5 files changed, 23 insertions, 26 deletions

diff --git a/net/sunrpc/xprtrdma/fmr_ops.c b/net/sunrpc/xprtrdma/fmr_ops.c
index b289e10..4aeb104 100644
--- a/net/sunrpc/xprtrdma/fmr_ops.c
+++ b/net/sunrpc/xprtrdma/fmr_ops.c
@@ -48,7 +48,7 @@ static size_t
 fmr_op_maxpages(struct rpcrdma_xprt *r_xprt)
 {
 	return min_t(unsigned int, RPCRDMA_MAX_DATA_SEGS,
-		     rpcrdma_max_segments(r_xprt) * RPCRDMA_MAX_FMR_SGES);
+		     RPCRDMA_MAX_HDR_SEGS * RPCRDMA_MAX_FMR_SGES);
 }
 
 static int
diff --git a/net/sunrpc/xprtrdma/frwr_ops.c b/net/sunrpc/xprtrdma/frwr_ops.c
index c250924..2f37598 100644
--- a/net/sunrpc/xprtrdma/frwr_ops.c
+++ b/net/sunrpc/xprtrdma/frwr_ops.c
@@ -243,7 +243,7 @@ frwr_op_maxpages(struct rpcrdma_xprt *r_xprt)
 	struct rpcrdma_ia *ia = &r_xprt->rx_ia;
 
 	return min_t(unsigned int, RPCRDMA_MAX_DATA_SEGS,
-		     rpcrdma_max_segments(r_xprt) * ia->ri_max_frmr_depth);
+		     RPCRDMA_MAX_HDR_SEGS * ia->ri_max_frmr_depth);
 }
 
 static void
diff --git a/net/sunrpc/xprtrdma/physical_ops.c b/net/sunrpc/xprtrdma/physical_ops.c
index 481b9b6..e16ed54 100644
--- a/net/sunrpc/xprtrdma/physical_ops.c
+++ b/net/sunrpc/xprtrdma/physical_ops.c
@@ -47,7 +47,7 @@ static size_t
 physical_op_maxpages(struct rpcrdma_xprt *r_xprt)
 {
 	return min_t(unsigned int, RPCRDMA_MAX_DATA_SEGS,
-		     rpcrdma_max_segments(r_xprt));
+		     RPCRDMA_MAX_HDR_SEGS);
 }
 
 static int
diff --git a/net/sunrpc/xprtrdma/verbs.c b/net/sunrpc/xprtrdma/verbs.c
index f5ed9f9..9f8d6c1 100644
--- a/net/sunrpc/xprtrdma/verbs.c
+++ b/net/sunrpc/xprtrdma/verbs.c
@@ -1271,25 +1271,3 @@ out_rc:
 	rpcrdma_recv_buffer_put(rep);
 	return rc;
 }
-
-/* How many chunk list items fit within our inline buffers?
- */
-unsigned int
-rpcrdma_max_segments(struct rpcrdma_xprt *r_xprt)
-{
-	struct rpcrdma_create_data_internal *cdata = &r_xprt->rx_data;
-	int bytes, segments;
-
-	bytes = min_t(unsigned int, cdata->inline_wsize, cdata->inline_rsize);
-	bytes -= RPCRDMA_HDRLEN_MIN;
-	if (bytes < sizeof(struct rpcrdma_segment) * 2) {
-		pr_warn("RPC:       %s: inline threshold too small\n",
-			__func__);
-		return 0;
-	}
-
-	segments = 1 << (fls(bytes / sizeof(struct rpcrdma_segment)) - 1);
-	dprintk("RPC:       %s: max chunk list size = %d segments\n",
-		__func__, segments);
-	return segments;
-}
diff --git a/net/sunrpc/xprtrdma/xprt_rdma.h b/net/sunrpc/xprtrdma/xprt_rdma.h
index 7723e5f..0028748 100644
--- a/net/sunrpc/xprtrdma/xprt_rdma.h
+++ b/net/sunrpc/xprtrdma/xprt_rdma.h
@@ -144,6 +144,26 @@ rdmab_to_msg(struct rpcrdma_regbuf *rb)
 
 #define RPCRDMA_DEF_GFP		(GFP_NOIO | __GFP_NOWARN)
 
+/* To ensure a transport can always make forward progress,
+ * the number of RDMA segments allowed in header chunk lists
+ * is capped at 8. This prevents less-capable devices and
+ * memory registrations from overrunning the Send buffer
+ * while building chunk lists.
+ *
+ * Elements of the Read list take up more room than the
+ * Write list or Reply chunk. 8 read segments means the Read
+ * list (or Write list or Reply chunk) cannot consume more
+ * than
+ *
+ * ((8 + 2) * read segment size) + 1 XDR words, or 244 bytes.
+ *
+ * And the fixed part of the header is another 24 bytes.
+ *
+ * The smallest inline threshold is 1024 bytes, ensuring that
+ * at least 750 bytes are available for RPC messages.
+ */
+#define RPCRDMA_MAX_HDR_SEGS	(8)
+
 /*
  * struct rpcrdma_rep -- this structure encapsulates state required to recv
  * and complete a reply, asychronously. It needs several pieces of
@@ -456,7 +476,6 @@ struct rpcrdma_regbuf *rpcrdma_alloc_regbuf(struct rpcrdma_ia *,
 void rpcrdma_free_regbuf(struct rpcrdma_ia *,
 			 struct rpcrdma_regbuf *);
 
-unsigned int rpcrdma_max_segments(struct rpcrdma_xprt *);
 int rpcrdma_ep_post_extra_recv(struct rpcrdma_xprt *, unsigned int);
 
 int frwr_alloc_recovery_wq(void);