utils: add errno logs for exception case

src/lxc/utils.c

@@ -1418,8 +1418,10 @@ static int lxc_get_unused_loop_dev_legacy(char *loop_name)
 	int dfd = -1, fd = -1, ret = -1;
 
 	dir = opendir("/dev");
-	if (!dir)
+	if (!dir) {
+		SYSERROR("Failed to open \"/dev\"");
 		return -1;
+	}
 
 	while ((dp = readdir(dir))) {
 		if (strncmp(dp->d_name, "loop", 4) != 0)
@@ -1467,12 +1469,16 @@ static int lxc_get_unused_loop_dev(char *name_loop)
 	int fd_ctl = -1, fd_tmp = -1;
 
 	fd_ctl = open("/dev/loop-control", O_RDWR | O_CLOEXEC);
-	if (fd_ctl < 0)
+	if (fd_ctl < 0) {
+		SYSERROR("Failed to open loop control");
 		return -ENODEV;
+	}
 
 	loop_nr = ioctl(fd_ctl, LOOP_CTL_GET_FREE);
-	if (loop_nr < 0)
+	if (loop_nr < 0) {
+		SYSERROR("Failed to get loop control");
 		goto on_error;
+	}
 
 	ret = snprintf(name_loop, LO_NAME_SIZE, "/dev/loop%d", loop_nr);
 	if (ret < 0 || ret >= LO_NAME_SIZE)
@@ -1480,7 +1486,7 @@ static int lxc_get_unused_loop_dev(char *name_loop)
 
 	fd_tmp = open(name_loop, O_RDWR | O_CLOEXEC);
 	if (fd_tmp < 0)
-		goto on_error;
+		SYSERROR("Failed to open loop \"%s\"", name_loop);
 
 on_error:
 	close(fd_ctl);
@@ -1495,26 +1501,34 @@ int lxc_prepare_loop_dev(const char *source, char *loop_dev, int flags)
 
 	fd_loop = lxc_get_unused_loop_dev(loop_dev);
 	if (fd_loop < 0) {
-		if (fd_loop == -ENODEV)
-			fd_loop = lxc_get_unused_loop_dev_legacy(loop_dev);
-		else
+		if (fd_loop != -ENODEV)
+			goto on_error;
+
+		fd_loop = lxc_get_unused_loop_dev_legacy(loop_dev);
+		if (fd_loop < 0)
 			goto on_error;
 	}
 
 	fd_img = open(source, O_RDWR | O_CLOEXEC);
-	if (fd_img < 0)
+	if (fd_img < 0) {
+		SYSERROR("Failed to open source \"%s\"", source);
 		goto on_error;
+	}
 
 	ret = ioctl(fd_loop, LOOP_SET_FD, fd_img);
-	if (ret < 0)
+	if (ret < 0) {
+		SYSERROR("Failed to set loop fd");
 		goto on_error;
+	}
 
 	memset(&lo64, 0, sizeof(lo64));
 	lo64.lo_flags = flags;
 
 	ret = ioctl(fd_loop, LOOP_SET_STATUS64, &lo64);
-	if (ret < 0)
+	if (ret < 0) {
+		SYSERROR("Failed to set loop status64");
 		goto on_error;
+	}
 
 	fret = 0;
 
@@ -1681,10 +1695,8 @@ int lxc_set_death_signal(int signal, pid_t parent)
 			return -1;
 	}
 
-	if (ret < 0) {
-		SYSERROR("Failed to set PR_SET_PDEATHSIG to %d", signal);
+	if (ret < 0)
 		return -1;
-	}
 
 	return 0;
 }