[PATCH 50/50] xfs: use reference counts to free clean buffer items

[Mark Tinguely]

On 08/13/13 22:57, Dave Chinner wrote:
> On Tue, Aug 13, 2013 at 05:00:25PM -0500, Mark Tinguely wrote:
>> On 08/13/13 16:46, Dave Chinner wrote:
>>> On Tue, Aug 13, 2013 at 10:03:19AM -0500, Mark Tinguely wrote:
>>>> On 08/12/13 05:50, Dave Chinner wrote:
>>>>> From: Dave Chinner<dchinner at redhat.com>
>>>>>
>>>>> When a transaction is cancelled and the buffer log item is clean in
>>
>> ...
>>
>>>>
>>>> why is a clean buffer on the AIL? Racing with a completion handler?
>>>
>>> "clean" means that it wasn't dirtied in the transaction - it can be
>>> in the AIL and holding a reference count that way.
>>
>> I am wondering because it should not have made it into the CIL if it
>> was not dirtied in a transaction - at least according to the the log
>> item descriptor flag at least.
>
> CIL != AIL. IOWs, the bli_refcount going to zero doesn't always
> mean the bli should be freed. All a zero value means is that it is
> not tracked by any transaction. If the item is not going to be
> placed in the AIL (or not already in the AIL) then it can be
> released (freed). Clean or aborted items are not going into the AIL,
> so they can be freed immeidately. Everything else needs to avoid
> freeing the item until the correct state is reached, even if the ref
> count goes to zero.
>

yep.

You are saying that the problem is releasing a buffer that is clean and 
also in the AIL, I am just trying to figure out if you are fixing a 
symptom or the problem.

--Mark.