linux-kernel - RE: [PATCH 2/2] vmbus: make hv_get_ringbuffer

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Date:   Tue, 28 Nov 2017 15:58:16 +0000
From:   KY Srinivasan <kys@...rosoft.com>
To:     Greg KH <gregkh@...uxfoundation.org>
CC:     "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        "devel@...uxdriverproject.org" <devel@...uxdriverproject.org>,
        "olaf@...fle.de" <olaf@...fle.de>,
        "apw@...onical.com" <apw@...onical.com>,
        "vkuznets@...hat.com" <vkuznets@...hat.com>,
        "jasowang@...hat.com" <jasowang@...hat.com>,
        "leann.ogasawara@...onical.com" <leann.ogasawara@...onical.com>,
        "marcelo.cerri@...onical.com" <marcelo.cerri@...onical.com>,
        Stephen Hemminger <sthemmin@...rosoft.com>,
        Stephen Hemminger <stephen@...workplumber.org>
Subject: RE: [PATCH 2/2] vmbus: make hv_get_ringbuffer_availbytes local



> -----Original Message-----
> From: Greg KH [mailto:gregkh@...uxfoundation.org]
> Sent: Tuesday, November 28, 2017 7:35 AM
> To: KY Srinivasan <kys@...rosoft.com>
> Cc: linux-kernel@...r.kernel.org; devel@...uxdriverproject.org;
> olaf@...fle.de; apw@...onical.com; vkuznets@...hat.com;
> jasowang@...hat.com; leann.ogasawara@...onical.com;
> marcelo.cerri@...onical.com; Stephen Hemminger
> <sthemmin@...rosoft.com>; Stephen Hemminger
> <stephen@...workplumber.org>
> Subject: Re: [PATCH 2/2] vmbus: make hv_get_ringbuffer_availbytes local
> 
> On Tue, Nov 14, 2017 at 10:52:08AM -0700, kys@...hange.microsoft.com
> wrote:
> > From: Stephen Hemminger <stephen@...workplumber.org>
> >
> > hv_get_ringbuffer_availbytes is only used by the debug info
> > routine so make it static. Also, add READ_ONCE() to avoid any
> > possible issues with potentially volatile index values.
> >
> > Signed-off-by: Stephen Hemminger <sthemmin@...rosoft.com>
> > Signed-off-by: K. Y. Srinivasan <kys@...rosoft.com>
> > ---
> >  drivers/hv/ring_buffer.c |   23 +++++++++++++++++++++++
> >  include/linux/hyperv.h   |   22 ----------------------
> >  2 files changed, 23 insertions(+), 22 deletions(-)
> >
> > diff --git a/drivers/hv/ring_buffer.c b/drivers/hv/ring_buffer.c
> > index 12eb8ca..50e0714 100644
> > --- a/drivers/hv/ring_buffer.c
> > +++ b/drivers/hv/ring_buffer.c
> > @@ -140,6 +140,29 @@ static u32 hv_copyto_ringbuffer(
> >  	return start_write_offset;
> >  }
> >
> > +/*
> > + *
> > + * hv_get_ringbuffer_availbytes()
> > + *
> > + * Get number of bytes available to read and to write to
> > + * for the specified ring buffer
> > + */
> > +static void
> > +hv_get_ringbuffer_availbytes(const struct hv_ring_buffer_info *rbi,
> > +			     u32 *read, u32 *write)
> > +{
> > +	u32 read_loc, write_loc, dsize;
> > +
> > +	/* Capture the read/write indices before they changed */
> > +	read_loc = READ_ONCE(rbi->ring_buffer->read_index);
> > +	write_loc = READ_ONCE(rbi->ring_buffer->write_index);
> > +	dsize = rbi->ring_datasize;
> > +
> > +	*write = write_loc >= read_loc ? dsize - (write_loc - read_loc) :
> > +		read_loc - write_loc;
> > +	*read = dsize - *write;
> > +}
> > +
> >  /* Get various debug metrics for the specified ring buffer. */
> >  void hv_ringbuffer_get_debuginfo(const struct hv_ring_buffer_info
> *ring_info,
> >  				 struct hv_ring_buffer_debug_info
> *debug_info)
> > diff --git a/include/linux/hyperv.h b/include/linux/hyperv.h
> > index 6c93366..93bd6fc 100644
> > --- a/include/linux/hyperv.h
> > +++ b/include/linux/hyperv.h
> > @@ -127,28 +127,6 @@ struct hv_ring_buffer_info {
> >  	u32 priv_read_index;
> >  };
> >
> > -/*
> > - *
> > - * hv_get_ringbuffer_availbytes()
> > - *
> > - * Get number of bytes available to read and to write to
> > - * for the specified ring buffer
> > - */
> > -static inline void
> > -hv_get_ringbuffer_availbytes(const struct hv_ring_buffer_info *rbi,
> > -			     u32 *read, u32 *write)
> > -{
> > -	u32 read_loc, write_loc, dsize;
> > -
> > -	/* Capture the read/write indices before they changed */
> > -	read_loc = rbi->ring_buffer->read_index;
> > -	write_loc = rbi->ring_buffer->write_index;
> > -	dsize = rbi->ring_datasize;
> > -
> > -	*write = write_loc >= read_loc ? dsize - (write_loc - read_loc) :
> > -		read_loc - write_loc;
> > -	*read = dsize - *write;
> > -}
> >
> >  static inline u32 hv_get_bytes_to_read(const struct hv_ring_buffer_info
> *rbi)
> >  {
> > --
> > 1.7.1
> 
> This breaks the build.
> 
> Please be more careful...

Sorry about that. I did not have a build issue on the tree I tested. I will rebase and send.

K. Y
> 
> greg k-h