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Bug 1348283

Summary: thin pool does not contain 'F' failed attr right away after error target is loaded and resumed
Product: Red Hat Enterprise Linux 7 Reporter: Corey Marthaler <cmarthal>
Component: lvm2Assignee: LVM and device-mapper development team <lvm-team>
lvm2 sub component: Thin Provisioning QA Contact: cluster-qe <cluster-qe>
Status: CLOSED NOTABUG Docs Contact:
Severity: low    
Priority: unspecified CC: agk, heinzm, jbrassow, msnitzer, prajnoha, prockai, thornber, zkabelac
Version: 7.3   
Target Milestone: rc   
Target Release: ---   
Hardware: x86_64   
OS: Linux   
Whiteboard:
Fixed In Version: Doc Type: If docs needed, set a value
Doc Text:
Story Points: ---
Clone Of: Environment:
Last Closed: 2016-06-21 11:38:54 UTC Type: Bug
Regression: --- Mount Type: ---
Documentation: --- CRM:
Verified Versions: Category: ---
oVirt Team: --- RHEL 7.3 requirements from Atomic Host:
Cloudforms Team: --- Target Upstream Version:
Embargoed:

Description Corey Marthaler 2016-06-20 16:47:06 UTC 
Description of problem:
This is the same test case used to verify bug 1021878 in rhel6.8.

In rhel7, lvm doesn't pick up the failed attribute unless a 'dmsetup status' is run.


# with or without lvmetad running

    thin_pool_autoextend_threshold = 70

[root@host-083 ~]# ps -ef | grep dmeventd
root      1206     1  0 11:32 ?        00:00:00 /usr/sbin/dmeventd -f



[...]
Swapping the current meta device table (snapper_thinp-POOL_tmeta: 0 8192 linear 8:49 2048) for an error target
dmsetup suspend snapper_thinp-POOL_tmeta
Loading in new meta device table (0 8192 error 8:49 2048)
dmsetup load snapper_thinp-POOL_tmeta --table " 0 8192 error 8:49 2048"
dmsetup resume snapper_thinp-POOL_tmeta

attr=twi-aotz--
thin pool device should have the (F)ailed attribute set

[root@host-083 ~]# lvs -a -o +devices
  LV              Attr       LSize Pool Origin Data%  Meta% Devices
  POOL            twi-aotz-- 5.00g             6.88   4.79  POOL_tdata(0)
  [POOL_tdata]    Twi-ao---- 5.00g                          /dev/sdc1(1)
  [POOL_tmeta]    ewi-ao---- 4.00m                          /dev/sdd1(0)
  [lvol0_pmspare] ewi------- 4.00m                          /dev/sdc1(0)
  origin          Vwi-a-tz-- 1.00g POOL        32.93
  other1          Vwi-a-tz-- 1.00g POOL        0.00
  other2          Vwi-a-tz-- 1.00g POOL        0.00
  other3          Vwi-a-tz-- 1.00g POOL        0.00
  other4          Vwi-a-tz-- 1.00g POOL        0.00
  other5          Vwi-a-tz-- 1.00g POOL        0.00
  snap1           Vwi-a-tz-- 1.00g POOL origin 16.63

[root@host-083 ~]# pvscan --cache
[root@host-083 ~]# lvs -a -o +devices
  LV              Attr       LSize Pool Origin Data%  Meta% Devices
  POOL            twi-aotz-- 5.00g             6.88   4.79  POOL_tdata(0)
  [POOL_tdata]    Twi-ao---- 5.00g                          /dev/sdc1(1)
  [POOL_tmeta]    ewi-ao---- 4.00m                          /dev/sdd1(0)
  [lvol0_pmspare] ewi------- 4.00m                          /dev/sdc1(0)
  origin          Vwi-a-tz-- 1.00g POOL        32.93
  other1          Vwi-a-tz-- 1.00g POOL        0.00
  other2          Vwi-a-tz-- 1.00g POOL        0.00
  other3          Vwi-a-tz-- 1.00g POOL        0.00
  other4          Vwi-a-tz-- 1.00g POOL        0.00
  other5          Vwi-a-tz-- 1.00g POOL        0.00
  snap1           Vwi-a-tz-- 1.00g POOL origin 16.63


# As soon as dmsetup status is run, it gets triggered:

[root@host-083 ~]# dmsetup status
snapper_thinp-origin: 0 2097152 thin 690688 2097151
snapper_thinp-POOL: 0 10485760 linear 
snapper_thinp-snap1: 0 2097152 thin 348672 2097151
snapper_thinp-other5: 0 2097152 thin 0 -
snapper_thinp-other4: 0 2097152 thin 0 -
snapper_thinp-other3: 0 2097152 thin 0 -
snapper_thinp-POOL-tpool: 0 10485760 thin-pool Error
snapper_thinp-POOL_tdata: 0 10485760 linear 
snapper_thinp-other2: 0 2097152 thin Fail
snapper_thinp-POOL_tmeta: 0 8192 error 
snapper_thinp-other1: 0 2097152 thin Fail

