blkdiscard: new applet

function                                             old     new   delta
blkdiscard_main                                        -     264    +264

Signed-off-by: Ari Sundholm <ari@tuxera.com>
Signed-off-by: Denys Vlasenko <vda.linux@googlemail.com>

util-linux/blkdiscard.c

@@ -0,0 +1,83 @@
+/*
+ * Mini blkdiscard implementation for busybox
+ *
+ * Copyright (C) 2015 by Ari Sundholm <ari@tuxera.com> and Tuxera Inc.
+ *
+ * Licensed under GPLv2 or later, see file LICENSE in this source tree.
+ */
+
+//config:config BLKDISCARD
+//config:	bool "blkdiscard"
+//config:	default y
+//config:	help
+//config:	  blkdiscard discards sectors on a given device.
+
+//kbuild:lib-$(CONFIG_BLKDISCARD) += blkdiscard.o
+//applet:IF_BLKDISCARD(APPLET(blkdiscard, BB_DIR_USR_BIN, BB_SUID_DROP))
+
+//usage:#define blkdiscard_trivial_usage
+//usage:       "[-o OFS] [-l LEN] [-s] DEVICE"
+//usage:#define blkdiscard_full_usage "\n\n"
+//usage:	"Discard sectors on DEVICE\n"
+//usage:	"\n	-o OFS	Byte offset into device"
+//usage:	"\n	-l LEN	Number of bytes to discard"
+//usage:	"\n	-s	Perform a secure discard"
+//usage:
+//usage:#define blkdiscard_example_usage
+//usage:	"$ blkdiscard -o 0 -l 1G /dev/sdb"
+
+#include "libbb.h"
+#include <linux/fs.h>
+
+int blkdiscard_main(int argc, char **argv) MAIN_EXTERNALLY_VISIBLE;
+int blkdiscard_main(int argc UNUSED_PARAM, char **argv)
+{
+	unsigned opts;
+	const char *offset_str = "0";
+	const char *length_str;
+	uint64_t offset; /* Leaving these two variables out does not  */
+	uint64_t length; /* shrink code size and hampers readability. */
+	uint64_t range[2];
+//	struct stat st;
+	int fd;
+
+	enum {
+		OPT_OFFSET = (1 << 0),
+		OPT_LENGTH = (1 << 1),
+		OPT_SECURE = (1 << 2),
+	};
+
+	opt_complementary = "=1";
+	opts = getopt32(argv, "o:l:s", &offset_str, &length_str);
+	argv += optind;
+
+	fd = xopen(argv[0], O_RDWR|O_EXCL);
+//Why bother, BLK[SEC]DISCARD will fail on non-blockdevs anyway?
+//	xfstat(fd, &st);
+//	if (!S_ISBLK(st.st_mode))
+//		bb_error_msg_and_die("%s: not a block device", argv[0]);
+
+	offset = xatoull_sfx(offset_str, kMG_suffixes);
+
+	if (opts & OPT_LENGTH)
+		length = xatoull_sfx(length_str, kMG_suffixes);
+	else {
+		xioctl(fd, BLKGETSIZE64, &length);
+		length -= offset;
+	}
+
+	range[0] = offset;
+	range[1] = length;
+	ioctl_or_perror_and_die(fd,
+			(opts & OPT_SECURE) ? BLKSECDISCARD : BLKDISCARD,
+			&range,
+			"%s: %s failed",
+			argv[0],
+			(opts & OPT_SECURE) ? "BLKSECDISCARD" : "BLKDISCARD"
+	);
+
+	if (ENABLE_FEATURE_CLEAN_UP)
+		close(fd);
+
+	return EXIT_SUCCESS;
+}