CURRENT (r248103): x11/nvidia-driver fails to compile: @/vm/vm_pager.h:127:2: error: use of undeclared identifier 'RA_WLOCKED'

I rebuild the kernel module for x11/nvidia-driver on a regular basis via
/etc/src.conf setting of

PORTS_MODULES+=                x11/nvidia-driver

but this time, the port gets deleted and - fails to compile (tried
310.32 and 313.26, the latter worked for me before very well).

The compilation error is shown below.

[...]
===> src (all)
cc -O2 -pipe -O3 -march=native -fno-strict-aliasing -O3 -march=native
-DNV_VERSION_STRING=\"313.26\" -D__KERNEL__ -DNVRM -Wno-unused-function
-Wuninitialized -O -mno-red-zone -mcmodel=kernel -UDEBUG -U_DEBUG
-DNDEBUG -O3 -Wno-error=unused-variable -Werror -D_KERNEL -DKLD_MODULE
-nostdinc  -I. -I. -I_at_ -I_at_/contrib/altq -fno-common
-fno-omit-frame-pointer  -mno-aes -mno-avx -mcmodel=kernel -mno-red-zone
-mno-mmx -mno-sse -msoft-float  -fno-asynchronous-unwind-tables
-ffreestanding -fstack-protector -std=iso9899:1999 -Qunused-arguments
-fstack-protector -Wall -Wredundant-decls -Wnested-externs
-Wstrict-prototypes  -Wmissing-prototypes -Wpointer-arith -Winline
-Wcast-qual  -Wundef -Wno-pointer-sign -fformat-extensions
-Wmissing-include-dirs -fdiagnostics-show-option
-Wno-error-tautological-compare -Wno-error-empty-body
-Wno-error-parentheses-equality -c nvidia_ctl.c
In file included from nvidia_ctl.c:14:
In file included from ./nv-freebsd.h:77:
_at_/vm/vm_pager.h:127:2: error: implicit declaration of function
'rw_assert' is invalid in C99 [-Werror,-Wimplicit-function-declaration]
        VM_OBJECT_ASSERT_WLOCKED(object);
        ^
_at_/vm/vm_object.h:212:2: note: expanded from macro 'VM_OBJECT_ASSERT_WLOCKED'
        rw_assert(&(object)->lock, RA_WLOCKED)
        ^
In file included from nvidia_ctl.c:14:
In file included from ./nv-freebsd.h:77:
_at_/vm/vm_pager.h:127:2: error: use of undeclared identifier 'RA_WLOCKED'
        VM_OBJECT_ASSERT_WLOCKED(object);
        ^
_at_/vm/vm_object.h:212:29: note: expanded from macro
'VM_OBJECT_ASSERT_WLOCKED'
        rw_assert(&(object)->lock, RA_WLOCKED)
                                   ^
In file included from nvidia_ctl.c:14:
In file included from ./nv-freebsd.h:77:
_at_/vm/vm_pager.h:144:2: error: use of undeclared identifier 'RA_WLOCKED'
        VM_OBJECT_ASSERT_WLOCKED(object);
        ^
_at_/vm/vm_object.h:212:29: note: expanded from macro
'VM_OBJECT_ASSERT_WLOCKED'
        rw_assert(&(object)->lock, RA_WLOCKED)
                                   ^
In file included from nvidia_ctl.c:14:
In file included from ./nv-freebsd.h:77:
_at_/vm/vm_pager.h:168:2: error: use of undeclared identifier 'RA_WLOCKED'
        VM_OBJECT_ASSERT_WLOCKED(object);
        ^
_at_/vm/vm_object.h:212:29: note: expanded from macro
'VM_OBJECT_ASSERT_WLOCKED'
        rw_assert(&(object)->lock, RA_WLOCKED)
                                   ^
In file included from nvidia_ctl.c:14:
In file included from ./nv-freebsd.h:77:
_at_/vm/vm_pager.h:191:2: error: use of undeclared identifier 'RA_WLOCKED'
        VM_OBJECT_ASSERT_WLOCKED(m->object);
        ^
_at_/vm/vm_object.h:212:29: note: expanded from macro
'VM_OBJECT_ASSERT_WLOCKED'
        rw_assert(&(object)->lock, RA_WLOCKED)
                                   ^
5 errors generated.
*** [nvidia_ctl.o] Error code 1

Stop in /usr/ports/x11/nvidia-driver/work/NVIDIA-FreeBSD-x86_64-313.26/src.
*** [all] Error code 1

Stop in /usr/ports/x11/nvidia-driver/work/NVIDIA-FreeBSD-x86_64-313.26.
*** [do-build] Error code 1

Stop in /usr/ports/x11/nvidia-driver.
*** [build] Error code 1