librbd: assertion failure race condition if watch disconnected

It's possible for librbd's watch of the header object to be reset by
connection issues just prior to the image being removed.  This will
causes an assertion failure which assumes at least one watcher on the
image.

Fixes: #12176
Backport: hammer, firefly
Signed-off-by: Jason Dillaman <dillaman@redhat.com>

diff --git a/src/librbd/internal.cc b/src/librbd/internal.cc
index 44ecf54fcb0e82d3a207ae2be70430997cf86558..9316e473a25c244cbc67e81833c8aa079b7e92e3 100644 (file)
--- a/src/librbd/internal.cc
+++ b/src/librbd/internal.cc
@@ -1964,7 +1964,6 @@ reprotect_and_return_err:
         close_image(ictx);
         return -EBUSY;
       }
-      assert(watchers.size() == 1);
 
       trim_image(ictx, 0, prog_ctx);