Add compatibility layer for {kmap,kunmap}_atomic

Starting from linux-2.6.37, {kmap,kunmap}_atomic takes 1 argument instead of 2.
We use zfs_{kmap,kunmap}_atomic as wrappers and always take 2 argument, but
ignore the 2nd for newer kernel.

Signed-off-by: Chunwei Chen <[email protected]>
Signed-off-by: Brian Behlendorf <[email protected]>

config/kernel-kmap-atomic-args.m4

@@ -0,0 +1,20 @@
+dnl #
+dnl # 2.6.37 API change
+dnl # kmap_atomic changed from assigning hard-coded named slot to using
+dnl # push/pop based dynamical allocation.
+dnl #
+AC_DEFUN([ZFS_AC_KERNEL_KMAP_ATOMIC_ARGS], [
+	AC_MSG_CHECKING([whether kmap_atomic wants 1 args])
+	ZFS_LINUX_TRY_COMPILE([
+		#include <linux/pagemap.h>
+	],[
+		struct page page;
+		kmap_atomic(&page);
+	],[
+		AC_MSG_RESULT(yes)
+		AC_DEFINE(HAVE_1ARG_KMAP_ATOMIC, 1,
+		          [kmap_atomic wants 1 args])
+	],[
+		AC_MSG_RESULT(no)
+	])
+])

config/kernel.m4

@@ -100,6 +100,7 @@ AC_DEFUN([ZFS_AC_CONFIG_KERNEL], [
 	ZFS_AC_KERNEL_LSEEK_EXECUTE
 	ZFS_AC_KERNEL_VFS_ITERATE
 	ZFS_AC_KERNEL_VFS_RW_ITERATE
+	ZFS_AC_KERNEL_KMAP_ATOMIC_ARGS
 
 	AS_IF([test "$LINUX_OBJ" != "$LINUX"], [
 		KERNELMAKE_PARAMS="$KERNELMAKE_PARAMS O=$LINUX_OBJ"

include/linux/Makefile.am

@@ -5,7 +5,8 @@ KERNEL_H = \
 	$(top_srcdir)/include/linux/xattr_compat.h \
 	$(top_srcdir)/include/linux/vfs_compat.h \
 	$(top_srcdir)/include/linux/blkdev_compat.h \
-	$(top_srcdir)/include/linux/utsname_compat.h
+	$(top_srcdir)/include/linux/utsname_compat.h \
+	$(top_srcdir)/include/linux/kmap_compat.h
 
 USER_H =
 

include/linux/kmap_compat.h

@@ -0,0 +1,40 @@
+/*
+ * CDDL HEADER START
+ *
+ * The contents of this file are subject to the terms of the
+ * Common Development and Distribution License (the "License").
+ * You may not use this file except in compliance with the License.
+ *
+ * You can obtain a copy of the license at usr/src/OPENSOLARIS.LICENSE
+ * or http://www.opensolaris.org/os/licensing.
+ * See the License for the specific language governing permissions
+ * and limitations under the License.
+ *
+ * When distributing Covered Code, include this CDDL HEADER in each
+ * file and include the License file at usr/src/OPENSOLARIS.LICENSE.
+ * If applicable, add the following below this CDDL HEADER, with the
+ * fields enclosed by brackets "[]" replaced with your own identifying
+ * information: Portions Copyright [yyyy] [name of copyright owner]
+ *
+ * CDDL HEADER END
+ */
+
+/*
+ * Copyright (c) 2015 by Chunwei Chen. All rights reserved.
+ */
+
+#ifndef _ZFS_KMAP_H
+#define	_ZFS_KMAP_H
+
+#include <linux/highmem.h>
+
+#ifdef HAVE_1ARG_KMAP_ATOMIC
+/* 2.6.37 API change */
+#define	zfs_kmap_atomic(page, km_type)		kmap_atomic(page)
+#define	zfs_kunmap_atomic(addr, km_type)	kunmap_atomic(addr)
+#else
+#define	zfs_kmap_atomic(page, km_type)		kmap_atomic(page, km_type)
+#define	zfs_kunmap_atomic(addr, km_type)	kunmap_atomic(addr, km_type)
+#endif
+
+#endif	/* _ZFS_KMAP_H */