From: Ari Sundholm <[email protected]>
This applet discards blocks on a given device.
Tested with multiple 32-bit and 64-bit kernel versions and two different SSDs.
function old new delta
blkdiscard_main - 300 +300
.rodata 154690 154795 +105
packed_usage 30275 30310 +35
applet_names 2499 2510 +11
applet_main 2904 2912 +8
applet_nameofs 726 728 +2
------------------------------------------------------------------------------
(add/remove: 2/0 grow/shrink: 5/0 up/down: 461/0) Total: 461 bytes
v2: Use a common error message format string when !S_ISBLK() to save space.
v3: Make the applet configuration option default to n and add a comment
regarding two not strictly necessary variables which help readability.
Signed-off-by: Ari Sundholm <[email protected]>
---
util-linux/blkdiscard.c | 86 +++++++++++++++++++++++++++++++++++++++++++++++++
1 file changed, 86 insertions(+)
create mode 100644 util-linux/blkdiscard.c
diff --git a/util-linux/blkdiscard.c b/util-linux/blkdiscard.c
new file mode 100644
index 0000000..0d28da2
--- /dev/null
+++ b/util-linux/blkdiscard.c
@@ -0,0 +1,86 @@
+/*
+ * Mini blkdiscard implementation for busybox
+ *
+ * Copyright (C) 2015 by Ari Sundholm <[email protected]> and Tuxera Inc.
+ *
+ * Licensed under GPLv2 or later, see file LICENSE in this source tree.
+ */
+
+//config:config BLKDISCARD
+//config: bool "blkdiscard"
+//config: default n
+//config: help
+//config: blkdiscard discards sectors on a given device.
+
+//kbuild:lib-$(CONFIG_BLKDISCARD) += blkdiscard.o
+//applet:IF_BLKDISCARD(APPLET_NOFORK(blkdiscard, blkdiscard, BB_DIR_USR_BIN,
BB_SUID_DROP, blkdiscard))
+
+//usage:#define blkdiscard_trivial_usage
+//usage: "[-o offset] [-l length] [-s] device"
+//usage:#define blkdiscard_full_usage "\n\n"
+//usage: "Discard sectors on the given device\n"
+//usage: "\n -o offset Byte offset into device (default: 0)"
+//usage: "\n -l length Number of bytes to discard (default:
size of device)"
+//usage: "\n -s Perform a secure discard"
+//usage:
+//usage:#define blkdiscard_example_usage
+//usage: "$ blkdiscard -o 0 -l 1G /dev/sdb"
+
+#include "libbb.h"
+#include <linux/fs.h>
+
+/* This is a NOFORK applet. Be very careful! */
+
+int blkdiscard_main(int argc, char **argv) MAIN_EXTERNALLY_VISIBLE;
+int blkdiscard_main(int argc UNUSED_PARAM, char **argv)
+{
+ unsigned opts;
+ char *offset_str;
+ char *length_str;
+ uint64_t offset = 0; /* 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);
+
+ xstat(argv[optind], &st);
+ if (!S_ISBLK(st.st_mode))
+ bb_error_msg_and_die("%s: not a block device", argv[optind]);
+
+ fd = xopen(argv[optind], O_RDWR|O_EXCL);
+
+ if (opts & OPT_OFFSET)
+ offset = xatoull_sfx(offset_str, kMG_suffixes);
+
+ if (opts & OPT_LENGTH)
+ length = xatoull_sfx(length_str, kMG_suffixes);
+ else {
+ ioctl_or_perror_and_die(fd, BLKGETSIZE64, &length,
+ "Failed to get device size");
+ length -= offset;
+ }
+
+ range[0] = offset;
+ range[1] = length;
+ ioctl_or_perror_and_die(fd,
+ (opts & OPT_SECURE)
+ ? BLKSECDISCARD
+ : BLKDISCARD, &range,
+ "%s failed",
+ (opts & OPT_SECURE)
+ ? "BLKSECDISCARD"
+ : "BLKDISCARD");
+
+ xclose(fd);
+
+ return EXIT_SUCCESS;
+}
--
1.9.1
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