partprobe: new applet

function                                             old     new   delta
partprobe_main                                         -      79     +79
packed_usage                                       31485   31511     +26
applet_names                                        2608    2618     +10
applet_main                                         1512    1516      +4
applet_install_loc                                   189     190      +1
------------------------------------------------------------------------------
(add/remove: 2/0 grow/shrink: 4/0 up/down: 120/0)             Total: 120 bytes

Signed-off-by: Denys Vlasenko <vda.linux@googlemail.com>

miscutils/partprobe.c

@@ -0,0 +1,56 @@
+/* vi: set sw=4 ts=4: */
+/*
+ * Copyright (C) 2017 Denys Vlasenko <vda.linux@googlemail.com>
+ *
+ * Licensed under GPLv2, see file LICENSE in this source tree.
+ */
+//config:config PARTPROBE
+//config:	bool "partprobe"
+//config:	default y
+//config:	select PLATFORM_LINUX
+//config:	help
+//config:	  Ask kernel to rescan partition table.
+
+//applet:IF_PARTPROBE(APPLET(partprobe, BB_DIR_USR_SBIN, BB_SUID_DROP))
+
+//kbuild:lib-$(CONFIG_PARTPROBE) += partprobe.o
+
+#include <linux/fs.h>
+#include "libbb.h"
+#ifndef BLKRRPART
+# define BLKRRPART _IO(0x12,95)
+#endif
+
+//usage:#define partprobe_trivial_usage
+//usage:	"DEVICE..."
+//usage:#define partprobe_full_usage "\n\n"
+//usage:	"Ask kernel to rescan partition table"
+//
+// partprobe (GNU parted) 3.2:
+// -d, --dry-run	Don't update the kernel
+// -s, --summary	Show a summary of devices and their partitions
+
+int partprobe_main(int argc, char **argv) MAIN_EXTERNALLY_VISIBLE;
+int partprobe_main(int argc UNUSED_PARAM, char **argv)
+{
+	getopt32(argv, "");
+	argv += optind;
+
+	/* "partprobe" with no arguments just does nothing */
+
+	while (*argv) {
+		int fd = xopen(*argv, O_RDONLY);
+		/*
+		 * Newer versions of parted scan partition tables themselves and
+		 * use BLKPG ioctl (BLKPG_DEL_PARTITION / BLKPG_ADD_PARTITION)
+		 * since this way kernel does not need to know
+		 * partition table formats.
+		 * We use good old BLKRRPART:
+		 */
+		ioctl_or_perror_and_die(fd, BLKRRPART, NULL, "%s", *argv);
+		close(fd);
+		argv++;
+	}
+
+	return EXIT_SUCCESS;
+}