@@ -96,6 +96,42 @@ static bool rpcrdma_results_inline(struct rpc_rqst *rqst)
return repsize <= RPCRDMA_INLINE_READ_THRESHOLD(rqst);
}
+static int
+rpcrdma_tail_pullup(struct xdr_buf *buf)
+{
+ size_t tlen = buf->tail[0].iov_len;
+ size_t skip = tlen & 3;
+
+ /* Do not include the tail if it is only an XDR pad */
+ if (tlen < 4)
+ return 0;
+
+ /* xdr_write_pages() adds a pad at the beginning of the tail
+ * if the content in "buf->pages" is unaligned. Force the
+ * tail's actual content to land at the next XDR position
+ * after the head instead.
+ */
+ if (skip) {
+ unsigned char *src, *dst;
+ unsigned int count;
+
+ src = buf->tail[0].iov_base;
+ dst = buf->head[0].iov_base;
+ dst += buf->head[0].iov_len;
+
+ src += skip;
+ tlen -= skip;
+
+ dprintk("RPC: %s: skip=%zu, memmove(%p, %p, %zu)\n",
+ __func__, skip, dst, src, tlen);
+
+ for (count = tlen; count; count--)
+ *dst++ = *src++;
+ }
+
+ return tlen;
+}
+
/*
* Chunk assembly from upper layer xdr_buf.
*
@@ -147,6 +183,10 @@ rpcrdma_convert_iovs(struct xdr_buf *xdrbuf, unsigned int pos,
if (len && n == nsegs)
return -EIO;
+ /* When encoding the read list, the tail is always sent inline */
+ if (type == rpcrdma_readch)
+ 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. */
@@ -476,8 +516,8 @@ rpcrdma_marshal_req(struct rpc_rqst *rqst)
headerp->rm_body.rm_nochunks.rm_empty[2] = xdr_zero;
/* new length after pullup */
rpclen = rqst->rq_svec[0].iov_len;
- }
-
+ } else if (rtype == rpcrdma_readch)
+ rpclen += rpcrdma_tail_pullup(&rqst->rq_snd_buf);
if (rtype != rpcrdma_noch) {
hdrlen = rpcrdma_create_chunks(rqst, &rqst->rq_snd_buf,
headerp, rtype);
Currently xprtrdma appends an extra chunk element to the RPC/RDMA read chunk list of each NFSv4 WRITE compound. The extra element contains the final GETATTR operation in the compound. The result is an extra RDMA READ operation to transfer a very short piece of each NFS WRITE compound (typically 16 bytes). This is inefficient. It is also incorrect. The client is sending the trailing GETATTR at the same Position as the preceding WRITE data payload. Whether or not RFC 5667 allows the GETATTR to appear in a read chunk, RFC 5666 requires that these two separate RPC arguments appear at two distinct Positions. It can also be argued that the GETATTR operation is not bulk data, and therefore RFC 5667 forbids its appearance in a read chunk at all. Although RFC 5667 is not precise about when using a read list with NFSv4 COMPOUND is allowed, the intent is that only data arguments not touched by NFS (ie, read and write payloads) are to be sent using RDMA READ or WRITE. The NFS client constructs GETATTR arguments itself, and therefore is required to send the trailing GETATTR operation as additional inline content, not as a data payload. NB: This change is not backwards compatible. Some older servers do not accept inline content following the read list. The Linux NFS server should handle this content correctly as of commit a97c331f9aa9 ("svcrdma: Handle additional inline content"). Signed-off-by: Chuck Lever <chuck.lever@oracle.com> Tested-by: Devesh Sharma <devesh.sharma@avagotech.com> --- net/sunrpc/xprtrdma/rpc_rdma.c | 44 ++++++++++++++++++++++++++++++++++++++-- 1 file changed, 42 insertions(+), 2 deletions(-) -- To unsubscribe from this list: send the line "unsubscribe linux-rdma" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html