Linux compat 2.6.37, invalidate_inodes()

In the 2.6.37 kernel the function invalidate_inodes() is no longer
exported for use by modules.  This memory management functionality
is needed to invalidate the inodes attached to a super block without
unmounting the filesystem.

Because this function still exists in the kernel and the prototype
is available is a common header all we strictly need is the symbol
address.  The address is obtained using spl_kallsyms_lookup_name()
and assigned to the variable invalidate_inodes_fn.  Then a #define
is used to replace all instances of invalidate_inodes() with a
call to the acquired address.  All the complexity is hidden behind
HAVE_INVALIDATE_INODES and invalidate_inodes() can be used as usual.

Long term we should try to get this, or another, interface made
available to modules again.

config/spl-build.m4

@@ -74,6 +74,7 @@ AC_DEFUN([SPL_AC_CONFIG_KERNEL], [
 	SPL_AC_KVASPRINTF
 	SPL_AC_3ARGS_FILE_FSYNC
 	SPL_AC_EXPORTED_RWSEM_IS_LOCKED
+	SPL_AC_KERNEL_INVALIDATE_INODES
 ])
 
 AC_DEFUN([SPL_AC_MODULE_SYMVERS], [
@@ -1685,3 +1686,18 @@ AC_DEFUN([SPL_AC_EXPORTED_RWSEM_IS_LOCKED], [
 		[rwsem_is_locked() acquires sem->wait_lock])],
 		[])
 ])
+
+dnl #
+dnl # 2.6.37 API compat,
+dnl # The function invalidate_inodes() is no longer exported by the kernel.
+dnl # The prototype however is still available which means it is safe
+dnl # to acquire the symbol's address using spl_kallsyms_lookup_name().
+dnl #
+AC_DEFUN([SPL_AC_KERNEL_INVALIDATE_INODES], [
+	SPL_CHECK_SYMBOL_EXPORT(
+		[invalidate_inodes],
+		[],
+		[AC_DEFINE(HAVE_INVALIDATE_INODES, 1,
+		[invalidate_inodes() is available])],
+		[])
+])

configure

@@ -15334,6 +15334,47 @@ _ACEOF
 	fi
 
 
+
+	{ $as_echo "$as_me:$LINENO: checking whether symbol invalidate_inodes is exported" >&5
+$as_echo_n "checking whether symbol invalidate_inodes is exported... " >&6; }
+	grep -q -E '[[:space:]]invalidate_inodes[[:space:]]' \
+		$LINUX_OBJ/Module*.symvers 2>/dev/null
+	rc=$?
+	if test $rc -ne 0; then
+		export=0
+		for file in ; do
+			grep -q -E "EXPORT_SYMBOL.*(invalidate_inodes)" \
+				"$LINUX_OBJ/$file" 2>/dev/null
+			rc=$?
+		        if test $rc -eq 0; then
+		                export=1
+		                break;
+		        fi
+		done
+		if test $export -eq 0; then
+			{ $as_echo "$as_me:$LINENO: result: no" >&5
+$as_echo "no" >&6; }
+
+		else
+			{ $as_echo "$as_me:$LINENO: result: yes" >&5
+$as_echo "yes" >&6; }
+
+cat >>confdefs.h <<\_ACEOF
+#define HAVE_INVALIDATE_INODES 1
+_ACEOF
+
+		fi
+	else
+		{ $as_echo "$as_me:$LINENO: result: yes" >&5
+$as_echo "yes" >&6; }
+
+cat >>confdefs.h <<\_ACEOF
+#define HAVE_INVALIDATE_INODES 1
+_ACEOF
+
+	fi
+
+
  ;;
                 user)
 
@@ -19029,6 +19070,47 @@ _ACEOF
 
 
 
