Re: [patch] svcrdma: endian bug in send_write_chunks()

On 1/12/12 1:28 PM, Trond Myklebust wrote:

On Thu, 2012-01-12 at 13:24 -0600, Tom Tucker wrote:

quoted

On 1/12/12 1:15 PM, Trond Myklebust wrote:

quoted

On Thu, 2012-01-12 at 11:21 -0500, J. Bruce Fields wrote:

quoted

On Thu, Jan 12, 2012 at 09:47:22AM +0300, Dan Carpenter wrote:

quoted

Sparse complains because arg_ch->rs_length is declared as network
endian but we're treating it as CPU endian.

This looks like it would actually change behavior on a little endian
architecture, so how did this work before?

quoted

 From some quick grepping, I see assignments both of the form

	...rs_length = ntohl(...)

and

	...rs_length = htonl(...)

but only see one declaration for a field named rs_length.

So my best guess would be that the code is ugly but working as is, and
needs cleanup by someone who knows how this field was intended to be
used.

It looks to me as if rs_handle and rs_offset are being similarly abused.
Basically, we need a serious clean up in svc_rdma_marshall.c to separate
out those variables that are in XDR-encoded form and those that are not.

The abuse is taking place because the marshal/unmarshall is being done
in-place and it seemed wasteful at the time to add a chunk of memory to
preserve the aesthetic. A union would 'work', but you still wouldn't
'know' whether the data was NBO or not by where it was -- which seems like
the intent of the __beXX in the first place.

These are not variables that are used in hundreds of different places:
why not just do the conversion from big-endian to cpu-endian when you
actually need to use them?

That would work fine actually. At the time, I was trying to put all that 
marshalling logic in that one file and reuse the already present 
client-side header file that copies that stuff when it decodes it.

I'll dig around a little bit and see what might be the simplest way to 
clean this up.

Tom


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