Re: kern/42455: tstile hang with nfs

[yamt%mwd.biglobe.ne.jp@localhost (YAMAMOTO Takashi)]

hi,

>>  hi,
>>  
>>  >>  >  I added some more debug lines and figured out that the macro
>>  >>  >  nfsm_wcc_data() drops the mbuf chain w/o decreasing
>>  >>  >  ctxt.nwc_mbufcount.
>>  >>  
>>  >>  The nfsm_wcc_data() macro calls the nfsm_postop_attr() macro.
>>  >>  The nfsm_postop_attr() macro calls nfsm_loadattrcache() function.
>>  >>  The nfsm_loadattrcache() function calls nfsm_disct() function.
>>  >>  
>>  >>  nfsm_disct() is the function in error which drops the mbuf chain.
>>  
>>  are you sure?
> 
> yes, absolutely and reproducable.
> 
>>  iirc, nwc_mbufcount is about sending mbuf.  otoh, nfsm_disct
>>  is for received mbuf.
> 
> nfs_writerpc *does* call nfsm_disct() through nfsm_wcc_data,
> nfsm_postop_attr and nfsm_loadattrcache in this order.
> 
> So you are saying this should never happen?

i'm saying i don't understand.

nfs_writerpc sends a request to the server, using mreq and mb.
it's what nwc_mbufcount is used for.

it then parses the reply from the server, using mrep and md.
it's what nfsm_wcc_data/nfsm_postop_attr/nfsm_loadattrcache/nfsm_disct are
used for.

i don't understand how a problem in the latter causes the nwc_mbufcount
problem.  the above two are somehow mixed up?

YAMAMOTO Takashi

> 
> Christoph