Date: Mon, 2 Aug 1999 08:17:14 -0700 (PDT) From: Matthew Dillon <dillon@apollo.backplane.com> To: Matthew Dillon <dillon@apollo.backplane.com> Cc: Alfred Perlstein <bright@rush.net>, hackers@FreeBSD.ORG Subject: Re: confusion about nfsm_srvmtofh bad behavior? Message-ID: <199908021517.IAA13341@apollo.backplane.com> References: <Pine.BSF.3.96.990802072500.20420l-100000@cygnus.rush.net> <199908021513.IAA13285@apollo.backplane.com>
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::> it then rewinds the mbuf pointers (i think) because of the
::> over "dissection" above.
::> ---
::>
::> why does it do the copy, then rewind it, it seems like it knows
::> it's doing something wrong and instead of fixing it, it just
::> compensates after the fact.
::
::yes, replying to my own message.
::
::the only thing i can think of is that the extra data is safely
::ignored because the routines that use these macros seem to
::pass the version of NFS to all the function that they call...
::
::however unless i'm wrong (which i probably am) nfsV2 stuff
::could be made faster if it was correctly noted and less data
::was copied. It would also DTRT and not access data it isn't
::supposed to :)
::
::it seems like all of the V3 handles are the same length so
::there isn't much to do there...
::
::-Alfred
:
: Well, I must say that it certainly looks like a bug. It is not going
: to blow anything up since the nfsm_dissect() will break out if it runs
: out of buffer space, but it certainly seems inefficient. I am somewhat
: loath to fix anything in NFS that does not create a demonstrateable
: problem for fear of creating new problems, though, it is quite possible
: that the server code depends on the extra junk in the file handle for
: V2 mounts - A full audit of nfs_nqlease.c and nfs_serv.c would be
: necessary before this could be fixed.
:
: -Matt
: Matthew Dillon
: <dillon@backplane.com>
Oh, p.s. But in the mean time, if you or someone would like to commit
an XXX comment to document the potential bug / performance problem, I
think that would be very appropriate. e.g.
/*
* Extract file handle from NFS stream. XXX note that the extraction of
* the file handle for an NFSv2 mount appears to be rather odd. It is copying
* NFSX_V3FH bytes instead of NFSX_V2FH and then rewinding the mbuf index.
*/
#define nfsm_srvmtofh(f) \
{ int fhlen = NFSX_V3FH; \
if (nfsd->nd_flag & ND_NFSV3) { \
nfsm_dissect(tl, u_int32_t *, NFSX_UNSIGNED); \
fhlen = fxdr_unsigned(int, *tl); \
...
-Matt
Matthew Dillon
<dillon@backplane.com>
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