Linux 2.6.31 Compatibility Updates

SPL_AC_2ARGS_SET_FS_PWD macro updated to explicitly include
linux/fs_struct.h which was dropped from linux/sched.h.

min_wmark_pages, low_wmark_pages, high_wmark_pages macros
introduced in newer kernels.  For older kernels mm_compat.h
was introduced to define them as needed as direct mappings
to per zone min_pages, low_pages, max_pages.

include/sys/kmem.h

@@ -36,7 +36,7 @@ extern "C" {
 #include <linux/module.h>
 #include <linux/slab.h>
 #include <linux/vmalloc.h>
-#include <linux/mm.h>
+#include <linux/mm_compat.h>
 #include <linux/spinlock.h>
 #include <linux/rwsem.h>
 #include <linux/hash.h>

include/sys/vnode.h

@@ -39,6 +39,7 @@ extern "C" {
 #include <linux/namei.h>
 #include <linux/file.h>
 #include <linux/fs.h>
+#include <linux/fs_struct.h>
 #include <linux/mount.h>
 #include <sys/kmem.h>
 #include <sys/mutex.h>