Enable previous version support

Add ioctl to query previous versions of file

Allows listing snapshots on files on SMB3 mounts.

Signed-off-by: Steve French <smfrench@gmail.com>
diff --git a/fs/cifs/cifs_ioctl.h b/fs/cifs/cifs_ioctl.h
index 0065256..57ff075 100644
--- a/fs/cifs/cifs_ioctl.h
+++ b/fs/cifs/cifs_ioctl.h
@@ -36,7 +36,15 @@
 	__u64   cifs_posix_caps;
 } __packed;
 
+struct smb_snapshot_array {
+	__u32	number_of_snapshots;
+	__u32	number_of_snapshots_returned;
+	__u32	snapshot_array_size;
+	/*	snapshots[]; */
+} __packed;
+
 #define CIFS_IOCTL_MAGIC	0xCF
 #define CIFS_IOC_COPYCHUNK_FILE	_IOW(CIFS_IOCTL_MAGIC, 3, int)
 #define CIFS_IOC_SET_INTEGRITY  _IO(CIFS_IOCTL_MAGIC, 4)
 #define CIFS_IOC_GET_MNT_INFO _IOR(CIFS_IOCTL_MAGIC, 5, struct smb_mnt_fs_info)
+#define CIFS_ENUMERATE_SNAPSHOTS _IOR(CIFS_IOCTL_MAGIC, 6, struct smb_snapshot_array)