[lustre-discuss] Lustre/ZFS snapshots mount error

Tue Aug 28 04:52:52 PDT 2018

The MDS situation is very basic: active/passive mds0/mds1 for both fas & fsB.  fsA has the combined msg/mdt in a single zfs filesystem, and fsB has its own mdt in a separate zfs filesystem.  mds0 is primary for all.

fsA & fsB DO both have changelogs enabled to feed robinhood databases.

What’s the recommended procedure here we should follow before mounting the snapshots?

1) disable changelogs on the active mdt’s (this will compromise robinhood, requiring a rescan…), or
2) temporarily halt changelog consumption / cleanup (e.g. stop robinhood in our case) and then mount the snapshot?

Thanks for the help!

--
Benjamin S. Kirk, Ph.D.
NASA Lyndon B. Johnson Space Center
Acting Chief, Aeroscience & Flight Mechanics Division

On Aug 27, 2018, at 7:33 PM, Yong, Fan <fan.yong at intel.com<mailto:fan.yong at intel.com>> wrote:

According to the stack trace, someone was trying to cleanup old empty llogs during mount the snapshot. We do NOT allow any modification during mount snapshot; otherwise, it will trigger ZFS backend BUG(). That is why we add LASSERT() when start the transaction. One possible solution is that, we can add some check in the llog logic to avoid modifying llog under snapshot mode.

--
Cheers,
Nasf

-----Original Message-----
From: lustre-discuss [mailto:lustre-discuss-bounces at lists.lustre.org] On Behalf Of Andreas Dilger
Sent: Tuesday, August 28, 2018 5:57 AM
To: Kirk, Benjamin (JSC-EG311) <benjamin.kirk at nasa.gov<mailto:benjamin.kirk at nasa.gov>>
Cc: lustre-discuss at lists.lustre.org<mailto:lustre-discuss at lists.lustre.org>
Subject: Re: [lustre-discuss] Lustre/ZFS snapshots mount error

It's probably best to file an LU ticket for this issue.

It looks like there is something with the log processing at mount that is trying to modify the configuration files.  I'm not sure whether that should be allowed or not.

Does fab have the same MGS as fsA?  Does it have the same MDS node as fsA?
If it has a different MDS, you might consider to give it its own MGS as well.
That doesn't have to be a separate MGS node, just a separate filesystem (ZFS fileset in the same zpool) on the MDS node.

Cheers, Andreas

On Aug 27, 2018, at 10:18, Kirk, Benjamin (JSC-EG311) <benjamin.kirk at nasa.gov<mailto:benjamin.kirk at nasa.gov>> wrote:

Hi all,

We have two filesystems, fsA & fsB (eadc below).  Both of which get snapshots taken daily, rotated over a week.  It’s a beautiful feature we’ve been using in production ever since it was introduced with 2.10.

-) We’ve got Lustre/ZFS 2.10.4 on CentOS 7.5.
-) Both fsA & fsB have changelogs active.
-) fsA has combined mgt/mdt on a single ZFS filesystem.
-) fsB has a single mdt on a single ZFS filesystem.
-) for fsA, I have no issues mounting any of the snapshots via lctl.
-) for fsB, I can mount the most three recent snapshots, then encounter errors:

[root at hpfs-fsl-mds0 ~]# lctl snapshot_mount -F eadc -n eadc_AutoSS-Mon
mounted the snapshot eadc_AutoSS-Mon with fsname 3d40bbc
[root at hpfs-fsl-mds0 ~]# lctl snapshot_umount -F eadc -n
eadc_AutoSS-Mon
[root at hpfs-fsl-mds0 ~]# lctl snapshot_mount -F eadc -n eadc_AutoSS-Sun
mounted the snapshot eadc_AutoSS-Sun with fsname 584c07a
[root at hpfs-fsl-mds0 ~]# lctl snapshot_umount -F eadc -n
eadc_AutoSS-Sun
[root at hpfs-fsl-mds0 ~]# lctl snapshot_mount -F eadc -n eadc_AutoSS-Sat
mounted the snapshot eadc_AutoSS-Sat with fsname 4e646fe
[root at hpfs-fsl-mds0 ~]# lctl snapshot_umount -F eadc -n
eadc_AutoSS-Sat
[root at hpfs-fsl-mds0 ~]# lctl snapshot_mount -F eadc -n eadc_AutoSS-Fri
mount.lustre: mount metadata/meta-eadc at eadc_AutoSS-Fri at
/mnt/eadc_AutoSS-Fri_MDT0000 failed: Read-only file system Can't mount
the snapshot eadc_AutoSS-Fri: Read-only file system

