netdev - Re: [PATCH net] net/smc: delete buf_desc from buffer list under lock protection

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Message-ID: <ef374ef8-a19e-7b9b-67a1-5b89fb505545@huawei.com>
Date: Wed, 31 Jul 2024 18:32:18 +0800
From: shaozhengchao <shaozhengchao@...wei.com>
To: Wen Gu <guwen@...ux.alibaba.com>, <wenjia@...ux.ibm.com>,
	<jaka@...ux.ibm.com>, <davem@...emloft.net>, <edumazet@...gle.com>,
	<kuba@...nel.org>, <pabeni@...hat.com>
CC: <alibuda@...ux.alibaba.com>, <tonylu@...ux.alibaba.com>,
	<linux-s390@...r.kernel.org>, <netdev@...r.kernel.org>,
	<linux-kernel@...r.kernel.org>
Subject: Re: [PATCH net] net/smc: delete buf_desc from buffer list under lock
 protection

Hi Wen Gu:
   "The operations to link group buffer list should be protected by
sndbufs_lock or rmbs_lock" It seems that the logic is smooth. But will
this really happen? Because no process is in use with the link group,
does this mean that there is no concurrent scenario?

Thank you

Zhengchao Shao

On 2024/7/31 17:31, Wen Gu wrote:
> The operations to link group buffer list should be protected by
> sndbufs_lock or rmbs_lock. So fix it.
> 
> Fixes: 3e034725c0d8 ("net/smc: common functions for RMBs and send buffers")
> Signed-off-by: Wen Gu <guwen@...ux.alibaba.com>
> ---
>   net/smc/smc_core.c | 10 ++++++++--
>   1 file changed, 8 insertions(+), 2 deletions(-)
> 
> diff --git a/net/smc/smc_core.c b/net/smc/smc_core.c
> index 3b95828d9976..ecfea8c38da9 100644
> --- a/net/smc/smc_core.c
> +++ b/net/smc/smc_core.c
> @@ -1368,18 +1368,24 @@ static void __smc_lgr_free_bufs(struct smc_link_group *lgr, bool is_rmb)
>   {
>   	struct smc_buf_desc *buf_desc, *bf_desc;
>   	struct list_head *buf_list;
> +	struct rw_semaphore *lock;
>   	int i;
>   
>   	for (i = 0; i < SMC_RMBE_SIZES; i++) {
> -		if (is_rmb)
> +		if (is_rmb) {
>   			buf_list = &lgr->rmbs[i];
> -		else
> +			lock = &lgr->rmbs_lock;
> +		} else {
>   			buf_list = &lgr->sndbufs[i];
> +			lock = &lgr->sndbufs_lock;
> +		}
> +		down_write(lock);
>   		list_for_each_entry_safe(buf_desc, bf_desc, buf_list,
>   					 list) {
>   			list_del(&buf_desc->list);
>   			smc_buf_free(lgr, is_rmb, buf_desc);
>   		}
> +		up_write(lock);
>   	}
>   }
>