[pnfs] [PATCH] wrong hold count on clr_ref

[Benny Halevy]

Marc Eshel wrote:
> The first change is needed since know we have a compound rpc with 2 ops.
> Problem 6 still needs be fixed and until we do comment the BUG_ON so we 
> can see the layout return working. 
> 
> 6. The serve is not waiting for the client to return the layout before 
> calling destroy_layoutrecall() it because the hold count clr_ref is not 
> set correctly. This problem is not fixed except for removing the BUG that 
> causes the crash. 

The BUG_ON causes the crash on purpose and it's right,
removing it just invites trouble down the road.
Can you please try adding a kref_get(&clr->clr_ref)
in hash_layoutrecall instead? This was the original intent...

> 
>> From: Marc Eshel <eshel at almaden.ibm.com>
>>
>>
>> ---
>>
>>  fs/nfsd/nfs4callback.c |    2 +-
>>  fs/nfsd/nfs4state.c    |    2 +-
>>  2 files changed, 2 insertions(+), 2 deletions(-)
>>
>> diff --git a/fs/nfsd/nfs4callback.c b/fs/nfsd/nfs4callback.c
>> index b7bc5c3..da20278 100644
>> --- a/fs/nfsd/nfs4callback.c
>> +++ b/fs/nfsd/nfs4callback.c
>> @@ -413,7 +413,7 @@ nfs41_xdr_enc_cb_layout(struct rpc_rqst 
>>     struct nfs4_layoutrecall *args = rpc_args->args_op;
>>     struct nfs4_cb_compound_hdr hdr = {
>>        .ident = 0,
>> -      .nops   = 1,
>> +      .nops   = 2,
>>     };
>>
>>     xdr_init_encode(&xdr, &req->rq_snd_buf, p);
>> diff --git a/fs/nfsd/nfs4state.c b/fs/nfsd/nfs4state.c
>> index 2fe5414..e48f08d 100644
>> --- a/fs/nfsd/nfs4state.c
>> +++ b/fs/nfsd/nfs4state.c
>> @@ -4029,7 +4029,7 @@ destroy_layoutrecall(struct kref *kref)
>>        container_of(kref, struct nfs4_layoutrecall, clr_ref);
>>     dprintk("pNFS %s: clr %p fp %p clp %p\n", __FUNCTION__, clr,
>>             clr->clr_file, clr->clr_client);
>> -   BUG_ON(!list_empty(&clr->clr_perclnt));
>> +//???   BUG_ON(!list_empty(&clr->clr_perclnt));
>>     if (clr->clr_file)
>>        put_nfs4_file(clr->clr_file);
>>     kmem_cache_free(pnfs_layoutrecall_slab, clr);
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> 
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