Re: [PATCH V2 03/17] xprtrdma: Enable RDMA pad optimization by default

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On Apr 21, 2014, at 6:01 PM, Chuck Lever <chuck.lever@xxxxxxxxxx> wrote:

> Section 4 of RFC 5667 (NFS/RDMA) says:
> 
>> The server MUST ignore any Read list for other NFS procedures,
>> as well as additional Read list entries beyond the first in the
>> list.
> 
> Our XDR code adds a zero pad at the end of NFS WRITEs and SYMLINKs
> whose content is not a multiple of 4 octets long.  xprtrdma treats
> the tail buffer containing the zero pad as a separate read chunk,
> which the server ignores.
> 
> Enable the pad optimization so our NFS client avoids sending zeroes
> the server is just going to ignore.

Looks like the Linux NFS/RDMA server is not spec compliant here.
When pad optimization is enabled, the Linux NFS/RDMA server returns
GARBAGEARGS for WRITEs whose length does not align with an XDR_QUAD.

Dropping this one for now.


> Signed-off-by: Chuck Lever <chuck.lever@xxxxxxxxxx>
> ---
> 
> net/sunrpc/xprtrdma/transport.c |    2 +-
> 1 files changed, 1 insertions(+), 1 deletions(-)
> 
> diff --git a/net/sunrpc/xprtrdma/transport.c b/net/sunrpc/xprtrdma/transport.c
> index 1eb9c46..f94a6c4 100644
> --- a/net/sunrpc/xprtrdma/transport.c
> +++ b/net/sunrpc/xprtrdma/transport.c
> @@ -73,7 +73,7 @@ static unsigned int xprt_rdma_max_inline_read = RPCRDMA_DEF_INLINE;
> static unsigned int xprt_rdma_max_inline_write = RPCRDMA_DEF_INLINE;
> static unsigned int xprt_rdma_inline_write_padding;
> static unsigned int xprt_rdma_memreg_strategy = RPCRDMA_FRMR;
> -                int xprt_rdma_pad_optimize = 0;
> +int		    xprt_rdma_pad_optimize = 1;
> 
> #ifdef RPC_DEBUG
> 
> 
> --
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--
Chuck Lever
chuck[dot]lever[at]oracle[dot]com



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