xprtrdma: Eliminate per-transport "max pages"

To support device hotplug and migrating a connection between devices
of different capabilities, we have to guarantee that all in-kernel
devices can support the same max NFS payload size (1 megabyte).

This means that possibly one or two in-tree devices are no longer
supported for NFS/RDMA because they cannot support 1MB rsize/wsize.
The only one I confirmed was cxgb3, but it has already been removed
from the kernel.
Signed-off-by: Chuck Lever <chuck.lever@oracle.com>
Signed-off-by: Anna Schumaker <Anna.Schumaker@Netapp.com>

net/sunrpc/xprtrdma/frwr_ops.c

@@ -178,7 +178,7 @@ int frwr_init_mr(struct rpcrdma_ia *ia, struct rpcrdma_mr *mr)
  *	ep->rep_attr.cap.max_send_wr
  *	ep->rep_attr.cap.max_recv_wr
  *	ep->rep_max_requests
- *	ia->ri_max_segs
+ *	ia->ri_max_rdma_segs
  *
  * And these FRWR-related fields:
  *	ia->ri_max_frwr_depth
@@ -209,14 +209,12 @@ int frwr_open(struct rpcrdma_ia *ia, struct rpcrdma_ep *ep)
 	 * capability, but perform optimally when the MRs are not larger
 	 * than a page.
 	 */
-	if (attrs->max_sge_rd > 1)
+	if (attrs->max_sge_rd > RPCRDMA_MAX_HDR_SEGS)
 		ia->ri_max_frwr_depth = attrs->max_sge_rd;
 	else
 		ia->ri_max_frwr_depth = attrs->max_fast_reg_page_list_len;
 	if (ia->ri_max_frwr_depth > RPCRDMA_MAX_DATA_SEGS)
 		ia->ri_max_frwr_depth = RPCRDMA_MAX_DATA_SEGS;
-	dprintk("RPC:       %s: max FR page list depth = %u\n",
-		__func__, ia->ri_max_frwr_depth);
 
 	/* Add room for frwr register and invalidate WRs.
 	 * 1. FRWR reg WR for head
@@ -260,30 +258,22 @@ int frwr_open(struct rpcrdma_ia *ia, struct rpcrdma_ep *ep)
 	ep->rep_attr.cap.max_recv_wr += RPCRDMA_BACKWARD_WRS;
 	ep->rep_attr.cap.max_recv_wr += 1; /* for ib_drain_rq */
 
-	ia->ri_max_segs =
+	ia->ri_max_rdma_segs =
 		DIV_ROUND_UP(RPCRDMA_MAX_DATA_SEGS, ia->ri_max_frwr_depth);
 	/* Reply chunks require segments for head and tail buffers */
-	ia->ri_max_segs += 2;
-	if (ia->ri_max_segs > RPCRDMA_MAX_HDR_SEGS)
-		ia->ri_max_segs = RPCRDMA_MAX_HDR_SEGS;
-	return 0;
-}
+	ia->ri_max_rdma_segs += 2;
+	if (ia->ri_max_rdma_segs > RPCRDMA_MAX_HDR_SEGS)
+		ia->ri_max_rdma_segs = RPCRDMA_MAX_HDR_SEGS;
 
-/**
- * frwr_maxpages - Compute size of largest payload
- * @r_xprt: transport
- *
- * Returns maximum size of an RPC message, in pages.
- *
- * FRWR mode conveys a list of pages per chunk segment. The
- * maximum length of that list is the FRWR page list depth.
+	/* Ensure the underlying device is capable of conveying the
+	 * largest r/wsize NFS will ask for. This guarantees that
+	 * failing over from one RDMA device to another will not
+	 * break NFS I/O.
 	 */
-size_t frwr_maxpages(struct rpcrdma_xprt *r_xprt)
-{
-	struct rpcrdma_ia *ia = &r_xprt->rx_ia;
+	if ((ia->ri_max_rdma_segs * ia->ri_max_frwr_depth) < RPCRDMA_MAX_SEGS)
+		return -ENOMEM;
 
-	return min_t(unsigned int, RPCRDMA_MAX_DATA_SEGS,
-		     (ia->ri_max_segs - 2) * ia->ri_max_frwr_depth);
+	return 0;
 }
 
