[PATCH -mm 9/10][RFC] aio: usb gadget remove aio file ops

[Nate Diller <nate@agami.com>]

This removes the aio implementation from the usb gadget file system.  Aside
from making very creative (!) use of the aio retry path, it can't be of any
use performance-wise because it always kmalloc()s a bounce buffer for the
*whole* I/O size.  Perhaps the only reason to keep it around is the ability
to cancel I/O requests, which only applies when using the user space async
I/O interface.  I highly doubt that is enough incentive to justify the extra
complexity here or in user-space, so I think it's a safe bet to remove this. 
If that feature still desired, it would be possible to implement a sync
interface that does an interruptible sleep.

I can be convinced otherwise, but the alternatives are difficult.  See for
example the "fuse, get_user_pages, flush_anon_page, aliasing caches and all
that again" LKML thread recently for why it's waaay easier to kmalloc a
bounce buffer here, and (ab)use the retry interface.

---

diff -urpN -X dontdiff a/drivers/usb/gadget/inode.c b/drivers/usb/gadget/inode.c
--- a/drivers/usb/gadget/inode.c	2007-01-10 13:23:46.000000000 -0800
+++ b/drivers/usb/gadget/inode.c	2007-01-10 16:56:09.000000000 -0800
@@ -527,218 +527,6 @@ static int ep_ioctl (struct inode *inode
 
