usb: gadget: f_fs: add aio support

This patch adds asynchronous I/O support for FunctionFS endpoint files.
It adds ffs_epfile_aio_write() and ffs_epfile_aio_read() functions responsible
for preparing AIO operations.

It also modifies ffs_epfile_io() function, adding aio handling code. Instead
of extending list of parameters of this function, there is new struct
ffs_io_data which contains all information needed to perform I/O operation.
Pointer to this struct replaces "buf" and "len" parameters of ffs_epfile_io()
function. Allocated buffer is freed immediately only after sync operation,
because in async IO it's freed in complete funcion. For each async operation
an USB request is allocated, because it allows to have more than one request
queued on single endpoint.

According to changes in ffs_epfile_io() function, functions ffs_epfile_write()
and ffs_epfile_read() are updated to use new API.

For asynchronous I/O operations there is new request complete function named
ffs_epfile_async_io_complete(), which completes AIO operation, and frees
used memory.
Signed-off-by: Robert Baldyga <r.baldyga@samsung.com>
Acked-by: Michal Nazarewicz <mina86@mina86.com>
Signed-off-by: Felipe Balbi <balbi@ti.com>

drivers/usb/gadget/f_fs.c

@@ -28,6 +28,8 @@
 #include <linux/usb/composite.h>
 #include <linux/usb/functionfs.h>
 
+#include <linux/aio.h>
+#include <linux/mmu_context.h>
 #include <linux/poll.h>
 
 #include "u_fs.h"
@@ -158,6 +160,25 @@ struct ffs_epfile {
 	unsigned char			_pad;
 };
 
+/*  ffs_io_data structure ***************************************************/
+
+struct ffs_io_data {
+	bool aio;
+	bool read;
+
+	struct kiocb *kiocb;
+	const struct iovec *iovec;
+	unsigned long nr_segs;
+	char __user *buf;
+	size_t len;
+
+	struct mm_struct *mm;
+	struct work_struct work;
+
+	struct usb_ep *ep;
+	struct usb_request *req;
+};
+
 static int  __must_check ffs_epfiles_create(struct ffs_data *ffs);
 static void ffs_epfiles_destroy(struct ffs_epfile *epfiles, unsigned count);
 
@@ -635,8 +656,52 @@ static void ffs_epfile_io_complete(struct usb_ep *_ep, struct usb_request *req)
 	}
 }
 
-static ssize_t ffs_epfile_io(struct file *file,
-			     char __user *buf, size_t len, int read)
+static void ffs_user_copy_worker(struct work_struct *work)
+{
+	struct ffs_io_data *io_data = container_of(work, struct ffs_io_data,
+						   work);
+	int ret = io_data->req->status ? io_data->req->status :
+					 io_data->req->actual;
+
+	if (io_data->read && ret > 0) {
+		int i;
+		size_t pos = 0;
+		use_mm(io_data->mm);
+		for (i = 0; i < io_data->nr_segs; i++) {
+			if (unlikely(copy_to_user(io_data->iovec[i].iov_base,
+						 &io_data->buf[pos],
+						 io_data->iovec[i].iov_len))) {
+				ret = -EFAULT;
+				break;
+			}
+			pos += io_data->iovec[i].iov_len;
+		}
+		unuse_mm(io_data->mm);
+	}
+
+	aio_complete(io_data->kiocb, ret, ret);
+
+	usb_ep_free_request(io_data->ep, io_data->req);
+
+	io_data->kiocb->private = NULL;
+	if (io_data->read)
+		kfree(io_data->iovec);
+	kfree(io_data->buf);
+	kfree(io_data);
+}
+
+static void ffs_epfile_async_io_complete(struct usb_ep *_ep,
+					 struct usb_request *req)
+{
+	struct ffs_io_data *io_data = req->context;
+
+	ENTER();
+
+	INIT_WORK(&io_data->work, ffs_user_copy_worker);
+	schedule_work(&io_data->work);
+}
+
+static ssize_t ffs_epfile_io(struct file *file, struct ffs_io_data *io_data)
 {
 	struct ffs_epfile *epfile = file->private_data;
 	struct usb_gadget *gadget = epfile->ffs->gadget;
@@ -667,7 +732,7 @@ static ssize_t ffs_epfile_io(struct file *file,
 	}
 
