[LU-4384] Hit unsupported incompat filesystem feature error after downgrade system from 2.6 to 2.5.0

• Type: Bug
• Resolution: Fixed
• Priority: Blocker
• Fix Version/s: Lustre 2.6.0, Lustre 2.5.2
• Affects Version/s: Lustre 2.4.0, Lustre 2.5.0, Lustre 2.6.0
• Labels: MB mn4
• Severity: 3
• Assignee: Mikhail Pershin
• Reporter: Sarah Liu

Description

Before upgrade, server and client are running 2.5.0 ldiskfs, then upgrade the whole system to lustre-master build #1791, it passed; then downgrade the system to 2.5.0 again, when mounting the OST, got following error:

OST console shows:

Lustre: DEBUG MARKER: == upgrade-downgrade Lustre version and system information == 11:31:49 (1386963109)
Lustre: Lustre: Build Version: 2.5.0-RC1--PRISTINE-2.6.32-358.18.1.el6_lustre.x86_64
LNet: Added LNI 10.10.19.53@tcp [8/256/0/180]
LNet: Accept secure, port 988
Lustre: DEBUG MARKER: == upgrade-downgrade End == 11:31:52 (1386963112)
LDISKFS-fs (sdb1): mounted filesystem with ordered data mode. quota=on. Opts: 
LustreError: 33847:0:(ofd_fs.c:588:ofd_server_data_init()) lustre-OST0000: unsupported incompat filesystem feature(s) 10
LustreError: 33847:0:(obd_config.c:572:class_setup()) setup lustre-OST0000 failed (-22)
LustreError: 33847:0:(obd_config.c:1591:class_config_llog_handler()) MGC10.10.19.62@tcp: cfg command failed: rc = -22
Lustre:    cmd=cf003 0:lustre-OST0000  1:dev  2:0  3:f  
LustreError: 15b-f: MGC10.10.19.62@tcp: The configuration from log 'lustre-OST0000'failed from the MGS (-22).  Make sure this client and the MGS are running compatible versions of Lustre.
LustreError: 15c-8: MGC10.10.19.62@tcp: The configuration from log 'lustre-OST0000' failed (-22). This may be the result of communication errors between this node and the MGS, a bad configuration, or other errors. See the syslog for more information.
LustreError: 33730:0:(obd_mount_server.c:1257:server_start_targets()) failed to start server lustre-OST0000: -22
LustreError: 33730:0:(obd_mount_server.c:1732:server_fill_super()) Unable to start targets: -22
LustreError: 33730:0:(obd_mount_server.c:848:lustre_disconnect_lwp()) lustre-MDT0000-lwp-OST0000: Can't end config log lustre-client.
LustreError: 33730:0:(obd_mount_server.c:1426:server_put_super()) lustre-OST0000: failed to disconnect lwp. (rc=-2)
LustreError: 33730:0:(obd_config.c:619:class_cleanup()) Device 3 not setup
Lustre: server umount lustre-OST0000 complete
LustreError: 33730:0:(obd_mount.c:1311:lustre_fill_super()) Unable to mount /dev/sdb1 (-22)
[root@wtm-88 ~]# 

Issue Links

• is related to: LU-3467 Unified request handler on OST