 /*----------------------------------------------------------------------*/
 
-/* ASYNCHRONOUS ENDPOINT I/O OPERATIONS (bulk/intr/iso) */
-
-struct kiocb_priv {
-	struct usb_request	*req;
-	struct ep_data		*epdata;
-	void			*buf;
-	const struct iovec	*iv;
-	unsigned long		nr_segs;
-	unsigned		actual;
-};
-
-static int ep_aio_cancel(struct kiocb *iocb, struct io_event *e)
-{
-	struct kiocb_priv	*priv = iocb->private;
-	struct ep_data		*epdata;
-	int			value;
-
-	local_irq_disable();
-	epdata = priv->epdata;
-	// spin_lock(&epdata->dev->lock);
-	kiocbSetCancelled(iocb);
-	if (likely(epdata && epdata->ep && priv->req))
-		value = usb_ep_dequeue (epdata->ep, priv->req);
-	else
-		value = -EINVAL;
-	// spin_unlock(&epdata->dev->lock);
-	local_irq_enable();
-
-	aio_put_req(iocb);
-	return value;
-}
-
-static int ep_aio_read_retry(struct kiocb *iocb)
-{
-	struct kiocb_priv	*priv = iocb->private;
-	ssize_t			total;
-	int			i, err = 0;
-
-  	/* we "retry" to get the right mm context for this: */
-
- 	/* copy stuff into user buffers */
- 	total = priv->actual;
- 	for (i=0; i < priv->nr_segs; i++) {
- 		ssize_t this = min((ssize_t)(priv->iv[i].iov_len), total);
-
- 		if (copy_to_user(priv->iv[i].iov_base, priv->buf, this)) {
- 			err = -EFAULT;
- 			break;
- 		}
-
- 		total -= this;
- 		if (total == 0)
- 			break;
- 	}
-  	kfree(priv->buf);
-  	kfree(priv);
-  	aio_put_req(iocb);
- 	return err;
-}
-
-static void ep_aio_complete(struct usb_ep *ep, struct usb_request *req)
-{
-	struct kiocb		*iocb = req->context;
-	struct kiocb_priv	*priv = iocb->private;
-	struct ep_data		*epdata = priv->epdata;
-
-	/* lock against disconnect (and ideally, cancel) */
-	spin_lock(&epdata->dev->lock);
-	priv->req = NULL;
-	priv->epdata = NULL;
-	if (priv->iv == NULL
-			|| unlikely(req->actual == 0)
-			|| unlikely(kiocbIsCancelled(iocb))) {
-		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->status);
-	} else {
-		/* retry() won't report both; so we hide some faults */
-		if (unlikely(0 != req->status))
-			DBG(epdata->dev, "%s fault %d len %d\n",
-				ep->name, req->status, req->actual);
-
-		priv->buf = req->buf;
-		priv->actual = req->actual;
-		kick_iocb(iocb);
-	}
-	spin_unlock(&epdata->dev->lock);
-
-	usb_ep_free_request(ep, req);
-	put_ep(epdata);
-}
-
-static ssize_t
-ep_aio_rwtail(
-	struct kiocb	*iocb,
-	char		*buf,
-	size_t		len,
-	struct ep_data	*epdata,
-	const struct iovec *iv,
-	unsigned long 	nr_segs
-)
-{
-	struct kiocb_priv	*priv;
-	struct usb_request	*req;
-	ssize_t			value;
-
-	priv = kmalloc(sizeof *priv, GFP_KERNEL);
-	if (!priv) {
-		value = -ENOMEM;
-fail:
-		kfree(buf);
-		return value;
-	}
-	iocb->private = priv;
-	priv->iv = iv;
-	priv->nr_segs = nr_segs;
-
-	value = get_ready_ep(iocb->ki_filp->f_flags, epdata);
-	if (unlikely(value < 0)) {
-		kfree(priv);
-		goto fail;
-	}
-
-	iocb->ki_cancel = ep_aio_cancel;
-	get_ep(epdata);
-	priv->epdata = epdata;
-	priv->actual = 0;
-
-	/* each kiocb is coupled to one usb_request, but we can't
-	 * allocate or submit those if the host disconnected.
-	 */
-	spin_lock_irq(&epdata->dev->lock);
-	if (likely(epdata->ep)) {
-		req = usb_ep_alloc_request(epdata->ep, GFP_ATOMIC);
-		if (likely(req)) {
-			priv->req = req;
-			req->buf = buf;
-			req->length = len;
-			req->complete = ep_aio_complete;
-			req->context = iocb;
-			value = usb_ep_queue(epdata->ep, req, GFP_ATOMIC);
-			if (unlikely(0 != value))
-				usb_ep_free_request(epdata->ep, req);
-		} else
-			value = -EAGAIN;
-	} else
-		value = -ENODEV;
-	spin_unlock_irq(&epdata->dev->lock);
-
-	up(&epdata->lock);
-
-	if (unlikely(value)) {
-		kfree(priv);
-		put_ep(epdata);
-	} else
-		value = (iv ? -EIOCBRETRY : -EIOCBQUEUED);
-	return value;
-}
-
-static ssize_t
-ep_aio_read(struct kiocb *iocb, const struct iovec *iov,
-		unsigned long nr_segs, loff_t o)
-{
-	struct ep_data		*epdata = iocb->ki_filp->private_data;
-	char			*buf;
-	size_t			len = iov_length(iov, nr_segs);
-
-	if (unlikely(epdata->desc.bEndpointAddress & USB_DIR_IN))
-		return -EINVAL;
-
-	buf = kmalloc(len, GFP_KERNEL);
-	if (unlikely(!buf))
-		return -ENOMEM;
-
-	iocb->ki_retry = ep_aio_read_retry;
-	return ep_aio_rwtail(iocb, buf, len, epdata, iov, nr_segs);
-}
-
-static ssize_t
-ep_aio_write(struct kiocb *iocb, const struct iovec *iov,
-		unsigned long nr_segs, loff_t o)
-{
-	struct ep_data		*epdata = iocb->ki_filp->private_data;
-	char			*buf;
-	size_t			len = 0;
-	int			i = 0;
-
-	if (unlikely(!(epdata->desc.bEndpointAddress & USB_DIR_IN)))
-		return -EINVAL;
-
-	buf = kmalloc(iov_length(iov, nr_segs), GFP_KERNEL);
-	if (unlikely(!buf))
-		return -ENOMEM;
-
-	for (i=0; i < nr_segs; i++) {
-		if (unlikely(copy_from_user(&buf[len], iov[i].iov_base,
-				iov[i].iov_len) != 0)) {
-			kfree(buf);
-			return -EFAULT;
-		}
-		len += iov[i].iov_len;
-	}
-	return ep_aio_rwtail(iocb, buf, len, epdata, NULL, 0);
-}
-
-/*----------------------------------------------------------------------*/
-
 /* used after endpoint configuration */
 static const struct file_operations ep_io_operations = {
 	.owner =	THIS_MODULE,
@@ -748,9 +536,6 @@ static const struct file_operations ep_i
 	.write =	ep_write,
 	.ioctl =	ep_ioctl,
 	.release =	ep_release,
-
-	.aio_read =	ep_aio_read,
-	.aio_write =	ep_aio_write,
 };
 
 /* ENDPOINT INITIALIZATION