])
])
+dnl #
+dnl # 3.3 API change
+dnl # The super_block structure was changed to use an hlist_node instead
+dnl # of a list_head for the .s_instance linkage.
+dnl #
+dnl # This was done in part to resolve a race in the iterate_supers_type()
+dnl # function which was introduced in Linux 3.0 kernel. The iterator
+dnl # was supposed to provide a safe way to call an arbitrary function on
+dnl # all super blocks of a specific type. Unfortunately, because a
+dnl # list_head was used it was possible for iterate_supers_type() to
+dnl # get stuck spinning a super block which was just deactivated.
+dnl #
+dnl # This can occur because when the list head is removed from the
+dnl # fs_supers list it is reinitialized to point to itself. If the
+dnl # iterate_supers_type() function happened to be processing the
+dnl # removed list_head it will get stuck spinning on that list_head.
+dnl #
+dnl # To resolve the issue for existing 3.0 - 3.2 kernels we detect when
+dnl # a list_head is used. Then to prevent the spinning from occurring
+dnl # the .next pointer is set to the fs_supers list_head which ensures
+dnl # the iterate_supers_type() function will always terminate.
+dnl #
+AC_DEFUN([ZFS_AC_KERNEL_S_INSTANCES_LIST_HEAD], [
+ AC_MSG_CHECKING([whether super_block has s_instances list_head])
+ ZFS_LINUX_TRY_COMPILE([
+ #include <linux/fs.h>
+ ],[
+ struct super_block sb __attribute__ ((unused));
+
+ INIT_LIST_HEAD(&sb.s_instances);
+ ],[
+ AC_MSG_RESULT(yes)
+ AC_DEFINE(HAVE_S_INSTANCES_LIST_HEAD, 1,
+ [struct super_block has s_instances list_head])
+ ],[
+ AC_MSG_RESULT(no)
+ ])
+])
+
AC_DEFUN([ZFS_AC_KERNEL_NR_CACHED_OBJECTS], [
AC_MSG_CHECKING([whether sops->nr_cached_objects() exists])
ZFS_LINUX_TRY_COMPILE([