usb: gadget: f_fs: remove loop from I/O function

When endpoint changes (due to it being disabled or alt setting changed),
mimic the action as if the change happened after the request has been
queued, instead of retrying with the new endpoint.
Signed-off-by: Michal Nazarewicz <mina86@mina86.com>
Cc: David Cohen <david.a.cohen@linux.intel.com>
Signed-off-by: Felipe Balbi <balbi@ti.com>

drivers/usb/gadget/f_fs.c

@@ -758,12 +758,6 @@ static ssize_t ffs_epfile_io(struct file *file,
 	ssize_t ret;
 	int halt;
 
-	goto first_try;
-	do {
-		spin_unlock_irq(&epfile->ffs->eps_lock);
-		mutex_unlock(&epfile->mutex);
-
-first_try:
 	/* Are we still active? */
 	if (WARN_ON(epfile->ffs->state != FFS_ACTIVE)) {
 		ret = -ENODEV;
@@ -778,8 +772,8 @@ static ssize_t ffs_epfile_io(struct file *file,
 			goto error;
 		}
 
-			if (wait_event_interruptible(epfile->wait,
-						     (ep = epfile->ep))) {
+		ret = wait_event_interruptible(epfile->wait, (ep = epfile->ep));
+		if (ret) {
 			ret = -EINTR;
 			goto error;
 		}
@@ -793,38 +787,30 @@ static ssize_t ffs_epfile_io(struct file *file,
 	}
 
 	/* Allocate & copy */
-		if (!halt && !data) {
-			data = kzalloc(len, GFP_KERNEL);
+	if (!halt) {
+		data = kmalloc(len, GFP_KERNEL);
 		if (unlikely(!data))
 			return -ENOMEM;
 
-			if (!read &&
-			    unlikely(__copy_from_user(data, buf, len))) {
+		if (!read && unlikely(copy_from_user(data, buf, len))) {
 			ret = -EFAULT;
 			goto error;
 		}
 	}
 
 	/* We will be using request */
-		ret = ffs_mutex_lock(&epfile->mutex,
-				     file->f_flags & O_NONBLOCK);
+	ret = ffs_mutex_lock(&epfile->mutex, file->f_flags & O_NONBLOCK);
 	if (unlikely(ret))
 		goto error;
 
-		/*
-		 * We're called from user space, we can use _irq rather then
-		 * _irqsave
-		 */
 	spin_lock_irq(&epfile->ffs->eps_lock);
 
-		/*
-		 * While we were acquiring mutex endpoint got disabled
-		 * or changed?
-		 */
-	} while (unlikely(epfile->ep != ep));
-
+	if (epfile->ep != ep) {
+		/* In the meantime, endpoint got disabled or changed. */
+		ret = -ESHUTDOWN;
+		spin_unlock_irq(&epfile->ffs->eps_lock);
+	} else if (halt) {
 		/* Halt */
-	if (unlikely(halt)) {
 		if (likely(epfile->ep == ep) && !WARN_ON(!ep->ep))
 			usb_ep_set_halt(ep->ep);
 		spin_unlock_irq(&epfile->ffs->eps_lock);