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

[Li Zefan <lizf@cn.fujitsu.com>]

Yan, Zheng wrote:
> Add a mutex to btrfs_init_reloc_root() to prevent the reloc tree
> creation from concurrent execution.

Thanks!

Unfortunately I can still encounter BUG() in difference places in
each run:

kernel BUG at fs/btrfs/extent-tree.c:6173!

kernel BUG at fs/btrfs/volumes.c:2567!

> 
> On Mon, Jun 13, 2011 at 3:13 PM, Li Zefan <lizf@cn.fujitsu.com> wrote:
>> 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.