ceph_test_rados: do not let rollback race with snap delete

Note that the OSD behaves in a weird way when you rollback to a non-
existent snap, so the test probably isn't the only party at fault here.

Fixes (test half of): #6254
Backport: dumpling, cuttlefish
Signed-off-by: Sage Weil <sage@inktank.com>
(cherry picked from commit 55d279b98553ba4542219b126fc7159b20b18b1f)

Conflicts:

	src/test/osd/RadosModel.h
	src/test/osd/TestRados.cc

2 files changed, 10 insertions, 3 deletions

diff --git a/src/test/osd/RadosModel.h b/src/test/osd/RadosModel.h
index b022d24dc91..74c90aa7972 100644
--- a/src/test/osd/RadosModel.h
+++ b/src/test/osd/RadosModel.h
@@ -139,6 +139,7 @@ public:
   map<int, map<string,ObjectDesc> > pool_obj_cont;
   set<string> oid_in_use;
   set<string> oid_not_in_use;
+  set<int> snaps_in_use;
   int current_snap;
   string pool_name;
   librados::IoCtx io_ctx;
@@ -1298,6 +1299,8 @@ public:
     }
     context->oid_in_use.insert(oid);
     context->oid_not_in_use.erase(oid);
+    context->snaps_in_use.insert(roll_back_to);
+
     context->roll_back(oid, roll_back_to);
     uint64_t snap = context->snaps[roll_back_to];
 
@@ -1323,7 +1326,8 @@ public:
       Mutex::Locker l(context->state_lock);
       context->oid_in_use.erase(oid);
       context->oid_not_in_use.insert(oid);
-    }
+      context->snaps_in_use.erase(roll_back_to);
+   }
   }
 
   string getType()
diff --git a/src/test/osd/TestRados.cc b/src/test/osd/TestRados.cc
index 6ac661c0629..52e1a047e26 100644
--- a/src/test/osd/TestRados.cc
+++ b/src/test/osd/TestRados.cc
@@ -119,10 +119,13 @@ private:
       }
 
     case TEST_OP_ROLLBACK:
-      if (context.snaps.empty()) {
+      if (context.snaps.size() <= context.snaps_in_use.size()) {
 	return NULL;
-      } else {
+      }
+      while (true) {
 	int snap = rand_choose(context.snaps)->first;
+	if (context.snaps_in_use.count(snap))
+	  continue;  // in use; try again!
 	string oid = *(rand_choose(context.oid_not_in_use));
 	cout << "RollingBack " << oid << " to " << snap << std::endl;
         return new RollbackOp(&context, oid, snap);