mds: xlock versionlock on rename if witnesses

This ensures that we don't pipeline dentry linkage updates when there
are witnesses.  That can cause problems because replicas don't see
projected dentry linkage info, and will get confused when they look at
the replica of the srcdn and it's, say, NULL and not srci.

diff --git a/src/mds/Server.cc b/src/mds/Server.cc
index 71bd8941084c36d8933cafde88b900831defd251..0ad13d5fa155da82be32a6ed8bcc3099d6faefbc 100644 (file)
--- a/src/mds/Server.cc
+++ b/src/mds/Server.cc
@@ -4082,6 +4082,25 @@ void Server::handle_client_rename(MDRequest *mdr)
     dout(10) << "straydn is " << *straydn << dendl;
   }
 
+  // -- prepare witness list --
+  /*
+   * NOTE: we use _all_ replicas as witnesses.
+   * this probably isn't totally necessary (esp for file renames),
+   * but if/when we change that, we have to make sure rejoin is
+   * sufficiently robust to handle strong rejoins from survivors
+   * with totally wrong dentry->inode linkage.
+   * (currently, it can ignore rename effects, because the resolve
+   * stage will sort them out.)
+   */
+  set<int> witnesses = mdr->more()->extra_witnesses;
+  if (srcdn->is_auth())
+    srcdn->list_replicas(witnesses);
+  else
+    witnesses.insert(srcdn->authority().first);
+  destdn->list_replicas(witnesses);
+  dout(10) << " witnesses " << witnesses << ", have " << mdr->more()->witnessed << dendl;
+
+
   // -- locks --
 
   // straydn?
@@ -4090,12 +4109,20 @@ void Server::handle_client_rename(MDRequest *mdr)
     wrlocks.insert(&straydn->get_dir()->inode->nestlock);
   }
 
+  // xlock versionlock on srci if there are any witnesses
+  //  replicas can't see projected dentry linkages, and will get confused
+  //  if we try to pipeline things.
+  if (!witnesses.empty())
+    xlocks.insert(&srci->versionlock);
+
+  /*
   // xlock versionlock on srci if remote?
   //  this ensures it gets safely remotely auth_pinned, avoiding deadlock;
   //  strictly speaking, having the slave node freeze the inode is 
   //  otherwise sufficient for avoiding conflicts with inode locks, etc.
-  if (!srcdn->is_auth() && srcdnl->is_primary())
-    xlocks.insert(&srci->versionlock);
+  if (!srcdn->is_auth() && srcdnl->is_primary())  // xlock versionlock on srci if there are any witnesses
+      xlocks.insert(&srci->versionlock);
+  */
 
   // we need to update srci's ctime.  xlock its least contended lock to do that...
   xlocks.insert(&srci->linklock);
@@ -4159,22 +4186,6 @@ void Server::handle_client_rename(MDRequest *mdr)
     mdr->now = g_clock.real_now();
 
   // -- prepare witnesses --
-  /*
-   * NOTE: we use _all_ replicas as witnesses.
-   * this probably isn't totally necessary (esp for file renames),
-   * but if/when we change that, we have to make sure rejoin is
-   * sufficiently robust to handle strong rejoins from survivors
-   * with totally wrong dentry->inode linkage.
-   * (currently, it can ignore rename effects, because the resolve
-   * stage will sort them out.)
-   */
-  set<int> witnesses = mdr->more()->extra_witnesses;
-  if (srcdn->is_auth())
-    srcdn->list_replicas(witnesses);
-  else
-    witnesses.insert(srcdn->authority().first);
-  destdn->list_replicas(witnesses);
-  dout(10) << " witnesses " << witnesses << ", have " << mdr->more()->witnessed << dendl;
 
   // do srcdn auth last
   int last = -1;