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.

config/spl-build.m4

@@ -1266,6 +1266,7 @@ AC_DEFUN([SPL_AC_2ARGS_SET_FS_PWD],
 	[AC_MSG_CHECKING([whether set_fs_pwd() wants 2 args])
 	SPL_LINUX_TRY_COMPILE([
 		#include <linux/sched.h>
+		#include <linux/fs_struct.h>
 	],[
 		set_fs_pwd(NULL, NULL);
 	],[

configure

@@ -21871,6 +21871,7 @@ cat >>conftest.$ac_ext <<_ACEOF
 
 
 		#include <linux/sched.h>
+		#include <linux/fs_struct.h>
 
 int
 main (void)
@@ -25119,6 +25120,7 @@ cat >>conftest.$ac_ext <<_ACEOF
 
 
 		#include <linux/sched.h>
+		#include <linux/fs_struct.h>
 
 int
 main (void)

include/linux/mm_compat.h

@@ -0,0 +1,22 @@
+#ifndef _SPL_MM_COMPAT_H
+#define _SPL_MM_COMPAT_H
+
+#include <linux/mm.h>
+
+/*
+ * Linux 2.6.31 API Change.
+ * Individual pages_{min,low,high} moved in to watermark array.
+ */
+#ifndef min_wmark_pages
+#define min_wmark_pages(z)	(z->pages_min)
+#endif
+
+#ifndef low_wmark_pages
+#define low_wmark_pages(z)	(z->pages_low)
+#endif
+
+#ifndef high_wmark_pages
+#define high_wmark_pages(z)	(z->pages_high)
+#endif
+
+#endif /* SPL_MM_COMPAT_H */

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>

module/spl/spl-kmem.c

@@ -1826,9 +1826,9 @@ spl_kmem_init_globals(void)
                 if (!populated_zone(zone))
                         continue;
 
-		minfree += zone->pages_min;
-		desfree += zone->pages_low;
-		lotsfree += zone->pages_high;
+		minfree += min_wmark_pages(zone);
+		desfree += low_wmark_pages(zone);
+		lotsfree += high_wmark_pages(zone);
 	}
 
 	/* Solaris default values */