userfaultfd: teach vma_merge to merge across vma->vm_userfaultfd_ctx

vma->vm_userfaultfd_ctx is yet another vma parameter that vma_merge
must be aware about so that we can merge vmas back like they were
originally before arming the userfaultfd on some memory range.

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>

1 files changed, 2 insertions, 1 deletions

diff --git a/mm/mlock.c b/mm/mlock.c
index 6fd2cf15e868..25936680064f 100644
--- a/mm/mlock.c
+++ b/mm/mlock.c
@@ -510,7 +510,8 @@ static int mlock_fixup(struct vm_area_struct *vma, struct vm_area_struct **prev,
 
         pgoff = vma->vm_pgoff + ((start - vma->vm_start) >> PAGE_SHIFT);
         *prev = vma_merge(mm, *prev, start, end, newflags, vma->anon_vma,
-                          vma->vm_file, pgoff, vma_policy(vma));
+                          vma->vm_file, pgoff, vma_policy(vma),
+                          vma->vm_userfaultfd_ctx);
         if (*prev) {
                 vma = *prev;
                 goto success;