The relevant bits from dmesg are
[1353434.417762] Lustre: 3d40bbc-MDT0000: set dev_rdonly on this
device [1353434.417765] Lustre: Skipped 3 previous similar messages
[1353434.649480] Lustre: 3d40bbc-MDT0000: Imperative Recovery enabled,
recovery window shrunk from 300-900 down to 150-900 [1353434.649484]
Lustre: Skipped 3 previous similar messages [1353434.866228] Lustre:
3d40bbc-MDD0000: changelog on [1353434.866233] Lustre: Skipped 1
previous similar message [1353435.427744] Lustre: 3d40bbc-MDT0000:
Connection restored to ... at tcp (at ... at tcp) [1353435.427747] Lustre:
Skipped 23 previous similar messages [1353445.255899] Lustre: Failing
over 3d40bbc-MDT0000 [1353445.255903] Lustre: Skipped 3 previous
similar messages [1353445.256150] LustreError: 11-0:
3d40bbc-OST0000-osc-MDT0000: operation ost_disconnect to node ... at tcp
failed: rc = -107 [1353445.257896] LustreError: Skipped 23 previous
similar messages [1353445.353874] Lustre: server umount
3d40bbc-MDT0000 complete [1353445.353877] Lustre: Skipped 3 previous
similar messages [1353475.302224] Lustre: 4e646fe-MDD0000: changelog
on [1353475.302228] Lustre: Skipped 1 previous similar message [1353498.964016] LustreError: 25582:0:(osd_handler.c:341:osd_trans_create()) 36ca26b-MDT0000-osd: someone try to start transaction under readonly mode, should be disabled.
[1353498.967260] LustreError: 25582:0:(osd_handler.c:341:osd_trans_create()) Skipped 1 previous similar message
[1353498.968829] CPU: 6 PID: 25582 Comm: mount.lustre Kdump: loaded Tainted: P           OE  ------------   3.10.0-862.6.3.el7.x86_64 #1
[1353498.968830] Hardware name: Supermicro SYS-6027TR-D71FRF/X9DRT,
BIOS 3.2a 08/04/2015 [1353498.968832] Call Trace:
[1353498.968841]  [<ffffffffb5b0e80e>] dump_stack+0x19/0x1b
[1353498.968851]  [<ffffffffc0cbe5db>] osd_trans_create+0x38b/0x3d0
[osd_zfs] [1353498.968876]  [<ffffffffc1116044>]
llog_destroy+0x1f4/0x3f0 [obdclass] [1353498.968887]
[<ffffffffc111f0f6>] llog_cat_reverse_process_cb+0x246/0x3f0
[obdclass] [1353498.968897]  [<ffffffffc111a32c>]
llog_reverse_process+0x38c/0xaa0 [obdclass] [1353498.968910]
[<ffffffffc111eeb0>] ? llog_cat_process_cb+0x4e0/0x4e0 [obdclass]
[1353498.968922]  [<ffffffffc111af69>]
llog_cat_reverse_process+0x179/0x270 [obdclass] [1353498.968932]
[<ffffffffc1115585>] ? llog_init_handle+0xd5/0x9a0 [obdclass]
[1353498.968943]  [<ffffffffc1116e78>] ? llog_open_create+0x78/0x320
[obdclass] [1353498.968949]  [<ffffffffc12e55f0>] ?
mdd_root_get+0xf0/0xf0 [mdd] [1353498.968954]  [<ffffffffc12ec7af>]
mdd_prepare+0x13ff/0x1c70 [mdd] [1353498.968966]  [<ffffffffc166b037>]
mdt_prepare+0x57/0x3b0 [mdt] [1353498.968983]  [<ffffffffc1183afd>]
server_start_targets+0x234d/0x2bd0 [obdclass] [1353498.968999]
[<ffffffffc1153500>] ? class_config_dump_handler+0x7e0/0x7e0
[obdclass] [1353498.969012]  [<ffffffffc118541d>]
server_fill_super+0x109d/0x185a [obdclass] [1353498.969025]
[<ffffffffc115cef8>] lustre_fill_super+0x328/0x950 [obdclass]
[1353498.969038]  [<ffffffffc115cbd0>] ?
lustre_common_put_super+0x270/0x270 [obdclass] [1353498.969041]
[<ffffffffb561f3bf>] mount_nodev+0x4f/0xb0 [1353498.969053]
[<ffffffffc1154f18>] lustre_mount+0x38/0x60 [obdclass]
