[dm-devel] dm-thinp BUG at drivers/md/persistent-data/dm-btree-remove.c:188

[Eric Wheeler]

On Fri, 15 Feb 2013, thornber at redhat.com wrote:
> On Thu, Feb 14, 2013 at 06:07:56PM -0800, Eric Wheeler wrote:
> Discard support is the main user of the btree_remove, so turning off
> discard support in the pool should be a good temporary fix.

Yep, I did just that and it seems to be stable at the moment.

> Could you let me know what sort of work load you were applying to the
> ext4 fs to cause this to happen?  If I can reproduce this I should be
> able to get a fix to you v. quickly.

I'm sure it was very light load.  Backups happen at night using 
rdiff-backup, but the failure was happening during the day outside of a 
backup period.

I do have a MySQL replication writing to a volume, so that would generate 
a few writes---but its an extremely-low-write database, so that seems 
unlikely.

The best I can think is something like mlocate was scanning the disk, so 
maybe just a filesystem traversal was doing it---but mlocate would have 
been read-only.

I wouldn't think so, but is it possible for a read to cause a discard 
under dm-thinp?

-Eric

--
Eric Wheeler
www.globallinuxsecurity.pro