change in VFS layer API?

[Julian Elischer]

On 10/25/14, 10:47 AM, Julian Elischer wrote:
> On 10/25/14, 1:18 AM, K. Macy wrote:
>> On Fri, Oct 24, 2014 at 9:45 AM, Julian Elischer 
>> <julian at freebsd.org> wrote:
>>> Can anyone point me at a VFS API contract change that occurred 
>>> over the last
>>> 5 years where a filesystem written to teh old contract would end 
>>> up with
>>> extra references to all its vnodes/objects? Specifically a 
>>> proprietary
>>> filesystem that ran on 8.0 now can be compiled but ends up with extra
>>> references on its vnodes and can not free them.
>>>
>> I think the contract for some functions has become unclear. I've found
>> that the opensolaris' compatibility layer traverse' vput of the
>> initial vnode passed in triggers negative reference count panics. It
>> is clear that some callers of lookup expect the reference to be
>> maintained on error so the unconditional vput was (well is - this
>> patch isn't in base) wrong, but in the case of success it isn't clear.
>> Doing the vput on success will still eventually (as in a few seconds
>> of this torture test script) cause a negative reference count panic. I
>> think there needs to be an audit of VFS function contract compliance.
>> Preferably by someone who knows what they are. I can only infer from
>> cumulative context.
>
> I have evidence that the API has actually changed somehow.
>
> The old API would have extra calls to remove references to nodes.
> We don't seem to be seeing those extra calls any more.
> I'll have more info later.
My colleague who works on the filesystem in question suspects
a change in the interplay between _inactive and _reclaim of a znode/vnode,
resulting in extra references on the nodes.

Doesn't ring any bells with anyone?


>> Thanks.
>>
>> -K
>>
>>
>
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