mds: don't purge strays when mds is in clientreplay state

MDS does not trim log when it's in clientreplay state. If mds hang
at clientreplay state (due to bug), purging strays can submit lots
of log events and create very large mds log.

Signed-off-by: "Yan, Zheng" <zyan@redhat.com>

src/mds/MDCache.h

@@ -146,6 +146,10 @@ class MDCache {
     stray_index = (stray_index+1)%NUM_STRAY;
   }
 
+  void activate_stray_manager() {
+    stray_manager.activate();
+  }
+
   /**
    * Call this when you know that a CDentry is ready to be passed
    * on to StrayManager (i.e. this is a stray you've just created)

src/mds/MDSRank.cc

@@ -1285,6 +1285,7 @@ void MDSRank::active_start()
   mdcache->start_files_to_recover();
 
   mdcache->reissue_all_caps();
+  mdcache->activate_stray_manager();
 
   finish_contexts(g_ceph_context, waiting_for_active);  // kick waiters
 }

src/mds/StrayManager.cc

@@ -433,6 +433,11 @@ bool StrayManager::_consume(CDentry *dn, bool trunc, uint32_t ops_required)
 {
   const int files_avail = g_conf->mds_max_purge_files - files_purging;
 
+  if (!started) {
+    dout(20) << __func__ << ": haven't started purging yet" << dendl;
+    return false;
+  }
+
   if (files_avail <= 0) {
     dout(20) << __func__ << ": throttling on max files" << dendl;
     return false;
@@ -732,6 +737,13 @@ bool StrayManager::__eval_stray(CDentry *dn, bool delay)
   }
 }
 
+void StrayManager::activate()
+{
+  dout(10) << __func__ << dendl;
+  started = true;
+  _advance();
+}
+
 bool StrayManager::eval_stray(CDentry *dn, bool delay)
 {
   // avoid nested eval_stray
@@ -838,7 +850,7 @@ void StrayManager::migrate_stray(CDentry *dn, mds_rank_t to)
 
 StrayManager::StrayManager(MDSRank *mds)
   : delayed_eval_stray(member_offset(CDentry, item_stray)),
-    mds(mds), logger(NULL),
+    mds(mds), logger(NULL), started(false),
     ops_in_flight(0), files_purging(0),
     max_purge_ops(0), 
     num_strays(0), num_strays_purging(0), num_strays_delayed(0),

src/mds/StrayManager.h

@@ -55,6 +55,8 @@ class StrayManager
   MDSRank *mds;
   PerfCounters *logger;
 
+  bool started;
+
   // Throttled allowances
   uint64_t ops_in_flight;
   uint64_t files_purging;
@@ -168,6 +170,7 @@ class StrayManager
   public:
   explicit StrayManager(MDSRank *mds);
   void set_logger(PerfCounters *l) {logger = l;}
+  void activate();
 
   bool eval_stray(CDentry *dn, bool delay=false);