UML - Send pointers instead of structures to I/O thread

Index: linux-2.6.21-mm/arch/um/drivers/ubd_kern.c
===================================================================
@@ -503,7 +503,7 @@ static struct list_head restart = LIST_H
 /* Called without dev->lock held, and only in interrupt context. */
 static void ubd_handler(void)
 {
-	struct io_thread_req req;
+	struct io_thread_req *req;
 	struct request *rq;
 	struct ubd *ubd;
 	struct list_head *list, *next_ele;

@@ -511,7 +511,8 @@ static void ubd_handler(void)
 	int n;
 
 	while(1){
-		n = os_read_file_k(thread_fd, &req, sizeof(req));
+		n = os_read_file_k(thread_fd, &req,
+				   sizeof(struct io_thread_req *));
 		if(n != sizeof(req)){
 			if(n == -EAGAIN)
 				break;

@@ -520,10 +521,11 @@ static void ubd_handler(void)
 			return;
 		}
 
-		rq = req.req;
-		rq->nr_sectors -= req.length >> 9;
+		rq = req->req;
+		rq->nr_sectors -= req->length >> 9;
 		if(rq->nr_sectors == 0)
 			ubd_finish(rq, rq->hard_nr_sectors << 9);
+		kfree(req);
 	}
 	reactivate_fd(thread_fd, UBD_IRQ);
 

@@ -1078,7 +1080,7 @@ static void prepare_request(struct reque
 /* Called with dev->lock held */
 static void do_ubd_request(request_queue_t *q)
 {
-	struct io_thread_req io_req;
+	struct io_thread_req *io_req;
 	struct request *req;
 	int n;
 

@@ -1099,13 +1101,20 @@ static void do_ubd_request(request_queue
 		while(dev->start_sg < dev->end_sg){
 			struct scatterlist *sg = &dev->sg[dev->start_sg];
 
-			prepare_request(req, &io_req,
+			io_req = kmalloc(sizeof(struct io_thread_req),
+					 GFP_KERNEL | GFP_ATOMIC);
+			if(io_req == NULL){
+				if(list_empty(&dev->restart))
+					list_add(&dev->restart, &restart);
+				return;
+			}
+			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)){
+			n = os_write_file_k(thread_fd, &io_req,
+					    sizeof(struct io_thread_req *));
+			if(n != sizeof(struct io_thread_req *)){
 				if(n != -EAGAIN)
 					printk("write to io thread failed, "
 					       "errno = %d\n", -n);

@@ -1437,13 +1446,14 @@ static int io_count = 0;
 
 int io_thread(void *arg)
 {
-	struct io_thread_req req;
+	struct io_thread_req *req;
 	int n;
 
 	ignore_sigwinch_sig();
 	while(1){
-		n = os_read_file_k(kernel_fd, &req, sizeof(req));
-		if(n != sizeof(req)){
+		n = os_read_file_k(kernel_fd, &req,
+				 sizeof(struct io_thread_req *));
+		if(n != sizeof(struct io_thread_req *)){
 			if(n < 0)
 				printk("io_thread - read failed, fd = %d, "
 				       "err = %d\n", kernel_fd, -n);

@@ -1454,9 +1464,10 @@ int io_thread(void *arg)
 			continue;
 		}
 		io_count++;
-		do_io(&req);
-		n = os_write_file_k(kernel_fd, &req, sizeof(req));
-		if(n != sizeof(req))
+		do_io(req);
+		n = os_write_file_k(kernel_fd, &req,
+				  sizeof(struct io_thread_req *));
+		if(n != sizeof(struct io_thread_req *))
 			printk("io_thread - write failed, fd = %d, err = %d\n",
 			       kernel_fd, -n);
 	}