rbd: decrement obj request count when deleting

Decrement the obj_request_count value when deleting an object
request from its image request's list.  Rearrange a few lines
in the surrounding code.

This resolves:
    http://tracker.ceph.com/issues/3940

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 fc1a045..d3d15d0 100644 (file)
--- a/drivers/block/rbd.c
+++ b/drivers/block/rbd.c
@@ -1063,22 +1063,29 @@ static void rbd_img_request_put(struct rbd_img_request *img_request)
 static inline void rbd_img_obj_request_add(struct rbd_img_request *img_request,
                                        struct rbd_obj_request *obj_request)
 {
+       rbd_assert(obj_request->img_request == NULL);
+
        rbd_obj_request_get(obj_request);
        obj_request->img_request = img_request;
-       list_add_tail(&obj_request->links, &img_request->obj_requests);
-       obj_request->which = img_request->obj_request_count++;
+       obj_request->which = img_request->obj_request_count;
        rbd_assert(obj_request->which != BAD_WHICH);
+       img_request->obj_request_count++;
+       list_add_tail(&obj_request->links, &img_request->obj_requests);
 }
 
 static inline void rbd_img_obj_request_del(struct rbd_img_request *img_request,
                                        struct rbd_obj_request *obj_request)
 {
        rbd_assert(obj_request->which != BAD_WHICH);
-       obj_request->which = BAD_WHICH;
+
        list_del(&obj_request->links);
+       rbd_assert(img_request->obj_request_count > 0);
+       img_request->obj_request_count--;
+       rbd_assert(obj_request->which == img_request->obj_request_count);
+       obj_request->which = BAD_WHICH;
        rbd_assert(obj_request->img_request == img_request);
-       obj_request->callback = NULL;
        obj_request->img_request = NULL;
+       obj_request->callback = NULL;
        rbd_obj_request_put(obj_request);
 }
 
@@ -1472,6 +1479,7 @@ static void rbd_img_request_destroy(struct kref *kref)
 
        for_each_obj_request_safe(img_request, obj_request, next_obj_request)
                rbd_img_obj_request_del(img_request, obj_request);
+       rbd_assert(img_request->obj_request_count == 0);
 
        if (img_request->write_request)
                ceph_put_snap_context(img_request->snapc);