cdrom: factor out a cdrom_multisession helper

Factor out a version of the CDROMMULTISESSION ioctl handler that can
be called directly from kernel space.
Signed-off-by: Christoph Hellwig <hch@lst.de>
Reviewed-by: Damien Le Moal <damien.lemoal@wdc.com>
Reviewed-by: Hannes Reinecke <hare@suse.de>
Signed-off-by: Jens Axboe <axboe@kernel.dk>

drivers/cdrom/cdrom.c

@@ -2295,37 +2295,46 @@ static int cdrom_read_cdda(struct cdrom_device_info *cdi, __u8 __user *ubuf,
 	return cdrom_read_cdda_old(cdi, ubuf, lba, nframes);	
 }
 
-static int cdrom_ioctl_multisession(struct cdrom_device_info *cdi,
-		void __user *argp)
+int cdrom_multisession(struct cdrom_device_info *cdi,
+		struct cdrom_multisession *info)
 {
-	struct cdrom_multisession ms_info;
 	u8 requested_format;
 	int ret;
 
-	cd_dbg(CD_DO_IOCTL, "entering CDROMMULTISESSION\n");
-
 	if (!(cdi->ops->capability & CDC_MULTI_SESSION))
 		return -ENOSYS;
 
-	if (copy_from_user(&ms_info, argp, sizeof(ms_info)))
-		return -EFAULT;
-
-	requested_format = ms_info.addr_format;
+	requested_format = info->addr_format;
 	if (requested_format != CDROM_MSF && requested_format != CDROM_LBA)
 		return -EINVAL;
-	ms_info.addr_format = CDROM_LBA;
+	info->addr_format = CDROM_LBA;
 
-	ret = cdi->ops->get_last_session(cdi, &ms_info);
-	if (ret)
-		return ret;
+	ret = cdi->ops->get_last_session(cdi, info);
+	if (!ret)
+		sanitize_format(&info->addr, &info->addr_format,
+				requested_format);
+	return ret;
+}
+EXPORT_SYMBOL_GPL(cdrom_multisession);
 
-	sanitize_format(&ms_info.addr, &ms_info.addr_format, requested_format);
+static int cdrom_ioctl_multisession(struct cdrom_device_info *cdi,
+		void __user *argp)
+{
+	struct cdrom_multisession info;
+	int ret;
+
+	cd_dbg(CD_DO_IOCTL, "entering CDROMMULTISESSION\n");
 
-	if (copy_to_user(argp, &ms_info, sizeof(ms_info)))
+	if (copy_from_user(&info, argp, sizeof(info)))
+		return -EFAULT;
+	ret = cdrom_multisession(cdi, &info);
+	if (ret)
+		return ret;
+	if (copy_to_user(argp, &info, sizeof(info)))
 		return -EFAULT;
 
 	cd_dbg(CD_DO_IOCTL, "CDROMMULTISESSION successful\n");
-	return 0;
+	return ret;
 }
 
 static int cdrom_ioctl_eject(struct cdrom_device_info *cdi)

include/linux/cdrom.h

@@ -94,6 +94,8 @@ struct cdrom_device_ops {
 			       struct packet_command *);
 };
 
+int cdrom_multisession(struct cdrom_device_info *cdi,
+		struct cdrom_multisession *info);
 int cdrom_read_tocentry(struct cdrom_device_info *cdi,
 		struct cdrom_tocentry *entry);