diff --git a/arch/um/drivers/ubd_kern.c b/arch/um/drivers/ubd_kern.c
index 6d163c9e28857773bc0c0fc05c36e262a04fbb36..5ef47b73ce99d3f0f1b4bfba6b088128a0e10746 100644
--- a/arch/um/drivers/ubd_kern.c
+++ b/arch/um/drivers/ubd_kern.c
@@ -149,7 +149,10 @@ struct cow {
         int data_offset;
 };
 
+#define MAX_SG 64
+
 struct ubd {
+	struct list_head restart;
 	/* name (and fd, below) of the file opened for writing, either the
 	 * backing or the cow file. */
 	char *file;
@@ -164,7 +167,9 @@ struct ubd {
 	struct platform_device pdev;
 	struct request_queue *queue;
 	spinlock_t lock;
-	int active;
+	struct scatterlist sg[MAX_SG];
+	struct request *request;
+	int start_sg, end_sg;
 };
 
 #define DEFAULT_COW { \
@@ -186,7 +191,9 @@ struct ubd {
 	.shared =		0, \
         .cow =			DEFAULT_COW, \
 	.lock =			SPIN_LOCK_UNLOCKED,	\
-	.active =		0, \
+	.request =		NULL, \
+	.start_sg =		0, \
+	.end_sg =		0, \
 }
 
 /* Protected by ubd_lock */
@@ -466,60 +473,67 @@ static void do_ubd_request(request_queue_t * q);
 /* Only changed by ubd_init, which is an initcall. */
 int thread_fd = -1;
 
-/* call ubd_finish if you need to serialize */
-static void __ubd_finish(struct request *req, int error)
+static void ubd_end_request(struct request *req, int bytes, int uptodate)
 {
-	int nsect;
-
-	if(error){
-		end_request(req, 0);
-		return;
+	if (!end_that_request_first(req, uptodate, bytes >> 9)) {
+		struct ubd *dev = req->rq_disk->private_data;
+		unsigned long flags;
+
+		add_disk_randomness(req->rq_disk);
+		spin_lock_irqsave(&dev->lock, flags);
+		end_that_request_last(req, uptodate);
+		spin_unlock_irqrestore(&dev->lock, flags);
 	}
-	nsect = req->current_nr_sectors;
-	req->sector += nsect;
-	req->buffer += nsect << 9;
-	req->errors = 0;
-	req->nr_sectors -= nsect;
-	req->current_nr_sectors = 0;
-	end_request(req, 1);
 }
 
 /* Callable only from interrupt context - otherwise you need to do
  * spin_lock_irq()/spin_lock_irqsave() */
-static inline void ubd_finish(struct request *req, int error)
+static inline void ubd_finish(struct request *req, int bytes)
 {
-	struct ubd *dev = req->rq_disk->private_data;
-
-	spin_lock(&dev->lock);
-	__ubd_finish(req, error);
-	spin_unlock(&dev->lock);
+	if(bytes < 0){
+		ubd_end_request(req, 0, 0);
+		return;
+	}
+	ubd_end_request(req, bytes, 1);
 }
 
+static LIST_HEAD(restart);
+
 /* XXX - move this inside ubd_intr. */
 /* Called without dev->lock held, and only in interrupt context. */
 static void ubd_handler(void)
 {
 	struct io_thread_req req;
 	struct request *rq;
-	struct ubd *dev;
+	struct ubd *ubd;
+	struct list_head *list, *next_ele;
+	unsigned long flags;
 	int n;
 
-	n = os_read_file_k(thread_fd, &req, sizeof(req));
-	if(n != sizeof(req)){
-		printk(KERN_ERR "Pid %d - spurious interrupt in ubd_handler, "
-		       "err = %d\n", os_getpid(), -n);
-		return;
-	}
-
-	rq = req.req;
-	dev = rq->rq_disk->private_data;
-	dev->active = 0;
+	while(1){
+		n = os_read_file_k(thread_fd, &req, sizeof(req));
+		if(n != sizeof(req)){
+			if(n == -EAGAIN)
+				break;
+			printk(KERN_ERR "spurious interrupt in ubd_handler, "
+			       "err = %d\n", -n);
+			return;
+		}
 
-	ubd_finish(rq, req.error);
+		rq = req.req;
+		rq->nr_sectors -= req.length >> 9;
+		if(rq->nr_sectors == 0)
+			ubd_finish(rq, rq->hard_nr_sectors << 9);
+	}
 	reactivate_fd(thread_fd, UBD_IRQ);
-	spin_lock(&dev->lock);
-	do_ubd_request(dev->queue);
-	spin_unlock(&dev->lock);
+
+	list_for_each_safe(list, next_ele, &restart){
+		ubd = container_of(list, struct ubd, restart);
+		list_del_init(&ubd->restart);
+		spin_lock_irqsave(&ubd->lock, flags);
+		do_ubd_request(ubd->queue);
+		spin_unlock_irqrestore(&ubd->lock, flags);
+	}
 }
 
 static irqreturn_t ubd_intr(int irq, void *dev)
@@ -684,6 +698,8 @@ static int ubd_add(int n, char **error_out)
 
 	ubd_dev->size = ROUND_BLOCK(ubd_dev->size);
 
