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Subject[PATCH 1/3] Vmbus: Add function to report available ring buffer to write in total ring size percentage
Date
From: Long Li <longli@microsoft.com>

Netvsc has a similar function to calculate how much ring buffer in
percentage is available to write. This function is useful for storvsc and
other vmbus devices.

Define a similar function in vmbus to be used by storvsc.

Signed-off-by: Long Li <longli@microsoft.com>
---
drivers/hv/ring_buffer.c | 2 ++
include/linux/hyperv.h | 12 ++++++++++++
2 files changed, 14 insertions(+)

diff --git a/drivers/hv/ring_buffer.c b/drivers/hv/ring_buffer.c
index 8699bb969e7e..3c836c099a8f 100644
--- a/drivers/hv/ring_buffer.c
+++ b/drivers/hv/ring_buffer.c
@@ -227,6 +227,8 @@ int hv_ringbuffer_init(struct hv_ring_buffer_info *ring_info,
ring_info->ring_buffer->feature_bits.value = 1;

ring_info->ring_size = page_cnt << PAGE_SHIFT;
+ ring_info->ring_size_div10_reciprocal =
+ reciprocal_value(ring_info->ring_size / 10);
ring_info->ring_datasize = ring_info->ring_size -
sizeof(struct hv_ring_buffer);

diff --git a/include/linux/hyperv.h b/include/linux/hyperv.h
index 2048f3c3b68a..eb7204851089 100644
--- a/include/linux/hyperv.h
+++ b/include/linux/hyperv.h
@@ -36,6 +36,7 @@
#include <linux/device.h>
#include <linux/mod_devicetable.h>
#include <linux/interrupt.h>
+#include <linux/reciprocal_div.h>

#define MAX_PAGE_BUFFER_COUNT 32
#define MAX_MULTIPAGE_BUFFER_COUNT 32 /* 128K */
@@ -121,6 +122,7 @@ struct hv_ring_buffer {
struct hv_ring_buffer_info {
struct hv_ring_buffer *ring_buffer;
u32 ring_size; /* Include the shared header */
+ struct reciprocal_value ring_size_div10_reciprocal;
spinlock_t ring_lock;

u32 ring_datasize; /* < ring_size */
@@ -155,6 +157,16 @@ static inline u32 hv_get_bytes_to_write(const struct hv_ring_buffer_info *rbi)
return write;
}

+static inline u32 hv_get_avail_to_write_percent(
+ const struct hv_ring_buffer_info *rbi)
+{
+ u32 avail_write = hv_get_bytes_to_write(rbi);
+
+ return reciprocal_divide(
+ (avail_write << 3) + (avail_write << 1),
+ rbi->ring_size_div10_reciprocal);
+}
+
/*
* VMBUS version is 32 bit entity broken up into
* two 16 bit quantities: major_number. minor_number.
--
2.14.1
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