vmbus: make hv_get_ringbuffer_availbytes local

The last use of hv_get_ringbuffer_availbytes in drivers is now
gone. 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: NStephen Hemminger <sthemmin@microsoft.com>
Signed-off-by: NDavid S. Miller <davem@davemloft.net>

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)

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)
 {