linux-kernel - Re: [PATCH 3/5] Drivers: hv: kvp: Fix the recent regression caused by incorrect clean-up

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Date:   Wed, 17 Oct 2018 09:22:56 +0300
From:   Dan Carpenter <dan.carpenter@...cle.com>
To:     Greg KH <gregkh@...uxfoundation.org>
Cc:     kys@...rosoft.com, olaf@...fle.de, sthemmin@...rosoft.com,
        jasowang@...hat.com, linux-kernel@...r.kernel.org,
        Stable@...r.kernel.org, Michael.H.Kelley@...rosoft.com,
        apw@...onical.com, devel@...uxdriverproject.org,
        vkuznets@...hat.com, Haiyang Zhang <haiyangz@...rosoft.com>
Subject: Re: [PATCH 3/5] Drivers: hv: kvp: Fix the recent regression caused
 by incorrect clean-up

On Wed, Oct 17, 2018 at 07:07:05AM +0200, Greg KH wrote:
> On Wed, Oct 17, 2018 at 03:14:04AM +0000, kys@...uxonhyperv.com wrote:
> > From: Dexuan Cui <decui@...rosoft.com>
> > 
> > In kvp_send_key(), we do need call process_ib_ipinfo() if
> > message->kvp_hdr.operation is KVP_OP_GET_IP_INFO, because it turns out
> > the userland hv_kvp_daemon needs the info of operation, adapter_id and
> > addr_family. With the incorrect fc62c3b1977d, the host can't get the
> > VM's IP via KVP.
> > 
> > And, fc62c3b1977d added a "break;", but actually forgot to initialize
> > the key_size/value in the case of KVP_OP_SET, so the default key_size of
> > 0 is passed to the kvp daemon, and the pool files
> > /var/lib/hyperv/.kvp_pool_* can't be updated.
> > 
> > This patch effectively rolls back the previous fc62c3b1977d, and
> > correctly fixes the "this statement may fall through" warnings.
> > 
> > This patch is tested on WS 2012 R2 and 2016.
> > 
> > Fixes: fc62c3b1977d ("Drivers: hv: kvp: Fix two "this statement may fall through" warnings")
> > Signed-off-by: Dexuan Cui <decui@...rosoft.com>
> > Cc: K. Y. Srinivasan <kys@...rosoft.com>
> > Cc: Haiyang Zhang <haiyangz@...rosoft.com>
> > Cc: Stephen Hemminger <sthemmin@...rosoft.com>
> > Cc: <Stable@...r.kernel.org>
> > Signed-off-by: K. Y. Srinivasan <kys@...rosoft.com>
> > ---
> >  drivers/hv/hv_kvp.c | 26 ++++++++++++++++++++++----
> >  1 file changed, 22 insertions(+), 4 deletions(-)
> > 
> > diff --git a/drivers/hv/hv_kvp.c b/drivers/hv/hv_kvp.c
> > index a7513a8a8e37..9fbb15c62c6c 100644
> > --- a/drivers/hv/hv_kvp.c
> > +++ b/drivers/hv/hv_kvp.c
> > @@ -353,6 +353,9 @@ static void process_ib_ipinfo(void *in_msg, void *out_msg, int op)
> >  
> >  		out->body.kvp_ip_val.dhcp_enabled = in->kvp_ip_val.dhcp_enabled;
> >  
> > +		__attribute__ ((fallthrough));
> 
> The comment should be sufficient for this, right?  I haven't seen many
> uses of this attribute before, how common is it?
>

It's not common at all.  It should be wrapped in a macro and put into
compiler.h.

But I hope it does become adopted.  It's better than randomly grepping
for non-standard comments.

regards,
dan carpenter