Linux 2.6.28 compat, insert_inode_locked()

Added insert_inode_locked() helper function, prior to this most callers
used insert_inode_hash().  The older method doesn't check for collisions
in the inode_hashtable but it still acceptible for use.  Fallback to
using insert_inode_hash() when insert_inode_locked() is unavailable.

config/kernel-insert-inode-locked.m4

@@ -0,0 +1,12 @@
+dnl #
+dnl # 2.6.28 API change
+dnl # Added insert_inode_locked() helper function.
+dnl #
+AC_DEFUN([ZFS_AC_KERNEL_INSERT_INODE_LOCKED], [
+	ZFS_CHECK_SYMBOL_EXPORT(
+		[insert_inode_locked],
+		[fs/inode.c],
+		[AC_DEFINE(HAVE_INSERT_INODE_LOCKED, 1,
+		[insert_inode_locked() is available])],
+		[])
+])

config/kernel.m4

@@ -34,6 +34,7 @@ AC_DEFUN([ZFS_AC_CONFIG_KERNEL], [
 	ZFS_AC_KERNEL_XATTR_HANDLER_SET
 	ZFS_AC_KERNEL_FSYNC_2ARGS
 	ZFS_AC_KERNEL_EVICT_INODE
+	ZFS_AC_KERNEL_INSERT_INODE_LOCKED
 
 	if test "$LINUX_OBJ" != "$LINUX"; then
 		KERNELMAKE_PARAMS="$KERNELMAKE_PARAMS O=$LINUX_OBJ"