linux-kernel - Re: [PATCH net 3/3] net/smc: Resolve the race between SMC-R link access and clear

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Date:   Tue, 11 Jan 2022 23:49:07 +0800
From:   Wen Gu <guwen@...ux.alibaba.com>
To:     Karsten Graul <kgraul@...ux.ibm.com>, davem@...emloft.net,
        kuba@...nel.org
Cc:     linux-s390@...r.kernel.org, netdev@...r.kernel.org,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH net 3/3] net/smc: Resolve the race between SMC-R link
 access and clear

Thanks for your review.

On 2022/1/11 4:40 pm, Karsten Graul wrote:
> On 10/01/2022 10:26, Wen Gu wrote:
>> @@ -1226,15 +1245,23 @@ void smcr_link_clear(struct smc_link *lnk, bool log)
>>   	smc_wr_free_link(lnk);
>>   	smc_ib_destroy_queue_pair(lnk);
>>   	smc_ib_dealloc_protection_domain(lnk);
>> -	smc_wr_free_link_mem(lnk);
>> -	smc_lgr_put(lnk->lgr); /* lgr_hold in smcr_link_init() */
>>   	smc_ibdev_cnt_dec(lnk);
>>   	put_device(&lnk->smcibdev->ibdev->dev);
>>   	smcibdev = lnk->smcibdev;
>> -	memset(lnk, 0, sizeof(struct smc_link));
>> -	lnk->state = SMC_LNK_UNUSED;
>>   	if (!atomic_dec_return(&smcibdev->lnk_cnt))
>>   		wake_up(&smcibdev->lnks_deleted);
> 
> Same here, waiter should not be woken up until the link memory is actually freed.
> 

OK, I will correct this as well.

And similarly I want to move smc_ibdev_cnt_dec() and put_device() to
__smcr_link_clear() as well to ensure that put link related resources
only when link is actually cleared. What do you think?

Thanks,
Wen Gu