[test]
vfs object                    = glusterfs
glusterfs:volume              = test
path                          = /
browseable                    = yes
writable                      = no
guest ok                      = no
map archive                   = no
# level2 oplocks                = no
# blocking locks                = no
follow symlinks               = yes
# strict locking                = no
# posix locking                 = no
# oplocks                       = no
# fake oplocks                  = yes
directory mask                = 0000
force directory mode          = 0700
create mask                   = 0000
force create mode             = 0700
# force security mode           = 2770
# force directory security mode = 2770
glusterfs:logfile           = /var/log/samba/glusterfs-vol-test-%M.log
glusterfs:loglevel          = 7
write list = root
read list =
valid users = root
# performance feature
inherit permissions = yes
wide links = no
kernel share modes = no
#aio read size = 65536 #16384
#aio write size = 65536 #16384
aio write behind = true
write cache size = 2097152
max xmit = 65536
large readwrite = yes
read raw = Yes
write raw = Yes
socket options = TCP_NODELAY IPTOS_LOWDELAY SO_RCVBUF=131072 SO_SNDBUF=131072

Could you please install the missing debuginfo packages and reproduce the issue. Then post a 'bt full' please.

Thanks!

#0  0x00007f8e3e4575f7 in raise () from /lib64/libc.so.6
No symbol table info available.
#1  0x00007f8e3e458ce8 in abort () from /lib64/libc.so.6
No symbol table info available.
#2  0x00007f8e3fdbf98b in dump_core () at ../source3/lib/dumpcore.c:337
        called = true
        __FUNCTION__ = "dump_core"
#3  0x00007f8e3fdb21a7 in smb_panic_s3 (why=<optimized out>) at ../source3/lib/util.c:811
        cmd = <optimized out>
        result = <optimized out>
        __FUNCTION__ = "smb_panic_s3"
#4  0x00007f8e41c3791f in smb_panic (why=why@entry=0x7f8e4191d2d0 "cups_pcap_load_async: reinit_after_fork() failed") at ../lib/util/fault.c:166
No locals.
#5  0x00007f8e4178b7db in cups_pcap_load_async (pfd=0x7f8e43601ba0, msg_ctx=0x7f8e435e51f0, ev=0x7f8e435e5100) at ../source3/printing/print_cups.c:480
        fds = {18, 38}
        pid = 0
        status = <optimized out>
#6  cups_cache_reload (ev=ev@entry=0x7f8e435e5100, msg_ctx=msg_ctx@entry=0x7f8e435e51f0, 
    post_cache_fill_fn=post_cache_fill_fn@entry=0x7f8e41774210 <reload_pcap_change_notify>) at ../source3/printing/print_cups.c:581
        cb_args = 0x7f8e43601ba0
        p_pipe_fd = 0x7f8e43601ba0
        __FUNCTION__ = "cups_cache_reload"
#7  0x00007f8e4178849e in pcap_cache_reload (ev=0x7f8e435e5100, msg_ctx=0x7f8e435e51f0, 
    post_cache_fill_fn=post_cache_fill_fn@entry=0x7f8e41774210 <reload_pcap_change_notify>) at ../source3/printing/pcap.c:150
        pcap_name = 0x7f8e3fded58b "cups"
        pcap_reloaded = false
        post_cache_fill_fn_handled = false
        pcache = 0x0
        __FUNCTION__ = "pcap_cache_reload"
#8  0x00007f8e41774594 in print_queue_housekeeping (now=<optimized out>, pvt=<optimized out>) at ../source3/printing/queue_process.c:170
        state = 0x7f8e435e59d0
        printcap_cache_time = <optimized out>
        t = 170447
        __FUNCTION__ = "print_queue_housekeeping"
#9  0x00007f8e3fdc78ce in smbd_idle_event_handler (ctx=0x7f8e435e5100, te=<optimized out>, now=..., private_data=<optimized out>) at ../source3/lib/events.c:428
        event = 0x7f8e43600810
        __FUNCTION__ = "smbd_idle_event_handler"
#10 0x00007f8e3e7eb22f in tevent_common_loop_timer_delay () from /lib64/libtevent.so.0
No symbol table info available.
#11 0x00007f8e3fdc7f69 in run_events_poll (ev=0x7f8e435e5100, pollrtn=0, pfds=0x7f8e43600f70, num_pfds=5) at ../source3/lib/events.c:199
        tval = {tv_sec = 1465700974, tv_usec = 599954}
#12 0x00007f8e3fdc8160 in s3_event_loop_once (ev=0x7f8e435e5100, location=<optimized out>) at ../source3/lib/events.c:326

