mds: only return pdnvec for full path_traverse

We should only return the pdnvec for a full traverse.  i.e., either a
success, or a failure in which we instantiate a null dn for the trailing
entry.  This makes pdnvec well defined, and allows callers like
rdlock_path_pin_ref() to reply with a null lease when appropriate.

Signed-off-by: Sage Weil <sage@newdream.net>

diff --git a/src/mds/MDCache.cc b/src/mds/MDCache.cc
index 83b41eaa7e48219d1d2e1f0a560183791690972e..817b7500bc4f1f4b23aa1abf10bad185bce43b64 100644 (file)
--- a/src/mds/MDCache.cc
+++ b/src/mds/MDCache.cc
@@ -5774,6 +5774,14 @@ Context *MDCache::_get_waiter(MDRequest *mdr, Message *req)
   }
 }
 
+/*
+ * Returns 0 on success, >0 if request has been put on hold or otherwise dealt with,
+ * <0 if there's been a failure the caller needs to clean up from.
+ *
+ * on succes, @pdnvec points to a vector of dentries we traverse.  
+ * on failure, @pdnvec it is either the full trace, up to and
+ *             including the final null dn, or empty.
+ */
 int MDCache::path_traverse(MDRequest *mdr, Message *req,     // who
                           const filepath& path,                   // what
                            vector<CDentry*> *pdnvec,         // result
@@ -6004,8 +6012,11 @@ int MDCache::path_traverse(MDRequest *mdr, Message *req,     // who
       if (curdir->is_complete()) {
         // file not found
        if (pdnvec) {
-         // instantiate a null dn
-         if (dn) {
+         // instantiate a null dn?
+         if (depth < path.depth()-1){
+           dout(20) << " didn't traverse full path; not returning pdnvec" << dendl;
+           dn = NULL;
+         } else if (dn) {
            dout(20) << " had null " << *dn << dendl;
            assert(dnl->is_null());
          } else if (curdir->is_frozen()) {
@@ -6019,6 +6030,8 @@ int MDCache::path_traverse(MDRequest *mdr, Message *req,     // who
          }
          if (dn)
            pdnvec->push_back(dn);
+         else
+           pdnvec->clear();   // do not confuse likes of rdlock_path_pin_ref();
        }
         return -ENOENT;
       } else {