From 745f234be12b6191b15eae8dd415cc81a9137f47 Mon Sep 17 00:00:00 2001
From: Andrea Arcangeli <aarcange@redhat.com>
Date: Fri, 4 Sep 2015 15:46:14 -0700
Subject: [PATCH] userfaultfd: add vm_userfaultfd_ctx to the vm_area_struct

This adds the vm_userfaultfd_ctx to the vm_area_struct.

Signed-off-by: Andrea Arcangeli <aarcange@redhat.com>
Acked-by: Pavel Emelyanov <xemul@parallels.com>
Cc: Sanidhya Kashyap <sanidhya.gatech@gmail.com>
Cc: zhang.zhanghailiang@huawei.com
Cc: "Kirill A. Shutemov" <kirill@shutemov.name>
Cc: Andres Lagar-Cavilla <andreslc@google.com>
Cc: Dave Hansen <dave.hansen@intel.com>
Cc: Paolo Bonzini <pbonzini@redhat.com>
Cc: Rik van Riel <riel@redhat.com>
Cc: Mel Gorman <mgorman@suse.de>
Cc: Andy Lutomirski <luto@amacapital.net>
Cc: Hugh Dickins <hughd@google.com>
Cc: Peter Feiner <pfeiner@google.com>
Cc: "Dr. David Alan Gilbert" <dgilbert@redhat.com>
Cc: Johannes Weiner <hannes@cmpxchg.org>
Cc: "Huangpeng (Peter)" <peter.huangpeng@huawei.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
---
 include/linux/mm_types.h | 11 +++++++++++
 kernel/fork.c            |  1 +
 2 files changed, 12 insertions(+)

diff --git a/include/linux/mm_types.h b/include/linux/mm_types.h
index 15549578d559..26a30c3566f0 100644
--- a/include/linux/mm_types.h
+++ b/include/linux/mm_types.h
@@ -256,6 +256,16 @@ struct vm_region {
 						* this region */
 };
 
+#ifdef CONFIG_USERFAULTFD
+#define NULL_VM_UFFD_CTX ((struct vm_userfaultfd_ctx) { NULL, })
+struct vm_userfaultfd_ctx {
+	struct userfaultfd_ctx *ctx;
+};
+#else /* CONFIG_USERFAULTFD */
+#define NULL_VM_UFFD_CTX ((struct vm_userfaultfd_ctx) {})
+struct vm_userfaultfd_ctx {};
+#endif /* CONFIG_USERFAULTFD */
+
 /*
  * This struct defines a memory VMM memory area. There is one of these
  * per VM-area/task.  A VM area is any part of the process virtual memory
@@ -322,6 +332,7 @@ struct vm_area_struct {
 #ifdef CONFIG_NUMA
 	struct mempolicy *vm_policy;	/* NUMA policy for the VMA */
 #endif
+	struct vm_userfaultfd_ctx vm_userfaultfd_ctx;
 };
 
 struct core_thread {
diff --git a/kernel/fork.c b/kernel/fork.c
index 03aa2e6de7a4..ceb4eb4abb9d 100644
--- a/kernel/fork.c
+++ b/kernel/fork.c
@@ -456,6 +456,7 @@ static int dup_mmap(struct mm_struct *mm, struct mm_struct *oldmm)
 			goto fail_nomem_anon_vma_fork;
 		tmp->vm_flags &= ~VM_LOCKED;
 		tmp->vm_next = tmp->vm_prev = NULL;
+		tmp->vm_userfaultfd_ctx = NULL_VM_UFFD_CTX;
 		file = tmp->vm_file;
 		if (file) {
 			struct inode *inode = file_inode(file);
-- 
2.20.1