usb: f_fs: refactor ffs_epfile_io

Eliminate one of the return paths by using a ‘goto error_mutex’ and
rearrange some if-bodies which results in reduction of the indention level
and thus hopefully makes the function easier to read and reason about.
Signed-off-by: Michal Nazarewicz <mina86@mina86.com>
Signed-off-by: Felipe Balbi <balbi@kernel.org>

drivers/usb/gadget/function/f_fs.c

@@ -684,6 +684,7 @@ static void ffs_epfile_async_io_complete(struct usb_ep *_ep,
 static ssize_t ffs_epfile_io(struct file *file, struct ffs_io_data *io_data)
 {
 	struct ffs_epfile *epfile = file->private_data;
+	struct usb_request *req;
 	struct ffs_ep *ep;
 	char *data = NULL;
 	ssize_t ret, data_len = -EINVAL;
@@ -713,7 +714,8 @@ static ssize_t ffs_epfile_io(struct file *file, struct ffs_io_data *io_data)
 	if (!halt) {
 		/*
 		 * if we _do_ wait above, the epfile->ffs->gadget might be NULL
-		 * before the waiting completes, so do not assign to 'gadget' earlier
+		 * before the waiting completes, so do not assign to 'gadget'
+		 * earlier
 		 */
 		struct usb_gadget *gadget = epfile->ffs->gadget;
 		size_t copied;
@@ -755,17 +757,12 @@ static ssize_t ffs_epfile_io(struct file *file, struct ffs_io_data *io_data)
 	if (epfile->ep != ep) {
 		/* In the meantime, endpoint got disabled or changed. */
 		ret = -ESHUTDOWN;
-		goto error_lock;
 	} else if (halt) {
 		/* Halt */
 		if (likely(epfile->ep == ep) && !WARN_ON(!ep->ep))
 			usb_ep_set_halt(ep->ep);
-		spin_unlock_irq(&epfile->ffs->eps_lock);
 		ret = -EBADMSG;
-	} else {
-		/* Fire the request */
-		struct usb_request *req;
-
+	} else if (unlikely(data_len == -EINVAL)) {
 		/*
 		 * Sanity Check: even though data_len can't be used
 		 * uninitialized at the time I write this comment, some
@@ -777,82 +774,74 @@ static ssize_t ffs_epfile_io(struct file *file, struct ffs_io_data *io_data)
 		 * For such reason, we're adding this redundant sanity check
 		 * here.
 		 */
-		if (unlikely(data_len == -EINVAL)) {
-			WARN(1, "%s: data_len == -EINVAL\n", __func__);
-			ret = -EINVAL;
-			goto error_lock;
-		}
-
-		if (io_data->aio) {
-			req = usb_ep_alloc_request(ep->ep, GFP_KERNEL);
-			if (unlikely(!req)) {
-				ret = -ENOMEM;
-				goto error_lock;
-			}
-
-			req->buf      = data;
-			req->length   = data_len;
+		WARN(1, "%s: data_len == -EINVAL\n", __func__);
+		ret = -EINVAL;
+	} else if (!io_data->aio) {
+		DECLARE_COMPLETION_ONSTACK(done);
 
-			io_data->buf = data;
-			io_data->ep = ep->ep;
-			io_data->req = req;
-			io_data->ffs = epfile->ffs;
+		req = ep->req;
+		req->buf      = data;
+		req->length   = data_len;
 
-			req->context  = io_data;
-			req->complete = ffs_epfile_async_io_complete;
+		req->context  = &done;
+		req->complete = ffs_epfile_io_complete;
 
-			ret = usb_ep_queue(ep->ep, req, GFP_ATOMIC);
-			if (unlikely(ret)) {
-				usb_ep_free_request(ep->ep, req);
-				goto error_lock;
-			}
-			ret = -EIOCBQUEUED;
+		ret = usb_ep_queue(ep->ep, req, GFP_ATOMIC);
+		if (unlikely(ret < 0))
+			goto error_lock;
 
-			spin_unlock_irq(&epfile->ffs->eps_lock);
-		} else {
-			DECLARE_COMPLETION_ONSTACK(done);
+		spin_unlock_irq(&epfile->ffs->eps_lock);
 
-			req = ep->req;
-			req->buf      = data;
-			req->length   = data_len;
+		if (unlikely(wait_for_completion_interruptible(&done))) {
+			ret = -EINTR;
+			usb_ep_dequeue(ep->ep, req);
+			goto error_mutex;
+		}
 
-			req->context  = &done;
-			req->complete = ffs_epfile_io_complete;
+		/*
+		 * XXX We may end up silently droping data here.  Since data_len
+		 * (i.e. req->length) may be bigger than len (after being
+		 * rounded up to maxpacketsize), we may end up with more data
+		 * then user space has space for.
+		 */
+		ret = ep->status;
+		if (io_data->read && ret > 0) {
+			ret = copy_to_iter(data, ret, &io_data->data);
+			if (!ret)
+				ret = -EFAULT;
+		}
+		goto error_mutex;
+	} else if (!(req = usb_ep_alloc_request(ep->ep, GFP_KERNEL))) {
+		ret = -ENOMEM;
+	} else {
+		req->buf      = data;
+		req->length   = data_len;
 
-			ret = usb_ep_queue(ep->ep, req, GFP_ATOMIC);
+		io_data->buf = data;
+		io_data->ep = ep->ep;
+		io_data->req = req;
+		io_data->ffs = epfile->ffs;
 
-			spin_unlock_irq(&epfile->ffs->eps_lock);
+		req->context  = io_data;
+		req->complete = ffs_epfile_async_io_complete;
 
-			if (unlikely(ret < 0)) {
-				/* nop */
-			} else if (unlikely(
-				   wait_for_completion_interruptible(&done))) {
-				ret = -EINTR;
-				usb_ep_dequeue(ep->ep, req);
-			} else {
-				/*
-				 * XXX We may end up silently droping data
-				 * here.  Since data_len (i.e. req->length) may
-				 * be bigger than len (after being rounded up
-				 * to maxpacketsize), we may end up with more
-				 * data then user space has space for.
-				 */
-				ret = ep->status;
-				if (io_data->read && ret > 0) {
-					ret = copy_to_iter(data, ret, &io_data->data);
-					if (!ret)
-						ret = -EFAULT;
-				}
-			}
-			kfree(data);
+		ret = usb_ep_queue(ep->ep, req, GFP_ATOMIC);
+		if (unlikely(ret)) {
+			usb_ep_free_request(ep->ep, req);
+			goto error_lock;
 		}
-	}
 
-	mutex_unlock(&epfile->mutex);
-	return ret;
+		ret = -EIOCBQUEUED;
+		/*
+		 * Do not kfree the buffer in this function.  It will be freed
+		 * by ffs_user_copy_worker.
+		 */
+		data = NULL;
+	}
 
 error_lock:
 	spin_unlock_irq(&epfile->ffs->eps_lock);
+error_mutex:
 	mutex_unlock(&epfile->mutex);
 error:
 	kfree(data);