userfaultfd: non-cooperative: add mremap() event

The event denotes that an area [start:end] moves to different location.
Length change isn't reported as "new" addresses, if they appear on the
uffd reader side they will not contain any data and the latter can just
zeromap them.

Waiting for the event ACK is also done outside of mmap sem, as for fork
event.

Link: http://lkml.kernel.org/r/20161216144821.5183-12-aarcange@redhat.com
Signed-off-by: Pavel Emelyanov <xemul@parallels.com>
Signed-off-by: Mike Rapoport <rppt@linux.vnet.ibm.com>
Signed-off-by: Andrea Arcangeli <aarcange@redhat.com>
Cc: "Dr. David Alan Gilbert" <dgilbert@redhat.com>
Cc: Hillf Danton <hillf.zj@alibaba-inc.com>
Cc: Michael Rapoport <RAPOPORT@il.ibm.com>
Cc: Mike Kravetz <mike.kravetz@oracle.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

1 files changed, 17 insertions, 0 deletions

diff --git a/include/linux/userfaultfd_k.h b/include/linux/userfaultfd_k.h
index 79002bca1f43..7f318a46044b 100644
--- a/include/linux/userfaultfd_k.h
+++ b/include/linux/userfaultfd_k.h
@@ -55,6 +55,12 @@ static inline bool userfaultfd_armed(struct vm_area_struct *vma)
 extern int dup_userfaultfd(struct vm_area_struct *, struct list_head *);
 extern void dup_userfaultfd_complete(struct list_head *);
 
+extern void mremap_userfaultfd_prep(struct vm_area_struct *,
+                                    struct vm_userfaultfd_ctx *);
+extern void mremap_userfaultfd_complete(struct vm_userfaultfd_ctx,
+                                        unsigned long from, unsigned long to,
+                                        unsigned long len);
+
 #else /* CONFIG_USERFAULTFD */
 
 /* mm helpers */
@@ -89,6 +95,17 @@ static inline void dup_userfaultfd_complete(struct list_head *l)
 {
 }
 
+static inline void mremap_userfaultfd_prep(struct vm_area_struct *vma,
+                                           struct vm_userfaultfd_ctx *ctx)
+{
+}
+
+static inline void mremap_userfaultfd_complete(struct vm_userfaultfd_ctx ctx,
+                                               unsigned long from,
+                                               unsigned long to,
+                                               unsigned long len)
+{
+}
 #endif /* CONFIG_USERFAULTFD */
 
 #endif /* _LINUX_USERFAULTFD_K_H */