#0  0x00007f8e3e4575f7 in raise () from /lib64/libc.so.6
No symbol table info available.
#1  0x00007f8e3e458ce8 in abort () from /lib64/libc.so.6
No symbol table info available.
#2  0x00007f8e3fdbf98b in dump_core () at ../source3/lib/dumpcore.c:337
        called = true
        __FUNCTION__ = "dump_core"
#3  0x00007f8e3fdb21a7 in smb_panic_s3 (why=<optimized out>) at ../source3/lib/util.c:811
        cmd = <optimized out>
        result = <optimized out>
        __FUNCTION__ = "smb_panic_s3"
#4  0x00007f8e41c3791f in smb_panic (why=why@entry=0x7f8e4191d2d0 "cups_pcap_load_async: reinit_after_fork() failed") at ../lib/util/fault.c:166
No locals.
#5  0x00007f8e4178b7db in cups_pcap_load_async (pfd=0x7f8e43601ba0, msg_ctx=0x7f8e435e51f0, ev=0x7f8e435e5100) at ../source3/printing/print_cups.c:480
        fds = {18, 38}
        pid = 0
        status = <optimized out>
#6  cups_cache_reload (ev=ev@entry=0x7f8e435e5100, msg_ctx=msg_ctx@entry=0x7f8e435e51f0, 
    post_cache_fill_fn=post_cache_fill_fn@entry=0x7f8e41774210 <reload_pcap_change_notify>) at ../source3/printing/print_cups.c:581
        cb_args = 0x7f8e43601ba0
        p_pipe_fd = 0x7f8e43601ba0
        __FUNCTION__ = "cups_cache_reload"
#7  0x00007f8e4178849e in pcap_cache_reload (ev=0x7f8e435e5100, msg_ctx=0x7f8e435e51f0, 
    post_cache_fill_fn=post_cache_fill_fn@entry=0x7f8e41774210 <reload_pcap_change_notify>) at ../source3/printing/pcap.c:150
        pcap_name = 0x7f8e3fded58b "cups"
        pcap_reloaded = false
        post_cache_fill_fn_handled = false
        pcache = 0x0
        __FUNCTION__ = "pcap_cache_reload"
#8  0x00007f8e41774594 in print_queue_housekeeping (now=<optimized out>, pvt=<optimized out>) at ../source3/printing/queue_process.c:170
        state = 0x7f8e435e59d0
        printcap_cache_time = <optimized out>
        t = 170447
        __FUNCTION__ = "print_queue_housekeeping"
#9  0x00007f8e3fdc78ce in smbd_idle_event_handler (ctx=0x7f8e435e5100, te=<optimized out>, now=..., private_data=<optimized out>) at ../source3/lib/events.c:428
        event = 0x7f8e43600810
        __FUNCTION__ = "smbd_idle_event_handler"
#10 0x00007f8e3e7eb22f in tevent_common_loop_timer_delay () from /lib64/libtevent.so.0
No symbol table info available.
#11 0x00007f8e3fdc7f69 in run_events_poll (ev=0x7f8e435e5100, pollrtn=0, pfds=0x7f8e43600f70, num_pfds=5) at ../source3/lib/events.c:199
        tval = {tv_sec = 1465700974, tv_usec = 599954}
#12 0x00007f8e3fdc8160 in s3_event_loop_once (ev=0x7f8e435e5100, location=<optimized out>) at ../source3/lib/events.c:326
---Type <return> to continue, or q <return> to quit---
        state = 0x7f8e43600bd0
        timeout = 59951
        num_pfds = 5
        ret = <optimized out>
        poll_errno = 4
#13 0x00007f8e3e7e70fd in _tevent_loop_once () from /lib64/libtevent.so.0
No symbol table info available.
#14 0x00007f8e3e7e729b in tevent_common_loop_wait () from /lib64/libtevent.so.0
No symbol table info available.
#15 0x00007f8e417748b8 in start_background_queue (ev=ev@entry=0x7f8e435e5100, msg_ctx=msg_ctx@entry=0x7f8e435e51f0, logfile=logfile@entry=0x0)
    at ../source3/printing/queue_process.c:427
        fde = <optimized out>
        ret = <optimized out>
        status = <optimized out>
        pid = <optimized out>
        pause_pipe = {-1, 39}
        __FUNCTION__ = "start_background_queue"
#16 0x00007f8e41774b9b in printing_subsystem_init (ev_ctx=ev_ctx@entry=0x7f8e435e5100, msg_ctx=msg_ctx@entry=0x7f8e435e51f0, start_daemons=start_daemons@entry=true, 
    background_queue=<optimized out>) at ../source3/printing/queue_process.c:459
        pid = -1
#17 0x00007f8e42297fbb in main (argc=<optimized out>, argv=<optimized out>) at ../source3/smbd/server.c:1554
        bgq = <optimized out>
        is_daemon = <optimized out>
        interactive = <optimized out>
        Fork = true
        no_process_group = 64
        log_stdout = <optimized out>
        ports = 0x0
        profile_level = 0x0
        opt = <optimized out>
