linux-kernel - [PATCH 4.19 43/44] svcrdma: Reduce max_send

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Date:   Wed, 13 Feb 2019 19:38:44 +0100
From:   Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To:     linux-kernel@...r.kernel.org
Cc:     Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        stable@...r.kernel.org, Chuck Lever <chuck.lever@...cle.com>,
        Sagi Grimberg <sagi@...mberg.me>,
        "J. Bruce Fields" <bfields@...hat.com>,
        Don Dutile <ddutile@...hat.com>
Subject: [PATCH 4.19 43/44] svcrdma: Reduce max_send_sges

4.19-stable review patch.  If anyone has any objections, please let me know.

------------------

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

commit f3c1fd0ee294abd4367dfa72d89f016c682202f0 upstream.

There's no need to request a large number of send SGEs because the
inline threshold already constrains the number of SGEs per Send.

Signed-off-by: Chuck Lever <chuck.lever@...cle.com>
Reviewed-by: Sagi Grimberg <sagi@...mberg.me>
Signed-off-by: J. Bruce Fields <bfields@...hat.com>
Cc: Don Dutile <ddutile@...hat.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@...uxfoundation.org>

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

--- a/net/sunrpc/xprtrdma/svc_rdma_transport.c
+++ b/net/sunrpc/xprtrdma/svc_rdma_transport.c
@@ -475,10 +475,12 @@ static struct svc_xprt *svc_rdma_accept(
 
 	/* Qualify the transport resource defaults with the
 	 * capabilities of this particular device */
-	newxprt->sc_max_send_sges = dev->attrs.max_send_sge;
-	/* transport hdr, head iovec, one page list entry, tail iovec */
-	if (newxprt->sc_max_send_sges < 4) {
-		pr_err("svcrdma: too few Send SGEs available (%d)\n",
+	/* Transport header, head iovec, tail iovec */
+	newxprt->sc_max_send_sges = 3;
+	/* Add one SGE per page list entry */
+	newxprt->sc_max_send_sges += svcrdma_max_req_size / PAGE_SIZE;
+	if (newxprt->sc_max_send_sges > dev->attrs.max_send_sge) {
+		pr_err("svcrdma: too few Send SGEs available (%d needed)\n",
 		       newxprt->sc_max_send_sges);
 		goto errout;
 	}