1 files changed, 27 insertions, 0 deletions

diff --git a/include/linux/hyperv.h b/include/linux/hyperv.h
index 5852545e6bba..6af8738ae7e9 100644
--- a/include/linux/hyperv.h
+++ b/include/linux/hyperv.h
@@ -274,6 +274,33 @@ struct hv_ring_buffer_debug_info {
         u32 bytes_avail_towrite;
 };
 
+
+/*
+ *
+ * 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(struct hv_ring_buffer_info *rbi,
+                          u32 *read, u32 *write)
+{
+        u32 read_loc, write_loc, dsize;
+
+        smp_read_barrier_depends();
+
+        /* 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;
+}
+
+
 /*
  * We use the same version numbering for all Hyper-V modules.
  *