[-next] rename of VM_NR_PDFLUSH_THREADS breaks strace compilation

[Heiko Carstens]

Hi Rafael,

your patch 77cab92a2cb1 ("sysctl: clean up nr_pdflush_threads
leftover") in linux-next breaks strace compilation if used with kernel
headers from linux-next.

This:

--- a/include/uapi/linux/sysctl.h
+++ b/include/uapi/linux/sysctl.h
[...]
-       VM_NR_PDFLUSH_THREADS=15, /* nr_pdflush_threads */
+       VM_UNUSED15=15,         /* was: int: nr_pdflush_threads */

causes this when trying to build strace:

+ ./bootstrap
configure.ac:54: installing './compile'
configure.ac:47: installing './config.guess'
configure.ac:47: installing './config.sub'
configure.ac:45: installing './install-sh'
configure.ac:45: installing './missing'
Makefile.am: installing './depcomp'
Makefile.am:975: warning: variable 'ioctlsort_LDFLAGS' is defined but no program or
Makefile.am:975: library has 'ioctlsort' as canonical name (possible typo)
parallel-tests: installing './test-driver'
+ ./configure
++ nproc
+ make -j 10
In file included from defs.h:308,
from sysctl.c:31:
xlat/sysctl_vm.h:23:7: error: ‘VM_NR_PDFLUSH_THREADS’ undeclared here (not in a function)
XLAT(VM_NR_PDFLUSH_THREADS),
^~~~~~~~~~~~~~~~~~~~~
xlat.h:49:35: note: in definition of macro ‘XLAT’
# define XLAT(val)   { (unsigned)(val), #val }
^~~