From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752925AbcCUI3Y (ORCPT ); Mon, 21 Mar 2016 04:29:24 -0400 Received: from mx1.redhat.com ([209.132.183.28]:42152 "EHLO mx1.redhat.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751787AbcCUI3Q (ORCPT ); Mon, 21 Mar 2016 04:29:16 -0400 From: Vitaly Kuznetsov To: "K. Y. Srinivasan" 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 References: <1458350038-32624-1-git-send-email-kys@microsoft.com> <1458350065-32666-1-git-send-email-kys@microsoft.com> <1458350065-32666-5-git-send-email-kys@microsoft.com> Date: Mon, 21 Mar 2016 09:29:12 +0100 In-Reply-To: <1458350065-32666-5-git-send-email-kys@microsoft.com> (K. Y. Srinivasan's message of "Fri, 18 Mar 2016 18:14:25 -0700") Message-ID: <87oaa81bfr.fsf@vitty.brq.redhat.com> User-Agent: Gnus/5.13 (Gnus v5.13) Emacs/24.5 (gnu/linux) MIME-Version: 1.0 Content-Type: text/plain Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org "K. Y. Srinivasan" writes: > Implement copy-free read APIs. > > Signed-off-by: K. Y. Srinivasan > --- > 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. > +{ > + 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'? > + return false; > + > + *desc = cur_desc; > + return true; > +} > +EXPORT_SYMBOL_GPL(get_next_pkt_raw); > + > +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->ring_buffer->read_index; > + u32 packetlen = desc->len8 << 3; > + u32 dsize = ring_info->ring_datasize; > + > + if ((read_loc + packetlen + 8) > dsize) > + BUG(); > + > + /* > + * Make sure all reads are done before we update the read index since > + * the writer may start writing to the read area once the read index > + * is updated. > + */ > + virt_mb(); > + ring_info->ring_buffer->read_index += packetlen + 8; > + > + if (hv_need_to_signal_on_read(ring_info)) > + vmbus_set_event(channel); > +} > +EXPORT_SYMBOL_GPL(put_pkt_raw); > diff --git a/include/linux/hyperv.h b/include/linux/hyperv.h > index a6b053c..455f3f0 100644 > --- a/include/linux/hyperv.h > +++ b/include/linux/hyperv.h > @@ -1035,6 +1035,12 @@ extern int vmbus_recvpacket_raw(struct vmbus_channel *channel, > u32 *buffer_actual_len, > u64 *requestid); > > +bool get_next_pkt_raw(struct vmbus_channel *channel, > + struct vmpacket_descriptor **desc); > + > +void put_pkt_raw(struct vmbus_channel *channel, > + struct vmpacket_descriptor *desc); > + > > extern void vmbus_ontimer(unsigned long data); -- Vitaly