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Groups > linux.kernel > #1674295

[PATCH 4/6] vmbus: eliminate duplicate cached index

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From: Stephen Hemminger <stephen@networkplumber.org>

Don't need cached read index anymore now that packet iterator
is used. The iterator has the original read index until the
visible read_index is updated.

Signed-off-by: Stephen Hemminger <sthemmin@microsoft.com>
Signed-off-by: K. Y. Srinivasan <kys@microsoft.com>
---
 drivers/hv/ring_buffer.c |   17 ++++-------------
 include/linux/hyperv.h   |   14 --------------
 2 files changed, 4 insertions(+), 27 deletions(-)

diff --git a/drivers/hv/ring_buffer.c b/drivers/hv/ring_buffer.c
index a9021f1..b0f7952 100644
--- a/drivers/hv/ring_buffer.c
+++ b/drivers/hv/ring_buffer.c
@@ -358,9 +358,6 @@ struct vmpacket_descriptor *hv_pkt_iter_first(struct vmbus_channel *channel)
 {
 	struct hv_ring_buffer_info *rbi = &channel->inbound;
 
-	/* set state for later hv_pkt_iter_close */
-	rbi->cached_read_index = rbi->ring_buffer->read_index;
-
 	if (hv_pkt_iter_avail(rbi) < sizeof(struct vmpacket_descriptor))
 		return NULL;
 
@@ -388,10 +385,7 @@ struct vmpacket_descriptor *
 		rbi->priv_read_index -= dsize;
 
 	/* more data? */
-	if (hv_pkt_iter_avail(rbi) < sizeof(struct vmpacket_descriptor))
-		return NULL;
-	else
-		return hv_get_ring_buffer(rbi) + rbi->priv_read_index;
+	return hv_pkt_iter_first(channel);
 }
 EXPORT_SYMBOL_GPL(__hv_pkt_iter_next);
 
@@ -401,7 +395,7 @@ struct vmpacket_descriptor *
 void hv_pkt_iter_close(struct vmbus_channel *channel)
 {
 	struct hv_ring_buffer_info *rbi = &channel->inbound;
-	u32 cur_write_sz, cached_write_sz;
+	u32 orig_write_sz = hv_get_bytes_to_write(rbi);
 	u32 pending_sz;
 
 	/*
@@ -430,13 +424,10 @@ void hv_pkt_iter_close(struct vmbus_channel *channel)
 	if (pending_sz == 0)
 		return;
 
-	cur_write_sz = hv_get_bytes_to_write(rbi);
-
-	if (cur_write_sz < pending_sz)
+	if (hv_get_bytes_to_write(rbi) < pending_sz)
 		return;
 
-	cached_write_sz = hv_get_cached_bytes_to_write(rbi);
-	if (cached_write_sz < pending_sz)
+	if (orig_write_sz < pending_sz)
 		vmbus_setevent(channel);
 }
 EXPORT_SYMBOL_GPL(hv_pkt_iter_close);
diff --git a/include/linux/hyperv.h b/include/linux/hyperv.h
index 0262267..9ede1fb 100644
--- a/include/linux/hyperv.h
+++ b/include/linux/hyperv.h
@@ -125,7 +125,6 @@ struct hv_ring_buffer_info {
 
 	u32 ring_datasize;		/* < ring_size */
 	u32 priv_read_index;
-	u32 cached_read_index;
 };
 
 /*
@@ -178,19 +177,6 @@ static inline u32 hv_get_bytes_to_write(const struct hv_ring_buffer_info *rbi)
 	return write;
 }
 
-static inline u32 hv_get_cached_bytes_to_write(
-	const struct hv_ring_buffer_info *rbi)
-{
-	u32 read_loc, write_loc, dsize, write;
-
-	dsize = rbi->ring_datasize;
-	read_loc = rbi->cached_read_index;
-	write_loc = rbi->ring_buffer->write_index;
-
-	write = write_loc >= read_loc ? dsize - (write_loc - read_loc) :
-		read_loc - write_loc;
-	return write;
-}
 /*
  * VMBUS version is 32 bit entity broken up into
  * two 16 bit quantities: major_number. minor_number.
-- 
1.7.1

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Thread

[PATCH 0/6] Drivers: hv: vmbus: Ringbuffer cleanup and optimizations kys@exchange.microsoft.com - 2017-06-25 21:40 +0200
  [PATCH 6/6] vmbus: add prefetch to ring buffer iterator kys@exchange.microsoft.com - 2017-06-25 21:40 +0200
  [PATCH 1/6] vmbus: simplify hv_ringbuffer_read kys@exchange.microsoft.com - 2017-06-25 21:40 +0200
  [PATCH 5/6] vmbus: more host signalling avoidance kys@exchange.microsoft.com - 2017-06-25 21:40 +0200
  [PATCH 4/6] vmbus: eliminate duplicate cached index kys@exchange.microsoft.com - 2017-06-25 21:40 +0200
  [PATCH 3/6] vmbus: refactor hv_signal_on_read kys@exchange.microsoft.com - 2017-06-25 21:40 +0200

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