mds: add MDSContext subclasses

These allow contexts within the MDS to identify themselves
as either 'internal' contexts (expecting to be called within
the big MDS lock) or 'IO' contexts (which should take the big
mds lock themselves when called back).

Signed-off-by: John Spray <john.spray@redhat.com>

diff --git a/src/mds/MDSContext.cc b/src/mds/MDSContext.cc
new file mode 100644 (file)
index 0000000..4894aec
--- /dev/null
+++ b/src/mds/MDSContext.cc
@@ -0,0 +1,57 @@
+// -*- mode:C++; tab-width:8; c-basic-offset:2; indent-tabs-mode:t -*- 
+// vim: ts=8 sw=2 smarttab
+/*
+ * Ceph - scalable distributed file system
+ *
+ * Copyright (C) 2012 Red Hat
+ *
+ * This is free software; you can redistribute it and/or
+ * modify it under the terms of the GNU Lesser General Public
+ * License version 2.1, as published by the Free Software 
+ * Foundation.  See file COPYING.
+ * 
+ */
+
+
+#include "MDS.h"
+
+#include "MDSContext.h"
+
+#include "common/dout.h"
+#define dout_subsys ceph_subsys_mds
+
+
+void MDSInternalContextBase::complete(int r) {
+  MDS *mds = get_mds();
+
+  dout(10) << "MDSInternalContextBase::complete: " << typeid(*this).name() << dendl;
+  assert(mds != NULL);
+  assert(mds->mds_lock.is_locked_by_me());
+  MDSContext::complete(r);
+}
+
+
+MDS *MDSInternalContext::get_mds() {
+  return mds;
+}
+
+
+void MDSIOContextBase::complete(int r) {
+  MDS *mds = get_mds();
+
+  dout(10) << "MDSIOContextBase::complete: " << typeid(*this).name() << dendl;
+  assert(mds != NULL);
+  Mutex::Locker l(mds->mds_lock);
+  MDSContext::complete(r);
+}
+
+MDS *MDSIOContext::get_mds() {
+  return mds;
+}
+
+MDS *MDSInternalContextGather::get_mds()
+{
+  derr << "Forbidden call to MDSInternalContextGather::get_mds by " << typeid(*this).name() << dendl;
+  assert(0);
+}
+

diff --git a/src/mds/MDSContext.h b/src/mds/MDSContext.h
new file mode 100644 (file)
index 0000000..0d30705
--- /dev/null
+++ b/src/mds/MDSContext.h
@@ -0,0 +1,135 @@
+// -*- mode:C++; tab-width:8; c-basic-offset:2; indent-tabs-mode:t -*- 
+// vim: ts=8 sw=2 smarttab
+/*
+ * Ceph - scalable distributed file system
+ *
+ * Copyright (C) 2012 Red Hat
+ *
+ * This is free software; you can redistribute it and/or
+ * modify it under the terms of the GNU Lesser General Public
+ * License version 2.1, as published by the Free Software 
+ * Foundation.  See file COPYING.
+ * 
+ */
+
+
+#ifndef MDS_CONTEXT_H
+#define MDS_CONTEXT_H
+
+#include "include/Context.h"
+
+class MDS;
+
+
+/**
+ * Completion which has access to a reference to the global MDS instance.
+ *
+ * This class exists so that Context subclasses can provide the MDS pointer
+ * from a pointer they already had, e.g. MDCache or Locker, rather than
+ * necessarily having to carry around an extra MDS* pointer. 
+ */
+class MDSContext : public Context
+{
+protected:
+  virtual MDS *get_mds() = 0;
+};
+
+
+/**
+ * A context which must be called with the big MDS lock held.  Subclass
+ * this with a get_mds implementation.
+ */
+class MDSInternalContextBase : public MDSContext
+{
+public:
+    void complete(int r);
+};
+
+/**
+ * General purpose, lets you pass in an MDS pointer.
+ */
+class MDSInternalContext : public MDSInternalContextBase
+{
+protected:
+  MDS *mds;
+  virtual MDS* get_mds();
+
+public:
+  MDSInternalContext(MDS *mds_) : mds(mds_) {}
+};
+
+
+class MDSIOContextBase : public MDSContext
+{
+    void complete(int r);
+};
+
+/**
+ * Completion for an I/O operation, takes big MDS lock
+ * before executing finish function.
+ */
+class MDSIOContext : public MDSIOContextBase
+{
+protected:
+  MDS *mds;
+  virtual MDS* get_mds();
+
+public:
+  MDSIOContext(MDS *mds_) : mds(mds_) {}
+};
+
+
+/**
+ * No-op for callers expecting MDSInternalContextBase
+ */
+class C_MDSInternalNoop : public MDSInternalContext
+{
+public:
+  C_MDSInternalNoop() : MDSInternalContext(NULL) {}
+  void finish(int r) {}
+  void complete(int r) {}
+};
+
+
+/**
+ * This class is used where you have an MDSInternalContextBase but
+ * you sometimes want to call it back from an I/O completion.
+ */
+class C_IO_Wrapper : public MDSIOContext
+{
+private:
+  MDSInternalContextBase *wrapped;
+public:
+  C_IO_Wrapper(MDS *mds_, MDSInternalContextBase *wrapped_) : MDSIOContext(mds_), wrapped(wrapped_) {
+    assert(wrapped != NULL);
+  }
+  virtual void finish(int r) {
+    wrapped->complete(r);
+  }
+};
+
+
+/**
+ * Gather needs a default-constructable class
+ */
+class MDSInternalContextGather : public MDSInternalContextBase
+{
+protected:
+  MDS *get_mds();
+};
+
+
+class MDSGather : public C_GatherBase<MDSInternalContextBase, MDSInternalContextGather>
+{
+public:
+  MDSGather(CephContext *cct, MDSInternalContextBase *onfinish) : C_GatherBase<MDSInternalContextBase, MDSInternalContextGather>(cct, onfinish) {}
+protected:
+  virtual MDS *get_mds() {return NULL;}
+};
+
+
+typedef C_GatherBuilderBase<MDSInternalContextBase, MDSGather> MDSGatherBuilder;
+
+
+#endif  // MDS_CONTEXT_H
+

diff --git a/src/mds/Makefile.am b/src/mds/Makefile.am
index 9cb725cbabcb6946b78e85ebc85c5fa544710600..4901d36b24ba8c3759fc326594f99d6d44b5712c 100644 (file)
--- a/src/mds/Makefile.am
+++ b/src/mds/Makefile.am
@@ -24,6 +24,7 @@ libmds_la_SOURCES = \
        mds/SnapServer.cc \
        mds/snap.cc \
        mds/SessionMap.cc \
+       mds/MDSContext.cc \
        mds/MDLog.cc \
        common/TrackedOp.cc
 libmds_la_LIBADD = $(LIBOSDC)
@@ -49,6 +50,7 @@ noinst_HEADERS += \
        mds/RecoveryQueue.h \
        mds/MDLog.h \
        mds/MDS.h \
+       mds/MDSContext.h \
        mds/MDSMap.h \
        mds/MDSTable.h \
        mds/MDSTableServer.h \