Description of problem:
=======================

While trying to remove-brick with replica count 2 from the existing volume(replica 2), glusterd crashes with following bt:

#0  0x00007fcdd03e681c in subvol_matcher_update	(req=0x25989cc)	at glusterd-brick-ops.c:662
#1  __glusterd_handle_remove_brick (req=0x25989cc) at glusterd-brick-ops.c:985
#2  0x00007fcdd03542bf in glusterd_big_locked_handler (req=0x25989cc, actor_fn=0x7fcdd03e5f90 <__glusterd_handle_remove_brick>)	at glusterd-handler.c:83
#3  0x0000003b0d8655b2 in synctask_wrap	(old_task=<value optimized out>) at syncop.c:375
#4  0x0000003b028438f0 in ?? ()	from /lib64/libc.so.6
#5  0x0000000000000000 in ?? ()
(gdb) 

Logs suggest:
=============

[2015-06-10 14:18:01.134630] I [glusterd-handler.c:1404:__glusterd_handle_cli_get_volume] 0-glusterd: Received get vol req
[2015-06-10 14:18:01.137158] I [glusterd-handler.c:1404:__glusterd_handle_cli_get_volume] 0-glusterd: Received get vol req
[2015-06-10 14:18:28.239515] I [glusterd-brick-ops.c:779:__glusterd_handle_remove_brick] 0-management: Received rem brick req
[2015-06-10 14:18:28.239593] I [glusterd-brick-ops.c:849:__glusterd_handle_remove_brick] 0-management: request to change replica-count to 2
pending frames:
frame : type(0) op(0)
patchset: git://git.gluster.com/glusterfs.git
signal received: 11
time of crash: 
2015-06-10 14:18:28
configuration details:
argp 1
backtrace 1
dlfcn 1
libpthread 1
llistxattr 1
setfsid 1
spinlock 1
epoll.h 1
xattr.h 1
st_atim.tv_nsec 1
package-string: glusterfs 3.7.1
/usr/lib64/libglusterfs.so.0(_gf_msg_backtrace_nomem+0xb6)[0x3b0d824b66]
/usr/lib64/libglusterfs.so.0(gf_print_trace+0x33f)[0x3b0d84359f]
/lib64/libc.so.6[0x3b028326a0]
/usr/lib64/glusterfs/3.7.1/xlator/mgmt/glusterd.so(__glusterd_handle_remove_brick+0x88c)[0x7fcdd03e681c]
/usr/lib64/glusterfs/3.7.1/xlator/mgmt/glusterd.so(glusterd_big_locked_handler+0x3f)[0x7fcdd03542bf]
/usr/lib64/libglusterfs.so.0(synctask_wrap+0x12)[0x3b0d8655b2]
/lib64/libc.so.6[0x3b028438f0]
---------
(END) 



Version-Release number of selected component (if applicable):
=============================================================

glusterfs-3.7.1-1.el6rhs.x86_64


How reproducible:
==================

Always


Steps to Reproduce:
===================
1. Create 2x2 volume
2. Remove 2 bricks, one from each subvolume and use replica count as 2


Actual results:
===============

Glusterd crash


Expected results:
=================

Removing brick with replica count 2 from replica count 2 is a failure case, it should print usage or fail gracefully.