On Jun 2, 2008, at 12:49 PM, J. Bruce Fields wrote:
On Thu, May 29, 2008 at 12:24:58PM -0400, Chuck Lever wrote:
By the way, here is a pointer to the old work:
http://git.linux-nfs.org/?p=cel/cel-2.6.git;a=shortlog;h=drop-20070423
The work in this snapshot is only partially complete.
There are many many issues to fix up. One of the bigger ones is that
the RPC layer still takes the BKL during XDR encoding and
decoding. But
I wanted to create something that could be fully or partially
shared by
the client and server implementations, and that would be more
rigorous
about static and dynamic type checking.
In addition, the NFSv4 routines use a new style of managing the RPC
buffer that I wanted to adopt for the other in-kernel XDR routines,
then
convert the RPC client to use only the new style when invoking XDR
routines. I never got that far, but I still think it's a reasonable
goal.
To find something manageable to start with, what's the minimum first
step that that would achieve Benny's goal of replacing those server-
side
xdr macros?
If we're going to do this, I think we want to replace the macros in
both the server and the client.
Thus you want to have a set of shared static inline functions that
manage static type checking, data conversion, and bounds checking for
basic XDR data types. There are a short series of patches near the
beginning of that branch that introduce these helpers. Look at
06e537f7 through cf1ba5ab.
The last one adds generic warning messages on XDR encode and decode
errors. We can certainly remove (or provide a kernel config switch
for) the decode warnings as they could cause a DoS, but the encode
error messages might be useful, and would allow us to remove many of
the ad hoc printk's from the XDR functions themselves, resulting in
smaller code.
Then, 986ac05e defines the set of NFSv4 XDR data types laid out in
RFC3530. The following patches start to fix up the client-side
encoders; I didn't get to the client-side decoders, or to the server.
The real effort is going to be reworking the encoders and decoders for
the big NFSv4 datatypes, like for instance the arguments and results
that contain attributes.
From a quick glance at the patches: a kerneldoc comment for each xdr
encode/decode seems like overkill, since it's mostly boilerplate;
could
we document those arguments just once with the definition of
kxdrproc_t,
then refer to that comment as necessary?
A lot of the changes in that drop are excessive; it was a prototype,
so I used the comments to keep track of where I was heading. However,
in general I think it's important to document the assumptions relating
to the arguments, and the possible return values, for each public
function.
Many of the comments in these patches also copy the definition of the
XDR data type from the RFC, and call out the RFC section where it is
specified. This provides a clear connection between the
implementation and the spec to allow easier code review and maintenance.
--
Chuck Lever
chuck[dot]lever[at]oracle[dot]com
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