From mboxrd@z Thu Jan  1 00:00:00 1970
From: "J. Bruce Fields" <bfields@fieldses.org>
Subject: Re: [PATCH 7/7] nfsd: nfs4xdr decode_stateid helper function
Date: Wed, 13 Aug 2008 14:30:41 -0400
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Cc: Benny Halevy <bhalevy@panasas.com>,
	NFS list <linux-nfs@vger.kernel.org>,
	pNFS Mailing List <pnfs@linux-nfs.org>,
	Chuck Lever <chucklever@gmail.com>
To: Trond Myklebust <trond.myklebust@fys.uio.no>
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On Wed, Aug 13, 2008 at 01:59:09PM -0400, Trond Myklebust wrote:
> On Wed, 2008-08-13 at 11:03 -0400, J. Bruce Fields wrote:
> > On Wed, Aug 13, 2008 at 10:31:54AM +0300, Benny Halevy wrote:
> > > On Aug. 12, 2008, 22:04 +0300, "J. Bruce Fields" <bfields@fieldses.org> wrote:
> > > > On Tue, Aug 12, 2008 at 08:46:18PM +0300, Benny Halevy wrote:
> > > >> Signed-off-by: Benny Halevy <bhalevy@panasas.com>
> > > >> ---
> > > >>  fs/nfsd/nfs4xdr.c |   99 +++++++++++++++++++++++++++++-----------------------
> > > >>  1 files changed, 55 insertions(+), 44 deletions(-)
> > > >>
> > > >> diff --git a/fs/nfsd/nfs4xdr.c b/fs/nfsd/nfs4xdr.c
> > > >> index 47ac498..9570b1b 100644
> > > >> --- a/fs/nfsd/nfs4xdr.c
> > > >> +++ b/fs/nfsd/nfs4xdr.c
> > > >>  static __be32
> > > >> @@ -929,9 +939,10 @@ nfsd4_decode_write(struct nfsd4_compoundargs *argp, struct nfsd4_write *write)
> > > >>  	int len;
> > > >>  	DECODE_HEAD;
> > > >>  
> > > >> -	READ_BUF(sizeof(stateid_opaque_t) + 20);
> > > >> -	READ32(write->wr_stateid.si_generation);
> > > >> -	COPYMEM(&write->wr_stateid.si_opaque, sizeof(stateid_opaque_t));
> > > >> +	status = nfsd4_decode_stateid(argp, &write->wr_stateid);
> > > >> +	if (status)
> > > >> +		return status;
> > > >> +	READ_BUF(16);
> > > > 
> > > > How did that 20 become a 16?
> > > 
> > > It was sizeof(stateid_opaque_t) + 20 == sizeof(stateid_t) - 4 + 20 ==
> > > sizeof(stateid_t) + 16.
> > 
> > Whoops!  Even now I still fall into the stateid_opaque_t/stateid_t trap!
> 
> Which is a good reason for ditching the entire confusing typedef, and
> replacing it with a packed structure instead:
> 
> struct stateid {
> 	__be32 generation;
> 	char opaque[12];
> } __attribute__((packed));

So without the ((packed)), all arrays get aligned to 8-byte boundaries
on 64-bit machines?  (What do I need to read to catch up here?)

Anyway, yes, I'd rather get rid of stateid_opaque_t.

--b.