linux-user: Add support for two btrfs ioctls used for subvolume

This patch implements functionality for following ioctl:

BTRFS_IOC_DEFAULT_SUBVOL - Setting a default subvolume

    Set a default subvolume for a btrfs filesystem. The third
    ioctl's argument is a '__u64' (unsigned long long) which
    represents the id of a subvolume that is to be set as
    the default.

BTRFS_IOC_GET_SUBVOL_ROOTREF - Getting tree and directory id of subvolumes

    Read tree and directory id of subvolumes from a btrfs
    filesystem. The tree and directory id's are returned in the
    ioctl's third argument which represents a pointer to a
    following type:

    struct btrfs_ioctl_get_subvol_rootref_args {
		/* in/out, minimum id of rootref's treeid to be searched */
		__u64 min_treeid;

		/* out */
		struct {
			__u64 treeid;
			__u64 dirid;
		} rootref[BTRFS_MAX_ROOTREF_BUFFER_NUM];

		/* out, number of found items */
		__u8 num_items;
		__u8 align[7];
     };

     Before calling this ioctl, 'min_treeid' field should be filled
     with value that represent the minimum value for the tree id.

Implementation notes:

    Ioctl BTRFS_IOC_GET_SUBVOL_ROOTREF uses the above mentioned structure
    type as third argument. That is the reason why a aproppriate thunk
    structure definition is added in file 'syscall_types.h'.

Signed-off-by: Filip Bozuta <Filip.Bozuta@syrmia.com>
Tested-by: Daniel P. Berrangé <berrange@redhat.com>
Message-Id: <20200823195014.116226-7-Filip.Bozuta@syrmia.com>
Signed-off-by: Laurent Vivier <laurent@vivier.eu>
diff --git a/linux-user/ioctls.h b/linux-user/ioctls.h
index 2380751..dc2f3d2 100644
--- a/linux-user/ioctls.h
+++ b/linux-user/ioctls.h
@@ -206,6 +206,9 @@
      IOCTL(BTRFS_IOC_INO_LOOKUP, IOC_RW,
            MK_PTR(MK_STRUCT(STRUCT_btrfs_ioctl_ino_lookup_args)))
 #endif
+#ifdef BTRFS_IOC_DEFAULT_SUBVOL
+     IOCTL(BTRFS_IOC_DEFAULT_SUBVOL, IOC_W, MK_PTR(TYPE_ULONGLONG))
+#endif
 #ifdef BTRFS_IOC_SUBVOL_GETFLAGS
      IOCTL(BTRFS_IOC_SUBVOL_GETFLAGS, IOC_R, MK_PTR(TYPE_ULONGLONG))
 #endif
@@ -248,6 +251,10 @@
      IOCTL(BTRFS_IOC_GET_SUBVOL_INFO, IOC_R,
            MK_PTR(MK_STRUCT(STRUCT_btrfs_ioctl_get_subvol_info_args)))
 #endif
+#ifdef BTRFS_IOC_GET_SUBVOL_ROOTREF
+     IOCTL(BTRFS_IOC_GET_SUBVOL_ROOTREF, IOC_RW,
+           MK_PTR(MK_STRUCT(STRUCT_btrfs_ioctl_get_subvol_rootref_args)))
+#endif
 #ifdef BTRFS_IOC_INO_LOOKUP_USER
      IOCTL(BTRFS_IOC_INO_LOOKUP_USER, IOC_RW,
            MK_PTR(MK_STRUCT(STRUCT_btrfs_ioctl_ino_lookup_user_args)))