| From | Greg Kroah-Hartman <> | Subject | [PATCH 4.9 76/84] ntb_transport: fix bug calculating num_qps_mw | Date | Mon, 28 Aug 2017 10:05:41 +0200 |
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4.9-stable review patch. If anyone has any objections, please let me know.
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From: Logan Gunthorpe <logang@deltatee.com>
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.
Signed-off-by: Logan Gunthorpe <logang@deltatee.com> Fixes: e26a5843f7f5 ("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> Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
--- drivers/ntb/ntb_transport.c | 4 ++-- 1 file changed, 2 insertions(+), 2 deletions(-)
--- a/drivers/ntb/ntb_transport.c +++ b/drivers/ntb/ntb_transport.c @@ -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;
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