RE: [PATCH 5/5] Drivers: hv: vmbus: Implement copy-free read APIs

From	KY Srinivasan <kys@microsoft.com>
Newsgroups	linux.kernel
Subject	RE: [PATCH 5/5] Drivers: hv: vmbus: Implement copy-free read APIs
Date	2016-03-22 00:50 +0100
Message-ID	<rfhK9-4mP-7@gated-at.bofh.it> (permalink)
References	<rec9Q-3HN-3@gated-at.bofh.it> <rec9Q-3HN-5@gated-at.bofh.it> <rec9R-3HN-21@gated-at.bofh.it> <rf3nQ-2Wt-9@gated-at.bofh.it>
Organization	linux.* mail to news gateway

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> -----Original Message-----
> From: Vitaly Kuznetsov [mailto:vkuznets@redhat.com]
> Sent: Monday, March 21, 2016 1:29 AM
> To: KY Srinivasan <kys@microsoft.com>
> Cc: gregkh@linuxfoundation.org; linux-kernel@vger.kernel.org;
> devel@linuxdriverproject.org; olaf@aepfle.de; apw@canonical.com;
> jasowang@redhat.com
> Subject: Re: [PATCH 5/5] Drivers: hv: vmbus: Implement copy-free read APIs
> 
> "K. Y. Srinivasan" <kys@microsoft.com> writes:
> 
> > Implement copy-free read APIs.
> >
> > Signed-off-by: K. Y. Srinivasan <kys@microsoft.com>
> > ---
> >  drivers/hv/ring_buffer.c |   55
> ++++++++++++++++++++++++++++++++++++++++++++++
> >  include/linux/hyperv.h   |    6 +++++
> >  2 files changed, 61 insertions(+), 0 deletions(-)
> >
> > diff --git a/drivers/hv/ring_buffer.c b/drivers/hv/ring_buffer.c
> > index c2c2b2e..c80e1f3 100644
> > --- a/drivers/hv/ring_buffer.c
> > +++ b/drivers/hv/ring_buffer.c
> > @@ -444,3 +444,58 @@ int hv_ringbuffer_read(struct hv_ring_buffer_info
> *inring_info,
> >
> >  	return ret;
> >  }
> > +
> > +/*
> > + * In-place read functions.
> > + */
> > +bool get_next_pkt_raw(struct vmbus_channel *channel,
> > +		      struct vmpacket_descriptor **desc)
> 
> I suggest we make these functions return pointers and use
> ERR_PTR()/IS_ERR() when we need to return an error.

Either we get a pointer to a descriptor or not; there is no other
error here. I will change the signature accordingly.

> 
> > +{
> > +	struct hv_ring_buffer_info *ring_info = &channel->inbound;
> > +	u32 read_loc = ring_info->ring_buffer->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 bytes_avail_toread = hv_get_bytes_to_read(ring_info);
> > +
> > +	if (bytes_avail_toread < sizeof(struct vmpacket_descriptor))
> > +		return false;
> > +
> > +	if ((read_loc + sizeof(*desc)) > dsize)
> > +		return false;
> > +
> > +	cur_desc = ring_buffer + read_loc;
> > +	packetlen = cur_desc->len8 << 3;
> > +
> > +	if ((read_loc + packetlen + 8) > (dsize - 1))
> 
> Could you please add a define for this '8'?

Sure.

K. Y

Thread

[PATCH 0/5] Drivers: hv: vmbus  "K. Y. Srinivasan" <kys@microsoft.com> - 2016-03-19 00:40 +0100
  [PATCH 4/5] Drivers: hv: vmbus: Use the new virt_xx barrier code "K. Y. Srinivasan" <kys@microsoft.com> - 2016-03-19 00:40 +0100
  [PATCH 1/5] Drivers: hv: vmbus: Introduce functions for estimating room in the ring buffer "K. Y. Srinivasan" <kys@microsoft.com> - 2016-03-19 00:40 +0100
    [PATCH 3/5] Drivers: hv: vmbus: Fix a bug in hv_need_to_signal_on_read() "K. Y. Srinivasan" <kys@microsoft.com> - 2016-03-19 00:40 +0100
      Re: [PATCH 3/5] Drivers: hv: vmbus: Fix a bug in hv_need_to_signal_on_read() Vitaly Kuznetsov <vkuznets@redhat.com> - 2016-03-21 09:20 +0100
        RE: [PATCH 3/5] Drivers: hv: vmbus: Fix a bug in  hv_need_to_signal_on_read() KY Srinivasan <kys@microsoft.com> - 2016-03-22 01:10 +0100
          Re: [PATCH 3/5] Drivers: hv: vmbus: Fix a bug in hv_need_to_signal_on_read() Vitaly Kuznetsov <vkuznets@redhat.com> - 2016-03-22 11:00 +0100
            RE: [PATCH 3/5] Drivers: hv: vmbus: Fix a bug in  hv_need_to_signal_on_read() KY Srinivasan <kys@microsoft.com> - 2016-03-22 16:00 +0100
            RE: [PATCH 3/5] Drivers: hv: vmbus: Fix a bug in  hv_need_to_signal_on_read() KY Srinivasan <kys@microsoft.com> - 2016-03-22 18:20 +0100
    [PATCH 5/5] Drivers: hv: vmbus: Implement copy-free read APIs "K. Y. Srinivasan" <kys@microsoft.com> - 2016-03-19 00:40 +0100
      Re: [PATCH 5/5] Drivers: hv: vmbus: Implement copy-free read APIs Vitaly Kuznetsov <vkuznets@redhat.com> - 2016-03-21 09:30 +0100
        RE: [PATCH 5/5] Drivers: hv: vmbus: Implement copy-free read APIs KY Srinivasan <kys@microsoft.com> - 2016-03-22 00:50 +0100
  RE: [PATCH 0/5] Drivers: hv: vmbus  KY Srinivasan <kys@microsoft.com> - 2016-03-23 20:50 +0100

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