[#LU-8297] mount with missing key leads to leaked MGC device and LBUG

Mounting a kerberized Lustre FS but with the needed lustre_root key not installed on the client (e3) leak a partially initialized MGC device:

e3:~# LOAD=1 /usr/lib64/lustre/tests/llmount.sh
...
e3:~# lctl set_param debug='+mount sec trace'
debug=+mount sec trace
error: set_param: setting /proc/sys/lnet/debug=+mount sec trace: Invalid argument
e3:~# lctl set_param debug='+sec trace'
debug=+sec trace
e3:~# lctl set_param debug_mb=64
debug_mb=64
e3:~# lctl clear; mount e1@tcp:/lustre /mnt/lustre -t lustre -o user_xattr,flock,mgssec=krb5p; lctl dk > mount.dk
mount.lustre: mount e1@tcp:/lustre at /mnt/lustre failed: Connection refused
e3:~# lctl dl
  0 UP mgc MGC192.168.122.181@tcp 93abf5fe-744b-364d-3106-e11ed3e6c2ca 4
e3:~# mount e1@tcp:/lustre /mnt/lustre -t lustre -o user_xattr,flock,mgssec=krb5p

Message from syslogd@e3 at Jun 13 13:00:22 ...
 kernel:LustreError: 4678:0:(import.c:553:import_select_connection()) ASSERTION( dlmexp != ((void *)0) ) failed:

Message from syslogd@e3 at Jun 13 13:00:22 ...
 kernel:LustreError: 4678:0:(import.c:553:import_select_connection()) LBUG

[ 3061.041621] LustreError: 4518:0:(gss_keyring.c:791:gss_sec_lookup_ctx_kr()) failed request key: -126
[ 3061.044555] LustreError: 4518:0:(sec.c:440:sptlrpc_req_get_ctx()) req ffff8800365d4000: fail to get context
[ 3061.047399] LustreError: 4518:0:(obd_mount.c:467:lustre_start_mgc()) connect failed -111
[ 3061.049724] LustreError: 4518:0:(obd_mount.c:1342:lustre_fill_super()) Unable to mount  (-111)
[ 3132.373912] LustreError: 4678:0:(import.c:553:import_select_connection()) ASSERTION( dlmexp != ((void *)0) ) failed: 
[ 3132.377365] LustreError: 4678:0:(import.c:553:import_select_connection()) LBUG
[ 3132.379678] Pid: 4678, comm: mount.lustre
[ 3132.379717] 
Call Trace:
[ 3132.379755]  [<ffffffffa04e1853>] libcfs_debug_dumpstack+0x53/0x80 [libcfs]
[ 3132.379765]  [<ffffffffa04e1df5>] lbug_with_loc+0x45/0xc0 [libcfs]
[ 3132.379806]  [<ffffffffa08a7c3d>] ptlrpc_connect_import+0x133d/0x1380 [ptlrpc]
[ 3132.379834]  [<ffffffffa0882258>] ptlrpc_recover_import+0x258/0x550 [ptlrpc]
[ 3132.379863]  [<ffffffffa089d8e8>] ? ptlrpc_pinger_ir_up+0x78/0x90 [ptlrpc]
[ 3132.379868]  [<ffffffffa09d38ce>] ? mgc_import_event+0x10e/0x2c0 [mgc]
[ 3132.379895]  [<ffffffffa08aae48>] ptlrpc_reconnect_import+0x78/0x1e0 [ptlrpc]
[ 3132.379908]  [<ffffffffa04f2167>] ? libcfs_debug_msg+0x57/0x80 [libcfs]
[ 3132.379913]  [<ffffffffa09d992a>] mgc_set_info_async+0x6ea/0x1620 [mgc]
[ 3132.379923]  [<ffffffffa04f2167>] ? libcfs_debug_msg+0x57/0x80 [libcfs]
[ 3132.379957]  [<ffffffffa0671370>] lustre_start_mgc+0x1570/0x2a90 [obdclass]
[ 3132.379980]  [<ffffffffa0673266>] lustre_fill_super+0x246/0xb80 [obdclass]
[ 3132.380000]  [<ffffffffa0673020>] ? lustre_fill_super+0x0/0xb80 [obdclass]
[ 3132.380027]  [<ffffffff811e1ded>] mount_nodev+0x4d/0xb0
[ 3132.380048]  [<ffffffffa06695e8>] lustre_mount+0x38/0x60 [obdclass]
[ 3132.380052]  [<ffffffff811e2799>] mount_fs+0x39/0x1b0
[ 3132.380056]  [<ffffffff811fe05f>] vfs_kern_mount+0x5f/0xf0
[ 3132.380059]  [<ffffffff812005ae>] do_mount+0x24e/0xa40
[ 3132.380063]  [<ffffffff8116dffe>] ? __get_free_pages+0xe/0x50
[ 3132.380067]  [<ffffffff81200e36>] SyS_mount+0x96/0xf0
[ 3132.380072]  [<ffffffff81645ec9>] system_call_fastpath+0x16/0x1b
[ 3132.380073] 
[ 3132.380345] Kernel panic - not syncing: LBUG
[ 3132.381034] CPU: 0 PID: 4678 Comm: mount.lustre Tainted: G           OE  ------------   3.10.0-327.13.1.el7.x86_64 #1

[LU-8297] mount with missing key leads to leaked MGC device and LBUG Created: 13/Jun/16 Updated: 26/Jul/16 Resolved: 26/Jul/16
Status:	Resolved
Project:	Lustre
Component/s:	None
Affects Version/s:	Lustre 2.9.0
Fix Version/s:	Lustre 2.9.0

[LU-8297] mount with missing key leads to leaked MGC device and LBUG Created: 13/Jun/16 Updated: 26/Jul/16 Resolved: 26/Jul/16