Allocate/destroy a 'vmalloc' VM area: alloc_vm_area and free_vm_area
The alloc function ensures that page tables are constructed for the
region of kernel virtual address space and mapped into init_mm.

Signed-off-by: Jeremy Fitzhardinge <jeremy@xensource.com>
Signed-off-by: Ian Pratt <ian.pratt@xensource.com>
Signed-off-by: Christian Limpach <Christian.Limpach@cl.cam.ac.uk>
Signed-off-by: Chris Wright <chrisw@sous-sol.org>
Cc: "Jan Beulich" <JBeulich@novell.com>
Cc: "Andi Kleen" <ak@muc.de>

---
 arch/i386/mm/fault.c    |   43 +++++++++++++++++++++++++++++++++++++++++++
 include/linux/vmalloc.h |    4 ++++
 2 files changed, 47 insertions(+)

===================================================================
--- a/arch/i386/mm/fault.c
+++ b/arch/i386/mm/fault.c
@@ -23,6 +23,7 @@
 #include <linux/module.h>
 #include <linux/kprobes.h>
 #include <linux/uaccess.h>
+#include <linux/vmalloc.h>
 
 #include <asm/system.h>
 #include <asm/desc.h>
@@ -624,3 +625,45 @@ void _vmalloc_sync_all(void)
 			start = address + PGDIR_SIZE;
 	}
 }
+
+
+static int f(pte_t *pte, struct page *pmd_page, unsigned long addr, void *data)
+{
+	/* apply_to_page_range() does all the hard work. */
+	return 0;
+}
+
+struct vm_struct *alloc_vm_area(unsigned long size)
+{
+	struct vm_struct *area;
+
+	area = get_vm_area(size, VM_IOREMAP);
+	if (area == NULL)
+		return NULL;
+
+	/*
+	 * This ensures that page tables are constructed for this region
+	 * of kernel virtual address space and mapped into init_mm.
+	 */
+	if (apply_to_page_range(&init_mm, (unsigned long)area->addr,
+				area->size, f, NULL)) {
+		free_vm_area(area);
+		return NULL;
+	}
+
+	/* Make sure the pagetables are constructed in process kernel
+	   mappings */
+	vmalloc_sync_all();
+
+	return area;
+}
+EXPORT_SYMBOL_GPL(alloc_vm_area);
+
+void free_vm_area(struct vm_struct *area)
+{
+	struct vm_struct *ret;
+	ret = remove_vm_area(area->addr);
+	BUG_ON(ret != area);
+	kfree(area);
+}
+EXPORT_SYMBOL_GPL(free_vm_area);
===================================================================
--- a/include/linux/vmalloc.h
+++ b/include/linux/vmalloc.h
@@ -68,6 +68,10 @@ extern int map_vm_area(struct vm_struct 
 			struct page ***pages);
 extern void unmap_vm_area(struct vm_struct *area);
 
+/* Allocate/destroy a 'vmalloc' VM area. */
+extern struct vm_struct *alloc_vm_area(unsigned long size);
+extern void free_vm_area(struct vm_struct *area);
+
 /*
  *	Internals.  Dont't use..
  */

-- 

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