From: Christoph Lameter <clameter@sgi.com>
Subject: [HUGE] Support VM_PFNMAP

Support VM_PFNMAP in hugetlbfs. This is useful for drivers that want
to map large contiguous regions of memory.

Signed-off-by: Christoph Lameter <clameter@sgi.com>

Index: linux-2.6/mm/hugetlb.c
===================================================================
--- linux-2.6.orig/mm/hugetlb.c	2008-04-10 13:06:32.000000000 -0700
+++ linux-2.6/mm/hugetlb.c	2008-04-10 13:06:58.000000000 -0700
@@ -811,6 +811,9 @@
 		if (pte_none(pte))
 			continue;
 
+		if (vma->vm_flags & VM_PFNMAP)
+			continue;
+
 		page = pte_page(pte);
 		if (pte_dirty(pte))
 			set_page_dirty(page);
@@ -965,6 +968,65 @@
 	goto out;
 }
 
+static int hugetlb_no_pfn(struct mm_struct *mm, struct vm_area_struct *vma,
+		unsigned long address, pte_t *ptep, int write_access)
+{
+	unsigned long pfn;
+
+	BUG_ON(!(vma->vm_flags & VM_PFNMAP));
+
+	pfn = vma->vm_ops->nopfn(vma, address & HPAGE_MASK);
+	if (unlikely(pfn == NOPFN_OOM))
+		return VM_FAULT_OOM;
+	else if (unlikely(pfn == NOPFN_SIGBUS))
+		return VM_FAULT_SIGBUS;
+	else if (unlikely(pfn == NOPFN_REFAULT))
+		return 0;
+
+	spin_lock(&mm->page_table_lock);
+        if (pte_none(*ptep)) {
+		pte_t new_pte;
+
+		new_pte = make_huge_pte(vma, pfn, ((vma->vm_flags & VM_WRITE)
+                                && (vma->vm_flags & VM_SHARED)));
+		set_huge_pte_at(mm, address, ptep, new_pte);
+	}
+	spin_unlock(&mm->page_table_lock);
+	return 0;
+}
+
+/**
+ * huge_insert_pfn - insert single huge pfn into user vma
+ * @vma: user vma to map to
+ * @addr: target user address of this page
+ * @pfn: source kernel pfn (must be properly aligned for a huge page)
+ */
+int huge_insert_pfn(struct vm_area_struct *vma, unsigned long addr,
+		unsigned long pfn)
+{
+	struct mm_struct *mm = vma->vm_mm;
+	pte_t *ptep;
+
+	BUG_ON(!(vma->vm_flags & VM_PFNMAP));
+	BUG_ON(addr & ~HPAGE_MASK);
+
+	ptep = huge_pte_alloc(mm, addr);
+	if (!ptep)
+		return VM_FAULT_OOM;
+
+	spin_lock(&mm->page_table_lock);
+        if (pte_none(*ptep)) {
+		pte_t new_pte;
+
+		new_pte = make_huge_pte(vma, pfn, ((vma->vm_flags & VM_WRITE)
+                                && (vma->vm_flags & VM_SHARED)));
+		set_huge_pte_at(mm, addr, ptep, new_pte);
+	}
+	spin_unlock(&mm->page_table_lock);
+	return 0;
+}
+EXPORT_SYMBOL(huge_insert_pfn);
+
 int hugetlb_fault(struct mm_struct *mm, struct vm_area_struct *vma,
 			unsigned long address, int write_access)
 {
@@ -985,7 +1047,13 @@
 	mutex_lock(&hugetlb_instantiation_mutex);
 	entry = *ptep;
 	if (pte_none(entry)) {
-		ret = hugetlb_no_page(mm, vma, address, ptep, write_access);
+		if (vma->vm_ops->nopfn)
+		 	ret = hugetlb_no_pfn(mm, vma, address, ptep,
+							write_access);
+		else
+			ret = hugetlb_no_page(mm, vma, address, ptep,
+							write_access);
+
 		mutex_unlock(&hugetlb_instantiation_mutex);
 		return ret;
 	}
Index: linux-2.6/include/linux/hugetlb.h
===================================================================
--- linux-2.6.orig/include/linux/hugetlb.h	2008-04-10 13:05:40.000000000 -0700
+++ linux-2.6/include/linux/hugetlb.h	2008-04-10 13:06:58.000000000 -0700
@@ -16,6 +16,9 @@
 	return vma->vm_flags & VM_HUGETLB;
 }
 
+int huge_insert_pfn(struct vm_area_struct *vma, unsigned long addr,
+		unsigned long pfn);
+
 int hugetlb_sysctl_handler(struct ctl_table *, int, struct file *, void __user *, size_t *, loff_t *);
 int hugetlb_overcommit_handler(struct ctl_table *, int, struct file *, void __user *, size_t *, loff_t *);
 int hugetlb_treat_movable_handler(struct ctl_table *, int, struct file *, void __user *, size_t *, loff_t *);