RE: [RFC PATCH 6/6] Drivers: hv: vmbus: Refactor the ring-buffer iterator functions

From: Michael Kelley (LINUX)
Date: Thu Apr 14 2022 - 23:49:00 EST


From: Andrea Parri (Microsoft) <parri.andrea@xxxxxxxxx> Sent: Wednesday, April 13, 2022 1:48 PM
>
> 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.
>
> Signed-off-by: Andrea Parri (Microsoft) <parri.andrea@xxxxxxxxx>
> ---
> drivers/hv/ring_buffer.c | 11 +++++------
> include/linux/hyperv.h | 35 ++++-------------------------------
> 2 files changed, 9 insertions(+), 37 deletions(-)
>
> diff --git a/drivers/hv/ring_buffer.c b/drivers/hv/ring_buffer.c
> index 3d215d9dec433..c9357dae2a2c8 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);
>
> /* Advance ring index to next packet descriptor */
> - __hv_pkt_iter_next(channel, desc, true);
> + __hv_pkt_iter_next(channel, desc);
>
> /* Notify host of update */
> hv_pkt_iter_close(channel);
> @@ -459,7 +459,8 @@ static u32 hv_pkt_iter_avail(const struct hv_ring_buffer_info
> *rbi)
> /*
> * Get first vmbus packet without copying it out of the ring buffer
> */
> -struct vmpacket_descriptor *hv_pkt_iter_first_raw(struct vmbus_channel *channel)
> +static struct vmpacket_descriptor *
> +hv_pkt_iter_first_raw(struct vmbus_channel *channel)
> {
> struct hv_ring_buffer_info *rbi = &channel->inbound;
>
> @@ -470,7 +471,6 @@ struct vmpacket_descriptor *hv_pkt_iter_first_raw(struct
> vmbus_channel *channel)
>
> return (struct vmpacket_descriptor *)(hv_get_ring_buffer(rbi) + rbi-
> >priv_read_index);
> }
> -EXPORT_SYMBOL_GPL(hv_pkt_iter_first_raw);

Does hv_pkt_iter_first_raw() need to be retained at all as a
separate function? I think after these changes, the only caller
is hv_pkt_iter_first(), in which case the code could just go
inline in hv_pkt_iter_first(). Doing that combining would
also allow the elimination of the duplicate call to
hv_pkt_iter_avail().

Michael

>
> /*
> * Get first vmbus packet from ring buffer after read_index
> @@ -534,8 +534,7 @@ 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 = &channel->inbound;
> u32 packetlen = desc->len8 << 3;
> @@ -548,7 +547,7 @@ __hv_pkt_iter_next(struct vmbus_channel *channel,
> rbi->priv_read_index -= dsize;
>
> /* more data? */
> - return copy ? hv_pkt_iter_first(channel) : hv_pkt_iter_first_raw(channel);
> + return hv_pkt_iter_first(channel);
> }
> EXPORT_SYMBOL_GPL(__hv_pkt_iter_next);
>
> 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;
> }
>
> -struct vmpacket_descriptor *
> -hv_pkt_iter_first_raw(struct vmbus_channel *channel);
> -
> struct vmpacket_descriptor *
> hv_pkt_iter_first(struct vmbus_channel *channel);
>
> struct vmpacket_descriptor *
> __hv_pkt_iter_next(struct vmbus_channel *channel,
> - const struct vmpacket_descriptor *pkt,
> - bool copy);
> + const struct vmpacket_descriptor *pkt);
>
> void hv_pkt_iter_close(struct vmbus_channel *channel);
>
> 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;
>
> - nxt = __hv_pkt_iter_next(channel, pkt, copy);
> + nxt = __hv_pkt_iter_next(channel, pkt);
> if (!nxt)
> hv_pkt_iter_close(channel);
>
> return nxt;
> }
>
> -/*
> - * 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 = hv_pkt_iter_first(channel); pkt; \
> pkt = hv_pkt_iter_next(channel, pkt))
> --
> 2.25.1