Re: [pnfs] [PATCH 7/7] nfsd: nfs4xdr decode_stateid helper function

Boaz Harrosh
2008-08-17T12:02:38Z

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));
>
> Trond
>

Please use the "__packed" Kernel macro for better compilers support.

And Yes I would suggest using "__packed" where ever a struct is defined
for on-the-wire. Even just for indication to fellow programmers that this
is going on the wire as is.

Boaz