userfaultfd: Rename uffd_api.bits into .features

This is (seems to be) the minimal thing that is required to unblock
standard uffd usage from the non-cooperative one.  Now more bits can be
added to the features field indicating e.g.  UFFD_FEATURE_FORK and others
needed for the latter use-case.

Signed-off-by: Pavel Emelyanov <xemul@parallels.com>
Signed-off-by: Andrea Arcangeli <aarcange@redhat.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, 9 insertions, 3 deletions

diff --git a/include/uapi/linux/userfaultfd.h b/include/uapi/linux/userfaultfd.h
index 09c2e2a8c9d6..330206016249 100644
--- a/include/uapi/linux/userfaultfd.h
+++ b/include/uapi/linux/userfaultfd.h
@@ -12,8 +12,8 @@
 #include <linux/types.h>
 
 #define UFFD_API ((__u64)0xAA)
-/* FIXME: add "|UFFD_BIT_WP" to UFFD_API_BITS after implementing it */
-#define UFFD_API_BITS (UFFD_BIT_WRITE)
+/* FIXME: add "|UFFD_FEATURE_WP" to UFFD_API_FEATURES after implementing it */
+#define UFFD_API_FEATURES (UFFD_FEATURE_WRITE_BIT)
 #define UFFD_API_IOCTLS                         \
         ((__u64)1 << _UFFDIO_REGISTER |         \
          (__u64)1 << _UFFDIO_UNREGISTER |       \
@@ -53,12 +53,18 @@
 #define UFFD_BIT_WP     (1<<1)  /* handle_userfault() reason VM_UFFD_WP */
 #define UFFD_BITS       2       /* two above bits used for UFFD_BIT_* mask */
 
+/*
+ * Features reported in uffdio_api.features field
+ */
+#define UFFD_FEATURE_WRITE_BIT  (1<<0) /* Corresponds to UFFD_BIT_WRITE */
+#define UFFD_FEATURE_WP_BIT     (1<<1) /* Corresponds to UFFD_BIT_WP */
+
 struct uffdio_api {
         /* userland asks for an API number */
         __u64 api;
 
         /* kernel answers below with the available features for the API */
-        __u64 bits;
+        __u64 features;
         __u64 ioctls;
 };