compat_hdio_ioctl: get rid of set_fs()

Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>

block/compat_ioctl.c

@@ -79,19 +79,16 @@ static int compat_hdio_getgeo(struct gendisk *disk, struct block_device *bdev,
 static int compat_hdio_ioctl(struct block_device *bdev, fmode_t mode,
 		unsigned int cmd, unsigned long arg)
 {
-	mm_segment_t old_fs = get_fs();
-	unsigned long kval;
-	unsigned int __user *uvp;
+	unsigned long *__user p;
 	int error;
 
-	set_fs(KERNEL_DS);
+	p = compat_alloc_user_space(sizeof(unsigned long));
 	error = __blkdev_driver_ioctl(bdev, mode,
-				cmd, (unsigned long)(&kval));
-	set_fs(old_fs);
-
+				cmd, (unsigned long)p);
 	if (error == 0) {
-		uvp = compat_ptr(arg);
-		if (put_user(kval, uvp))
+		unsigned int __user *uvp = compat_ptr(arg);
+		unsigned long v;
+		if (get_user(v, p) || put_user(v, uvp))
 			error = -EFAULT;
 	}
 	return error;