unix: add dm-ioctl constants and types

This interface is used by devicemapper framework to manage its block
devices.

Change-Id: If86a679461867dac18b56bdf005567ffc4b7f951
Reviewed-on: https://go-review.googlesource.com/c/sys/+/247437
Run-TryBot: Ian Lance Taylor <iant@golang.org>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: Ian Lance Taylor <iant@golang.org>

unix/linux/types.go

@@ -85,6 +85,7 @@ struct termios2 {
 #include <linux/cgroupstats.h>
 #include <linux/cryptouser.h>
 #include <linux/devlink.h>
+#include <linux/dm-ioctl.h>
 #include <linux/errqueue.h>
 #include <linux/fanotify.h>
 #include <linux/filter.h>
@@ -471,6 +472,25 @@ type FscryptRemoveKeyArg C.struct_fscrypt_remove_key_arg
 
 type FscryptGetKeyStatusArg C.struct_fscrypt_get_key_status_arg
 
+// Device Mapper
+
+type DmIoctl C.struct_dm_ioctl
+
+type DmTargetSpec C.struct_dm_target_spec
+
+type DmTargetDeps C.struct_dm_target_deps
+
+type DmNameList C.struct_dm_name_list
+
+type DmTargetVersions C.struct_dm_target_versions
+
+type DmTargetMsg C.struct_dm_target_msg
+
+const (
+	SizeofDmIoctl      = C.sizeof_struct_dm_ioctl
+	SizeofDmTargetSpec = C.sizeof_struct_dm_target_spec
+)
+
 // Structure for Keyctl
 
 type KeyctlDHParams C.struct_keyctl_dh_params