Drivers: hv: vmbus: Fix a bug in the channel callback dispatch code

commit affb1aff300ddee54df307812b38f166e8a865ef upstream.

Starting with Win8, we have implemented several optimizations to improve the
scalability and performance of the VMBUS transport between the Host and the
Guest. Some of the non-performance critical services cannot leverage these
optimization since they only read and process one message at a time.
Make adjustments to the callback dispatch code to account for the way
non-performance critical drivers handle reading of the channel.

Signed-off-by: K. Y. Srinivasan <kys@microsoft.com>
Signed-off-by: Jiri Slaby <jslaby@suse.cz>

diff --git a/drivers/hv/connection.c b/drivers/hv/connection.c
index 8dd98d4fc124605078aa6dc843258b13c8879b6b..59ef4e7afdd72c634d683fcc863574e901d9b26b 100644 (file)
--- a/drivers/hv/connection.c
+++ b/drivers/hv/connection.c
@@ -320,9 +320,13 @@ static void process_chn_event(u32 relid)
                 */
 
                do {
-                       hv_begin_read(&channel->inbound);
+                       if (read_state)
+                               hv_begin_read(&channel->inbound);
                        channel->onchannel_callback(arg);
-                       bytes_to_read = hv_end_read(&channel->inbound);
+                       if (read_state)
+                               bytes_to_read = hv_end_read(&channel->inbound);
+                       else
+                               bytes_to_read = 0;
                } while (read_state && (bytes_to_read != 0));
        } else {
                pr_err("no channel callback for relid - %u\n", relid);