+	{ $as_echo "$as_me:$LINENO: checking whether symbol invalidate_inodes is exported" >&5
+$as_echo_n "checking whether symbol invalidate_inodes is exported... " >&6; }
+	grep -q -E '[[:space:]]invalidate_inodes[[:space:]]' \
+		$LINUX_OBJ/Module*.symvers 2>/dev/null
+	rc=$?
+	if test $rc -ne 0; then
+		export=0
+		for file in ; do
+			grep -q -E "EXPORT_SYMBOL.*(invalidate_inodes)" \
+				"$LINUX_OBJ/$file" 2>/dev/null
+			rc=$?
+		        if test $rc -eq 0; then
+		                export=1
+		                break;
+		        fi
+		done
+		if test $export -eq 0; then
+			{ $as_echo "$as_me:$LINENO: result: no" >&5
+$as_echo "no" >&6; }
+
+		else
+			{ $as_echo "$as_me:$LINENO: result: yes" >&5
+$as_echo "yes" >&6; }
+
+cat >>confdefs.h <<\_ACEOF
+#define HAVE_INVALIDATE_INODES 1
+_ACEOF
+
+		fi
+	else
+		{ $as_echo "$as_me:$LINENO: result: yes" >&5
+$as_echo "yes" >&6; }
+
+cat >>confdefs.h <<\_ACEOF
+#define HAVE_INVALIDATE_INODES 1
+_ACEOF
+
+	fi
+
+
+
 
 
 	if test "x$AWK" != xgawk; then

include/linux/mm_compat.h

@@ -26,6 +26,7 @@
 #define _SPL_MM_COMPAT_H
 
 #include <linux/mm.h>
+#include <linux/fs.h>
 
 /*
  * Linux 2.6.31 API Change.
@@ -43,4 +44,16 @@
 #define high_wmark_pages(z)	(z->pages_high)
 #endif
 
+/*
+ * 2.6.37 API compat,
+ * The function invalidate_inodes() is no longer exported by the kernel.
+ * The prototype however is still available which means it is safe
+ * to acquire the symbol's address using spl_kallsyms_lookup_name().
+ */
+#ifndef HAVE_INVALIDATE_INODES
+typedef int (*invalidate_inodes_t)(struct super_block *sb);
+extern invalidate_inodes_t invalidate_inodes_fn;
+#define invalidate_inodes(sb)	invalidate_inodes_fn(sb)
+#endif /* HAVE_INVALIDATE_INODES */
+
 #endif /* SPL_MM_COMPAT_H */

module/spl/spl-kmem.c

@@ -180,6 +180,11 @@ spl_global_page_state(spl_zone_stat_item_t item)
 #endif /* NEED_GET_ZONE_COUNTS */
 EXPORT_SYMBOL(spl_global_page_state);
 
+#ifndef HAVE_INVALIDATE_INODES
+invalidate_inodes_t invalidate_inodes_fn = SYMBOL_POISON;
+EXPORT_SYMBOL(invalidate_inodes_fn);
+#endif /* HAVE_INVALIDATE_INODES */
+
 pgcnt_t
 spl_kmem_availrmem(void)
 {
@@ -2089,6 +2094,15 @@ spl_kmem_init_kallsyms_lookup(void)
 	 */
 	spl_kmem_init_globals();
 
+#ifndef HAVE_INVALIDATE_INODES
+	invalidate_inodes_fn = (invalidate_inodes_t)
+	spl_kallsyms_lookup_name("invalidate_inodes");
+	if (!invalidate_inodes_fn) {
+		printk(KERN_ERR "Error: Unknown symbol invalidate_inodes\n");
+		return -EFAULT;
+	}
+#endif /* HAVE_INVALIDATE_INODES */
+
 	return 0;
 }
 

spl_config.h.in

@@ -102,6 +102,9 @@
 /* Define to 1 if you have the <inttypes.h> header file. */
 #undef HAVE_INTTYPES_H
 
+/* invalidate_inodes() is available */
+#undef HAVE_INVALIDATE_INODES
+
 /* kallsyms_lookup_name() is available */
 #undef HAVE_KALLSYMS_LOOKUP_NAME