mei: add a spin lock to protect rd_completed queue

In order to support vtags we need to access read completed
queue out of driver big lock.
Add a spin lock to protect rd_completed queue.

Signed-off-by: Alexander Usyskin <alexander.usyskin@intel.com>
Signed-off-by: Tomas Winkler <tomas.winkler@intel.com>
Link: https://lore.kernel.org/r/20200818115147.2567012-7-tomas.winkler@intel.com
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

drivers/misc/mei/bus.c

@@ -152,7 +152,7 @@ ssize_t __mei_cl_recv(struct mei_cl *cl, u8 *buf, size_t length,
 		if (timeout) {
 			rets = wait_event_interruptible_timeout
 					(cl->rx_wait,
-					(!list_empty(&cl->rd_completed)) ||
+					mei_cl_read_cb(cl, NULL) ||
 					(!mei_cl_is_connected(cl)),
 					msecs_to_jiffies(timeout));
 			if (rets == 0)
@@ -165,7 +165,7 @@ ssize_t __mei_cl_recv(struct mei_cl *cl, u8 *buf, size_t length,
 		} else {
 			if (wait_event_interruptible
 					(cl->rx_wait,
-					(!list_empty(&cl->rd_completed)) ||
+					mei_cl_read_cb(cl, NULL) ||
 					(!mei_cl_is_connected(cl)))) {
 				if (signal_pending(current))
 					return -EINTR;
@@ -198,7 +198,7 @@ ssize_t __mei_cl_recv(struct mei_cl *cl, u8 *buf, size_t length,
 	rets = r_length;
 
 free:
-	mei_io_cb_free(cb);
+	mei_cl_del_rd_completed(cl, cb);
 out:
 	mutex_unlock(&bus->device_lock);
 

drivers/misc/mei/client.c

@@ -507,15 +507,19 @@ struct mei_cl_cb *mei_cl_enqueue_ctrl_wr_cb(struct mei_cl *cl, size_t length,
  *
  * Return: cb on success, NULL if cb is not found
  */
-struct mei_cl_cb *mei_cl_read_cb(const struct mei_cl *cl, const struct file *fp)
+struct mei_cl_cb *mei_cl_read_cb(struct mei_cl *cl, const struct file *fp)
 {
 	struct mei_cl_cb *cb;
+	struct mei_cl_cb *ret_cb = NULL;
 
+	spin_lock(&cl->rd_completed_lock);
 	list_for_each_entry(cb, &cl->rd_completed, list)
-		if (!fp || fp == cb->fp)
-			return cb;
-
-	return NULL;
+		if (!fp || fp == cb->fp) {
+			ret_cb = cb;
+			break;
+		}
+	spin_unlock(&cl->rd_completed_lock);
+	return ret_cb;
 }
 
 /**
@@ -541,7 +545,9 @@ int mei_cl_flush_queues(struct mei_cl *cl, const struct file *fp)
 	mei_io_list_flush_cl(&cl->dev->ctrl_wr_list, cl);
 	mei_io_list_flush_cl(&cl->dev->ctrl_rd_list, cl);
 	mei_io_list_free_fp(&cl->rd_pending, fp);
+	spin_lock(&cl->rd_completed_lock);
 	mei_io_list_free_fp(&cl->rd_completed, fp);
+	spin_unlock(&cl->rd_completed_lock);
 
 	return 0;
 }
@@ -559,6 +565,7 @@ static void mei_cl_init(struct mei_cl *cl, struct mei_device *dev)
 	init_waitqueue_head(&cl->rx_wait);
 	init_waitqueue_head(&cl->tx_wait);
 	init_waitqueue_head(&cl->ev_wait);
+	spin_lock_init(&cl->rd_completed_lock);
 	INIT_LIST_HEAD(&cl->rd_completed);
 	INIT_LIST_HEAD(&cl->rd_pending);
 	INIT_LIST_HEAD(&cl->link);
@@ -1230,6 +1237,34 @@ static int mei_cl_tx_flow_ctrl_creds_reduce(struct mei_cl *cl)
 	return 0;
 }
 