+	INIT_LIST_HEAD(&ubd_dev->restart);
+
 	err = -ENOMEM;
 	ubd_dev->queue = blk_init_queue(do_ubd_request, &ubd_dev->lock);
 	if (ubd_dev->queue == NULL) {
@@ -692,6 +708,7 @@ static int ubd_add(int n, char **error_out)
 	}
 	ubd_dev->queue->queuedata = ubd_dev;
 
+	blk_queue_max_hw_segments(ubd_dev->queue, MAX_SG);
 	err = ubd_disk_register(MAJOR_NR, ubd_dev->size, n, &ubd_gendisk[n]);
 	if(err){
 		*error_out = "Failed to register device";
@@ -1029,26 +1046,16 @@ static void cowify_req(struct io_thread_req *req, unsigned long *bitmap,
 }
 
 /* Called with dev->lock held */
-static int prepare_request(struct request *req, struct io_thread_req *io_req)
+static void prepare_request(struct request *req, struct io_thread_req *io_req,
+			    unsigned long long offset, int page_offset,
+			    int len, struct page *page)
 {
 	struct gendisk *disk = req->rq_disk;
 	struct ubd *ubd_dev = disk->private_data;
-	__u64 offset;
-	int len;
-
-	/* This should be impossible now */
-	if((rq_data_dir(req) == WRITE) && !ubd_dev->openflags.w){
-		printk("Write attempted on readonly ubd device %s\n",
-		       disk->disk_name);
-		end_request(req, 0);
-		return(1);
-	}
-
-	offset = ((__u64) req->sector) << 9;
-	len = req->current_nr_sectors << 9;
 
 	io_req->req = req;
-	io_req->fds[0] = (ubd_dev->cow.file != NULL) ? ubd_dev->cow.fd : ubd_dev->fd;
+	io_req->fds[0] = (ubd_dev->cow.file != NULL) ? ubd_dev->cow.fd :
+		ubd_dev->fd;
 	io_req->fds[1] = ubd_dev->fd;
 	io_req->cow_offset = -1;
 	io_req->offset = offset;
@@ -1059,14 +1066,13 @@ static int prepare_request(struct request *req, struct io_thread_req *io_req)
 	io_req->op = (rq_data_dir(req) == READ) ? UBD_READ : UBD_WRITE;
 	io_req->offsets[0] = 0;
 	io_req->offsets[1] = ubd_dev->cow.data_offset;
-	io_req->buffer = req->buffer;
+	io_req->buffer = page_address(page) + page_offset;
 	io_req->sectorsize = 1 << 9;
 
 	if(ubd_dev->cow.file != NULL)
-		cowify_req(io_req, ubd_dev->cow.bitmap, ubd_dev->cow.bitmap_offset,
-			   ubd_dev->cow.bitmap_len);
+		cowify_req(io_req, ubd_dev->cow.bitmap,
+			   ubd_dev->cow.bitmap_offset, ubd_dev->cow.bitmap_len);
 
-	return(0);
 }
 
 /* Called with dev->lock held */
@@ -1074,29 +1080,45 @@ static void do_ubd_request(request_queue_t *q)
 {
 	struct io_thread_req io_req;
 	struct request *req;
-	int err, n;
-
-	if(thread_fd == -1){
-		while((req = elv_next_request(q)) != NULL){
-			err = prepare_request(req, &io_req);
-			if(!err){
-				do_io(&io_req);
-				__ubd_finish(req, io_req.error);
-			}
-		}
-	}
-	else {
+	int n;
+
+	while(1){
 		struct ubd *dev = q->queuedata;
-		if(dev->active || (req = elv_next_request(q)) == NULL)
-			return;
-		err = prepare_request(req, &io_req);
-		if(!err){
-			dev->active = 1;
-			n = os_write_file_k(thread_fd, &io_req, sizeof(io_req));
-			if(n != sizeof(io_req))
-				printk("write to io thread failed, "
-				       "errno = %d\n", -n);
+		if(dev->end_sg == 0){
+			struct request *req = elv_next_request(q);
+			if(req == NULL)
+				return;
+
+			dev->request = req;
+			blkdev_dequeue_request(req);
+			dev->start_sg = 0;
+			dev->end_sg = blk_rq_map_sg(q, req, dev->sg);
+		}
+
+		req = dev->request;
+		while(dev->start_sg < dev->end_sg){
+			struct scatterlist *sg = &dev->sg[dev->start_sg];
+
+			prepare_request(req, &io_req,
+					(unsigned long long) req->sector << 9,
+					sg->offset, sg->length, sg->page);
+
+			n = os_write_file_k(thread_fd, (char *) &io_req,
+					    sizeof(io_req));
+			if(n != sizeof(io_req)){
+				if(n != -EAGAIN)
+					printk("write to io thread failed, "
+					       "errno = %d\n", -n);
+				else if(list_empty(&dev->restart))
+					list_add(&dev->restart, &restart);
+				return;
+			}
+
+			req->sector += sg->length >> 9;
+			dev->start_sg++;
 		}
+		dev->end_sg = 0;
+		dev->request = NULL;
 	}
 }