infa: introduce wrapper layer for compatibiliy with multiple kernels

This is needed for adaptation of the out-of-tree MARS version to multiple
kernel versions.

It will be much simplified after upstream merging, and/or
removed/replaced by something better.

kernel/compat.h

@@ -0,0 +1,46 @@
+/*
+ * MARS Long Distance Replication Software
+ *
+ * This file is part of MARS project: http://schoebel.github.io/mars/
+ *
+ * Copyright (C) 2010-2014 Thomas Schoebel-Theuer
+ * Copyright (C) 2011-2014 1&1 Internet AG
+ *
+ * This program is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by
+ * the Free Software Foundation; either version 2 of the License, or
+ * (at your option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License along
+ * with this program; if not, write to the Free Software Foundation, Inc.,
+ * 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA.
+ */
+
+#ifndef _MARS_COMPAT
+#define _MARS_COMPAT
+
+#include <linux/major.h>
+
+/* TRANSITIONAL compatibility to BOTH the old prepatch
+ * and the new wrappers around vfs_*().
+ */
+#ifdef MARS_MAJOR
+#define HAS_MARS_PREPATCH
+#else
+#define MARS_MAJOR (DRBD_MAJOR + 1)
+#endif
+
+#ifdef HAS_MARS_PREPATCH
+
+#include <linux/syscalls.h>
+
+#else /* HAS_MARS_PREPATCH */
+
+#endif /* HAS_MARS_PREPATCH */
+
+#endif /* _MARS_COMPAT */

kernel/sy_old/sy_generic.c

@@ -34,6 +34,8 @@
 #include <linux/file.h>
 #include <linux/blkdev.h>
 #include <linux/fs.h>
+#include <linux/namei.h>
+#include <linux/mount.h>
 #include <linux/utsname.h>
 
 #include "strategy.h"
@@ -41,7 +43,7 @@
 #include "../lib_mapfree.h"
 #include "../mars_client.h"
 
-#include <linux/syscalls.h>
+#include "../compat.h"
 #include <linux/namei.h>
 #include <linux/kthread.h>
 #include <linux/statfs.h>
@@ -51,6 +53,12 @@
 //      remove_this
 #include <linux/wait.h>
 #include <linux/version.h>
+
+#ifndef DCACHE_MISS_TYPE /* define accessors compatible to b18825a7c8e37a7cf6abb97a12a6ad71af160de7 */
+#define d_is_negative(dentry)     ((dentry)->d_inode == NULL)
+#define d_backing_inode(dentry)   ((dentry)->d_inode)
+#endif
+
 /* FIXME: some Redhat/openvz kernels seem to have both (backporting etc).
  * The folling is an incomplete quickfix / workaround. TBD.
  */
@@ -99,6 +107,57 @@ const struct meta mars_dent_meta[] = {
 };
 EXPORT_SYMBOL_GPL(mars_dent_meta);
 
+//      remove_this
+#ifndef HAS_MARS_PREPATCH
+/////////////////////////////////////////////////////////////////////
+
+/* The _compat_*() functions are needed for the out-of-tree version
+ * of MARS for adapdation to different kernel version.
+ */
+
+#ifdef SB_FREEZE_LEVELS
+/* since kernel 3.6 */
+/* see a8104a9fcdeb82e22d7acd55fca20746581067d3 */
+/* locking order changes in c30dabfe5d10c5fd70d882e5afb8f59f2942b194, we need to adapt */
+#define __NEW_PATH_CREATE
+#endif
+
+#ifndef FSCACHE_OP_DEAD
+/* since kernel 3.8 */
+/* see b9d6ba94b875192ef5e2dab92d72beea33b83c3d */
+#define  __HAS_RETRY_ESTALE
+#endif
+
+/* Hack because of 8bcb77fabd7cbabcad49f58750be8683febee92b
+ */
+static int __path_parent(const char *name, struct path *path, unsigned flags)
+{
+#ifdef user_path
+	return kern_path(name, flags | LOOKUP_PARENT | LOOKUP_DIRECTORY | LOOKUP_FOLLOW, path);
+#else
+	char *tmp;
+	int len;
+	int error;
+
+	len = strlen(name);
+	while (len > 0 && name[len] != '/')
+		len--;
+	if (unlikely(!len))
+		return -EINVAL;
+
+	tmp = brick_string_alloc(len + 1);
+	strncpy(tmp, name, len);
+	tmp[len] = '\0';
+
+	error = kern_path(tmp, flags | LOOKUP_DIRECTORY | LOOKUP_FOLLOW, path);
+
+	brick_string_free(tmp);
+	return error;
+#endif
+}
+
+#endif
+//      end_remove_this
 /////////////////////////////////////////////////////////////////////
 
 // some helpers