Return-Path: Received: from mail-it0-f65.google.com ([209.85.214.65]:32807 "EHLO mail-it0-f65.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1750923AbdAMRm7 (ORCPT ); Fri, 13 Jan 2017 12:42:59 -0500 Subject: [PATCH v1 1/5] xprtrdma: Fix Read chunk padding From: Chuck Lever To: linux-rdma@vger.kernel.org, linux-nfs@vger.kernel.org Date: Fri, 13 Jan 2017 12:42:57 -0500 Message-ID: <20170113174257.32692.37552.stgit@manet.1015granger.net> In-Reply-To: <20170113173023.32692.30661.stgit@manet.1015granger.net> References: <20170113173023.32692.30661.stgit@manet.1015granger.net> MIME-Version: 1.0 Content-Type: text/plain; charset="utf-8" Sender: linux-nfs-owner@vger.kernel.org List-ID: When pad optimization is disabled, rpcrdma_convert_iovs still does not add explicit XDR padding to a Read chunk. Commit 677eb17e94ed ("xprtrdma: Fix XDR tail buffer marshalling") incorrectly short-circuited the test for whether padding is needed, which appears later in rpcrdma_convert_iovs. However, if this is indeed a Read chunk (and not a Position-Zero Read chunk), the tail iovec _always_ contains the chunk's padding, and never anything else. So, it's easy to just skip the tail when padding optimization is enabled, and add the tail in a subsequent Read chunk segment, if disabled. Fixes: 677eb17e94ed ("xprtrdma: Fix XDR tail buffer marshalling") Signed-off-by: Chuck Lever --- net/sunrpc/xprtrdma/rpc_rdma.c | 10 ++++------ 1 file changed, 4 insertions(+), 6 deletions(-) diff --git a/net/sunrpc/xprtrdma/rpc_rdma.c b/net/sunrpc/xprtrdma/rpc_rdma.c index c52e0f2..a524d3c 100644 --- a/net/sunrpc/xprtrdma/rpc_rdma.c +++ b/net/sunrpc/xprtrdma/rpc_rdma.c @@ -226,8 +226,10 @@ static bool rpcrdma_results_inline(struct rpcrdma_xprt *r_xprt, if (len && n == RPCRDMA_MAX_SEGS) goto out_overflow; - /* When encoding the read list, the tail is always sent inline */ - if (type == rpcrdma_readch) + /* When encoding a Read chunk, the tail iovec contains an + * XDR pad and may be omitted. + */ + if (type == rpcrdma_readch && xprt_rdma_pad_optimize) return n; /* When encoding the Write list, some servers need to see an extra @@ -238,10 +240,6 @@ static bool rpcrdma_results_inline(struct rpcrdma_xprt *r_xprt, return n; if (xdrbuf->tail[0].iov_len) { - /* the rpcrdma protocol allows us to omit any trailing - * xdr pad bytes, saving the server an RDMA operation. */ - if (xdrbuf->tail[0].iov_len < 4 && xprt_rdma_pad_optimize) - return n; n = rpcrdma_convert_kvec(&xdrbuf->tail[0], seg, n); if (n == RPCRDMA_MAX_SEGS) goto out_overflow;