block: latency accounting

Account the total latency for read/write/flush requests.  This allows
management tools to average it based on a snapshot of the nr ops
counters and allow checking for SLAs or provide statistics.

Signed-off-by: Christoph Hellwig <hch@lst.de>
Signed-off-by: Kevin Wolf <kwolf@redhat.com>

1 files changed, 1 insertions, 0 deletions

diff --git a/block.h b/block.h
index df06af5982..3ac0b944eb 100644
--- a/block.h
+++ b/block.h
@@ -264,6 +264,7 @@ enum BlockAcctType {
 
 typedef struct BlockAcctCookie {
     int64_t bytes;
+    int64_t start_time_ns;
     enum BlockAcctType type;
 } BlockAcctCookie;