[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

Comments

[Peter Jones]

Landed for 2.6. Should land for 2.5.1 shortly.

[Emoly Liu]

The patch for b2_6 has been landed.

A backport for b2_5 is at http://review.whamcloud.com/#/c/8618/ .

[Emoly Liu]

Andreas, this patch won't result in warnings for every other OFD parameter that is not in the OSD, because the warnings only happen when the parameter isn't matched. But as you said in http://review.whamcloud.com/#/c/8238/3/lustre/obdclass/obd_config.c , this patch will make all the OFD parameters never get a warning.

I will improve the patch and add a test case.

[Andreas Dilger]

James, the uncertainty I have is that I think this patch will allow this specific parameter to be set, but it will result in warnings for every other OFD parameter that is not in the OSD. If I'm incorrect in this understanding, then I'm happier to land the patch.

[James A Simmons]

Did testing with the latest patch and works as expected. No more complaining as well. Thanks.

[Emoly Liu]

Yes, James, this error was reported because obdfilter didn't match the parameter in its static lproc var list, and then it passed the parameter to next module osd.

Andreas, IMHO, I want to pass the parent entry to get the whole sub entries list, but it's not so easy to follow the link to get the target.

[Andreas Dilger]

I guess the obdfilter code is complaining because it is processing the "ost" parameter, but the named parameter doesn't exist. This is desirable under normal usage.

It probably makes sense to add an explicit skip of this parameter name in the obdfilter config processing code, if that is possible. There may be a couple of other parameters that moved from obdfilter to osd that should also be skipped in obdfilter.

[James A Simmons]

Testing with your patch I'm getting.

[root@spoon45 tests]# lctl conf_param lustre-OST0000.ost.writethrough_cache_enable=1
[root@spoon45 tests]# dmesg
[ 1383.895301] Lustre: Modifying parameter lustre-OST0000.ost.writethrough_cache_enable in log lustre-OST0000
[ 1392.871703] LustreError: 20254:0:(obd_config.c:1341:class_process_proc_param()) lustre-OST0000: unknown param writethrough_cache_enable=1
[root@spoon45 tests]# cat /proc/fs/lustre/obdfilter/lustre-OST0000/writethrough_cache_enable
1

Its doing the right thing but I see a error reported in dmesg. Other than that the patch fixed this problem.

[Emoly Liu]

patch tracking at: http://review.whamcloud.com/8238

[James A Simmons]

Sorry I have been busy with LU-3373/LU-3319 work. Sounds like you have a better solution than what I have. I look forward to applying your solution to my work.