[lustre-discuss] no more free slots in catalog

Mon Dec 17 05:47:13 PST 2018

Julien,

Could you share the details (LBUG plus full back trace, primarily) with the list?  It would be good to know if it’s a known problem or not.

Thanks!

________________________________
From: lustre-discuss <lustre-discuss-bounces at lists.lustre.org> on behalf of Julien Rey <julien.rey at univ-paris-diderot.fr>
Sent: Monday, December 17, 2018 3:40:56 AM
To: lustre-discuss at lists.lustre.org
Subject: Re: [lustre-discuss] no more free slots in catalog

Le 11/12/2018 15:47, quentin.bouget at cea.fr<mailto:quentin.bouget at cea.fr> a écrit :
Le 11/12/2018 à 15:32, Julien Rey a écrit :
Le 11/12/2018 14:13, quentin.bouget at cea.fr<mailto:quentin.bouget at cea.fr> a écrit :
Le 11/12/2018 à 10:28, Julien Rey a écrit :
Le 10/12/2018 13:33, quentin.bouget at cea.fr<mailto:quentin.bouget at cea.fr> a écrit :
Le 10/12/2018 à 12:00, Julien Rey a écrit :
Hello,

We are running lustre 2.8.0-RC5--PRISTINE-2.6.32-573.12.1.el6_lustre.x86_64.

Since thursday we are getting a "bad address" error when trying to write on the lustre volume.

Looking at the logs on the MDS, we are getting this kind of messages :

Dec 10 06:26:18 localhost kernel: Lustre: 9593:0:(llog_cat.c:93:llog_cat_new_log()) lustre-MDD0000: there are no more free slots in catalog
Dec 10 06:26:18 localhost kernel: Lustre: 9593:0:(llog_cat.c:93:llog_cat_new_log()) Skipped 45157 previous similar messages
Dec 10 06:26:18 localhost kernel: LustreError: 9593:0:(mdd_dir.c:887:mdd_changelog_ns_store()) lustre-MDD0000: cannot store changelog record: type = 6, name = 'PEPFOLD-00016_bestene1-mc-SC-min-grompp.log', t = [0x20000a58f:0x858e:0x0], p = [0x20000a57d:0x17fd9:0x0]: rc = -28
Dec 10 06:26:18 localhost kernel: LustreError: 9593:0:(mdd_dir.c:887:mdd_changelog_ns_store()) Skipped 45157 previous similar messages

I saw here that this issue was supposed to be solved in 2.8.0:
https://jira.whamcloud.com/browse/LU-6556

Could someone help us unlocking this situation ?

Thanks.

Hello,

The log messages don't point at a "bad address" issue but rather at a "no space left on device" one ("rc = -28" --> -ENOSPC).

You most likely have, at some point, registered a changelog user on your mds and that user is not consuming changelogs.

You can check this by running:

[mds0]# lctl get_param mdd.*.changelog_users
mdd.lustre-MDT0000.changelog_users=
current index: 3
ID    index
cl1   0

The most important thing to look for is the distance between "current index" and the index for "cl1", "cl2", ...
I expect for at least one changelog user, that distance is 2^32 (the maximum number of changelog records).
Note that changelog indexes wrap around (0, 1, 2, ..., 4294967295, 0, 1, ...).

If I am right, then you can either deregister the changelog user:

[mds0]# lctl --device lustre-MDT0000 changelog_deregister cl1

or acknowledge the records:

[client]# lfs changelog_clear lustre-MDT0000 cl1 0

(clearing with index 0 is a shortcut for "acknowledge every changelog records")

Both those options may take a while.

There is a third one that might yield faster result, but it is also much more dangerous to use (you might want to check with your support first) :

[mds0]# umount /dev/mdt0
[mds0]# mount -t ldiskfs /dev/mdt0 /mnt/lustre-mdt0
[mds0]# rm /mnt/lustre-mdt0/changelog_catalog
[mds0]# rm /mnt/lustre-mdt0/changelog_users
[mds0]# umount /dev/mdt0
[mds0]# mount -t lustre /dev/mdt0 <...> # remount the mdt where it was

I cannot garantee this will not trash your filesystem. Use at your own risk.

---

In recent versions (2.12, maybe even 2.10), lustre comes with a builtin garbage collector for slow/inactive changelog users.

Regards,
Quentin Bouget

Hello Quentin,

Many thanks for your quick reply.

This is what I got when I issued the command you suggested:

[root at lustre-mds]# lctl get_param mdd.*.changelog_users

mdd.lustre-MDT0000.changelog_users=

current index: 4160462682

ID    index

cl1   21020582

I then issued the following command:

[root at lustre-mds]# lctl --device lustre-MDT0000 changelog_deregister cl1

It's been running for almost 20 hours now. Do you have an estimation of the time it could take ?
When you deregister a changelog user: every changelog record has to be invalidated (maybe this is batched, but I don't know enough about the on-disk structure to say).

I do not recall ever waiting that long. Then again, I never personally deregistered a changelog users with that many pending changelog records.

The changelog_deregister command still hasn't finished yet. Is there any way to track the state of the purge of records ?
I believe there is an "llog_reader" implemented in the lustre sources, but I never really used it.

If you just want to make sure Lustre is doing something, you can have a look at your mdt0: invalidating changelog records should generate a high load of small random writes.
If the device is idle, something is probably wrong.

Hard to tell. iostat doesn't show much I/O.

Is your filesystem still unavailable?

The following command doesn't show any registered changelog user:

cat /proc/fs/lustre/mdd/lustre-MDT0000/changelog_users

I tried to mount the lustre volume on a client. I don't get the "Bad Address" error anymore.

Best,
Yes, I don't think you need to wait for "changelog_deregister" to complete to start using your filesystem again.
If there is not any changelog user registered on your system, changelog records are not emitted.

Just try to wait until "changelog_deregister" completes before registering a new changelog user. =)

Best,

--
Julien REY

Plate-forme RPBS
Molécules Thérapeutiques In Silico (MTi)
Université Paris Diderot - Paris VII
tel : 01 57 27 83 95

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Quentin

--
Julien REY

Plate-forme RPBS
Molécules Thérapeutiques In Silico (MTi)
Université Paris Diderot - Paris VII
tel : 01 57 27 83 95

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Cheers,
Quentin

The changelog_deregister command eventually ended with an LBUG after a few days. The mds rebooted automatically. But at least it's working fine now. :)

Many thanks for your help.

Cheers,

--
Julien REY

Plate-forme RPBS
Molécules Thérapeutiques In Silico (MTi)
Université Paris Diderot - Paris VII
tel : 01 57 27 83 95
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