 	/* Do we halt? */
-	halt = !read == !epfile->in;
+	halt = (!io_data->read == !epfile->in);
 	if (halt && epfile->isoc) {
 		ret = -EINVAL;
 		goto error;
@@ -679,15 +744,32 @@ static ssize_t ffs_epfile_io(struct file *file,
 		 * Controller may require buffer size to be aligned to
 		 * maxpacketsize of an out endpoint.
 		 */
-		data_len = read ? usb_ep_align_maybe(gadget, ep->ep, len) : len;
+		data_len = io_data->read ?
+			   usb_ep_align_maybe(gadget, ep->ep, io_data->len) :
+			   io_data->len;
 
 		data = kmalloc(data_len, GFP_KERNEL);
 		if (unlikely(!data))
 			return -ENOMEM;
-
-		if (!read && unlikely(copy_from_user(data, buf, len))) {
-			ret = -EFAULT;
-			goto error;
+		if (io_data->aio && !io_data->read) {
+			int i;
+			size_t pos = 0;
+			for (i = 0; i < io_data->nr_segs; i++) {
+				if (unlikely(copy_from_user(&data[pos],
+					     io_data->iovec[i].iov_base,
+					     io_data->iovec[i].iov_len))) {
+					ret = -EFAULT;
+					goto error;
+				}
+				pos += io_data->iovec[i].iov_len;
+			}
+		} else {
+			if (!io_data->read &&
+			    unlikely(__copy_from_user(data, io_data->buf,
+						      io_data->len))) {
+				ret = -EFAULT;
+				goto error;
+			}
 		}
 	}
 
@@ -710,24 +792,52 @@ static ssize_t ffs_epfile_io(struct file *file,
 		ret = -EBADMSG;
 	} else {
 		/* Fire the request */
-		DECLARE_COMPLETION_ONSTACK(done);
+		struct usb_request *req;
 
-		struct usb_request *req = ep->req;
-		req->context  = &done;
-		req->complete = ffs_epfile_io_complete;
-		req->buf      = data;
-		req->length   = data_len;
+		if (io_data->aio) {
+			req = usb_ep_alloc_request(ep->ep, GFP_KERNEL);
+			if (unlikely(!req))
+				goto error;
 
-		ret = usb_ep_queue(ep->ep, req, GFP_ATOMIC);
+			req->buf      = data;
+			req->length   = io_data->len;
 
-		spin_unlock_irq(&epfile->ffs->eps_lock);
+			io_data->buf = data;
+			io_data->ep = ep->ep;
+			io_data->req = req;
 
-		if (unlikely(ret < 0)) {
-			/* nop */
-		} else if (unlikely(wait_for_completion_interruptible(&done))) {
-			ret = -EINTR;
-			usb_ep_dequeue(ep->ep, req);
+			req->context  = io_data;
+			req->complete = ffs_epfile_async_io_complete;
+
+			ret = usb_ep_queue(ep->ep, req, GFP_ATOMIC);
+			if (unlikely(ret)) {
+				usb_ep_free_request(ep->ep, req);
+				goto error;
+			}
+			ret = -EIOCBQUEUED;
+
+			spin_unlock_irq(&epfile->ffs->eps_lock);
 		} else {
+			DECLARE_COMPLETION_ONSTACK(done);
+
+			req = ep->req;
+			req->buf      = data;
+			req->length   = io_data->len;
+
+			req->context  = &done;
+			req->complete = ffs_epfile_io_complete;
+
+			ret = usb_ep_queue(ep->ep, req, GFP_ATOMIC);
+
+			spin_unlock_irq(&epfile->ffs->eps_lock);
+
+			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
@@ -736,14 +846,18 @@ static ssize_t ffs_epfile_io(struct file *file,
 			 * space for.
 			 */
 			ret = ep->status;
-			if (read && ret > 0 &&
-			    unlikely(copy_to_user(buf, data,
-						  min_t(size_t, ret, len))))
+			if (io_data->read && ret > 0 &&
+			    unlikely(copy_to_user(io_data->buf, data,
+						  min_t(size_t, ret,
+						  io_data->len))))
 				ret = -EFAULT;
+			}
+			kfree(data);
 		}
 	}
 
 	mutex_unlock(&epfile->mutex);
+	return ret;
 error:
 	kfree(data);
 	return ret;
@@ -753,17 +867,31 @@ static ssize_t
 ffs_epfile_write(struct file *file, const char __user *buf, size_t len,
 		 loff_t *ptr)
 {
+	struct ffs_io_data io_data;
+
 	ENTER();
 
