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Bug 1441157

Summary: lvm2 should be validating chunksize against size of dataLV and metadataLV
Product: Red Hat Enterprise Linux 7 Reporter: Zdenek Kabelac <zkabelac>
Component: lvm2Assignee: Zdenek Kabelac <zkabelac>
lvm2 sub component: Thin Provisioning QA Contact: cluster-qe <cluster-qe>
Status: CLOSED ERRATA Docs Contact:
Severity: unspecified    
Priority: unspecified CC: agk, cmarthal, heinzm, jbrassow, msnitzer, mthacker, ovasik, prajnoha, prockai, thornber, zkabelac
Version: 7.4   
Target Milestone: rc   
Target Release: ---   
Hardware: Unspecified   
OS: Unspecified   
Whiteboard:
Fixed In Version: lvm2-2.02.171-5.el7 Doc Type: If docs needed, set a value
Doc Text:
Story Points: ---
Clone Of: Environment:
Last Closed: 2017-08-01 21:52:19 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:
Attachments:
Description Flags
verbose lvcreate attempt none

Description Zdenek Kabelac 2017-04-11 10:58:08 UTC 
Description of problem:

lvm2 should better protect users by letting user know the chunksize in use is not big enough for given size of data LV and some max size of metadata.
Possibly also warn via syslog messages.

Create of a thin-pool with such chunksize is possibly good candidate for prompt confirmation as well.

Example is  thin-pool of 250TB with 16GB metadata size and 256K chunksize.

Version-Release number of selected component (if applicable):
2.02.169


How reproducible:


Steps to Reproduce:
1.
2.
3.

Actual results:


Expected results:


Additional info:
Comment 4 Zdenek Kabelac 2017-05-29 13:40:49 UTC 
Can I get attached  '-vvvv' trace for lvcreate command ?

While the lvm2 does 'warn' about to small chunk size  (and once fixed should prompt) - the following 'dm'  ioctl error is definitely not normal - and should have been detected earlier by lvm2 code.
Comment 5 Corey Marthaler 2017-05-30 15:24:51 UTC 
Created attachment 1283494 [details]
verbose lvcreate attempt
Comment 6 Jonathan Earl Brassow 2017-06-07 13:48:42 UTC 
As for how to fix, I would suggest rejecting any command that overrides the chunksize with one that causes the condition where the entire data space is not addressable.  You can then warn and prompt if the chunksize they've chosen does not allow X amount of growth.
Comment 7 Zdenek Kabelac 2017-06-08 11:45:24 UTC 
Upstream provides this solution:

https://www.redhat.com/archives/lvm-devel/2017-June/msg00019.html



So in general combination like 250T thin-pool size + 64K chunk size will be stopped 'lvcreate' time.


The next iteration will also handle 'resize' part.
Comment 8 Zdenek Kabelac 2017-06-08 11:52:09 UTC 
As for the attachment in comment 5 - looks like lvm2 was 'cheated' about so device sizes ?

Was there some  'pvresize --setphysicalvolumesize' used for a PV to create 250T volume ?

From trace it does look like underlying PV devices have in total just 105GiB. 

Reported ioctl error seems to suggest, mapped device on top of some PV simply cannot fit ?   (aka unrelated problem to this BZ).
Comment 9 Corey Marthaler 2017-06-08 21:12:22 UTC 
Yes, I did use --setphysicalvolumesize in comment #5. When I try stacking PVs on top of thin LVs, I don't see the problem.


[root@host-083 ~]# lvcreate  --thinpool undersized_chunks -L 250T --chunksize 256K  --poolmetadatasize 16G snapper_thinp_stack
  Using default stripesize 64.00 KiB.
  WARNING: Chunk size is smaller then suggested minimum size 1.00 MiB.
  Logical volume "undersized_chunks" created.
Comment 10 Zdenek Kabelac 2017-06-09 18:32:14 UTC 
So considering this bug as solved for now.

Resize limit will be processed for next version.
Comment 14 Zdenek Kabelac 2017-06-16 07:37:57 UTC 
There is nothing 'back and forth' here.

The logic in 2.02.171-4 - was the OLD one meant to be 'improved'.
(We provided this WARNING for a long time already, but appeared to be mostly ignored (i.e. Sky...)


Logic in 2.02.171-5 is new improved one - where we directly prohibit creation of a pool, where lvm2 knows in front - that even the 'biggest' metadata size (~16G)  can't address give amount of 'data' volume for thin-pool with specified chunk-size.


What we still miss for the future enhancement is - we need to 'limit' also related other tasks like lvresize.  And add new syslog warnings for existing thin-pool likely as well.
Comment 15 Corey Marthaler 2017-06-19 21:30:44 UTC 
Fix verified based on expected behavior listed in comment #14. lvm "directly prohibits creation" now.

[root@host-083 ~]# lvcreate  --thinpool POOL -L 250T --chunksize 256K  --poolmetadatasize 16G snapper_thinp_stack
  Using default stripesize 64.00 KiB.
  WARNING: Chunk size is smaller then suggested minimum size 1.00 MiB.
  Selected chunk size 256.00 KiB cannot address more then 63.25 TiB of thin pool data space.


lvm2-2.02.171-5.el7    BUILT: Wed Jun 14 10:33:32 CDT 2017
lvm2-libs-2.02.171-5.el7    BUILT: Wed Jun 14 10:33:32 CDT 2017
lvm2-cluster-2.02.171-5.el7    BUILT: Wed Jun 14 10:33:32 CDT 2017
device-mapper-1.02.140-5.el7    BUILT: Wed Jun 14 10:33:32 CDT 2017
device-mapper-libs-1.02.140-5.el7    BUILT: Wed Jun 14 10:33:32 CDT 2017
device-mapper-event-1.02.140-5.el7    BUILT: Wed Jun 14 10:33:32 CDT 2017
device-mapper-event-libs-1.02.140-5.el7    BUILT: Wed Jun 14 10:33:32 CDT 2017
device-mapper-persistent-data-0.7.0-0.1.rc6.el7    BUILT: Mon Mar 27 10:15:46 CDT 2017
Comment 16 errata-xmlrpc 2017-08-01 21:52:19 UTC 
Since the problem described in this bug report should be
resolved in a recent advisory, it has been closed with a
resolution of ERRATA.

For information on the advisory, and where to find the updated
files, follow the link below.

If the solution does not work for you, open a new bug report.

https://access.redhat.com/errata/RHBA-2017:2222