linux-kernel - Re: [PATCH rdma-next 2/5] RDMA/hns: Modify uar allocation algorithm to avoid bitmap exhaust

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Message-ID: <20180523060515.GD2933@mtr-leonro.mtl.com>
Date:   Wed, 23 May 2018 09:05:15 +0300
From:   Leon Romanovsky <leon@...nel.org>
To:     "Wei Hu (Xavier)" <xavier.huwei@...wei.com>
Cc:     dledford@...hat.com, jgg@...pe.ca, linux-rdma@...r.kernel.org,
        linux-kernel@...r.kernel.org, xavier.huwei@....com,
        lijun_nudt@....com
Subject: Re: [PATCH rdma-next 2/5] RDMA/hns: Modify uar allocation algorithm
 to avoid bitmap exhaust

On Thu, May 17, 2018 at 04:02:50PM +0800, Wei Hu (Xavier) wrote:
> This patch modified uar allocation algorithm in hns_roce_uar_alloc
> function to avoid bitmap exhaust.
>
> Signed-off-by: Wei Hu (Xavier) <xavier.huwei@...wei.com>
> ---
>  drivers/infiniband/hw/hns/hns_roce_device.h |  1 +
>  drivers/infiniband/hw/hns/hns_roce_pd.c     | 10 ++++++----
>  2 files changed, 7 insertions(+), 4 deletions(-)
>
> diff --git a/drivers/infiniband/hw/hns/hns_roce_device.h b/drivers/infiniband/hw/hns/hns_roce_device.h
> index 53c2f1b..412297d4 100644
> --- a/drivers/infiniband/hw/hns/hns_roce_device.h
> +++ b/drivers/infiniband/hw/hns/hns_roce_device.h
> @@ -214,6 +214,7 @@ enum {
>  struct hns_roce_uar {
>  	u64		pfn;
>  	unsigned long	index;
> +	unsigned long	logic_idx;
>  };
>
>  struct hns_roce_ucontext {
> diff --git a/drivers/infiniband/hw/hns/hns_roce_pd.c b/drivers/infiniband/hw/hns/hns_roce_pd.c
> index 4b41e04..b9f2c87 100644
> --- a/drivers/infiniband/hw/hns/hns_roce_pd.c
> +++ b/drivers/infiniband/hw/hns/hns_roce_pd.c
> @@ -107,13 +107,15 @@ int hns_roce_uar_alloc(struct hns_roce_dev *hr_dev, struct hns_roce_uar *uar)
>  	int ret = 0;
>
>  	/* Using bitmap to manager UAR index */
> -	ret = hns_roce_bitmap_alloc(&hr_dev->uar_table.bitmap, &uar->index);
> +	ret = hns_roce_bitmap_alloc(&hr_dev->uar_table.bitmap, &uar->logic_idx);
>  	if (ret == -1)
>  		return -ENOMEM;
>
> -	if (uar->index > 0)
> -		uar->index = (uar->index - 1) %
> +	if (uar->logic_idx > 0 && hr_dev->caps.phy_num_uars > 1)
> +		uar->index = (uar->logic_idx - 1) %
>  			     (hr_dev->caps.phy_num_uars - 1) + 1;
> +	else
> +		uar->index = 0;
>

Sorry, but maybe I didn't understand this change fully, but logic_idx is
not initialized at all and one of two (needs to check your uar
allocation): the logic_idx is always zero -> index will be zero too,
or logic_idx is random variable -> index will be random too.

What did you want to do?


>  	if (!dev_is_pci(hr_dev->dev)) {
>  		res = platform_get_resource(hr_dev->pdev, IORESOURCE_MEM, 0);
> @@ -132,7 +134,7 @@ int hns_roce_uar_alloc(struct hns_roce_dev *hr_dev, struct hns_roce_uar *uar)
>
>  void hns_roce_uar_free(struct hns_roce_dev *hr_dev, struct hns_roce_uar *uar)
>  {
> -	hns_roce_bitmap_free(&hr_dev->uar_table.bitmap, uar->index,
> +	hns_roce_bitmap_free(&hr_dev->uar_table.bitmap, uar->logic_idx,
>  			     BITMAP_NO_RR);
>  }
>
> --
> 1.9.1
>

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