Subject: Re: [PATCH] nfs41: get rid of unused struct nfs41_exchange_id_res members

From: Benny Halevy <[email-masked]>
Date: Wed, 06 May 2009 01:15:57 +0300

On 2009-05-06 01:12, Trond Myklebust wrote:
> On Tue, 2009-05-05 at 23:35 +0300, Benny Halevy wrote:
>> On 2009-05-05 23:28, Benny Halevy wrote:
>>> On May. 05, 2009, 22:41 +0300, Trond Myklebust <[email-masked]> wrote:
>>>> On Tue, 2009-05-05 at 15:39 -0400, Trond Myklebust wrote:
>>>>> On Tue, 2009-05-05 at 15:34 -0400, Trond Myklebust wrote:
>>>>>> On Fri, 2009-05-01 at 23:14 +0300, Benny Halevy wrote:
>>>>>>> struct nfs41_exchange_id_res is currently allocated on the stack
>>>>>>> insanely taking over 2K of stack space due to the NFS4_OPAQUE_LIMIT (1K(
>>>>>>> byte arrays embedded in server_owner and server_scope.
>>>>>>> Since these are not in use yet, this patch gets rid of them for the
>>>>>>> time being.
>>>>>>>
>>>>>>> Signed-off-by: Benny Halevy <[email-masked]>
>>>>>>> ---
>>>>>>>  fs/nfs/nfs4xdr.c        |   27 ++++++++++++++-------------
>>>>>>>  include/linux/nfs_xdr.h |    3 ---
>>>>>>>  2 files changed, 14 insertions(+), 16 deletions(-)
>>>>>>>
>>>>>>> diff --git a/fs/nfs/nfs4xdr.c b/fs/nfs/nfs4xdr.c
>>>>>>> index 80af0ae..3350d19 100644
>>>>>>> --- a/fs/nfs/nfs4xdr.c
>>>>>>> +++ b/fs/nfs/nfs4xdr.c
>>>>>>> @@ -4185,8 +4185,8 @@ static int decode_delegreturn(struct xdr_stream *xdr)
>>>>>>>  static int decode_exchange_id(struct xdr_stream *xdr,
>>>>>>>  			      struct nfs41_exchange_id_res *res)
>>>>>>>  {
>>>>>>> -	uint32_t *p;
>>>>>>> -	int status, dummy;
>>>>>>> +	uint32_t *p, dummy;
>>>> Oh, and 'p' _always_ has to be of type '__be32', otherwise the 'sparse'
>>>> checker will yell at you.
>>> Thanks!  I'll send a fixed version
>>> of this patch and also look into the rest of the xdr code.
>>>
>>>>>>> +	int status;
>>>>>>>  	struct nfs_client *clp = res->client;
>>>>>>>  
>>>>>>>  	status = decode_op_hdr(xdr, OP_EXCHANGE_ID);
>>>>>>> @@ -4204,25 +4204,26 @@ static int decode_exchange_id(struct xdr_stream *xdr,
>>>>>>>  	if (dummy != SP4_NONE)
>>>>>>>  		return -EIO;
>>>>>>>  
>>>>>>> -	/* minor_id */
>>>>>>> +	/* Throw away minor_id */
>>>>>>>  	READ_BUF(8);
>>>>>>> -	READ64(res->server_owner.minor_id);
>>>>>>> +	p += 8;
>>>>>>          ^^^^^^^^ Err... This isn't the same thing at all!
>>> Ouch, of course.  What did I smoke that day?
>>>
>>>>>> You're suddenly skipping 10=words instead of the original 2. READ_BUF()
>>>>>> will already take care of updating the 'p' pointer.
>>> Which p?
>>> It takes care of argp->p, not the local 'p' variable, doesn't it.
>> Grr, I meant "xdr->p" of course, via xdr_inline_decode
>> (argp is the server's READ_BUF, sigh)
>>
>>> p += 2 has an equivalent side effect on 'p' as doing READ64.
>>> I can do "p = argp;" instead though to reset 'p' onto
>> p = xdr->p; ...
> 
> Not necessary. Look again at the first line of the READ_BUF(nbytes)
> macro:
> 
> 	p = xdr_inline_decode(xdr, nbytes);
> 
> So the value of 'p' is always correctly set to the beginning of the
> buffer of length 'nbytes'.

Right, but then we want to skip over the buffer.

> 
> I'll make a point of removing those macro references from the client
> code in the next week or so. I'm getting really tired of them...

Yeah, I'm all for it.
Let me know if there's anything I can do to help with that.

Benny

> Cheers
>   Trond