-	return ffs_epfile_io(file, (char __user *)buf, len, 0);
+	io_data.aio = false;
+	io_data.read = false;
+	io_data.buf = (char * __user)buf;
+	io_data.len = len;
+
+	return ffs_epfile_io(file, &io_data);
 }
 
 static ssize_t
 ffs_epfile_read(struct file *file, char __user *buf, size_t len, loff_t *ptr)
 {
+	struct ffs_io_data io_data;
+
 	ENTER();
 
-	return ffs_epfile_io(file, buf, len, 1);
+	io_data.aio = false;
+	io_data.read = true;
+	io_data.buf = buf;
+	io_data.len = len;
+
+	return ffs_epfile_io(file, &io_data);
 }
 
 static int
@@ -782,6 +910,89 @@ ffs_epfile_open(struct inode *inode, struct file *file)
 	return 0;
 }
 
+static int ffs_aio_cancel(struct kiocb *kiocb)
+{
+	struct ffs_io_data *io_data = kiocb->private;
+	struct ffs_epfile *epfile = kiocb->ki_filp->private_data;
+	int value;
+
+	ENTER();
+
+	spin_lock_irq(&epfile->ffs->eps_lock);
+
+	if (likely(io_data && io_data->ep && io_data->req))
+		value = usb_ep_dequeue(io_data->ep, io_data->req);
+	else
+		value = -EINVAL;
+
+	spin_unlock_irq(&epfile->ffs->eps_lock);
+
+	return value;
+}
+
+static ssize_t ffs_epfile_aio_write(struct kiocb *kiocb,
+				    const struct iovec *iovec,
+				    unsigned long nr_segs, loff_t loff)
+{
+	struct ffs_io_data *io_data;
+
+	ENTER();
+
+	io_data = kmalloc(sizeof(*io_data), GFP_KERNEL);
+	if (unlikely(!io_data))
+		return -ENOMEM;
+
+	io_data->aio = true;
+	io_data->read = false;
+	io_data->kiocb = kiocb;
+	io_data->iovec = iovec;
+	io_data->nr_segs = nr_segs;
+	io_data->len = kiocb->ki_nbytes;
+	io_data->mm = current->mm;
+
+	kiocb->private = io_data;
+
+	kiocb_set_cancel_fn(kiocb, ffs_aio_cancel);
+
+	return ffs_epfile_io(kiocb->ki_filp, io_data);
+}
+
+static ssize_t ffs_epfile_aio_read(struct kiocb *kiocb,
+				   const struct iovec *iovec,
+				   unsigned long nr_segs, loff_t loff)
+{
+	struct ffs_io_data *io_data;
+	struct iovec *iovec_copy;
+
+	ENTER();
+
+	iovec_copy = kmalloc_array(nr_segs, sizeof(*iovec_copy), GFP_KERNEL);
+	if (unlikely(!iovec_copy))
+		return -ENOMEM;
+
+	memcpy(iovec_copy, iovec, sizeof(struct iovec)*nr_segs);
+
+	io_data = kmalloc(sizeof(*io_data), GFP_KERNEL);
+	if (unlikely(!io_data)) {
+		kfree(iovec_copy);
+		return -ENOMEM;
+	}
+
+	io_data->aio = true;
+	io_data->read = true;
+	io_data->kiocb = kiocb;
+	io_data->iovec = iovec_copy;
+	io_data->nr_segs = nr_segs;
+	io_data->len = kiocb->ki_nbytes;
+	io_data->mm = current->mm;
+
+	kiocb->private = io_data;
+
+	kiocb_set_cancel_fn(kiocb, ffs_aio_cancel);
+
+	return ffs_epfile_io(kiocb->ki_filp, io_data);
+}
+
 static int
 ffs_epfile_release(struct inode *inode, struct file *file)
 {
@@ -838,6 +1049,8 @@ static const struct file_operations ffs_epfile_operations = {
 	.open =		ffs_epfile_open,
 	.write =	ffs_epfile_write,
 	.read =		ffs_epfile_read,
+	.aio_write =	ffs_epfile_aio_write,
+	.aio_read =	ffs_epfile_aio_read,
 	.release =	ffs_epfile_release,
 	.unlocked_ioctl =	ffs_epfile_ioctl,
 };