Jun 20 11:27:04 host-083 kernel: device-mapper: thin: 253:4: metadata operation 'dm_pool_commit_metadata' failed: error = -5
Jun 20 11:27:04 host-083 kernel: device-mapper: thin: 253:4: aborting current metadata transaction
Jun 20 11:27:04 host-083 kernel: device-mapper: thin: 253:4: failed to abort metadata transaction
Jun 20 11:27:04 host-083 kernel: device-mapper: thin: 253:4: switching pool to failure mode
Jun 20 11:27:04 host-083 kernel: device-mapper: thin: 253:4: metadata operation 'dm_pool_commit_metadata' failed: error = -22
Jun 20 11:27:04 host-083 kernel: device-mapper: thin: 253:4: aborting current metadata transaction
Jun 20 11:27:04 host-083 kernel: device-mapper: thin: 253:4: failed to abort metadata transaction
Jun 20 11:27:04 host-083 kernel: device-mapper: thin: 253:4: switching pool to failure mode
Jun 20 11:27:04 host-083 kernel: device-mapper: thin metadata: couldn't read superblock
Jun 20 11:27:04 host-083 kernel: device-mapper: thin: 253:4: failed to set 'needs_check' flag in metadata[  730.758665] device-mapper: thin metadata: couldn't read superblock
Jun 20 11:27:04 host-083 kernel: device-mapper: thin: 253:4: dm_pool_get_metadata_transaction_id returned -22
Jun 20 11:27:04 host-083 kernel: device-mapper: thin metadata: couldn't read superblock
Jun 20 11:27:04 host-083 kernel: device-mapper: thin: 253:4: failed to set 'needs_check' flag in metadata
Jun 20 11:27:04 host-083 kernel: device-mapper: thin: 253:4: dm_pool_get_metadata_transaction_id returned -22
Jun 20 11:27:10 host-083 lvm[1118]: WARNING: Thin pool snapper_thinp-POOL-tpool metadata is now 100.00% full.
Jun 20 11:27:10 host-083 lvm[1118]: WARNING: Thin pool snapper_thinp-POOL-tpool data is now 100.00% full.


[root@host-083 ~]# lvs -a -o +devices
  LV              Attr       LSize Pool Origin Data%  Meta% Devices
  POOL            twi-aotzF- 5.00g                          POOL_tdata(0)
  [POOL_tdata]    Twi-ao---- 5.00g                          /dev/sdc1(1)
  [POOL_tmeta]    ewi-ao---- 4.00m                          /dev/sdd1(0)
  [lvol0_pmspare] ewi------- 4.00m                          /dev/sdc1(0)
  origin          Vwi-a-tzF- 1.00g POOL
  other1          Vwi-a-tzF- 1.00g POOL
  other2          Vwi-a-tzF- 1.00g POOL
  other3          Vwi-a-tzF- 1.00g POOL
  other4          Vwi-a-tzF- 1.00g POOL
  other5          Vwi-a-tzF- 1.00g POOL
  snap1           Vwi-a-tzF- 1.00g POOL origin




Version-Release number of selected component (if applicable):
3.10.0-419.el7.x86_64

lvm2-2.02.156-1.el7    BUILT: Mon Jun 13 03:05:51 CDT 2016
lvm2-libs-2.02.156-1.el7    BUILT: Mon Jun 13 03:05:51 CDT 2016
lvm2-cluster-2.02.156-1.el7    BUILT: Mon Jun 13 03:05:51 CDT 2016
device-mapper-1.02.126-1.el7    BUILT: Mon Jun 13 03:05:51 CDT 2016
device-mapper-libs-1.02.126-1.el7    BUILT: Mon Jun 13 03:05:51 CDT 2016
device-mapper-event-1.02.126-1.el7    BUILT: Mon Jun 13 03:05:51 CDT 2016
device-mapper-event-libs-1.02.126-1.el7    BUILT: Mon Jun 13 03:05:51 CDT 2016
device-mapper-persistent-data-0.6.2-0.1.rc8.el7    BUILT: Wed May  4 02:56:34 CDT 2016
cmirror-2.02.156-1.el7    BUILT: Mon Jun 13 03:05:51 CDT 2016
sanlock-3.3.0-1.el7    BUILT: Wed Feb 24 09:52:30 CST 2016
sanlock-lib-3.3.0-1.el7    BUILT: Wed Feb 24 09:52:30 CST 2016
lvm2-lockd-2.02.156-1.el7    BUILT: Mon Jun 13 03:05:51 CDT 2016


How reproducible:
Everytime
Comment 2 Zdenek Kabelac 2016-06-21 11:38:54 UTC 
This is actually a 'Feature' (and even major bug fix).

Now the longer story behind - older lvm2 has had a hidden problem in its device scan processing where it has unintentionally called status on device with 'flushing' - so commands like 'lvs' had basically always flushed thin-pool - causing   thin-pool commit point to happen - lots of associated actions....

Lvm2 command now does not cause flushing of thin-pool - also lvs displays  values 'known' in kernel without flushing - this is much faster and saves lots of disk access  at the price of possible impression of presented result.

The reason why we need to do it this way is - we have to avoid 'deadlock' - which would be the case  thin-pool flush would run out-of-space.  While such command would be waiting for resize - this actually could never happen - since we would be already holding VG lock.

So regarding to this BZ - lvm2 command is not supposed to be transitioning pool in 'F' state with i.e. lvs command -  it should be some user's write/fsync whatever command and lvm2 command should be 'plain' observer.

To get the matching 'dmsetup' behavior use:
dmsetup status --noflush --nolockfs