ia64 memory hotplug for hugetlbpages [1/3]

diff -dupr linux-2.6.7/arch/ia64/mm/hugetlbpage.c linux-2.6.7-FAULT/arch/ia64/mm/hugetlbpage.c
@@ -105,10 +105,12 @@ int copy_hugetlb_page_range(struct mm_st
 			goto nomem;
 		src_pte = huge_pte_offset(src, addr);
 		entry = *src_pte;
-		ptepage = pte_page(entry);
-		get_page(ptepage);
+		if (!pte_none(entry)) {
+			ptepage = pte_page(entry);
+			get_page(ptepage);
+			dst->rss += (HPAGE_SIZE / PAGE_SIZE);
+		}
 		set_pte(dst_pte, entry);
-		dst->rss += (HPAGE_SIZE / PAGE_SIZE);
 		addr += HPAGE_SIZE;
 	}
 	return 0;

@@ -130,6 +132,10 @@ follow_hugetlb_page(struct mm_struct *mm
 	do {
 		pstart = start & HPAGE_MASK;
 		ptep = huge_pte_offset(mm, start);
+		if (!ptep || pte_none(*ptep)) {
+			hugetlb_fault(mm, vma, 0, start);
+			ptep = huge_pte_offset(mm, start);
+		}
 		pte = *ptep;
 
 back1:

@@ -167,6 +173,13 @@ struct page *follow_huge_addr(struct mm_
 	if (!ptep || pte_none(*ptep))
 		return NULL;
 	page = pte_page(*ptep);
+	if (!page) {
+		struct vm_area_struct *vma = find_vma(mm, addr);
+		if (!vma)
+			return NULL;
+		hugetlb_fault(mm, vma, 0, addr);
+		page = pte_page(*ptep);
+	}
 	page += ((addr & ~HPAGE_MASK) >> PAGE_SHIFT);
 	return page;
 }

@@ -250,8 +263,8 @@ void unmap_hugepage_range(struct vm_area
 		page = pte_page(*pte);
 		put_page(page);
 		pte_clear(pte);
+		mm->rss -= (HPAGE_SIZE / PAGE_SIZE);
 	}
-	mm->rss -= (end - start) >> PAGE_SHIFT;
 	flush_tlb_range(vma, start, end);
 }
 

@@ -308,6 +321,68 @@ out:
 	return ret;
 }
 
+int hugetlb_fault(struct mm_struct *mm, struct vm_area_struct *vma, int write_access, unsigned long address)
+{
+	struct file *file = vma->vm_file;
+	struct address_space *mapping = file->f_dentry->d_inode->i_mapping;
+	struct page *page;
+	unsigned long idx;
+	pte_t *pte = huge_pte_alloc(mm, address);
+	int ret;
+
+	BUG_ON(vma->vm_start & ~HPAGE_MASK);
+	BUG_ON(vma->vm_end & ~HPAGE_MASK);
+
+	spin_lock(&mm->page_table_lock);
+
+	if (!pte) {
+		ret = VM_FAULT_SIGBUS;
+		goto out;
+	}
+
+	if (!pte_none(*pte)) {
+		ret = VM_FAULT_MINOR;
+		goto out;
+	}
+
+	idx = ((address - vma->vm_start) >> HPAGE_SHIFT)
+		+ (vma->vm_pgoff >> (HPAGE_SHIFT - PAGE_SHIFT));
+again:
+	page = find_get_page(mapping, idx);
+
+	if (!page) {
+		/* charge the fs quota first */
+		if (hugetlb_get_quota(mapping)) {
+			ret = VM_FAULT_SIGBUS;
+			goto out;
+		}
+		page = alloc_huge_page();
+		if (!page) {
+			hugetlb_put_quota(mapping);
+			ret = VM_FAULT_SIGBUS;
+			goto out;
+		}
+		ret = add_to_page_cache(page, mapping, idx, GFP_ATOMIC);
+		if (ret) {
+			hugetlb_put_quota(mapping);
+			put_page(page);
+			goto again;
+		}
+	}
+	if (pte_none(*pte)) {
+		set_huge_pte(mm, vma, page, pte, vma->vm_flags & VM_WRITE);
+		flush_tlb_range(vma, address, address + HPAGE_SIZE);
+		update_mmu_cache(vma, address, *pte);
+	} else {
+		put_page(page);
+	}
+	ret = VM_FAULT_MINOR;
+out:
+	spin_unlock(&mm->page_table_lock);
+	unlock_page(page);
+	return ret;
+}
+
 unsigned long hugetlb_get_unmapped_area(struct file *file, unsigned long addr, unsigned long len,
 		unsigned long pgoff, unsigned long flags)
 {