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

From: Trond Myklebust <[email-masked]>
Date: Tue, 05 May 2009 15:41:48 -0400

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.

> > > +	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!
> > 
> > You're suddenly skipping 10=words instead of the original 2. READ_BUF()
> > will already take care of updating the 'p' pointer.
> 
> BTW, this is exactly why the whole READ_BUF(), READ*(), WRITE*() macro
> crap is so utterly broken. The magic that happens to the 'p' pointer is
> completely opaque to someone unfamiliar with the code.
> 
> > >  
> > > -	/* Major id */
> > > +	/* Throw away Major id */
> > >  	READ_BUF(4);
> > > -	READ32(res->server_owner.major_id_sz);
> > > -	READ_BUF(res->server_owner.major_id_sz);
> > > -	COPYMEM(res->server_owner.major_id, res->server_owner.major_id_sz);
> > > +	READ32(dummy);
> > > +	READ_BUF(dummy);
> > > +	p += XDR_QUADLEN(dummy);
> >          ^^^^^^^^^^^^^^^^^^^^^^^^^ Ditto. You're skipping 2*dummy words.
> > 
> > >  
> > > -	/* server_scope */
> > > +	/* Throw away server_scope */
> > >  	READ_BUF(4);
> > > -	READ32(res->server_scope.server_scope_sz);
> > > -	READ_BUF(res->server_scope.server_scope_sz);
> > > -	COPYMEM(res->server_scope.server_scope,
> > > -		res->server_scope.server_scope_sz);
> > > +	READ32(dummy);
> > > +	READ_BUF(dummy);
> > > +	p += XDR_QUADLEN(dummy);
> >           ^^^^^^^^^^^^^^^^^^^^^^^^ Ditto
> > 
> > > +
> > >  	/* Throw away Implementation id array */
> > >  	READ_BUF(4);
> > >  	READ32(dummy);
> > > +	READ_BUF(dummy);
> > >  	p += XDR_QUADLEN(dummy);
> >           ^^^^^^^^^^^^^^^^^^^^^^^^ Ditto
> > 
> > >  
> > >  	return 0;
> > > diff --git a/include/linux/nfs_xdr.h b/include/linux/nfs_xdr.h
> > > index 071a6d1..62f63fb 100644
> > > --- a/include/linux/nfs_xdr.h
> > > +++ b/include/linux/nfs_xdr.h
> > > @@ -925,9 +925,6 @@ struct server_scope {
> > >  struct nfs41_exchange_id_res {
> > >  	struct nfs_client		*client;
> > >  	u32				flags;
> > > -	struct server_owner		server_owner;
> > > -	struct server_scope		server_scope;
> > > -	struct nfs_impl_id4		impl_id;
> > >  };
> > >  
> > >  struct nfs41_create_session_args {
> > 
>