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From:   "Michael Kelley (LINUX)" <mikelley@microsoft.com>
To:     "Andrea Parri (Microsoft)" <parri.andrea@gmail.com>,
        KY Srinivasan <kys@microsoft.com>,
        Haiyang Zhang <haiyangz@microsoft.com>,
        Stephen Hemminger <sthemmin@microsoft.com>,
        Wei Liu <wei.liu@kernel.org>, Dexuan Cui <decui@microsoft.com>,
        Stefano Garzarella <sgarzare@redhat.com>,
        David Miller <davem@davemloft.net>,
        Jakub Kicinski <kuba@kernel.org>,
        Paolo Abeni <pabeni@redhat.com>
CC:     "linux-hyperv@vger.kernel.org" <linux-hyperv@vger.kernel.org>,
        "virtualization@lists.linux-foundation.org" 
        <virtualization@lists.linux-foundation.org>,
        "netdev@vger.kernel.org" <netdev@vger.kernel.org>,
        "linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>
Subject: RE: [PATCH 5/5] Drivers: hv: vmbus: Refactor the ring-buffer iterator
 functions
Thread-Topic: [PATCH 5/5] Drivers: hv: vmbus: Refactor the ring-buffer
 iterator functions
Thread-Index: AQHYVPJSruHaMyZGKUm01yiVMWl9T6z5brnw
Date:   Wed, 20 Apr 2022 23:15:00 +0000
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References: <20220420200720.434717-1-parri.andrea@gmail.com>
 <20220420200720.434717-6-parri.andrea@gmail.com>
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From: Andrea Parri (Microsoft) <parri.andrea@gmail.com> Sent: Wednesday, Ap=
ril 20, 2022 1:07 PM
>=20
> With no users of hv_pkt_iter_next_raw() and no "external" users of
> hv_pkt_iter_first_raw(), the iterator functions can be refactored
> and simplified to remove some indirection/code.
>=20
> Signed-off-by: Andrea Parri (Microsoft) <parri.andrea@gmail.com>
> ---
>  drivers/hv/ring_buffer.c | 32 +++++++++-----------------------
>  include/linux/hyperv.h   | 35 ++++-------------------------------
>  2 files changed, 13 insertions(+), 54 deletions(-)
>=20
> diff --git a/drivers/hv/ring_buffer.c b/drivers/hv/ring_buffer.c
> index 3d215d9dec433..fa98b3a91206a 100644
> --- a/drivers/hv/ring_buffer.c
> +++ b/drivers/hv/ring_buffer.c
> @@ -421,7 +421,7 @@ int hv_ringbuffer_read(struct vmbus_channel *channel,
>  	memcpy(buffer, (const char *)desc + offset, packetlen);
>=20
>  	/* Advance ring index to next packet descriptor */
> -	__hv_pkt_iter_next(channel, desc, true);
> +	__hv_pkt_iter_next(channel, desc);
>=20
>  	/* Notify host of update */
>  	hv_pkt_iter_close(channel);
> @@ -456,22 +456,6 @@ static u32 hv_pkt_iter_avail(const struct hv_ring_bu=
ffer_info
> *rbi)
>  		return (rbi->ring_datasize - priv_read_loc) + write_loc;
>  }
>=20
> -/*
> - * Get first vmbus packet without copying it out of the ring buffer
> - */
> -struct vmpacket_descriptor *hv_pkt_iter_first_raw(struct vmbus_channel *=
channel)
> -{
> -	struct hv_ring_buffer_info *rbi =3D &channel->inbound;
> -
> -	hv_debug_delay_test(channel, MESSAGE_DELAY);
> -
> -	if (hv_pkt_iter_avail(rbi) < sizeof(struct vmpacket_descriptor))
> -		return NULL;
> -
> -	return (struct vmpacket_descriptor *)(hv_get_ring_buffer(rbi) + rbi-
> >priv_read_index);
> -}
> -EXPORT_SYMBOL_GPL(hv_pkt_iter_first_raw);
> -
>  /*
>   * Get first vmbus packet from ring buffer after read_index
>   *
> @@ -483,11 +467,14 @@ struct vmpacket_descriptor *hv_pkt_iter_first(struc=
t
> vmbus_channel *channel)
>  	struct vmpacket_descriptor *desc, *desc_copy;
>  	u32 bytes_avail, pkt_len, pkt_offset;
