Merge pull request #13084 from linuxbox2/wip-librgw-parentref

rgw_file:  interned RGWFileHandle objects need parent refs

src/rgw/rgw_file.cc

@@ -716,6 +716,19 @@ namespace rgw {
     } while (! (stop || shutdown));
   } /* RGWLibFS::gc */
 
+  RGWFileHandle::~RGWFileHandle() {
+    if (parent && (! parent->is_root())) {
+      /* safe because if parent->unref causes its deletion,
+       * there are a) by refcnt, no other objects/paths pointing
+       * to it and b) by the semantics of valid iteration of
+       * fh_lru (observed, e.g., by cohort_lru<T,...>::drain())
+       * no unsafe iterators reaching it either--n.b., this constraint
+       * is binding oncode which may in future attempt to e.g.,
+       * cause the eviction of objects in LRU order */
+      (void) get_fs()->fh_lru.unref(parent, cohort::lru::FLAG_NONE);
+    }
+  }
+
   void RGWFileHandle::encode_attrs(ceph::buffer::list& ux_key1,
 				   ceph::buffer::list& ux_attrs1)
   {

src/rgw/rgw_file.h

@@ -640,7 +640,7 @@ namespace rgw {
     typedef cohort::lru::TreeX<RGWFileHandle, FhTree, FhLT, FhEQ, fh_key,
 			       std::mutex> FHCache;
 
-    virtual ~RGWFileHandle() {}
+    virtual ~RGWFileHandle();
 
     class Factory : public cohort::lru::ObjectFactory
     {
@@ -958,6 +958,10 @@ namespace rgw {
 	  /* inserts, releasing latch */
 	  fh_cache.insert_latched(fh, lat, RGWFileHandle::FHCache::FLAG_UNLOCK);
 	  get<1>(fhr) |= RGWFileHandle::FLAG_CREATE;
+	  /* ref parent (non-initial ref cannot fail on valid object) */
+	  if (! parent->is_root()) {
+	    (void) fh_lru.ref(parent, cohort::lru::FLAG_NONE);
+	  }
 	  goto out; /* !LATCHED */
 	} else {
 	  lat.lock->unlock();