[1353498.969055]  [<ffffffffb561ff3e>] mount_fs+0x3e/0x1b0 [1353498.969060]  [<ffffffffb563d4b7>] vfs_kern_mount+0x67/0x110 [1353498.969062]  [<ffffffffb563fadf>] do_mount+0x1ef/0xce0 [1353498.969066]  [<ffffffffb55f7c2c>] ? kmem_cache_alloc_trace+0x3c/0x200 [1353498.969069]  [<ffffffffb5640913>] SyS_mount+0x83/0xd0 [1353498.969074]  [<ffffffffb5b20795>] system_call_fastpath+0x1c/0x21 [1353498.969079] LustreError: 25582:0:(llog_cat.c:1027:llog_cat_reverse_process_cb()) 36ca26b-MDD0000: fail to destroy empty log: rc = -30
[1353498.970785] CPU: 6 PID: 25582 Comm: mount.lustre Kdump: loaded Tainted: P           OE  ------------   3.10.0-862.6.3.el7.x86_64 #1
[1353498.970786] Hardware name: Supermicro SYS-6027TR-D71FRF/X9DRT,
BIOS 3.2a 08/04/2015 [1353498.970787] Call Trace:
[1353498.970790]  [<ffffffffb5b0e80e>] dump_stack+0x19/0x1b
[1353498.970795]  [<ffffffffc0cbe5db>] osd_trans_create+0x38b/0x3d0
[osd_zfs] [1353498.970807]  [<ffffffffc1117921>]
llog_cancel_rec+0xc1/0x880 [obdclass] [1353498.970817]
[<ffffffffc111e13b>] llog_cat_cleanup+0xdb/0x380 [obdclass]
[1353498.970827]  [<ffffffffc111f14d>]
llog_cat_reverse_process_cb+0x29d/0x3f0 [obdclass] [1353498.970838]
[<ffffffffc111a32c>] llog_reverse_process+0x38c/0xaa0 [obdclass]
[1353498.970848]  [<ffffffffc111eeb0>] ?
llog_cat_process_cb+0x4e0/0x4e0 [obdclass] [1353498.970858]
[<ffffffffc111af69>] llog_cat_reverse_process+0x179/0x270 [obdclass]
[1353498.970868]  [<ffffffffc1115585>] ? llog_init_handle+0xd5/0x9a0
[obdclass] [1353498.970878]  [<ffffffffc1116e78>] ?
llog_open_create+0x78/0x320 [obdclass] [1353498.970883]
[<ffffffffc12e55f0>] ? mdd_root_get+0xf0/0xf0 [mdd] [1353498.970887]
[<ffffffffc12ec7af>] mdd_prepare+0x13ff/0x1c70 [mdd] [1353498.970894]
[<ffffffffc166b037>] mdt_prepare+0x57/0x3b0 [mdt] [1353498.970908]
[<ffffffffc1183afd>] server_start_targets+0x234d/0x2bd0 [obdclass]
[1353498.970924]  [<ffffffffc1153500>] ?
class_config_dump_handler+0x7e0/0x7e0 [obdclass] [1353498.970938]
[<ffffffffc118541d>] server_fill_super+0x109d/0x185a [obdclass]
[1353498.970950]  [<ffffffffc115cef8>] lustre_fill_super+0x328/0x950
[obdclass] [1353498.970962]  [<ffffffffc115cbd0>] ?
lustre_common_put_super+0x270/0x270 [obdclass] [1353498.970964]
[<ffffffffb561f3bf>] mount_nodev+0x4f/0xb0 [1353498.970976]
[<ffffffffc1154f18>] lustre_mount+0x38/0x60 [obdclass]
[1353498.970978]  [<ffffffffb561ff3e>] mount_fs+0x3e/0x1b0
[1353498.970980]  [<ffffffffb563d4b7>] vfs_kern_mount+0x67/0x110
[1353498.970982]  [<ffffffffb563fadf>] do_mount+0x1ef/0xce0
[1353498.970984]  [<ffffffffb55f7c2c>] ?
kmem_cache_alloc_trace+0x3c/0x200 [1353498.970986]
[<ffffffffb5640913>] SyS_mount+0x83/0xd0 [1353498.970989]
[<ffffffffb5b20795>] system_call_fastpath+0x1c/0x21 [1353498.970996]
LustreError: 25582:0:(mdd_device.c:354:mdd_changelog_llog_init())
36ca26b-MDD0000: changelog init failed: rc = -30 [1353498.972790]
LustreError: 25582:0:(mdd_device.c:427:mdd_changelog_init())
36ca26b-MDD0000: changelog setup during init failed: rc = -30
[1353498.974525] LustreError:
25582:0:(mdd_device.c:1061:mdd_prepare()) 36ca26b-MDD0000: failed to
initialize changelog: rc = -30 [1353498.976229] LustreError:
25582:0:(obd_mount_server.c:1879:server_fill_super()) Unable to start
targets: -30 [1353499.072002] LustreError:
25582:0:(obd_mount.c:1582:lustre_fill_super()) Unable to mount  (-30)

I’m hoping those traces mean something to someone - any ideas?

Thanks!

--
Benjamin S. Kirk

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Cheers, Andreas
---
Andreas Dilger
CTO Whamcloud

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