[AIO] fix sync iocb use of retry mechanism

When the sync infrastructure is used to run a retry using read/write, 
we need to correctly use the buffer offset and byte counts from the 
iocb on subsequent calls to the aio method.

Signed-off-by: Benjamin LaHaise <bcrl@linux.intel.com>
diff -purN --exclude=description 55_iocb_intr/fs/read_write.c 57_intr_cancel/fs/read_write.c
--- 55_iocb_intr/fs/read_write.c	2005-08-08 17:15:42.000000000 -0400
+++ 57_intr_cancel/fs/read_write.c	2005-08-08 17:15:45.000000000 -0400
@@ -203,16 +203,33 @@ Einval:
 	return -EINVAL;
 }
 
-static void wait_on_retry_sync_kiocb(struct kiocb *iocb)
+static long wait_on_retry_sync_kiocb(struct kiocb *iocb)
 {
+	long (*cancel)(struct kiocb *, struct io_event *);
+	long ret = 0;
 	set_current_state(kiocbIsIntr(iocb) ? TASK_INTERRUPTIBLE
 					    : TASK_UNINTERRUPTIBLE);
 	if (!kiocbIsKicked(iocb))
 		schedule();
 	else
 		kiocbClearKicked(iocb);
+
+	/* If we were interrupted by a signal, issue a cancel to allow the
+	 * operation to clean up.
+	 */
+	cancel = iocb->ki_cancel;
+	if (kiocbIsIntr(iocb) && signal_pending(current) && cancel) {
+		struct io_event dummy_event;
+		dummy_event.res = 0;
+		if (!cancel(iocb, &dummy_event)) {
+			ret = dummy_event.res;
+			if (!ret)
+				printk(KERN_DEBUG "wait_on_retry_sync_kiocb: ki_cancel method %p is buggy\n", cancel);
+		}
+	}
 	kiocbClearIntr(iocb);
 	__set_current_state(TASK_RUNNING);
+	return ret;
 }
 
 ssize_t do_sync_read(struct file *filp, char __user *buf, size_t len, loff_t *ppos)
@@ -222,12 +239,16 @@ ssize_t do_sync_read(struct file *filp, 
 
 	init_sync_kiocb(&kiocb, filp);
 	kiocb.ki_pos = *ppos;
-	while (-EIOCBRETRY ==
-		(ret = filp->f_op->aio_read(&kiocb, buf, len, kiocb.ki_pos)))
-		wait_on_retry_sync_kiocb(&kiocb);
+	while (-EIOCBRETRY == 
+		(ret = filp->f_op->aio_read(&kiocb, buf, len, kiocb.ki_pos))) {
+		ret = wait_on_retry_sync_kiocb(&kiocb);
+		if (ret)
+			break;
+	}
 
 	if (-EIOCBQUEUED == ret)
 		ret = wait_on_sync_kiocb(&kiocb);
+	BUG_ON(!list_empty(&kiocb.ki_wait.task_list));
 	*ppos = kiocb.ki_pos;
 	return ret;
 }
@@ -273,12 +294,16 @@ ssize_t do_sync_write(struct file *filp,
 
 	init_sync_kiocb(&kiocb, filp);
 	kiocb.ki_pos = *ppos;
-	while (-EIOCBRETRY ==
-	       (ret = filp->f_op->aio_write(&kiocb, buf, len, kiocb.ki_pos)))
-		wait_on_retry_sync_kiocb(&kiocb);
+	while (-EIOCBRETRY == 
+	       (ret = filp->f_op->aio_write(&kiocb, buf, len, kiocb.ki_pos))) {
+		ret = wait_on_retry_sync_kiocb(&kiocb);
+		if (ret)
+			break;
+	}
 
 	if (-EIOCBQUEUED == ret)
 		ret = wait_on_sync_kiocb(&kiocb);
+	BUG_ON(!list_empty(&kiocb.ki_wait.task_list));
 	*ppos = kiocb.ki_pos;
 	return ret;
 }