build OK
msync_poc.c: In function 'makefile':
msync_poc.c:63:7: warning: unused variable 'z' [-Wunused-variable]
  char z[PGSZ];
       ^
msync_poc.c:62:10: warning: unused variable 'i' [-Wunused-variable]
  int fd, i;
          ^
Filesystem 512-blocks    Used    Avail Capacity  Mounted on
vbd0s1d      48959104 5246208 43712896    11%    /
msync_poc.c: In function 'makefile':
msync_poc.c:63:7: warning: unused variable (removed in final build)
final build on guest (hammer2 home dir):
DF5829 $ cc -O2 -Wall -o msync_poc msync_poc.c
BUILD_OK (clean, no warnings)