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Date: Tue, 31 Jan 2017 10:58:22 +0100
From: Johannes Thumshirn <jthumshirn@suse.de>
To: Dmitry Vyukov <dvyukov@google.com>
Cc: jejb@linux.vnet.ibm.com,
        "Martin K. Petersen" <martin.petersen@oracle.com>,
        linux-scsi <linux-scsi@vger.kernel.org>,
        LKML <linux-kernel@vger.kernel.org>, Al Viro <viro@zeniv.linux.org.uk>,
        syzkaller <syzkaller@googlegroups.com>, Hannes Reinecke <hare@suse.de>
Subject: Re: scsi: BUG in scsi_init_io
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On Tue, Jan 31, 2017 at 10:50:49AM +0100, Dmitry Vyukov wrote:
> On Tue, Jan 31, 2017 at 10:20 AM, Johannes Thumshirn <jthumshirn@suse.de> wrote:
> > On Tue, Jan 31, 2017 at 09:55:52AM +0100, Dmitry Vyukov wrote:

[...]

> Please-please-please, let's not use WARN for something that is not a
> kernel bug and is user-triggerable. This makes it impossible to
> automate kernel testing and requires hiring an army of people doing
> mechanical job of sorting out WARNING reports into kernel-bugs and
> non-kernel-bugs.
> If the message is absolutely necessary (while kernel does not
> generally explain every EINVAL on console), the following will do:
> 
>       if (!blk_rq_nr_phys_segments(rq)) {
>               pr_err("you are doing something wrong\n");
>               return -EINVAL;
>       }

Yes I understand that. OTOH having the WARN helps you finding the caller because
of to the stack trace. But arguably that could be accomplished with function
graph tracing as well. I'll re-send a v2 as a proper patch.

Thanks,
	Johannes

-- 
Johannes Thumshirn                                          Storage
jthumshirn@suse.de                                +49 911 74053 689
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