block: Add idle_time_ns to BlockDeviceStats

This patch adds the new field 'idle_time_ns' to the BlockDeviceStats
structure, indicating the time that has passed since the previous I/O
operation.

It also adds the block_acct_idle_time_ns() call, to ensure that all
references to the clock type used for accounting are in the same
place. This will later allow us to use a different clock for iotests.

Signed-off-by: Alberto Garcia <berto@igalia.com>
Message-id: 7d8cfcf931453e1a2443e6626e8c1edc347c7c8a.1446044837.git.berto@igalia.com
Signed-off-by: Stefan Hajnoczi <stefanha@redhat.com>
Signed-off-by: Kevin Wolf <kwolf@redhat.com>
diff --git a/hmp.c b/hmp.c
index d381283..2140605 100644
--- a/hmp.c
+++ b/hmp.c
@@ -522,6 +522,7 @@
                        " flush_total_time_ns=%" PRId64
                        " rd_merged=%" PRId64
                        " wr_merged=%" PRId64
+                       " idle_time_ns=%" PRId64
                        "\n",
                        stats->value->stats->rd_bytes,
                        stats->value->stats->wr_bytes,
@@ -532,7 +533,8 @@
                        stats->value->stats->rd_total_time_ns,
                        stats->value->stats->flush_total_time_ns,
                        stats->value->stats->rd_merged,
-                       stats->value->stats->wr_merged);
+                       stats->value->stats->wr_merged,
+                       stats->value->stats->idle_time_ns);
     }
 
     qapi_free_BlockStatsList(stats_list);