From: Chen Gang <gang.chen.5i5j@gmail.com>
To: Juergen Gross <jgross@suse.com>, Jan Beulich <JBeulich@suse.com>
Cc: xen-devel@lists.xenproject.org,
David Vrabel <david.vrabel@citrix.com>,
"linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>
Subject: Re: [PATCH] xen/xen-scsiback: Need go to fail after xenbus_dev_error()
Date: Mon, 29 Sep 2014 17:59:10 +0800 [thread overview]
Message-ID: <54292D6E.4060903__47375.55641118$1411984525$gmane$org@gmail.com> (raw)
In-Reply-To: <542927C3.8010204@suse.com>
On 9/29/14 17:34, Juergen Gross wrote:
> On 09/29/2014 11:31 AM, Chen Gang wrote:
>> On 9/29/14 16:41, Jan Beulich wrote:
>>>>>> On 29.09.14 at 06:32, <JGross@suse.com> wrote:
>>>> On 09/26/2014 06:38 PM, Chen Gang wrote:
>>>>> When failure occurs, after xenbus_dev_error(), need go to fail to let
>>>>> upper caller know about it.
>>>>>
>>>>> Signed-off-by: Chen Gang <gang.chen.5i5j@gmail.com>
>>>>> ---
>>>>> drivers/xen/xen-scsiback.c | 4 +++-
>>>>> 1 file changed, 3 insertions(+), 1 deletion(-)
>>>>>
>>>>> diff --git a/drivers/xen/xen-scsiback.c b/drivers/xen/xen-scsiback.c
>>>>> index 847bc9c..3e430e1 100644
>>>>> --- a/drivers/xen/xen-scsiback.c
>>>>> +++ b/drivers/xen/xen-scsiback.c
>>>>> @@ -1222,8 +1222,10 @@ static int scsiback_probe(struct xenbus_device *dev,
>>>>>
>>>>> err = xenbus_printf(XBT_NIL, dev->nodename, "feature-sg-grant", "%u",
>>>>> SG_ALL);
>>>>> - if (err)
>>>>> + if (err) {
>>>>> xenbus_dev_error(dev, err, "writing feature-sg-grant");
>>>>> + goto fail;
>>>>> + }
>>>>>
>>>>> xenbus_switch_state(dev, XenbusStateInitWait);
>>>>> return 0;
>>>>>
>>>>
>>>> Hmm, not testing for failure was on purpose. Advertising this feature
>>>> is just for tuning purposes, not mandatory.
>>>>
>>>> OTOH it would really be a strange error if this xenbus_printf() fails
>>>> but all other operations are working, and signaling an error at the
>>>> time when it first shows up is a good thing. So:
>>>
>>> I disagree - failure to announce optional features should not lead to
>>> general failure. And this should be consistent across drivers; for
>>> existing examples see xen_blkbk_flush_diskcache() and
>>> xen_blkbk_discard().
>>>
>>
>> During scsiback_probe(), can we sure that "feature-sg-grant" is optional
>> feature? For me, only according to its name, I guess not: it is about
>> security which is always necessary in kernel (although SG_ALL).
>
> It is optional. Otherwise the interface would be broken, as I've added
> this feature recently and "old" clients (pre 3.18) don't know about it.
>
> The feature is NOT about security, but about capability to support
> larger SCSI requests than the old interface did.
>
OK, thanks. All of you said sounds reasonable to me: "it is optional, need
print related warning and continue".
If no any additional reply within 2 days, I shall send patch v2 for it:
"use dev_warn() instead of xenbus_dev_error() and remove 'fail' code block"
Thanks.
--
Chen Gang
Open, share, and attitude like air, water, and life which God blessed
next prev parent reply other threads:[~2014-09-29 9:53 UTC|newest]
Thread overview: 22+ messages / expand[flat|nested] mbox.gz Atom feed top
2014-09-26 16:38 [PATCH] xen/xen-scsiback: Need go to fail after xenbus_dev_error() Chen Gang
2014-09-29 4:32 ` Juergen Gross
2014-09-29 4:32 ` [Xen-devel] " Juergen Gross
2014-09-29 8:41 ` Jan Beulich
2014-09-29 9:31 ` Chen Gang
2014-09-29 9:34 ` Juergen Gross
2014-09-29 9:34 ` [Xen-devel] " Juergen Gross
2014-09-29 9:59 ` Chen Gang [this message]
2014-09-29 9:59 ` Chen Gang
2014-09-29 13:57 ` David Vrabel
2014-09-29 13:57 ` [Xen-devel] " David Vrabel
2014-09-30 6:32 ` Chen Gang
2014-09-30 6:59 ` Juergen Gross
2014-09-30 6:59 ` [Xen-devel] " Juergen Gross
2014-09-30 7:50 ` Chen Gang
2014-09-30 7:50 ` [Xen-devel] " Chen Gang
2014-09-30 10:23 ` Chen Gang
2014-09-30 10:23 ` Chen Gang
2014-09-30 6:32 ` Chen Gang
2014-09-29 9:31 ` Chen Gang
2014-09-29 8:41 ` Jan Beulich
2014-09-26 16:38 Chen Gang
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