Improve file descriptor leak detection to display likely culprit and filename.

WHATS_NEW

@@ -1,5 +1,6 @@
 Version 2.02.40 - 
 ================================
+  Improve file descriptor leak detection to display likely culprit and filename.
   Change clustered mirror kernel module name from cmirror to dm-log-clustered.
   Avoid looping forever in _pv_analyze_mda_raw used by pvck.
   Change lvchange exit status to indicate if any part of the operation failed.

lib/datastruct/lvm-types.h

@@ -24,6 +24,7 @@
 /* Define some portable printing types */
 #define PRIsize_t "zu"
 #define PRIptrdiff_t "td"
+#define PRIpid_t PRId32
 
 struct str_list {
 	struct list list;

tools/lvmcmdline.c

@@ -1001,11 +1001,76 @@ static void _init_rand(void)
 	srand((unsigned) time(NULL) + (unsigned) getpid());
 }
 
-static void _close_stray_fds(void)
+static const char *_get_cmdline(pid_t pid)
+{
+	static char _proc_cmdline[32];
+	char buf[256];
+	int fd;
+
+	snprintf(buf, sizeof(buf), DEFAULT_PROC_DIR "/%u/cmdline", pid);
+	if ((fd = open(buf, O_RDONLY)) > 0) {
+		read(fd, _proc_cmdline, sizeof(_proc_cmdline) - 1);
+		_proc_cmdline[sizeof(_proc_cmdline) - 1] = '\0';
+		close(fd);
+	} else
+		_proc_cmdline[0] = '\0';
+
+	return _proc_cmdline;
+}
+
+static const char *_get_filename(int fd)
+{
+	static char filename[PATH_MAX];
+	char buf[32];	/* Assumes short DEFAULT_PROC_DIR */
+	int size;
+
+	snprintf(buf, sizeof(buf), DEFAULT_PROC_DIR "/self/fd/%u", fd);
+
+	if ((size = readlink(buf, filename, sizeof(filename) - 1)) == -1)
+		filename[0] = '\0';
+	else
+		filename[size] = '\0';
+
+	return filename;
+}
+
+static void _close_descriptor(int fd, unsigned suppress_warnings,
+			      const char *command, pid_t ppid,
+			      const char *parent_cmdline)
+{
+	int r;
+	const char *filename;
+
+	/* Ignore bad file descriptors */
+	if (fcntl(fd, F_GETFD) == -1 && errno == EBADF)
+		return;
+
+	if (!suppress_warnings)
+		filename = _get_filename(fd);
+
+	r = close(fd);
+	if (suppress_warnings)
+		return;
+
+	if (!r)
+		fprintf(stderr, "File descriptor %d (%s) leaked on "
+			"%s invocation.", fd, filename, command);
+	else if (errno == EBADF)
+		return;
+	else
+		fprintf(stderr, "Close failed on stray file descriptor "
+			"%d (%s): %s", fd, filename, strerror(errno));
+
+	fprintf(stderr, " Parent PID %" PRIpid_t ": %s\n", ppid, parent_cmdline);
+}
+
+static void _close_stray_fds(const char *command)
 {
 	struct rlimit rlim;
 	int fd;
-	int suppress_warnings = 0;
+	unsigned suppress_warnings = 0;
+	pid_t ppid = getppid();
+	const char *parent_cmdline = _get_cmdline(ppid);
 
 	if (getrlimit(RLIMIT_NOFILE, &rlim) < 0) {
 		fprintf(stderr, "getrlimit(RLIMIT_NOFILE) failed: %s\n",
@@ -1016,15 +1081,9 @@ static void _close_stray_fds(void)
 	if (getenv("LVM_SUPPRESS_FD_WARNINGS"))
 		suppress_warnings = 1;
 
-	for (fd = 3; fd < rlim.rlim_cur; fd++) {
+	for (fd = 3; fd < rlim.rlim_cur; fd++)
-		if (suppress_warnings)
+		_close_descriptor(fd, suppress_warnings, command, ppid,
-			close(fd);
+				  parent_cmdline);
-		else if (!close(fd))
-			fprintf(stderr, "File descriptor %d left open\n", fd);
-		else if (errno != EBADF)
-			fprintf(stderr, "Close failed on stray file "
-				"descriptor %d: %s\n", fd, strerror(errno));
-	}
 }
 
 struct cmd_context *init_lvm(unsigned is_static)
@@ -1162,13 +1221,13 @@ int lvm2_main(int argc, char **argv, unsigned is_static)
 	int ret, alias = 0;
 	struct cmd_context *cmd;
 
-	_close_stray_fds();
-
 	base = last_path_component(argv[0]);
 	if (strcmp(base, "lvm") && strcmp(base, "lvm.static") &&
 	    strcmp(base, "initrd-lvm"))
 		alias = 1;
 
+	_close_stray_fds(base);
+
 	if (is_static && strcmp(base, "lvm.static") &&
 	    path_exists(LVM_SHARED_PATH) &&
 	    !getenv("LVM_DID_EXEC")) {