1 files changed, 53 insertions, 0 deletions

diff --git a/mm/vmalloc.c b/mm/vmalloc.c
index 8e05a11155c9..3130c343088f 100644
--- a/mm/vmalloc.c
+++ b/mm/vmalloc.c
@@ -767,3 +767,56 @@ EXPORT_SYMBOL(remap_vmalloc_range);
 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(size_t 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);