>=20
> -	desc =3D hv_pkt_iter_first_raw(channel);
> -	if (!desc)
> +	hv_debug_delay_test(channel, MESSAGE_DELAY);
> +
> +	bytes_avail =3D hv_pkt_iter_avail(rbi);
> +	if (bytes_avail < sizeof(struct vmpacket_descriptor))
>  		return NULL;
> +	bytes_avail =3D min(rbi->pkt_buffer_size, bytes_avail);
>=20
> -	bytes_avail =3D min(rbi->pkt_buffer_size, hv_pkt_iter_avail(rbi));
> +	desc =3D (struct vmpacket_descriptor *)(hv_get_ring_buffer(rbi) + rbi-
> >priv_read_index);
>=20
>  	/*
>  	 * Ensure the compiler does not use references to incoming Hyper-V valu=
es
> (which
> @@ -534,8 +521,7 @@ EXPORT_SYMBOL_GPL(hv_pkt_iter_first);
>   */
>  struct vmpacket_descriptor *
>  __hv_pkt_iter_next(struct vmbus_channel *channel,
> -		   const struct vmpacket_descriptor *desc,
> -		   bool copy)
> +		   const struct vmpacket_descriptor *desc)
>  {
>  	struct hv_ring_buffer_info *rbi =3D &channel->inbound;
>  	u32 packetlen =3D desc->len8 << 3;
> @@ -548,7 +534,7 @@ __hv_pkt_iter_next(struct vmbus_channel *channel,
>  		rbi->priv_read_index -=3D dsize;
>=20
>  	/* more data? */
> -	return copy ? hv_pkt_iter_first(channel) : hv_pkt_iter_first_raw(channe=
l);
> +	return hv_pkt_iter_first(channel);
>  }
>  EXPORT_SYMBOL_GPL(__hv_pkt_iter_next);
>=20
> diff --git a/include/linux/hyperv.h b/include/linux/hyperv.h
> index 1112c5cf894e6..370adc9971d3e 100644
> --- a/include/linux/hyperv.h
> +++ b/include/linux/hyperv.h
> @@ -1673,55 +1673,28 @@ static inline u32 hv_pkt_len(const struct
> vmpacket_descriptor *desc)
>  	return desc->len8 << 3;
>  }
>=20
> -struct vmpacket_descriptor *
> -hv_pkt_iter_first_raw(struct vmbus_channel *channel);
> -
>  struct vmpacket_descriptor *
>  hv_pkt_iter_first(struct vmbus_channel *channel);
>=20
>  struct vmpacket_descriptor *
>  __hv_pkt_iter_next(struct vmbus_channel *channel,
> -		   const struct vmpacket_descriptor *pkt,
> -		   bool copy);
> +		   const struct vmpacket_descriptor *pkt);
>=20
>  void hv_pkt_iter_close(struct vmbus_channel *channel);
>=20
>  static inline struct vmpacket_descriptor *
> -hv_pkt_iter_next_pkt(struct vmbus_channel *channel,
> -		     const struct vmpacket_descriptor *pkt,
> -		     bool copy)
> +hv_pkt_iter_next(struct vmbus_channel *channel,
> +		 const struct vmpacket_descriptor *pkt)
>  {
>  	struct vmpacket_descriptor *nxt;
>=20
> -	nxt =3D __hv_pkt_iter_next(channel, pkt, copy);
> +	nxt =3D __hv_pkt_iter_next(channel, pkt);
>  	if (!nxt)
>  		hv_pkt_iter_close(channel);
>=20
>  	return nxt;
>  }
>=20
> -/*
> - * Get next packet descriptor without copying it out of the ring buffer
> - * If at end of list, return NULL and update host.
> - */
> -static inline struct vmpacket_descriptor *
> -hv_pkt_iter_next_raw(struct vmbus_channel *channel,
> -		     const struct vmpacket_descriptor *pkt)
> -{
> -	return hv_pkt_iter_next_pkt(channel, pkt, false);
> -}
> -
> -/*
> - * Get next packet descriptor from iterator
> - * If at end of list, return NULL and update host.
> - */
> -static inline struct vmpacket_descriptor *
> -hv_pkt_iter_next(struct vmbus_channel *channel,
> -		 const struct vmpacket_descriptor *pkt)
> -{
> -	return hv_pkt_iter_next_pkt(channel, pkt, true);
> -}
> -
>  #define foreach_vmbus_pkt(pkt, channel) \
>  	for (pkt =3D hv_pkt_iter_first(channel); pkt; \
>  	    pkt =3D hv_pkt_iter_next(channel, pkt))
> --
> 2.25.1

Reviewed-by: Michael Kelley <mikelley@microsoft.com>