 /**

net/sunrpc/xprtrdma/rpc_rdma.c

@@ -111,7 +111,7 @@ static unsigned int rpcrdma_max_reply_header_size(unsigned int maxsegs)
  */
 void rpcrdma_set_max_header_sizes(struct rpcrdma_xprt *r_xprt)
 {
-	unsigned int maxsegs = r_xprt->rx_ia.ri_max_segs;
+	unsigned int maxsegs = r_xprt->rx_ia.ri_max_rdma_segs;
 	struct rpcrdma_ep *ep = &r_xprt->rx_ep;
 
 	ep->rep_max_inline_send =

net/sunrpc/xprtrdma/transport.c

@@ -359,19 +359,13 @@ xprt_setup_rdma(struct xprt_create *args)
 	if (rc)
 		goto out3;
 
-	INIT_DELAYED_WORK(&new_xprt->rx_connect_worker,
-			  xprt_rdma_connect_worker);
-
-	xprt->max_payload = frwr_maxpages(new_xprt);
-	if (xprt->max_payload == 0)
-		goto out4;
-	xprt->max_payload <<= PAGE_SHIFT;
-	dprintk("RPC:       %s: transport data payload maximum: %zu bytes\n",
-		__func__, xprt->max_payload);
-
 	if (!try_module_get(THIS_MODULE))
 		goto out4;
 
+	INIT_DELAYED_WORK(&new_xprt->rx_connect_worker,
+			  xprt_rdma_connect_worker);
+	xprt->max_payload = RPCRDMA_MAX_DATA_SEGS << PAGE_SHIFT;
+
 	dprintk("RPC:       %s: %s:%s\n", __func__,
 		xprt->address_strings[RPC_DISPLAY_ADDR],
 		xprt->address_strings[RPC_DISPLAY_PORT]);

net/sunrpc/xprtrdma/verbs.c

@@ -936,7 +936,7 @@ rpcrdma_mrs_create(struct rpcrdma_xprt *r_xprt)
 	struct rpcrdma_ia *ia = &r_xprt->rx_ia;
 	unsigned int count;
 
-	for (count = 0; count < ia->ri_max_segs; count++) {
+	for (count = 0; count < ia->ri_max_rdma_segs; count++) {
 		struct rpcrdma_mr *mr;
 		int rc;
 
@@ -1018,7 +1018,7 @@ struct rpcrdma_req *rpcrdma_req_create(struct rpcrdma_xprt *r_xprt, size_t size,
 
 	/* Compute maximum header buffer size in bytes */
 	maxhdrsize = rpcrdma_fixed_maxsz + 3 +
-		     r_xprt->rx_ia.ri_max_segs * rpcrdma_readchunk_maxsz;
+		     r_xprt->rx_ia.ri_max_rdma_segs * rpcrdma_readchunk_maxsz;
 	maxhdrsize *= sizeof(__be32);
 	rb = rpcrdma_regbuf_alloc(__roundup_pow_of_two(maxhdrsize),
 				  DMA_TO_DEVICE, flags);

net/sunrpc/xprtrdma/xprt_rdma.h

@@ -71,7 +71,7 @@ struct rpcrdma_ia {
 	struct rdma_cm_id 	*ri_id;
 	struct ib_pd		*ri_pd;
 	int			ri_async_rc;
-	unsigned int		ri_max_segs;
+	unsigned int		ri_max_rdma_segs;
 	unsigned int		ri_max_frwr_depth;
 	bool			ri_implicit_roundup;
 	enum ib_mr_type		ri_mrtype;
@@ -539,7 +539,6 @@ void frwr_reset(struct rpcrdma_req *req);
 int frwr_open(struct rpcrdma_ia *ia, struct rpcrdma_ep *ep);
 int frwr_init_mr(struct rpcrdma_ia *ia, struct rpcrdma_mr *mr);
 void frwr_release_mr(struct rpcrdma_mr *mr);
-size_t frwr_maxpages(struct rpcrdma_xprt *r_xprt);
 struct rpcrdma_mr_seg *frwr_map(struct rpcrdma_xprt *r_xprt,
 				struct rpcrdma_mr_seg *seg,
 				int nsegs, bool writing, __be32 xid,