[PATCH 4.9 141/153] xprtrdma: Fix Read chunk padding

Greg Kroah-Hartman
2017-03-10T09:26:54Z

From: Chuck Lever <chuck.lever@oracle.com>

commit 24abdf1be15c478e2821d6fc903a4a4440beff02 upstream.

When pad optimization is disabled, rpcrdma_convert_iovs still
does not add explicit XDR round-up padding to a Read chunk.

Commit 677eb17e94ed ("xprtrdma: Fix XDR tail buffer marshalling")
incorrectly short-circuited the test for whether round-up padding
is needed that appears later in rpcrdma_convert_iovs.

However, if this is indeed a regular 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 <chuck.lever@oracle.com>
Signed-off-by: Anna Schumaker <Anna.Schumaker@Netapp.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

---
net/sunrpc/xprtrdma/rpc_rdma.c | 10 ++++------
1 file changed, 4 insertions(+), 6 deletions(-)

--- a/net/sunrpc/xprtrdma/rpc_rdma.c
+++ b/net/sunrpc/xprtrdma/rpc_rdma.c
@@ -226,8 +226,10 @@ rpcrdma_convert_iovs(struct xdr_buf *xdr
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 @@ rpcrdma_convert_iovs(struct xdr_buf *xdr
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;