Patch "ntb_transport: fix bug calculating num_qps_mw" has been added to the 4.9-stable tree

This is a note to let you know that I've just added the patch titled

ntb_transport: fix bug calculating num_qps_mw

to the 4.9-stable tree which can be found at:
http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary

The filename of the patch is:
ntb_transport-fix-bug-calculating-num_qps_mw.patch
and it can be found in the queue-4.9 subdirectory.

If you, or anyone else, feels it should not be added to the stable tree, please let <[email protected]> know about it.

From: Logan Gunthorpe <[email protected]>
Date: Mon, 5 Jun 2017 14:00:53 -0600
Subject: ntb_transport: fix bug calculating num_qps_mw

From: Logan Gunthorpe <[email protected]>

commit 8e8496e0e9564b66165f5219a4e8ed20b0d3fc6b upstream.

A divide by zero error occurs if qp_count is less than mw_count because num_qps_mw is calculated to be zero. The calculation appears to be incorrect.

The requirement is for num_qps_mw to be set to qp_count / mw_count with any remainder divided among the earlier mws.

For example, if mw_count is 5 and qp_count is 12 then mws 0 and 1 will have 3 qps per window and mws 2 through 4 will have 2 qps per window. Thus, when mw_num < qp_count % mw_count, num_qps_mw is 1 higher than when mw_num >= qp_count.

---
 drivers/ntb/ntb_transport.c |    4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

@@ -625,7 +625,7 @@ static int ntb_transport_setup_qp_mw(str
 	if (!mw->virt_addr)
 		return -ENOMEM;
 
-	if (qp_count % mw_count && mw_num + 1 < qp_count / mw_count)
+	if (mw_num < qp_count % mw_count)
 		num_qps_mw = qp_count / mw_count + 1;
 	else
 		num_qps_mw = qp_count / mw_count;

@@ -1002,7 +1002,7 @@ static int ntb_transport_init_queue(stru
 	qp->event_handler = NULL;
 	ntb_qp_link_down_reset(qp);
 
-	if (qp_count % mw_count && mw_num + 1 < qp_count / mw_count)
+	if (mw_num < qp_count % mw_count)
 		num_qps_mw = qp_count / mw_count + 1;
 	else
 		num_qps_mw = qp_count / mw_count;

Patches currently in stable-queue which might be from [email protected] are

queue-4.9/ntb-ntb_test-fix-bug-printing-ntb_perf-results.patch queue-4.9/ntb_transport-fix-bug-calculating-num_qps_mw.patch queue-4.9/ntb-ntb_test-ensure-the-link-is-up-before-trying-to-configure-the-mws.patch queue-4.9/ntb_transport-fix-qp-count-bug.patch