Acked-by: Namjae Jeon <linkinjeon@kernel.org>
Signed-off-by: Steve French <stfrench@microsoft.com>

Author: Dawei Li

fs/ksmbd/mgmt/user_session.c

@@ -25,7 +25,6 @@ static DECLARE_RWSEM(sessions_table_lock);
 struct ksmbd_session_rpc {
 	int			id;
 	unsigned int		method;
-	struct list_head	list;
 };
 
 static void free_channel_list(struct ksmbd_session *sess)
@@ -58,15 +57,14 @@ static void __session_rpc_close(struct ksmbd_session *sess,
 static void ksmbd_session_rpc_clear_list(struct ksmbd_session *sess)
 {
 	struct ksmbd_session_rpc *entry;
+	long index;
 
-	while (!list_empty(&sess->rpc_handle_list)) {
-		entry = list_entry(sess->rpc_handle_list.next,
-				   struct ksmbd_session_rpc,
-				   list);
-
-		list_del(&entry->list);
+	xa_for_each(&sess->rpc_handle_list, index, entry) {
+		xa_erase(&sess->rpc_handle_list, index);
 		__session_rpc_close(sess, entry);
 	}
+
+	xa_destroy(&sess->rpc_handle_list);
 }
 
 static int __rpc_method(char *rpc_name)
@@ -102,13 +100,13 @@ int ksmbd_session_rpc_open(struct ksmbd_session *sess, char *rpc_name)
 
 	entry = kzalloc(sizeof(struct ksmbd_session_rpc), GFP_KERNEL);
 	if (!entry)
-		return -EINVAL;
+		return -ENOMEM;
 
-	list_add(&entry->list, &sess->rpc_handle_list);
 	entry->method = method;
 	entry->id = ksmbd_ipc_id_alloc();
 	if (entry->id < 0)
 		goto free_entry;
+	xa_store(&sess->rpc_handle_list, entry->id, entry, GFP_KERNEL);
 
 	resp = ksmbd_rpc_open(sess, entry->id);
 	if (!resp)
@@ -117,9 +115,9 @@ int ksmbd_session_rpc_open(struct ksmbd_session *sess, char *rpc_name)
 	kvfree(resp);
 	return entry->id;
 free_id:
+	xa_erase(&sess->rpc_handle_list, entry->id);
 	ksmbd_rpc_id_free(entry->id);
 free_entry:
-	list_del(&entry->list);
 	kfree(entry);
 	return -EINVAL;
 }
@@ -128,24 +126,17 @@ void ksmbd_session_rpc_close(struct ksmbd_session *sess, int id)
 {
 	struct ksmbd_session_rpc *entry;
 
-	list_for_each_entry(entry, &sess->rpc_handle_list, list) {
-		if (entry->id == id) {
-			list_del(&entry->list);
-			__session_rpc_close(sess, entry);
-			break;
-		}
-	}
+	entry = xa_erase(&sess->rpc_handle_list, id);
+	if (entry)
+		__session_rpc_close(sess, entry);
 }
 
 int ksmbd_session_rpc_method(struct ksmbd_session *sess, int id)
 {
 	struct ksmbd_session_rpc *entry;
 
-	list_for_each_entry(entry, &sess->rpc_handle_list, list) {
-		if (entry->id == id)
-			return entry->method;
-	}
-	return 0;
+	entry = xa_load(&sess->rpc_handle_list, id);
+	return entry ? entry->method : 0;
 }
 
 void ksmbd_session_destroy(struct ksmbd_session *sess)
@@ -327,7 +318,7 @@ static struct ksmbd_session *__session_create(int protocol)
 	set_session_flag(sess, protocol);
 	xa_init(&sess->tree_conns);
 	xa_init(&sess->ksmbd_chann_list);
-	INIT_LIST_HEAD(&sess->rpc_handle_list);
+	xa_init(&sess->rpc_handle_list);
 	sess->sequence_number = 1;
 
 	ret = __init_smb2_session(sess);

fs/ksmbd/mgmt/user_session.h

@@ -52,7 +52,7 @@ struct ksmbd_session {
 	struct xarray			ksmbd_chann_list;
 	struct xarray			tree_conns;
 	struct ida			tree_conn_ida;
-	struct list_head		rpc_handle_list;
+	struct xarray			rpc_handle_list;
 
 	__u8				smb3encryptionkey[SMB3_ENC_DEC_KEY_SIZE];
 	__u8				smb3decryptionkey[SMB3_ENC_DEC_KEY_SIZE];