Linux 2.6.35 compat, fops->fsync()

The fsync() callback in the file_operations structure used to take
3 arguments.  The callback now only takes 2 arguments because the
dentry argument was determined to be unused by all consumers.  To
handle this a compatibility prototype was added to ensure the right
prototype is used.  Our implementation never used the dentry argument
either so it's just a matter of using the right prototype.

config/kernel-fsync.m4

@@ -0,0 +1,20 @@
+dnl #
+dnl # 2.6.35 API change
+dnl # The dentry argument was deamed unused and dropped in 2.6.36.
+dnl #
+AC_DEFUN([ZFS_AC_KERNEL_FSYNC_2ARGS], [
+	AC_MSG_CHECKING([whether fops->fsync() wants 2 args])
+	ZFS_LINUX_TRY_COMPILE([
+		#include <linux/fs.h>
+	],[
+		int (*fsync) (struct file *, int datasync) = NULL;
+		struct file_operations fops;
+
+		fops.fsync = fsync;
+	],[
+		AC_MSG_RESULT(yes)
+		AC_DEFINE(HAVE_2ARGS_FSYNC, 1, [fops->fsync() want 2 args])
+	],[
+		AC_MSG_RESULT(no)
+	])
+])

config/kernel.m4

@@ -29,6 +29,7 @@ AC_DEFUN([ZFS_AC_CONFIG_KERNEL], [
 	ZFS_AC_KERNEL_RQ_IS_SYNC
 	ZFS_AC_KERNEL_RQ_FOR_EACH_SEGMENT
 	ZFS_AC_KERNEL_CONST_XATTR_HANDLER
+	ZFS_AC_KERNEL_FSYNC_2ARGS
 
 	if test "$LINUX_OBJ" != "$LINUX"; then
 		KERNELMAKE_PARAMS="$KERNELMAKE_PARAMS O=$LINUX_OBJ"