Make umoven report success as 0, not >=0, stop returning success on partial reads

umoven() uses process_vm_readv() when available but it returns the
return value of that syscall, which is the number of bytes copied,
while its callers expect it to simply return zero on success.

It was causing syscalls that take a user-space argument to print
the abbreviated version, e.g.:

  epoll_ctl(5, EPOLL_CTL_ADD, 10, {...})

Instead of:

  epoll_ctl(5, EPOLL_CTL_ADD, 10, {EPOLLIN, {u32=10, u64=10}})

* util.c (umoven): Make umove[n] report success as 0, not >=0,
stop returning "success" on partial reads.

Signed-off-by: Denys Vlasenko <vda.linux@googlemail.com>
1 file changed