Re: [PATCH 2/3] SUNRPC: Fix large reads on NFS/RDMA

[Jeff Layton <jlayton@redhat.com>]

On Fri, 17 Jan 2014 14:38:16 -0500
Chuck Lever <chuck.lever@oracle.com> wrote:

> After commit a11a2bf4, "SUNRPC: Optimise away unnecessary data
> moves in xdr_align_pages", Thu Aug 2 13:21:43 2012, READs larger
> than a few hundred bytes via NFS/RDMA stopped working.  This
> commit exposed a long-standing bug in rpcrdma_inline_fixup().
> 
> I reproduce this with an rsize=4096 mount using the cthon04
> basic tests.  Test 5 fails with an EIO error.
> 
> For my reproducer, kernel log shows:
> 
>   NFS: server cheating in read reply: count 4096 > recvd 0
> 
> rpcrdma_inline_fixup() is zeroing the xdr_stream::page_len
> field, and xdr_align_pages() is now returning that value to
> the READ XDR decoder function.
> 
> That field is set up by xdr_inline_pages() by the READ XDR
> encoder function.  As far as I can tell, it is supposed to
> be left alone after that, as it describes the dimensions of
> the reply xdr_stream, not the contents of that stream.
> 
> Bugzilla: https://bugzilla.kernel.org/show_bug.cgi?id=68391
> Signed-off-by: Chuck Lever <chuck.lever@oracle.com>
> Cc: <stable@vger.kernel.org> # 3.7+
> ---
> 
>  net/sunrpc/xprtrdma/rpc_rdma.c |    4 +---
>  1 files changed, 1 insertions(+), 3 deletions(-)
> 
> diff --git a/net/sunrpc/xprtrdma/rpc_rdma.c b/net/sunrpc/xprtrdma/rpc_rdma.c
> index e03725b..96ead52 100644
> --- a/net/sunrpc/xprtrdma/rpc_rdma.c
> +++ b/net/sunrpc/xprtrdma/rpc_rdma.c
> @@ -649,9 +649,7 @@ rpcrdma_inline_fixup(struct rpc_rqst *rqst, char *srcp, int copy_len, int pad)
>  				break;
>  			page_base = 0;
>  		}
> -		rqst->rq_rcv_buf.page_len = olen - copy_len;
> -	} else
> -		rqst->rq_rcv_buf.page_len = 0;
> +	}
>  
>  	if (copy_len && rqst->rq_rcv_buf.tail[0].iov_len) {
>  		curlen = copy_len;
> 
> --
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Seems to fix the bug for me too...

Tested-by: Jeff Layton <jlayton@redhat.com>