[linux-lvm] Bug when creating snapshots on lvm on s390

Thu Apr 15 15:45:06 UTC 2004

Please disregard.  I need to read the whole email first.....

> -----Original Message-----
> From: Little, Chris [mailto:Chris.Little at okdhs.org]
> Sent: Thursday, April 15, 2004 10:40 AM
> To: 'LVM general discussion and development'
> Subject: RE: [linux-lvm] Bug when creating snapshots on lvm on s390
> 
> 
> This is a known issue.  I have a bug open with IBM who in 
> turn has opened
> one with SUSE :
> 
> ---------------
> 
> This is a short update from SuSE LVL3 folks.
> 
> his is a short status about the work that has been done to 
> fix this bug.
> 
> Since the bug has been posted, different SuSE developers have 
> been working
> on that.
> 
> They have found a way to track the problem:
> "by simply deleting and rewriting 200 MB to the first 
> original volume after
> creating the backups caused corruption on the second original volume."
> 
> <citat> of one developer
> 
> I have finally been able to reproduce it, on s390l2.
> 
> I have set up LVM similar to the setup described in the bug 
> report (three
> volume groups, several striped volumes on vg01), created two ext3
> filesystems
> (/dev/vg01/lvol[12]), filled them up with several copies of 
> /opt/kde3, then
> made backups (/dev/vg01/backup[12]) with the filesystems mounted as
> described
> above, then mounted those backups read-only.
> 
> No corruption on any volume so far.
> 
> After deleting some kde3 copies on /dev/vg01/lvol1 and 
> copying them back
> again
> with different names, seemingly random corruption reared its 
> ugly head on
> _all_ volumes. Try "for i in /mnt/*/? /mnt/*/?? /mnt/*/??? ; 
> do diff -r
> /opt/
> kde3 $i ; done" (ignore the dangling symlinks). 
> /var/log/messages may be
> worth
> a look as well.
> 
> </citat>
> 
> Afterwards we have contacted IBM Boeblingen, and they have 
> been also able to
> reproduce the issue in the vanilla LVM-code.  Even in version 1.0.7.
> 
> We tried to reproduce it on x86, but it was not possible, on 
> PPC we do not
> know yet.
> 
> Summary:
> 
> The corruption we see on S/390 can be caused anywhere in the kernel,
> starting
> from the memory subsystem to the iobuf on S/390 (suspection of Andrea
> Arcangeli) to the buffer header code within LVM(suspection of Martin
> Schwidefsky) to the remapping of blocks within LVM-snapshot 
> specific code
> paths(and there are many) inside LVM including LV locking issues and
> list-handling for the exception table which seems to be the 
> instance where
> the
> LVM code works out the snapshot-specific block mapping.
> 
> By next week, you will hear from me; our developers are 
> intensively working
> on that issue.
> 
> With kind regards, 
> 
> Thomas Fenton
> Staff Software Engineer
> IBM Integrated Technical Services
> Linux and NUMA-Q support
> > -----Original Message-----
> > From: Ihno Krumreich [mailto:ihno at suse.de]
> > Sent: Thursday, April 15, 2004 5:42 AM
> > To: linux-lvm at redhat.com; Mauelshagen at redhat.com
> > Cc: Bernhard Kaindl; Uwe Drechsel; Ulrich Hecht
> > Subject: [linux-lvm] Bug when creating snapshots on lvm on s390
> > 
> > 
> > Hi,
> > 
> > we have a filecorruption on a LVM-Volume when a
> > snapshot is created. This Problem seem to occur only
> > on s390 (31-Bit mode).
> > 
> > are there any known issues when using snapshots on lvm on s390?
> > 
> > regards 
> > 
> > Ihno Krumreich
> > 
> > How to create the bug:
> > 
> > - Create three volume groups, which are striped over multiple
> >   physical disks (9 x 2GByte).
> > - use the second volume group to create a logical volume
> > - create a file system on this LV (problem occurs with ext2, 
> > ext3, reiserfs)
> >   and put data in the filesystem
> > - create a snapshot of this LVOL
> > - the data on the original LVOL are corruptet
> > 
> > - It is important that the filesystem is mounted read/write
> >   If it is only mounted readonly and the snapshot is
> >   created the corruption does not occur.
> >   
> > 
> > Machine setup:
> > 
> > S390 31-Bit with SUSE linux Enterprise Server 8 Service Pack 3
> > Machine has 2 Gbyte RAM and 9 Model-3 DASD for the LVM.
> > 
> > SLES8 has LVM Version 1.0.5 with IBM patches for multipath support.
> > 
> > To exclude that Kernel modification from SUSE/IBM cause the
> > problem IBM has testet it with the vanilla kernel 2.4.21 and
> > LVM Version 1.0.7 and the problem is the same.
> > 
> > At SUSE we tried to reproduce the problem on x86, but without
> > success (kernel 2.4.21 with lvm 1.0.5).
> > 
> > In the attached tar-ball is a file which showes the corruption
> > starting at byte 0xc000 with a length of 0x1000 Bytes.
> > 
> > 
> > -- 
> > Best regards/Mit freundlichen Grüßen
> > 
> > Ihno Krumreich
> > 
> > "Never trust a computer you can lift."
> > --
> > Ihno Krumreich            ihno at suse.de
> > SuSE Linux AG             Projectmanager S390 & zSeries
> > Maxfeldstr. 5             +49-911-74053-439
> > D-90409 Nürnberg          http://www.suse.de
> > 
> > _______________________________________________
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> > linux-lvm at redhat.com
> > https://www.redhat.com/mailman/listinfo/linux-lvm
> > read the LVM HOW-TO at http://tldp.org/HOWTO/LVM-HOWTO/
> > 
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