iov_iter_pipe warning.

[Dave Jones]

WARNING: CPU: 0 PID: 9290 at lib/iov_iter.c:836 iov_iter_pipe+0x71/0x80
CPU: 0 PID: 9290 Comm: trinity-c7 Not tainted 4.11.0-rc3-think+ #3 
Call Trace:
 dump_stack+0x68/0x93
 __warn+0xcb/0xf0
 warn_slowpath_null+0x1d/0x20
 iov_iter_pipe+0x71/0x80
 generic_file_splice_read+0x37/0x140
 do_splice_to+0x79/0x90
 splice_direct_to_actor+0xb8/0x220
 ? generic_pipe_buf_nosteal+0x10/0x10
 do_splice_direct+0x9e/0xd0
 do_sendfile+0x1d7/0x3c0
 SyS_sendfile64+0x73/0xe0
 do_syscall_64+0x66/0x1d0
 entry_SYSCALL64_slow_path+0x25/0x25
RIP: 0033:0x7f86804bf0f9
RSP: 002b:00007ffd5e613038 EFLAGS: 00000246
 ORIG_RAX: 0000000000000028
RAX: ffffffffffffffda RBX: 0000000000000028 RCX: 00007f86804bf0f9
RDX: 00007f867e92a000 RSI: 000000000000018b RDI: 000000000000011b
RBP: 00007f8680b5d000 R08: 0000000000000000 R09: ffffffffffffff5b
R10: 0000000000221200 R11: 0000000000000246 R12: 0000000000000002
R13: 00007f8680b5d048 R14: 00007f8680b95ad8 R15: 00007f8680b5d000
---[ end trace e50d88214985fd43 ]---


 836         WARN_ON(pipe->nrbufs == pipe->buffers);