changetimerecorder: Brick process crashed at ctr xlator in notify fun…

…ction

Problem: Sometime brick process is getting crash in notify function at the
         time of cleanup db connection while brick mux is enabled.

Solution: In changetimerrecorder (ctr) notify function after cleanup
          db connection set to db_conn to NULL to avoid reuse the same
          db connection again.

Note: Below is the backtrace pattern showing by brick process
      #0  0x00007ff98a30c1f7 in raise () from /lib64/libc.so.6
      #1  0x00007ff98a30d8e8 in abort () from /lib64/libc.so.6
      #2  0x00007ff98a34bf47 in __libc_message () from /lib64/libc.so.6
      #3  0x00007ff98a351b54 in malloc_printerr () from /lib64/libc.so.6
      #4  0x00007ff98a3537aa in _int_free () from /lib64/libc.so.6
      #5  0x00007ff97d95e311 in gf_sql_connection_fini (sql_connection=sql_connection@entry=0x7ff8e8496b50) at gfdb_sqlite3.c:42
      #6  0x00007ff97d95e38a in gf_sqlite3_fini (db_conn=0x7ff92ca04470) at gfdb_sqlite3.c:507
      #7  0x00007ff97d957156 in fini_db (_conn_node=0x7ff92ca04470) at gfdb_data_store.c:326
      #8  0x00007ff97db78679 in notify (this=0x7ff92c5b3670, event=9, data=0x7ff92c5b5a00) at changetimerecorder.c:2178
      #9  0x00007ff98bca0dc2 in xlator_notify (xl=0x7ff92c5b3670, event=event@entry=9, data=data@entry=0x7ff92c5b5a00) at xlator.c:549
      #10 0x00007ff98bd3ac12 in default_notify (this=this@entry=0x7ff92c5b5a00, event=9, data=data@entry=0x7ff92c5b6d50) at defaults.c:3139

> BUG: 1475632
> Change-Id: Idd4bfdb4629c4799ac477ade81228065212683fb
> Signed-off-by: Mohit Agrawal <[email protected]>
> Reviewed-on: https://review.gluster.org/17888
> Reviewed-by: Jeff Darcy <[email protected]>
> Smoke: Gluster Build System <[email protected]>
> CentOS-regression: Gluster Build System <[email protected]>
> Reviewed-by: Atin Mukherjee <[email protected]>
> (cherry picked from commit fc0fce2)

BUG: 1476109
Change-Id: I96b7ab765b596cec5b779d7186ec549615e3b68b
Signed-off-by: Mohit Agrawal <[email protected]>
Reviewed-on: https://review.gluster.org/17902
Smoke: Gluster Build System <[email protected]>
Reviewed-by: Atin Mukherjee <[email protected]>
CentOS-regression: Gluster Build System <[email protected]>

xlators/features/changetimerecorder/src/changetimerecorder.c

@@ -2316,6 +2316,8 @@ notify (xlator_t *this, int event, void *data, ...)
                                 CTR_MSG_CLOSE_DB_CONN_FAILED, "Failed closing "
                                 "db connection");
                }
+               if (priv->_db_conn)
+                        priv->_db_conn = NULL;
        }
        ret = default_notify (this, event, data);