Re: [BUG] btrfs quota

Re: [BUG] btrfs quota

[Arne Jansen]

Hello Wang,

On 03/31/13 03:44, Wang Shilong wrote:
> Hello Arne, Jan,
> 
>  When i run stresstest with quota enabled, i hit a panic where
> btrfs_find_all_roots() is called. Would you please double check it.
> 

On what kernel version do you hit this (git commit id preferred)?
Can you send us the message from dmesg?

Thanks,
arne

>  stresstest -n 10000  -t 4.
> 
> Maybe there is still race condition when walking backref  trees, Jan
> would you please check the backref.c ..
> btrfs_find_all_roots() is called in btrfs_qgroup_account_ref () to find
> all roots that reference a extent. I think this is called because
> 
> we introduce referenced/exclusive concepts. The point is that i think
>  this concept's disadvantages outweigh the advantages:
>       <1>
> walking backref  tree is really time-consuming.
> <2> referenced/exclusive makes it really complex when snapshot happens.
> <3> quota has a high coupling with other module.
>      I'd prefer to just keep referenced value, it is not be elegant, but
> it helps more.
> 
> Thanks,
> Wang
> 
> 
> 
> 
> 

Re: [BUG] btrfs quota

[Wang Shilong]

Hello Arne,

> Hello Wang,
> 
> On 03/31/13 03:44, Wang Shilong wrote:
>> Hello Arne, Jan,
>> 
>> When i run stresstest with quota enabled, i hit a panic where
>> btrfs_find_all_roots() is called. Would you please double check it.
>> 
> 
> On what kernel version do you hit this (git commit id preferred)?
> Can you send us the message from dmesg?
> 

Maybe it is because my patch
[Btrfs: kill some BUG_ONs() in the find_parent_nodes()]

would you please review the patch V3 for me?

Thanks,
Wang
 
> Thanks,
> arne
> 
>> stresstest -n 10000  -t 4.
>> 
>> Maybe there is still race condition when walking backref  trees, Jan
>> would you please check the backref.c ..
>> btrfs_find_all_roots() is called in btrfs_qgroup_account_ref () to find
>> all roots that reference a extent. I think this is called because
>> 
>> we introduce referenced/exclusive concepts. The point is that i think
>> this concept's disadvantages outweigh the advantages:
>>      <1>
>> walking backref  tree is really time-consuming.
>> <2> referenced/exclusive makes it really complex when snapshot happens.
>> <3> quota has a high coupling with other module.
>>     I'd prefer to just keep referenced value, it is not be elegant, but
>> it helps more.
>> 
>> Thanks,
>> Wang
>> 
>> 
>> 
>> 
>> 
> 

Re: [BUG] btrfs quota

[Wang Shilong]

Hello Arne,

However, I remember that i have hit this panic in several kernel version.
And i will double check it tomorrow when i am in the work..

If possible, i will send you the message from dmesg.

Thanks,
Wang

> Hello Wang,
> 
> On 03/31/13 03:44, Wang Shilong wrote:
>> Hello Arne, Jan,
>> 
>> When i run stresstest with quota enabled, i hit a panic where
>> btrfs_find_all_roots() is called. Would you please double check it.
>> 
> 
> On what kernel version do you hit this (git commit id preferred)?
> Can you send us the message from dmesg?
> 
> Thanks,
> arne
> 
>> stresstest -n 10000  -t 4.
>> 
>> Maybe there is still race condition when walking backref  trees, Jan
>> would you please check the backref.c ..
>> btrfs_find_all_roots() is called in btrfs_qgroup_account_ref () to find
>> all roots that reference a extent. I think this is called because
>> 
>> we introduce referenced/exclusive concepts. The point is that i think
>> this concept's disadvantages outweigh the advantages:
>>      <1>
>> walking backref  tree is really time-consuming.
>> <2> referenced/exclusive makes it really complex when snapshot happens.
>> <3> quota has a high coupling with other module.
>>     I'd prefer to just keep referenced value, it is not be elegant, but
>> it helps more.
>> 
>> Thanks,
>> Wang
>> 
>> 
>> 
>> 
>> 
>