[PATCH 05/21] userfaultfd: add vm_userfaultfd_ctx to the vm_area_struct

[Andrea Arcangeli <aarcange@redhat.com>]

This adds the vm_userfaultfd_ctx to the vm_area_struct.

Signed-off-by: Andrea Arcangeli <aarcange@redhat.com>
---
 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 199a03a..fbf21f5 100644
--- a/include/linux/mm_types.h
+++ b/include/linux/mm_types.h
@@ -247,6 +247,16 @@ 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
@@ -313,6 +323,7 @@ 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 cf65139..cb215c0 100644
--- a/kernel/fork.c
+++ b/kernel/fork.c
@@ -425,6 +425,7 @@ 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);

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