+/**
+ * mei_cl_add_rd_completed - add read completed callback to list with lock
+ *
+ * @cl: host client
+ * @cb: callback block
+ *
+ */
+void mei_cl_add_rd_completed(struct mei_cl *cl, struct mei_cl_cb *cb)
+{
+	spin_lock(&cl->rd_completed_lock);
+	list_add_tail(&cb->list, &cl->rd_completed);
+	spin_unlock(&cl->rd_completed_lock);
+}
+
+/**
+ * mei_cl_del_rd_completed - free read completed callback with lock
+ *
+ * @cl: host client
+ * @cb: callback block
+ *
+ */
+void mei_cl_del_rd_completed(struct mei_cl *cl, struct mei_cl_cb *cb)
+{
+	spin_lock(&cl->rd_completed_lock);
+	mei_io_cb_free(cb);
+	spin_unlock(&cl->rd_completed_lock);
+}
+
 /**
  *  mei_cl_notify_fop2req - convert fop to proper request
  *
@@ -1897,7 +1932,7 @@ void mei_cl_complete(struct mei_cl *cl, struct mei_cl_cb *cb)
 		break;
 
 	case MEI_FOP_READ:
-		list_add_tail(&cb->list, &cl->rd_completed);
+		mei_cl_add_rd_completed(cl, cb);
 		if (!mei_cl_is_fixed_address(cl) &&
 		    !WARN_ON(!cl->rx_flow_ctrl_creds))
 			cl->rx_flow_ctrl_creds--;

drivers/misc/mei/client.h

@@ -133,8 +133,11 @@ int mei_cl_unlink(struct mei_cl *cl);
 
 struct mei_cl *mei_cl_alloc_linked(struct mei_device *dev);
 
-struct mei_cl_cb *mei_cl_read_cb(const struct mei_cl *cl,
-				 const struct file *fp);
+struct mei_cl_cb *mei_cl_read_cb(struct mei_cl *cl, const struct file *fp);
+
+void mei_cl_add_rd_completed(struct mei_cl *cl, struct mei_cl_cb *cb);
+void mei_cl_del_rd_completed(struct mei_cl *cl, struct mei_cl_cb *cb);
+
 struct mei_cl_cb *mei_cl_alloc_cb(struct mei_cl *cl, size_t length,
 				  enum mei_cb_file_ops type,
 				  const struct file *fp);

drivers/misc/mei/main.c

@@ -178,7 +178,7 @@ static ssize_t mei_read(struct file *file, char __user *ubuf,
 
 	mutex_unlock(&dev->device_lock);
 	if (wait_event_interruptible(cl->rx_wait,
-				     !list_empty(&cl->rd_completed) ||
+				     mei_cl_read_cb(cl, file) ||
 				     !mei_cl_is_connected(cl))) {
 		if (signal_pending(current))
 			return -EINTR;
@@ -229,7 +229,7 @@ static ssize_t mei_read(struct file *file, char __user *ubuf,
 		goto out;
 
 free:
-	mei_io_cb_free(cb);
+	mei_cl_del_rd_completed(cl, cb);
 	*offset = 0;
 
 out:
@@ -572,7 +572,7 @@ static __poll_t mei_poll(struct file *file, poll_table *wait)
 	if (req_events & (EPOLLIN | EPOLLRDNORM)) {
 		poll_wait(file, &cl->rx_wait, wait);
 
-		if (!list_empty(&cl->rd_completed))
+		if (mei_cl_read_cb(cl, file))
 			mask |= EPOLLIN | EPOLLRDNORM;
 		else
 			mei_cl_read_start(cl, mei_cl_mtu(cl), file);

drivers/misc/mei/mei_dev.h

@@ -217,6 +217,7 @@ struct mei_cl_cb {
  * @tx_cb_queued: number of tx callbacks in queue
  * @writing_state: state of the tx
  * @rd_pending: pending read credits
+ * @rd_completed_lock: protects rd_completed queue
  * @rd_completed: completed read
  *
  * @cldev: device on the mei client bus
@@ -242,6 +243,7 @@ struct mei_cl {
 	u8 tx_cb_queued;
 	enum mei_file_transaction_states writing_state;
 	struct list_head rd_pending;
+	spinlock_t rd_completed_lock; /* protects rd_completed queue */
 	struct list_head rd_completed;
 
 	struct mei_cl_device *cldev;