[LU-4221] lctl conf_param <obdname>.ost.writethrough_cache_enable=N does not work anymore

• Type: Bug
• Resolution: Fixed
• Priority: Blocker
• Fix Version/s: Lustre 2.6.0, Lustre 2.5.1
• Affects Version/s: Lustre 2.6.0
• Severity: 3
• Assignee: Emoly Liu
• Reporter: Michael MacDonald (Inactive)

Description

Using 2.5.0 RC1, which I assume is what went GA.

In previous releases of Lustre, it was possible to set this tunable via conf_param, but now it doesn't work:

[root@mgs ~]# lctl conf_param testfs-OST0000.ost.writethrough_cache_enable=0
[root@mgs ~]# cat /proc/fs/lustre/obdfilter/testfs-OST0000/writethrough_cache_enable
1

The command completes successfully, but we see the following in dmesg:

LustreError: 15418:0:(obd_config.c:1341:class_process_proc_param()) testfs-OST0000: unknown param writethrough_cache_enable=0
LustreError: 15418:0:(obd_config.c:1591:class_config_llog_handler()) MGC10.42.42.5@tcp: cfg command failed: rc = -38
Lustre:    cmd=cf00f 0:testfs-OST0000  1:ost.writethrough_cache_enable=0

I understand that conf_param is on its way to being deprecated, and that set_param -P is preferred. However, conf_param should still work, right? It seems that some things still work as they always have, e.g.:

[root@mgs ~]# lctl conf_param testfs-OST0000.ost.client_cache_seconds=4242
[root@mgs ~]# cat /proc/fs/lustre/obdfilter/testfs-OST0000/client_cache_seconds
4242

In dmesg:

Lustre: Modifying parameter testfs-OST0000.ost.client_cache_seconds in log testfs-OST0000