libceph: add function to ensure notifies are complete

Without a way to flush the osd client's notify workqueue, a watch
event that is unregistered could continue receiving callbacks
indefinitely.

Unregistering the event simply means no new notifies are added to the
queue, but there may still be events in the queue that will call the
watch callback for the event. If the queue is flushed after the event
is unregistered, the caller can be sure no more watch callbacks will
occur for the canceled watch.

Signed-off-by: Josh Durgin <josh.durgin@inktank.com>
Reviewed-by: Sage Weil <sage@inktank.com>
Reviewed-by: Alex Elder <elder@linaro.org>

diff --git a/include/linux/ceph/osd_client.h b/include/linux/ceph/osd_client.h
index ce6df39f60ff6f966144855ca0e1bdb04c312903..8f47625a06615dbf5cbc79ef5df2e2fd5cee6041 100644 (file)
--- a/include/linux/ceph/osd_client.h
+++ b/include/linux/ceph/osd_client.h
@@ -335,6 +335,8 @@ extern int ceph_osdc_wait_request(struct ceph_osd_client *osdc,
                                  struct ceph_osd_request *req);
 extern void ceph_osdc_sync(struct ceph_osd_client *osdc);
 
+extern void ceph_osdc_flush_notifies(struct ceph_osd_client *osdc);
+
 extern int ceph_osdc_readpages(struct ceph_osd_client *osdc,
                               struct ceph_vino vino,
                               struct ceph_file_layout *layout,

diff --git a/net/ceph/osd_client.c b/net/ceph/osd_client.c
index 1606f740d6ae0d1b7ea8aeb1ba8126fd7693888d..2b4b32aaa893b3117043e6a218fcde6c58f0aff4 100644 (file)
--- a/net/ceph/osd_client.c
+++ b/net/ceph/osd_client.c
@@ -2215,6 +2215,17 @@ void ceph_osdc_sync(struct ceph_osd_client *osdc)
 }
 EXPORT_SYMBOL(ceph_osdc_sync);
 
+/*
+ * Call all pending notify callbacks - for use after a watch is
+ * unregistered, to make sure no more callbacks for it will be invoked
+ */
+extern void ceph_osdc_flush_notifies(struct ceph_osd_client *osdc)
+{
+       flush_workqueue(osdc->notify_wq);
+}
+EXPORT_SYMBOL(ceph_osdc_flush_notifies);
+
+
 /*
  * init, shutdown
  */