userfaultfd: non-cooperative: add event for memory unmaps
When a non-cooperative userfaultfd monitor copies pages in the
background, it may encounter regions that were already unmapped.
Addition of UFFD_EVENT_UNMAP allows the uffd monitor to track precisely
changes in the virtual memory layout.
Since there might be different uffd contexts for the affected VMAs, we
first should create a temporary representation for the unmap event for
each uffd context and then notify them one by one to the appropriate
userfault file descriptors.
The event notification occurs after the mmap_sem has been released.
[arnd@arndb.de: fix nommu build]
Link: http://lkml.kernel.org/r/20170203165141.3665284-1-arnd@arndb.de
[mhocko@suse.com: fix nommu build]
Link: http://lkml.kernel.org/r/20170202091503.GA22823@dhcp22.suse.cz
Link: http://lkml.kernel.org/r/1485542673-24387-3-git-send-email-rppt@linux.vnet.ibm.com
Signed-off-by: Mike Rapoport <rppt@linux.vnet.ibm.com>
Signed-off-by: Michal Hocko <mhocko@suse.com>
Signed-off-by: Arnd Bergmann <arnd@arndb.de>
Acked-by: Hillf Danton <hillf.zj@alibaba-inc.com>
Cc: Andrea Arcangeli <aarcange@redhat.com>
Cc: "Dr. David Alan Gilbert" <dgilbert@redhat.com>
Cc: Mike Kravetz <mike.kravetz@oracle.com>
Cc: Pavel Emelyanov <xemul@virtuozzo.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
diff --git a/include/linux/userfaultfd_k.h b/include/linux/userfaultfd_k.h
index 2521542..a40be5d 100644
--- a/include/linux/userfaultfd_k.h
+++ b/include/linux/userfaultfd_k.h
@@ -66,6 +66,12 @@
unsigned long start,
unsigned long end);
+extern int userfaultfd_unmap_prep(struct vm_area_struct *vma,
+ unsigned long start, unsigned long end,
+ struct list_head *uf);
+extern void userfaultfd_unmap_complete(struct mm_struct *mm,
+ struct list_head *uf);
+
#else /* CONFIG_USERFAULTFD */
/* mm helpers */
@@ -118,6 +124,18 @@
unsigned long end)
{
}
+
+static inline int userfaultfd_unmap_prep(struct vm_area_struct *vma,
+ unsigned long start, unsigned long end,
+ struct list_head *uf)
+{
+ return 0;
+}
+
+static inline void userfaultfd_unmap_complete(struct mm_struct *mm,
+ struct list_head *uf)
+{
+}
#endif /* CONFIG_USERFAULTFD */
#endif /* _LINUX_USERFAULTFD_K_H */