Another segfault on client side (only sporadic)

["Bernhard J. M. Grün" <bernhard.gruen@xxxxxxxxxxxxxx>]

Hello developers,

We just discovered another segfault on client side. At the moment we
can't give you more information than our version number, a back trace
and our client configuration.

We use version 1.3.0 with patches up to patch-449.

The back trace looks as the follows:
Core was generated by `[glusterfs]
                              '.
Program terminated with signal 11, Segmentation fault.
#0  0x00002aaaaacbc2bd in afr_stat (frame=0x2aaabce32cb0,
    this=<value optimized out>, loc=0x2aaaac0fe168) at afr.c:2602
2602    afr.c: No such file or directory.
        in afr.c
(gdb) bt
#0  0x00002aaaaacbc2bd in afr_stat (frame=0x2aaabce32cb0,
    this=<value optimized out>, loc=0x2aaaac0fe168) at afr.c:2602
#1  0x00002aaaaaece1bb in iot_stat (frame=0x2aaabcc00860, this=0x6126d0,
    loc=0x2aaaac0fe168) at io-threads.c:651
#2  0x00002aaaab0d2252 in wb_stat (frame=0x2aaaad05c5e0, this=0x612fe0,
    loc=0x2aaaac0fe168) at write-behind.c:236
#3  0x0000000000405fd2 in fuse_getattr (req=<value optimized out>,
    ino=<value optimized out>, fi=<value optimized out>) at fuse-bridge.c:496
#4  0x0000000000407139 in fuse_transport_notify (xl=<value optimized out>,
    event=<value optimized out>, data=<value optimized out>)
    at fuse-bridge.c:2067
#5  0x00002af562b6a632 in sys_epoll_iteration (ctx=<value optimized out>)
    at epoll.c:53
#6  0x000000000040356b in main (argc=9, argv=0x7fff48169b78) at glusterfs.c:387

And here is our client configuration for that machine:
### Add client feature and attach to remote subvolume
volume client1
  type protocol/client
  option transport-type tcp/client     # for TCP/IP transport
  option remote-host 10.1.1.13     # IP address of the remote brick
  option remote-port 9999              # default server port is 6996
  option remote-subvolume iothreads        # name of the remote volume
end-volume

### Add client feature and attach to remote subvolume
volume client2
  type protocol/client
  option transport-type tcp/client     # for TCP/IP transport
  option remote-host 10.1.1.14     # IP address of the remote brick
  option remote-port 9999              # default server port is 6996
  option remote-subvolume iothreads        # name of the remote volume
end-volume

volume afrbricks
  type cluster/afr
  subvolumes client1 client2
  option replicate *:2
  option self-heal off
end-volume

volume iothreads    #iothreads can give performance a boost
   type performance/io-threads
   option thread-count 16
   subvolumes afrbricks
end-volume

### Add writeback feature
volume bricks
  type performance/write-behind
  option aggregate-size 0  # unit in bytes
  subvolumes iothreads
end-volume


We hope you can easily find and fix that error. Thank you in advance

Bernhard J. M. Grün