linux-kernel - Antw: [PATCH v2] scsi: avoid potential deadloop in iscsi_if

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Date:   Wed, 30 Oct 2019 12:22:37 +0000
From:   "wubo (T)" <wubo40@...wei.com>
To:     Ulrich Windl <Ulrich.Windl@...uni-regensburg.de>,
        open-iscsi <open-iscsi@...glegroups.com>,
        "jejb@...ux.ibm.com" <jejb@...ux.ibm.com>,
        "martin.petersen@...cle.com" <martin.petersen@...cle.com>,
        Chris Leech <cleech@...hat.com>, Lee Duncan <lduncan@...e.com>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        "linux-scsi@...r.kernel.org" <linux-scsi@...r.kernel.org>
CC:     "liuzhiqiang (I)" <liuzhiqiang26@...wei.com>,
        Mingfangsen <mingfangsen@...wei.com>
Subject: Antw: [PATCH v2] scsi: avoid potential deadloop in iscsi_if_rx func

> >>> "wubo (T)" <wubo40@...wei.com> schrieb am 30.10.2019 um 08:56 in
> Nachricht
> <EDBAAA0BBBA2AC4E9C8B6B81DEEE1D6915DFA0FE@...eml505-mbs.china.
> huawei.com>:
> > From: Bo Wu <wubo40@...wei.com>
> 
> ...
> > +			if (--retries < 0) {
> > +				printk(KERN_ERR "Send reply failed too many times. "
> > +				       "Max supported retries %u\n",
> ISCSI_SEND_MAX_ALLOWED);
> 
> Just for "personal taste": Why not simplify the message to:?
> +				printk(KERN_ERR "Send reply failed too many times
> (%u)\n",
>                                ISCSI_SEND_MAX_ALLOWED);
> 
> > +				break;
> > +			}
> > +
> 
> Maybe place the number after "many" as an alternative. I think as the
> message is expected to be rare, a short variant is justified.

Thanks for your suggestion. This problem occured when iscsi_if_send_reply returns -EAGAIN.
Consider possible other anomalies scenes. In order to get diagnostic information, it is better to replace "many" with error code.

Modify as follow:
if (--retries < 0) {
	printk(KERN_WARNING "Send reply failed, error %d\n", err);
	break;
}

> Also one could discuss wether the problem that originates "from external"
> should be KERN_ERR, or maybe just a warning, because the kernel itself can do
> little against that problem, and it's not a "kernel error" after all ;-)

You are right, This problem scene rarely appears .it is friendly to replace the error with warning.

> 
> Regards,
> Ulrich
> 
> 
> 

Thanks,
Bo Wu