mds: simplify and explain expiry finisher ctx

Signed-off-by: Patrick Donnelly <[email protected]>

Author: batrick

src/mds/MDSRank.cc

@@ -152,35 +152,23 @@ class C_Flush_Journal : public MDSInternalContext {
             << " segments to expire" << dendl;
 
     if (!expiry_gather.has_subs()) {
-      trim_segments();
+      trim_expired_segments();
       return;
     }
 
-    Context *ctx = new LambdaContext([this](int r) {
-        handle_expire_segments(r);
-      });
+    /* Because this context may be finished with the MDLog::submit_mutex held,
+     * complete it in the MDS finisher thread.
+     */
+    Context *ctx = new C_OnFinisher(new LambdaContext([this,mds=mds](int r) {
+        ceph_assert(r == 0); // MDLog is not allowed to raise errors via
+                             // wait_for_expiry
+        std::lock_guard locker(mds->mds_lock);
+        trim_expired_segments();
+      }), mds->finisher);
     expiry_gather.set_finisher(new MDSInternalContextWrapper(mds, ctx));
     expiry_gather.activate();
   }
 
-  void handle_expire_segments(int r) {
-    dout(20) << __func__ << ": r=" << r << dendl;
-
-    ceph_assert(r == 0); // MDLog is not allowed to raise errors via
-                         // wait_for_expiry
-    trim_segments();
-  }
-
-  void trim_segments() {
-    dout(20) << __func__ << dendl;
-
-    Context *ctx = new C_OnFinisher(new LambdaContext([this](int) {
-          std::lock_guard locker(mds->mds_lock);
-          trim_expired_segments();
-        }), mds->finisher);
-    ctx->complete(0);
-  }
-
   void trim_expired_segments() {
     ceph_assert(ceph_mutex_is_locked_by_me(mds->mds_lock));
     dout(5) << __func__ << ": expiry complete, expire_pos/trim_pos is now "