From: "Allen Hubbe" <Allen.Hubbe@dell.com>
To: 'Logan Gunthorpe' <logang@deltatee.com>, linux-ntb@googlegroups.com
Cc: 'Jon Mason' <jdmason@kudzu.us>, 'Dave Jiang' <dave.jiang@intel.com>
Subject: RE: [PATCH] ntb_transport: fix bug calculating num_qps_mw
Date: Tue, 6 Jun 2017 09:08:43 -0400 [thread overview]
Message-ID: <000101d2dec6$0648f060$12dad120$@dell.com> (raw)
In-Reply-To: <20170605200053.6912-3-logang@deltatee.com>
From: Logan Gunthorpe
> 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>
> Cc: Jon Mason <jdmason@kudzu.us>
> Cc: Dave Jiang <dave.jiang@intel.com>
> Cc: Allen Hubbe <Allen.Hubbe@emc.com>
Acked-by: Allen Hubbe <Allen.Hubbe@dell.com>
> ---
> drivers/ntb/ntb_transport.c | 4 ++--
> 1 file changed, 2 insertions(+), 2 deletions(-)
>
> diff --git a/drivers/ntb/ntb_transport.c b/drivers/ntb/ntb_transport.c
> index 0a778d2cab94..5b6b00ea6ed9 100644
> --- a/drivers/ntb/ntb_transport.c
> +++ b/drivers/ntb/ntb_transport.c
> @@ -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;
> --
> 2.11.0
next prev parent reply other threads:[~2017-06-06 13:09 UTC|newest]
Thread overview: 12+ messages / expand[flat|nested] mbox.gz Atom feed top
2017-06-05 20:00 [PATCH] ntb_netdev: set the net_device's parent Logan Gunthorpe
2017-06-05 20:00 ` [PATCH] ntb_transport: fix qp count bug Logan Gunthorpe
2017-06-06 13:08 ` Allen Hubbe
2017-06-09 21:09 ` Jon Mason
2017-06-05 20:00 ` [PATCH] ntb_transport: fix bug calculating num_qps_mw Logan Gunthorpe
2017-06-06 13:08 ` Allen Hubbe [this message]
2017-06-09 21:09 ` Jon Mason
2017-06-06 13:08 ` [PATCH] ntb_netdev: set the net_device's parent Allen Hubbe
2017-06-09 21:12 ` Jon Mason
2017-06-09 21:51 ` Logan Gunthorpe
2017-06-09 21:56 ` Jon Mason
2017-06-09 22:51 ` Logan Gunthorpe
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