RE: linux-next: manual merge of the char-misc tree with the net-next tree

[KY Srinivasan <kys@microsoft.com>]

> -----Original Message-----
> From: KY Srinivasan
> Sent: Tuesday, September 6, 2016 11:06 AM
> To: 'Greg KH' <greg@kroah.com>; Stephen Rothwell <sfr@canb.auug.org.au>
> Cc: Arnd Bergmann <arnd@arndb.de>; David Miller <davem@davemloft.net>;
> Networking <netdev@vger.kernel.org>; linux-next@vger.kernel.org; linux-
> kernel@vger.kernel.org; Stephen Hemminger <sthemmin@microsoft.com>;
> Vitaly Kuznetsov <vkuznets@redhat.com>
> Subject: RE: linux-next: manual merge of the char-misc tree with the net-next
> tree
> 
> 
> 
> > -----Original Message-----
> > From: Greg KH [mailto:greg@kroah.com]
> > Sent: Monday, September 5, 2016 5:04 PM
> > To: Stephen Rothwell <sfr@canb.auug.org.au>
> > Cc: Arnd Bergmann <arnd@arndb.de>; David Miller
> <davem@davemloft.net>;
> > Networking <netdev@vger.kernel.org>; linux-next@vger.kernel.org; linux-
> > kernel@vger.kernel.org; Stephen Hemminger <sthemmin@microsoft.com>;
> > Vitaly Kuznetsov <vkuznets@redhat.com>; KY Srinivasan
> <kys@microsoft.com>
> > Subject: Re: linux-next: manual merge of the char-misc tree with the net-next
> > tree
> >
> > On Mon, Sep 05, 2016 at 04:56:50PM +1000, Stephen Rothwell wrote:
> > > Hi all,
> > >
> > > Today's linux-next merge of the char-misc tree got a conflict in:
> > >
> > >   include/linux/hyperv.h
> > >
> > > between commit:
> > >
> > >   30d1de08c87d ("hv_netvsc: make inline functions static")
> > >
> > > from the net-next tree and commit:
> > >
> > >   bb08d431a914 ("Drivers: hv: ring_buffer: count on wrap around mappings
> in
> > get_next_pkt_raw()")
> > >
> > > from the char-misc tree.
> > >
> > > I fixed it up (the former moved the code modified by the latter, so the
> > > below patch applies to the new location of the code) and can carry the
> > > fix as necessary. This is now fixed as far as linux-next is concerned,
> > > but any non trivial conflicts should be mentioned to your upstream
> > > maintainer when your tree is submitted for merging.  You may also want
> > > to consider cooperating with the maintainer of the conflicting tree to
> > > minimise any particularly complex conflicts.
> > >
> > > From: Stephen Rothwell <sfr@canb.auug.org.au>
> > > Date: Mon, 5 Sep 2016 16:53:06 +1000
> > > Subject: [PATCH] Drivers: hv: ring_buffer: merge fix up for "hv_netvsc:
> make
> > >  inline functions static"
> > >
> > > Signed-off-by: Stephen Rothwell <sfr@canb.auug.org.au>
> > > ---
> > >  drivers/net/hyperv/netvsc.c | 32 +++++++++++---------------------
> > >  1 file changed, 11 insertions(+), 21 deletions(-)
> > >
> > > diff --git a/drivers/net/hyperv/netvsc.c b/drivers/net/hyperv/netvsc.c
> > > index 2a9ccc4d9e3c..026df6556068 100644
> > > --- a/drivers/net/hyperv/netvsc.c
> > > +++ b/drivers/net/hyperv/netvsc.c
> > > @@ -42,31 +42,23 @@ static struct vmpacket_descriptor *
> > >  get_next_pkt_raw(struct vmbus_channel *channel)
> > >  {
> > >  	struct hv_ring_buffer_info *ring_info = &channel->inbound;
> > > -	u32 read_loc = ring_info->priv_read_index;
> > > +	u32 priv_read_loc = ring_info->priv_read_index;
> > >  	void *ring_buffer = hv_get_ring_buffer(ring_info);
> > > -	struct vmpacket_descriptor *cur_desc;
> > > -	u32 packetlen;
> > >  	u32 dsize = ring_info->ring_datasize;
> > > -	u32 delta = read_loc - ring_info->ring_buffer->read_index;
> > > +	/*
> > > +	 * delta is the difference between what is available to read and
> > > +	 * what was already consumed in place. We commit read index after
> > > +	 * the whole batch is processed.
> > > +	 */
> > > +	u32 delta = priv_read_loc >= ring_info->ring_buffer->read_index ?
> > > +		priv_read_loc - ring_info->ring_buffer->read_index :
> > > +		(dsize - ring_info->ring_buffer->read_index) + priv_read_loc;
> > >  	u32 bytes_avail_toread = (hv_get_bytes_to_read(ring_info) - delta);
> > >
> > >  	if (bytes_avail_toread < sizeof(struct vmpacket_descriptor))
> > >  		return NULL;
> > >
> > > -	if ((read_loc + sizeof(*cur_desc)) > dsize)
> > > -		return NULL;
> > > -
> > > -	cur_desc = ring_buffer + read_loc;
> > > -	packetlen = cur_desc->len8 << 3;
> > > -
> > > -	/*
> > > -	 * If the packet under consideration is wrapping around,
> > > -	 * return failure.
> > > -	 */
> > > -	if ((read_loc + packetlen + VMBUS_PKT_TRAILER) > (dsize - 1))
> > > -		return NULL;
> > > -
> > > -	return cur_desc;
> > > +	return ring_buffer + priv_read_loc;
> > >  }
> > >
> > >  /*
> > > @@ -78,16 +70,14 @@ static void put_pkt_raw(struct vmbus_channel
> > *channel,
> > >  			struct vmpacket_descriptor *desc)
> > >  {
> > >  	struct hv_ring_buffer_info *ring_info = &channel->inbound;
> > > -	u32 read_loc = ring_info->priv_read_index;
> > >  	u32 packetlen = desc->len8 << 3;
> > >  	u32 dsize = ring_info->ring_datasize;
> > >
> > > -	BUG_ON((read_loc + packetlen + VMBUS_PKT_TRAILER) > dsize);
> > > -
> > >  	/*
> > >  	 * Include the packet trailer.
> > >  	 */
> > >  	ring_info->priv_read_index += packetlen + VMBUS_PKT_TRAILER;
> > > +	ring_info->priv_read_index %= dsize;
> > >  }
> > >
> > >  /*
> >
> > Ugh, messy.  Thanks for this.
> >
> > KY, how did this happen?
> Thanks Stephen. Greg, sorry about this. We should have split Vitaly's patch to
> avoid this inter-tree issue. Vitaly and I will work to fix this.

Stephen,

I am sending Greg a patch to revert commit bb08d431a914. This should address the
merge problem you ran into. Once net-next tree synchs up with the char-misc tree,
we will submit a patch to net-next to make the necessary adjustments.

Regards,

K. Y


> 
> Regards,
> 
> K. Y
> 
> >
> > greg k-h