fsync: new applet by Pekka Pessi (Pekka.Pessi AT nokia.com)

function                                             old     new   delta
fsync_main                                             -     128    +128
fdatasync                                              -      39     +39
packed_usage                                       26596   26622     +26
applet_names                                        2098    2104      +6
applet_main                                         1240    1244      +4
applet_nameofs                                       620     622      +2
applet_install_loc                                   155     156      +1
------------------------------------------------------------------------------
(add/remove: 2/0 grow/shrink: 5/0 up/down: 206/0)             Total: 206 bytes

Signed-off-by: Alexander Shishkin <virtuoso@slind.org>
Signed-off-by: Denys Vlasenko <vda.linux@googlemail.com>

coreutils/Config.in

@@ -249,6 +249,12 @@ config FOLD
 	help
 	  Wrap text to fit a specific width.
 
+config FSYNC
+	bool "fsync"
+	default n
+	help
+	  fsync is used to flush file-related cached blocks to disk.
+
 config HEAD
 	bool "head"
 	default n

coreutils/Kbuild

@@ -36,6 +36,7 @@ lib-$(CONFIG_EXPR)      += expr.o
 lib-$(CONFIG_EXPAND)    += expand.o
 lib-$(CONFIG_FALSE)     += false.o
 lib-$(CONFIG_FOLD)      += fold.o
+lib-$(CONFIG_FSYNC)     += fsync.o
 lib-$(CONFIG_HEAD)      += head.o
 lib-$(CONFIG_HOSTID)    += hostid.o
 lib-$(CONFIG_ID)        += id.o

coreutils/fsync.c

@@ -0,0 +1,41 @@
+/* vi: set sw=4 ts=4: */
+/*
+ * Mini fsync implementation for busybox
+ *
+ * Copyright (C) 2008 Nokia Corporation. All rights reserved.
+ *
+ * Licensed under GPLv2 or later, see file LICENSE in this tarball for details.
+ */
+#include "libbb.h"
+
+/* This is a NOFORK applet. Be very careful! */
+
+int fsync_main(int argc, char **argv) MAIN_EXTERNALLY_VISIBLE;
+int fsync_main(int argc UNUSED_PARAM, char **argv)
+{
+	int status;
+	int opts;
+
+	opts = getopt32(argv, "d"); /* fdatasync */
+	argv += optind;
+	if (!*argv) {
+		bb_show_usage();
+	}
+
+	status = EXIT_SUCCESS;
+	do {
+		int fd = open3_or_warn(*argv, O_NOATIME | O_NOCTTY | O_RDONLY, 0);
+
+		if (fd == -1) {
+			status = EXIT_FAILURE;
+			continue;
+		}
+		if ((opts ? fdatasync(fd) : fsync(fd))) {
+			//status = EXIT_FAILURE; - do we want this?
+			bb_simple_perror_msg(*argv);
+		}
+		close(fd);
+	} while (*++argv);
+
+	return status;
+}

include/applets.h

@@ -165,6 +165,7 @@ IF_FSCK(APPLET(fsck, _BB_DIR_SBIN, _BB_SUID_NEVER))
 //IF_E2FSCK(APPLET_ODDNAME(fsck.ext2, e2fsck, _BB_DIR_SBIN, _BB_SUID_NEVER, fsck_ext2))
 //IF_E2FSCK(APPLET_ODDNAME(fsck.ext3, e2fsck, _BB_DIR_SBIN, _BB_SUID_NEVER, fsck_ext3))
 IF_FSCK_MINIX(APPLET_ODDNAME(fsck.minix, fsck_minix, _BB_DIR_SBIN, _BB_SUID_NEVER, fsck_minix))
+IF_FSYNC(APPLET_NOFORK(fsync, fsync, _BB_DIR_BIN, _BB_SUID_NEVER, fsync))
 IF_FTPD(APPLET(ftpd, _BB_DIR_USR_SBIN, _BB_SUID_NEVER))
 IF_FTPGET(APPLET_ODDNAME(ftpget, ftpgetput, _BB_DIR_USR_BIN, _BB_SUID_NEVER, ftpget))
 IF_FTPPUT(APPLET_ODDNAME(ftpput, ftpgetput, _BB_DIR_USR_BIN, _BB_SUID_NEVER, ftpput))

include/usage.h

@@ -4209,7 +4209,14 @@
 #define sync_trivial_usage \
        ""
 #define sync_full_usage "\n\n" \
-       "Write all buffered filesystem blocks to disk"
+       "Write all buffered blocks to disk"
+
+#define fsync_trivial_usage \
+       "[OPTION]... FILE..."
+#define fsync_full_usage \
+       "Write files' buffered blocks to disk\n" \
+     "\nOptions:" \
+     "\n	-d	Avoid syncing metadata"
 
 #define sysctl_trivial_usage \
        "[OPTIONS]... [VALUE]..."