Re: bug caused by removal of trans_mutex? (Was: Re: kernel BUG at fs/btrfs/extent-tree.c:6164!)

[Chris Mason <chris.mason@oracle.com>]

Excerpts from Li Zefan's message of 2011-06-13 03:13:13 -0400:
> Cc: Josef
> 
> >>>>>>>> I encountered following panic using 'btrfs-unstable + for-linus'
> >>>>>>>> kernel.
> >>>>>>>>
> >>>>>>>> I ran "btrfs fi bal /test5" command, and mount option of /test5
> >>>>>>>> is as follows:
> >>>>>>>>
> >>>>>>>>  /dev/sdc3 on /test5 type btrfs (rw,space_cache,compress=lzo,inode_cache)
> >>>>>>>>
> >>>>>>> So, just a "btrfs fi bal" would lead to the bug?
> >>>>>> I think so.
> >>
> >> It should be specific to the inode caching code.  The balancing code is
> >> finding the inode map cache extents, but it doesn't know how to relocate
> >> them.
> > 
> > However, the panic has occurred even if inode_cahce is turned off.
> > Is this another problem?
> > 
> 
> I don't think free inode cache isthe cause of the bug here (even if inode_cache
> is turned on).
> 
> What I have found out is:
> 
> 1. git checkout a4abeea41adfa3c143c289045f4625dfaeba2212
> 
> So the top commit is the removal of trans_mutex and no delayed_inode patch
> or free inode cache patchset in the tree, and bug can be triggered.
> 
> 2. git checkout 2a1eb4614d984d5cd4c928784e9afcf5c07f93be
> 
> So the top commit is the one before trans_mutex removal, and no bug triggered.
> 
> 3. test linus' tree
> 
> bug triggered.
> 
> 4. revert that suspicoius commit manually from linus' tree
> 
> no bug.
> 
> so either that commit is buggy or it reveals some bugs covered by the trans_mutex.

Ok, what dataset are you balancing?

What are you doing concurrently with the balance?

I haven't been able to trigger this here.

-chris