Commit 8e8496e0 authored Jun 05, 2017 by Logan Gunthorpe Committed by Jon Mason Jun 19, 2017

ntb_transport: fix bug calculating num_qps_mw



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.

Signed-off-by: Logan Gunthorpe <logang@deltatee.com>
Fixes: e26a5843 ("NTB: Split ntb_hw_intel and ntb_transport drivers")
Acked-by: Allen Hubbe <Allen.Hubbe@dell.com>
Signed-off-by: Jon Mason <jdmason@kudzu.us>

parent cb827ee6

drivers/ntb/ntb_transport.c

+2 −2

Original line number	Diff line number	Diff line
		@@ -623,7 +623,7 @@ static int ntb_transport_setup_qp_mw(struct ntb_transport_ctx *nt,
		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;
		@@ -1000,7 +1000,7 @@ static int ntb_transport_init_queue(struct ntb_transport_ctx *nt,
		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;