linux-kernel - [PATCH 2/2] vmbus: make hv_get_ringbuffer

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Date:   Tue, 14 Nov 2017 10:52:08 -0700
From:   kys@...hange.microsoft.com
To:     gregkh@...uxfoundation.org, linux-kernel@...r.kernel.org,
        devel@...uxdriverproject.org, olaf@...fle.de, apw@...onical.com,
        vkuznets@...hat.com, jasowang@...hat.com,
        leann.ogasawara@...onical.com, marcelo.cerri@...onical.com,
        sthemmin@...rosoft.com
Cc:     Stephen Hemminger <stephen@...workplumber.org>,
        "K. Y. Srinivasan" <kys@...rosoft.com>
Subject: [PATCH 2/2] vmbus: make hv_get_ringbuffer_availbytes local

From: Stephen Hemminger <stephen@...workplumber.org>

hv_get_ringbuffer_availbytes is only used by the debug info
routine so make it static. Also, add READ_ONCE() to avoid any
possible issues with potentially volatile index values.

Signed-off-by: Stephen Hemminger <sthemmin@...rosoft.com>
Signed-off-by: K. Y. Srinivasan <kys@...rosoft.com>
---
 drivers/hv/ring_buffer.c |   23 +++++++++++++++++++++++
 include/linux/hyperv.h   |   22 ----------------------
 2 files changed, 23 insertions(+), 22 deletions(-)

diff --git a/drivers/hv/ring_buffer.c b/drivers/hv/ring_buffer.c
index 12eb8ca..50e0714 100644
--- a/drivers/hv/ring_buffer.c
+++ b/drivers/hv/ring_buffer.c
@@ -140,6 +140,29 @@ static u32 hv_copyto_ringbuffer(
 	return start_write_offset;
 }
 
+/*
+ *
+ * hv_get_ringbuffer_availbytes()
+ *
+ * Get number of bytes available to read and to write to
+ * for the specified ring buffer
+ */
+static void
+hv_get_ringbuffer_availbytes(const struct hv_ring_buffer_info *rbi,
+			     u32 *read, u32 *write)
+{
+	u32 read_loc, write_loc, dsize;
+
+	/* Capture the read/write indices before they changed */
+	read_loc = READ_ONCE(rbi->ring_buffer->read_index);
+	write_loc = READ_ONCE(rbi->ring_buffer->write_index);
+	dsize = rbi->ring_datasize;
+
+	*write = write_loc >= read_loc ? dsize - (write_loc - read_loc) :
+		read_loc - write_loc;
+	*read = dsize - *write;
+}
+
 /* Get various debug metrics for the specified ring buffer. */
 void hv_ringbuffer_get_debuginfo(const struct hv_ring_buffer_info *ring_info,
 				 struct hv_ring_buffer_debug_info *debug_info)
diff --git a/include/linux/hyperv.h b/include/linux/hyperv.h
index 6c93366..93bd6fc 100644
--- a/include/linux/hyperv.h
+++ b/include/linux/hyperv.h
@@ -127,28 +127,6 @@ struct hv_ring_buffer_info {
 	u32 priv_read_index;
 };
 
-/*
- *
- * hv_get_ringbuffer_availbytes()
- *
- * Get number of bytes available to read and to write to
- * for the specified ring buffer
- */
-static inline void
-hv_get_ringbuffer_availbytes(const struct hv_ring_buffer_info *rbi,
-			     u32 *read, u32 *write)
-{
-	u32 read_loc, write_loc, dsize;
-
-	/* Capture the read/write indices before they changed */
-	read_loc = rbi->ring_buffer->read_index;
-	write_loc = rbi->ring_buffer->write_index;
-	dsize = rbi->ring_datasize;
-
-	*write = write_loc >= read_loc ? dsize - (write_loc - read_loc) :
-		read_loc - write_loc;
-	*read = dsize - *write;
-}
 
 static inline u32 hv_get_bytes_to_read(const struct hv_ring_buffer_info *rbi)
 {
-- 
1.7.1