        pc = 0x7f8e414da120 <DEBUGLEVEL_CLASS>
        print_build_options = <optimized out>
        long_options = {{longName = 0x0, shortName = 0 '\000', argInfo = 4, arg = 0x7f8e3ee09320 <poptHelpOptions>, val = 0, 
            descrip = 0x7f8e4229e13b "Help options:", argDescrip = 0x0}, {longName = 0x7f8e4229e149 "daemon", shortName = 68 'D', argInfo = 0, arg = 0x0, val = 1000, 
            descrip = 0x7f8e4229e150 "Become a daemon (default)", argDescrip = 0x0}, {longName = 0x7f8e4229e16a "interactive", shortName = 105 'i', argInfo = 0, 
            arg = 0x0, val = 1001, descrip = 0x7f8e4229eca0 "Run interactive (not a daemon)", argDescrip = 0x0}, {longName = 0x7f8e4229e176 "foreground", 
            shortName = 70 'F', argInfo = 0, arg = 0x0, val = 1002, descrip = 0x7f8e4229ecc0 "Run daemon in foreground (for daemontools, etc.)", argDescrip = 0x0}, {
            longName = 0x7f8e4229e181 "no-process-group", shortName = 0 '\000', argInfo = 0, arg = 0x0, val = 1003, 
            descrip = 0x7f8e4229ecf8 "Don't create a new process group", argDescrip = 0x0}, {longName = 0x7f8e4229e192 "log-stdout", shortName = 83 'S', argInfo = 0, 
            arg = 0x0, val = 1004, descrip = 0x7f8e4229e19d "Log to stdout", argDescrip = 0x0}, {longName = 0x7f8e4229e1ab "build-options", shortName = 98 'b', 
            argInfo = 0, arg = 0x0, val = 98, descrip = 0x7f8e4229e1b9 "Print build options", argDescrip = 0x0}, {longName = 0x7f8e4229e1cd "port", 
            shortName = 112 'p', argInfo = 1, arg = 0x7ffc51b1c3c0, val = 0, descrip = 0x7f8e4229e1d2 "Listen on the specified ports", argDescrip = 0x0}, {
---Type <return> to continue, or q <return> to quit---
            longName = 0x7f8e4229e1f0 "profiling-level", shortName = 80 'P', argInfo = 1, arg = 0x7ffc51b1c3c8, val = 0, 
            descrip = 0x7f8e4229e200 "Set profiling level", argDescrip = 0x7f8e4229e214 "PROFILE_LEVEL"}, {longName = 0x0, shortName = 0 '\000', argInfo = 4, 
            arg = 0x7f8e4042e4a0 <popt_common_samba>, val = 0, descrip = 0x7f8e4229e222 "Common samba options:", argDescrip = 0x0}, {longName = 0x0, 
            shortName = 0 '\000', argInfo = 0, arg = 0x0, val = 0, descrip = 0x0, argDescrip = 0x0}}
        parent = 0x7f8e435e5e70
        frame = 0x7f8e435d5f10
        status = <optimized out>
        ev_ctx = 0x7f8e435e5100
        msg_ctx = 0x7f8e435e51f0
        server_id = {pid = 7494, task_id = 0, vnn = 0, unique_id = 2186658537011346510}
        se = <optimized out>
        np_dir = 0x7f8e435fc230 "/run/samba/ncalrpc/np"
        smbd_shim_fns = {cancel_pending_lock_requests_by_fid = 0x7f8e417f6f20 <smbd_cancel_pending_lock_requests_by_fid>, 
          send_stat_cache_delete_message = 0x7f8e417fcd60 <smbd_send_stat_cache_delete_message>, change_to_root_user = 0x7f8e417e44e0 <smbd_change_to_root_user>, 
          become_authenticated_pipe_user = 0x7f8e417e4570 <smbd_become_authenticated_pipe_user>, 
          unbecome_authenticated_pipe_user = 0x7f8e417e4620 <smbd_unbecome_authenticated_pipe_user>, 
          contend_level2_oplocks_begin = 0x7f8e41844f50 <smbd_contend_level2_oplocks_begin>, 
          contend_level2_oplocks_end = 0x7f8e41845210 <smbd_contend_level2_oplocks_end>, become_root = 0x7f8e417e4630 <smbd_become_root>, 
          unbecome_root = 0x7f8e417e4660 <smbd_unbecome_root>, exit_server = 0x7f8e4183d430 <smbd_exit_server>, 
          exit_server_cleanly = 0x7f8e4183d450 <smbd_exit_server_cleanly>}
        __FUNCTION__ = "main"

At that moment ctdb was about to stop.


Jun 12 11:10:55 node-2 systemd: Stopping CTDB...
Jun 12 11:10:55 node-2 systemd: Stopped Samba SMB Daemon.

To be honest, if ctdb is shutting down anything can happen. We see ctdb pretty much as a component similar to the kernel from a samba perspective, and if that exits we're just dead. We do not properly deal with it an in many cases just crash or deliberately panic.

no more feedback, closing, If you see a similar problem with Samba 4.12 or newer, please file a new bug report for that.