rbd: record aggregate image transfer count

Compute the total number of bytes transferred for an image
request--the sum across each of the request's object requests.
To avoid contention do it only when all object requests are
complete, in rbd_img_request_complete().

Signed-off-by: Alex Elder <elder@inktank.com>
Reviewed-by: Josh Durgin <josh.durgin@inktank.com>

diff --git a/drivers/block/rbd.c b/drivers/block/rbd.c
index 69eab66b6c670e8bb4881ba3115f6ce218b8fff5..e8374aec93da2a560aefb0a7f6c6e0c9ea0aa2a6 100644 (file)
--- a/drivers/block/rbd.c
+++ b/drivers/block/rbd.c
@@ -214,6 +214,7 @@ struct rbd_img_request {
        spinlock_t              completion_lock;/* protects next_completion */
        u32                     next_completion;
        rbd_img_callback_t      callback;
+       u64                     xferred;/* aggregate bytes transferred */
        int                     result; /* first nonzero obj_request result */
 
        u32                     obj_request_count;
@@ -1148,7 +1149,24 @@ static int rbd_obj_request_submit(struct ceph_osd_client *osdc,
 
 static void rbd_img_request_complete(struct rbd_img_request *img_request)
 {
+
        dout("%s: img %p\n", __func__, img_request);
+
+       /*
+        * If no error occurred, compute the aggregate transfer
+        * count for the image request.  We could instead use
+        * atomic64_cmpxchg() to update it as each object request
+        * completes; not clear which way is better off hand.
+        */
+       if (!img_request->result) {
+               struct rbd_obj_request *obj_request;
+               u64 xferred = 0;
+
+               for_each_obj_request(img_request, obj_request)
+                       xferred += obj_request->xferred;
+               img_request->xferred = xferred;
+       }
+
        if (img_request->callback)
                img_request->callback(img_request);
        else