From 8b97b620f41696f83375a250735268249ce8069a Mon Sep 17 00:00:00 2001
From: Christoph Lameter <clameter@sgi.com>
Date: Wed, 3 Oct 2007 20:42:44 -0700
Subject: vcompound: Debugging aid

Virtualized Compound Pages are rare in practice and thus subtle bugs may
creep in if we do not test the kernel with Virtualized Compounds.
CONFIG_VFALLBACK_ALWAYS results in virtualizable compound allocation
requests always result in virtualized compounds.

Signed-off-by: Christoph Lameter <clameter@sgi.com>
---
 lib/Kconfig.debug |   12 ++++++++++++
 mm/vmalloc.c      |   19 +++++++++++++++----
 2 files changed, 27 insertions(+), 4 deletions(-)

Index: linux-2.6.25-mm1/lib/Kconfig.debug
===================================================================
--- linux-2.6.25-mm1.orig/lib/Kconfig.debug	2008-04-25 23:17:40.341140277 -0700
+++ linux-2.6.25-mm1/lib/Kconfig.debug	2008-04-25 23:37:21.039899502 -0700
@@ -158,6 +158,18 @@ config DETECT_SOFTLOCKUP
 	   can be detected via the NMI-watchdog, on platforms that
 	   support it.)
 
+config VIRTUALIZE_COMPOUNDS_ALWAYS
+	bool "Always fall back to virtualzed compound pages"
+	default y
+	help
+	  Virtualized compound pages are only allocated if there is no linear
+	  memory available. They are a fallback and potential issues created by
+	  the use of virtual mappings instead of physically linear memory may
+	  not surface because of the infrequent need to create them. Enabling
+	  this option makes every allocation that allows a fallback to a
+	  virtual mapping use the virtual mapping. May have a significant
+	  performance impact.
+
 config SCHED_DEBUG
 	bool "Collect scheduler debugging info"
 	depends on DEBUG_KERNEL && PROC_FS
Index: linux-2.6.25-mm1/mm/vmalloc.c
===================================================================
--- linux-2.6.25-mm1.orig/mm/vmalloc.c	2008-04-25 23:28:50.922390376 -0700
+++ linux-2.6.25-mm1/mm/vmalloc.c	2008-04-26 00:58:56.420418839 -0700
@@ -496,7 +496,6 @@ static void *__vmalloc_area_node(struct 
 	unsigned int nr_pages, array_size, i;
 
 	nr_pages = (area->size - PAGE_SIZE) >> PAGE_SHIFT;
-	r
 	array_size = (nr_pages * sizeof(struct page *));
 
 	area->nr_pages = nr_pages;
@@ -1177,7 +1176,13 @@ struct page *alloc_vcompound(gfp_t flags
 	struct vm_struct *vm;
 	struct page *page;
 
-	page = alloc_pages(flags | __GFP_NORETRY | __GFP_NOWARN, order);
+#ifdef CONFIG_VFALLBACK_ALWAYS
+	if (system_state == SYSTEM_RUNNING && order)
+		page = NULL;
+	else
+#endif
+		page = alloc_pages(flags | __GFP_NORETRY | __GFP_NOWARN,
+								order);
 	if (page || !order)
 		return page;
 
@@ -1194,8 +1199,14 @@ void *__alloc_vcompound(gfp_t flags, int
 	struct vm_struct *vm;
 	void *addr;
 
-	addr = (void *)__get_free_pages(flags | __GFP_NORETRY | __GFP_NOWARN,
-								order);
+#ifdef CONFIG_VFALLBACK_ALWAYS
+	if (system_state == SYSTEM_RUNNING && order)
+		addr = NULL;
+	else
+#endif
+		addr = (void *)__get_free_pages(
+			flags | __GFP_NORETRY | __GFP_NOWARN, order);
+
 	if (addr || !order)
 		return addr;