common/pipe: add function to do pipe2(O_CLOEXEC)

Support old systems that don't have O_CLOEXEC.

Signed-off-by: Colin McCabe <colin.mccabe@dreamhost.com>

src/Makefile.am

@@ -817,6 +817,7 @@ libcommon_files = \
 	osd/osd_types.cc \
 	mds/MDSMap.cc \
 	common/common_init.cc \
+	common/pipe.c \
 	common/ceph_argparse.cc \
 	common/ceph_context.cc \
 	common/buffer.cc \
@@ -1024,6 +1025,7 @@ noinst_HEADERS = \
 	global/global_init.h \
 	global/global_context.h \
         common/common_init.h\
+        common/pipe.h\
 	common/code_environment.h \
         common/signal.h\
         global/signal_handler.h\

src/common/admin_socket.cc

@@ -12,13 +12,14 @@
  * 
  */
 
-#include "common/admin_socket.h"
-#include "common/perf_counters.h"
 #include "common/Thread.h"
+#include "common/admin_socket.h"
 #include "common/config.h"
 #include "common/config_obs.h"
 #include "common/dout.h"
 #include "common/errno.h"
+#include "common/perf_counters.h"
+#include "common/pipe.h"
 #include "common/safe_io.h"
 
 #include <errno.h>
@@ -110,11 +111,10 @@ public:
   static std::string create_shutdown_pipe(int *pipe_rd, int *pipe_wr)
   {
     int pipefd[2];
-    int ret = pipe2(pipefd, O_CLOEXEC);
+    int ret = pipe_cloexec(pipefd);
     if (ret < 0) {
-      int err = errno;
       ostringstream oss;
-      oss << "AdminSocket::create_shutdown_pipe error: " << cpp_strerror(err);
+      oss << "AdminSocket::create_shutdown_pipe error: " << cpp_strerror(ret);
       return oss.str();
     }
 

src/common/pipe.c

@@ -0,0 +1,44 @@
+// -*- 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) 2011 New Dream Network
+ *
+ * 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 "common/pipe.h"
+
+#include <errno.h>
+#include <fcntl.h>
+#include <unistd.h>
+#include <unistd.h>
+
+int pipe_cloexec(int pipefd[2])
+{
+#ifdef O_CLOEXEC
+	int ret;
+	ret = pipe2(pipefd, O_CLOEXEC);
+	if (ret) {
+		ret = -errno;
+		return ret;
+	}
+	return 0;
+#else
+	/* The old-fashioned, race-condition prone way that we have to fall back on if
+	 * O_CLOEXEC does not exist. */
+	int ret = pipe(pipefd);
+	if (ret) {
+		ret = -errno;
+		return ret;
+	}
+	fcntl(pipefd[0], F_SETFD, FD_CLOEXEC);
+	fcntl(pipefd[1], F_SETFD, FD_CLOEXEC);
+	return 0;
+#endif
+}

src/common/pipe.h

@@ -0,0 +1,33 @@
+// -*- 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) 2011 New Dream Network
+ *
+ * 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 CEPH_COMMON_PIPE_H
+#define CEPH_COMMON_PIPE_H
+
+#ifdef __cplusplus
+extern "C" {
+#endif
+
+/** Create a pipe and set both ends to have F_CLOEXEC
+ *
+ * @param pipefd	pipe array, just as in pipe(2)
+ * @return		0 on success, errno otherwise 
+ */
+int pipe_cloexec(int pipefd[2]);
+
+#ifdef __cplusplus
+}
+#endif
+
+#endif