mm: use mm_populate() for blocking remap_file_pages()

Signed-off-by: NMichel Lespinasse <walken@google.com>
Reviewed-by: NRik van Riel <riel@redhat.com>
Tested-by: NAndy Lutomirski <luto@amacapital.net>
Cc: Greg Ungerer <gregungerer@westnet.com.au>
Cc: David Howells <dhowells@redhat.com>
Signed-off-by: NAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>

mm/fremap.c

@@ -129,6 +129,7 @@ SYSCALL_DEFINE5(remap_file_pages, unsigned long, start, unsigned long, size,
 	struct vm_area_struct *vma;
 	int err = -EINVAL;
 	int has_write_lock = 0;
+	vm_flags_t vm_flags;
 
 	if (prot)
 		return err;
@@ -228,30 +229,16 @@ SYSCALL_DEFINE5(remap_file_pages, unsigned long, start, unsigned long, size,
 		/*
 		 * drop PG_Mlocked flag for over-mapped range
 		 */
-		vm_flags_t saved_flags = vma->vm_flags;
 		if (!has_write_lock)
 			goto get_write_lock;
+		vm_flags = vma->vm_flags;
 		munlock_vma_pages_range(vma, start, start + size);
-		vma->vm_flags = saved_flags;
+		vma->vm_flags = vm_flags;
 	}
 
 	mmu_notifier_invalidate_range_start(mm, start, start + size);
 	err = vma->vm_ops->remap_pages(vma, start, size, pgoff);
 	mmu_notifier_invalidate_range_end(mm, start, start + size);
-	if (!err) {
-		if (vma->vm_flags & VM_LOCKED) {
-			/*
-			 * might be mapping previously unmapped range of file
-			 */
-			mlock_vma_pages_range(vma, start, start + size);
-		} else if (!(flags & MAP_NONBLOCK)) {
-			if (unlikely(has_write_lock)) {
-				downgrade_write(&mm->mmap_sem);
-				has_write_lock = 0;
-			}
-			make_pages_present(start, start+size);
-		}
-	}
 
 	/*
 	 * We can't clear VM_NONLINEAR because we'd have to do
@@ -260,10 +247,13 @@ SYSCALL_DEFINE5(remap_file_pages, unsigned long, start, unsigned long, size,
 	 */
 
 out:
+	vm_flags = vma->vm_flags;
 	if (likely(!has_write_lock))
 		up_read(&mm->mmap_sem);
 	else
 		up_write(&mm->mmap_sem);
+	if (!err && ((vm_flags & VM_LOCKED) || !(flags & MAP_NONBLOCK)))
+		mm_populate(start, size);
 
 	return err;
 }