Description of problem:

Program received signal SIGSEGV, Segmentation fault.
0x00007fb751bb46c5 in wb_sync_cbk (frame=0x7fb7547c3338, cookie=0x7fb754a3cdbc, 
    this=0x22eeb40, op_ret=-1, op_errno=116, prebuf=0x0, postbuf=0x0)
    at write-behind.c:375
375	        file = local->file;
(gdb) bt
#0  0x00007fb751bb46c5 in wb_sync_cbk (frame=0x7fb7547c3338, cookie=0x7fb754a3cdbc, 
    this=0x22eeb40, op_ret=-1, op_errno=116, prebuf=0x0, postbuf=0x0)
    at write-behind.c:375
#1  0x00007fb751de5df9 in client3_1_writev (frame=0x7fb754a3cdbc, this=0x22ed860, 
    data=0x7fffd4332e10) at client3_1-fops.c:3587
#2  0x00007fb751dcfd0f in client_writev (frame=0x7fb754a3cdbc, this=0x22ed860, 
    fd=0x7fb75082219c, vector=0x22f8380, count=1, off=7995392, iobref=0x22f7cc0)
    at client.c:820
#3  0x00007fb751bb5123 in wb_sync (frame=0x7fb7547c35b0, file=0x22f8d40, 
    winds=0x7fffd43330a0) at write-behind.c:548
#4  0x00007fb751bbb6e9 in wb_do_ops (frame=0x7fb7547c35b0, file=0x22f8d40, 
    winds=0x7fffd43330a0, unwinds=0x7fffd4333090, other_requests=0x7fffd4333080)
    at write-behind.c:1859
#5  0x00007fb751bbbf5d in wb_process_queue (frame=0x7fb7547c35b0, file=0x22f8d40)
    at write-behind.c:2048
#6  0x00007fb751bb4854 in wb_sync_cbk (frame=0x7fb7547c35b0, cookie=0x7fb754a3c2fc, 
    this=0x22eeb40, op_ret=-1, op_errno=107, prebuf=0x7fffd4333210, 
    postbuf=0x7fffd43331a0) at write-behind.c:405
#7  0x00007fb751dda0e4 in client3_1_writev_cbk (req=0x7fb750eea02c, 
    iov=0x7fffd43333e0, count=1, myframe=0x7fb754a3c2fc) at client3_1-fops.c:692
#8  0x00007fb755bd89e1 in saved_frames_unwind (saved_frames=0x22e90f0)
    at rpc-clnt.c:385
#9  0x00007fb755bd8a90 in saved_frames_destroy (frames=0x22e90f0) at rpc-clnt.c:403
#10 0x00007fb755bd9005 in rpc_clnt_connection_cleanup (conn=0x22f6d40)
    at rpc-clnt.c:559
#11 0x00007fb755bd9ae6 in rpc_clnt_notify (trans=0x22f6e60, mydata=0x22f6d40, 
    event=RPC_TRANSPORT_DISCONNECT, data=0x22f6e60) at rpc-clnt.c:863
#12 0x00007fb755bd5d5c in rpc_transport_notify (this=0x22f6e60, 
    event=RPC_TRANSPORT_DISCONNECT, data=0x22f6e60) at rpc-transport.c:498
#13 0x00007fb752c1d213 in socket_event_poll_err (this=0x22f6e60) at socket.c:694
#14 0x00007fb752c21849 in socket_event_handler (fd=7, idx=1, data=0x22f6e60, 
    poll_in=1, poll_out=0, poll_err=16) at socket.c:1797
#15 0x00007fb755e2a6c4 in event_dispatch_epoll_handler (event_pool=0x22e3d90, 
    events=0x22e8040, i=0) at event.c:794
#16 0x00007fb755e2a8e7 in event_dispatch_epoll (event_pool=0x22e3d90) at event.c:856
#17 0x00007fb755e2ac72 in event_dispatch (event_pool=0x22e3d90) at event.c:956
#18 0x0000000000407a5e in main ()


How reproducible:

Mount a regular single-brick volume.  Start I/O (I used iozone).  Simulate a brick failure by stopping the glusterfsd process.  More than half the time, the client will crash as above.


Actual results:

See above.

Expected results:

I/O stoppage and/or errors on the client, followed by normal operation after the glusterfsd process is resumed and allows reconnection.

Additional info:

This was first observed using the SSL patch, but I wanted to reproduce it on mainline before reporting and I was able to do so on the first try.