USB: gadgetfs AIO tweaks

This patch (as837) fixes several mistakes in the AIO interface of the
gadgetfs driver:

	The ki_retry method is not supposed to do a put on the kiocb.
	The extra call to aio_put_req() causes memory corruption.
	(Note: This call was removed before, by patch as691, and then
	mysteriously re-introduced later.)

	Even if a read transfer is cancelled, we can and should send
	to the user all the data that did manage to get transferred.

	Testing for AIO cancellation in the I/O completion handler
	is both racy and (now) unnecessary.  aio_complete() does its
	own checking, in a safe manner.

Signed-off-by: Alan Stern <stern@rowland.harvard.edu>
Signed-off-by: David Brownell <dbrownell@users.sourceforge.net>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>

diff --git a/drivers/usb/gadget/inode.c b/drivers/usb/gadget/inode.c
index 1c5e1ee..34296e7 100644 (file)
--- a/drivers/usb/gadget/inode.c
+++ b/drivers/usb/gadget/inode.c
@@ -576,7 +576,6 @@ static ssize_t ep_aio_read_retry(struct kiocb *iocb)
        }
        kfree(priv->buf);
        kfree(priv);
-       aio_put_req(iocb);
        return len;
 }
 
@@ -590,18 +589,17 @@ static void ep_aio_complete(struct usb_ep *ep, struct usb_request *req)
        spin_lock(&epdata->dev->lock);
        priv->req = NULL;
        priv->epdata = NULL;
-       if (priv->iv == NULL
-                       || unlikely(req->actual == 0)
-                       || unlikely(kiocbIsCancelled(iocb))) {
+
+       /* if this was a write or a read returning no data then we
+        * don't need to copy anything to userspace, so we can
+        * complete the aio request immediately.
+        */
+       if (priv->iv == NULL || unlikely(req->actual == 0)) {
                kfree(req->buf);
                kfree(priv);
                iocb->private = NULL;
                /* aio_complete() reports bytes-transferred _and_ faults */
-               if (unlikely(kiocbIsCancelled(iocb)))
-                       aio_put_req(iocb);
-               else
-                       aio_complete(iocb,
-                               req->actual ? req->actual : req->status,
+               aio_complete(iocb, req->actual ? req->actual : req->status,
                                req->status);
        } else {
                /* retry() won't report both; so we hide some faults */