input/nfs: use the asynchronous libnfs API

More robust and cancellable.

src/lib/nfs/Connection.hxx

@@ -0,0 +1,160 @@
+/*
+ * Copyright (C) 2003-2014 The Music Player Daemon Project
+ * http://www.musicpd.org
+ *
+ * This program is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by
+ * the Free Software Foundation; either version 2 of the License, or
+ * (at your option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License along
+ * with this program; if not, write to the Free Software Foundation, Inc.,
+ * 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA.
+ */
+
+#ifndef MPD_NFS_CONNECTION_HXX
+#define MPD_NFS_CONNECTION_HXX
+
+#include "Lease.hxx"
+#include "Cancellable.hxx"
+#include "thread/Mutex.hxx"
+#include "event/SocketMonitor.hxx"
+#include "event/DeferredMonitor.hxx"
+#include "util/Error.hxx"
+
+#include <string>
+#include <list>
+
+struct nfs_context;
+class NfsCallback;
+
+/**
+ * An asynchronous connection to a NFS server.
+ */
+class NfsConnection : SocketMonitor, DeferredMonitor {
+	class CancellableCallback : public CancellablePointer<NfsCallback> {
+		NfsConnection &connection;
+
+	public:
+		explicit constexpr CancellableCallback(NfsCallback &_callback,
+						       NfsConnection &_connection)
+			:CancellablePointer<NfsCallback>(_callback),
+			 connection(_connection) {}
+
+		bool Open(nfs_context *context, const char *path, int flags,
+			  Error &error);
+		bool Stat(nfs_context *context, struct nfsfh *fh,
+			  Error &error);
+		bool Read(nfs_context *context, struct nfsfh *fh,
+			  uint64_t offset, size_t size,
+			  Error &error);
+
+	private:
+		static void Callback(int err, struct nfs_context *nfs,
+				     void *data, void *private_data);
+		void Callback(int err, void *data);
+	};
+
+	std::string server, export_name;
+
+	nfs_context *context;
+
+	Mutex mutex;
+
+	typedef std::list<NfsLease *> LeaseList;
+	LeaseList new_leases, active_leases;
+
+	typedef CancellableList<NfsCallback, CancellableCallback> CallbackList;
+	CallbackList callbacks;
+
+	Error postponed_mount_error;
+
+	/**
+	 * True when nfs_service() is being called.  During that,
+	 * nfs_client_free() is postponed, or libnfs will crash.  See
+	 * #postponed_destroy.
+	 */
+	bool in_service;
+
+	/**
+	 * True when OnSocketReady() is being called.  During that,
+	 * event updates are omitted.
+	 */
+	bool in_event;
+
+	/**
+	 * True when nfs_client_free() has been called while #in_service
+	 * was true.
+	 */
+	bool postponed_destroy;
+
+	bool mount_finished;
+
+public:
+	gcc_nonnull_all
+	NfsConnection(EventLoop &_loop,
+		      const char *_server, const char *_export_name)
+		:SocketMonitor(_loop), DeferredMonitor(_loop),
+		 server(_server), export_name(_export_name),
+		 context(nullptr) {}
+
+	~NfsConnection();
+
+	gcc_pure
+	const char *GetServer() const {
+		return server.c_str();
+	}
+
+	gcc_pure
+	const char *GetExportName() const {
+		return export_name.c_str();
+	}
+
+	/**
+	 * Ensure that the connection is established.  The connection
+	 * is kept up while at least one #NfsLease is registered.
+	 *
+	 * This method is thread-safe.  However, #NfsLease's methods
+	 * will be invoked from within the #EventLoop's thread.
+	 */
+	void AddLease(NfsLease &lease);
+	void RemoveLease(NfsLease &lease);
+
+	bool Open(const char *path, int flags, NfsCallback &callback,
+		  Error &error);
+	bool Stat(struct nfsfh *fh, NfsCallback &callback, Error &error);
+	bool Read(struct nfsfh *fh, uint64_t offset, size_t size,
+		  NfsCallback &callback, Error &error);
+	void Cancel(NfsCallback &callback);
+
+	void Close(struct nfsfh *fh);
+
+protected:
+	virtual void OnNfsConnectionError(Error &&error) = 0;
+
+private:
+	void DestroyContext();
+	bool MountInternal(Error &error);
+	void BroadcastMountSuccess();
+	void BroadcastMountError(Error &&error);
+	void BroadcastError(Error &&error);
+
+	static void MountCallback(int status, nfs_context *nfs, void *data,
+				  void *private_data);
+	void MountCallback(int status, nfs_context *nfs, void *data);
+
+	void ScheduleSocket();
+
+	/* virtual methods from SocketMonitor */
+	virtual bool OnSocketReady(unsigned flags) override;
+
+	/* virtual methods from DeferredMonitor */
+	virtual void RunDeferred() override;
+};
+
+#endif