[PATCH 06/21] userfaultfd: add VM_UFFD_MISSING and VM_UFFD_WP

Andrea Arcangeli
2015-03-05T17:17:49Z

These two flags gets set in vma->vm_flags to tell the VM common code
if the userfaultfd is armed and in which mode (only tracking missing
faults, only tracking wrprotect faults or both). If neither flags is
set it means the userfaultfd is not armed on the vma.

Signed-off-by: Andrea Arcangeli <aarcange@redhat.com>
---
include/linux/mm.h | 2 ++
kernel/fork.c | 2 +-
2 files changed, 3 insertions(+), 1 deletion(-)

diff --git a/include/linux/mm.h b/include/linux/mm.h
index 47a9392..762ef9d 100644
--- a/include/linux/mm.h
+++ b/include/linux/mm.h
@@ -123,8 +123,10 @@ extern unsigned int kobjsize(const void *objp);
#define VM_MAYSHARE 0x00000080

#define VM_GROWSDOWN 0x00000100 /* general info on the segment */
+#define VM_UFFD_MISSING 0x00000200 /* missing pages tracking */
#define VM_PFNMAP 0x00000400 /* Page-ranges managed without "struct page", just pure PFN */
#define VM_DENYWRITE 0x00000800 /* ETXTBSY on write attempts.. */
+#define VM_UFFD_WP 0x00001000 /* wrprotect pages tracking */

#define VM_LOCKED 0x00002000
#define VM_IO 0x00004000 /* Memory mapped I/O or similar */
diff --git a/kernel/fork.c b/kernel/fork.c
index cb215c0..cfab6e9 100644
--- a/kernel/fork.c
+++ b/kernel/fork.c
@@ -423,7 +423,7 @@ static int dup_mmap(struct mm_struct *mm, struct mm_struct *oldmm)
tmp->vm_mm = mm;
if (anon_vma_fork(tmp, mpnt))
goto fail_nomem_anon_vma_fork;
- tmp->vm_flags &= ~VM_LOCKED;
+ tmp->vm_flags &= ~(VM_LOCKED|VM_UFFD_MISSING|VM_UFFD_WP);
tmp->vm_next = tmp->vm_prev = NULL;
tmp->vm_userfaultfd_ctx = NULL_VM_UFFD_CTX;
file = tmp->vm_file;