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Subject[patch 01/28]xen: Allocate and free vmalloc areas
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>

---
include/linux/vmalloc.h | 4 +++
mm/vmalloc.c | 53 +++++++++++++++++++++++++++++++++++++++++++++++
2 files changed, 57 insertions(+)
===================================================================
--- a/include/linux/vmalloc.h
+++ b/include/linux/vmalloc.h
@@ -69,6 +69,10 @@ 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..
*/
===================================================================
--- a/mm/vmalloc.c
+++ b/mm/vmalloc.c
@@ -762,3 +762,56 @@ void __attribute__((weak)) vmalloc_sync
void __attribute__((weak)) vmalloc_sync_all(void)
{
}
+
+
+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;
+}
+
+/**
+ * alloc_vm_area - allocate a range of kernel address space
+ * @size: size of the area
+ * @returns: NULL on failure, vm_struct on success
+ *
+ * This function reserves a range of kernel address space, and
+ * allocates pagetables to map that range. No actual mappings
+ * are created. If the kernel address space is not shared
+ * between processes, it syncs the pagetable across all
+ * processes.
+ */
+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);
--

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