From d4581cb9a1d178cb31416eb30d501a0e46878e45 Mon Sep 17 00:00:00 2001
From: Eric Wong <normalperson@yhbt.net>
Date: Sun, 9 Aug 2009 15:33:48 -0700
Subject: [PATCH] Add `pcu-sync' command

This can be useful for calling fsync(2)/fdatasync(2) on
individual files (and/or their containing directories).  This
can be used when a system-wide sync(2) is too expensive on
a busy system.
---
 .gitignore |   1 +
 Makefile   |   3 +-
 sync.c     | 110 +++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
 3 files changed, 113 insertions(+), 1 deletion(-)
 create mode 100644 sync.c

diff --git a/.gitignore b/.gitignore
index 4b4583d..e4a8a6f 100644
--- a/.gitignore
+++ b/.gitignore
@@ -1,5 +1,6 @@
 pcu-mincore
 pcu-fadvise
+pcu-sync
 GIT-VERSION-FILE
 *.1
 *.html
diff --git a/Makefile b/Makefile
index 7871952..5d8a09e 100644
--- a/Makefile
+++ b/Makefile
@@ -22,8 +22,9 @@ LDFLAGS = -Wl,-O1
 
 pcu-mincore: mincore.c compat-util.h
 pcu-fadvise: fadvise.c compat-util.h
+pcu-sync: sync.c compat-util.h
 
-PCU_BIN := pcu-fadvise pcu-mincore
+PCU_BIN := pcu-fadvise pcu-mincore pcu-sync
 
 $(PCU_BIN):
 	$(CC) $(CFLAGS) $(LDFLAGS) -o $@+ $<
diff --git a/sync.c b/sync.c
new file mode 100644
index 0000000..994ca72
--- /dev/null
+++ b/sync.c
@@ -0,0 +1,110 @@
+#include "compat-util.h"
+#include <dirent.h>
+#include <libgen.h>
+
+#if defined(_POSIX_SYNCHRONIZED_IO) && _POSIX_SYNCHRONIZED_IO > 0
+static int have_fdatasync = 1;
+#else
+static int have_fdatasync;
+#endif
+
+/* TODO: sync_file_range() if on Linux */
+
+static int usage(const char * argv0)
+{
+	fprintf(stderr, "Usage: %s [-d] [-D] FILE...\n", argv0);
+	return 1;
+}
+
+static int do_sync(const char *path, int data_only, int directory)
+{
+	int fd;
+	const char *errfunc = "";
+
+	if ((fd = open(path, O_RDWR|O_NOATIME)) < 0) {
+		if (errno == EISDIR) {
+			directory = 1;
+			goto sync_dir;
+		}
+		errfunc = "open";
+		goto err;
+	}
+
+	if (data_only && have_fdatasync) {
+		if (fdatasync(fd) < 0) {
+			errfunc = "fdatasync";
+			goto err;
+		}
+	} else {
+		if (fsync(fd) < 0) {
+			errfunc = "fsync";
+			goto err;
+		}
+	}
+
+	if (close(fd) < 0) {
+		errfunc = "close";
+		goto err;
+	}
+
+sync_dir:
+	if (directory) {
+		char *dpath;
+		DIR *dir;
+
+		if (!(dpath = strdup(path))){
+			errfunc = "strdup";
+			goto err;
+		}
+		if (!(dir = opendir(dirname(dpath)))) {
+			errfunc = "opendir";
+			goto err;
+		}
+		if (fsync(dirfd(dir)) < 0) {
+			errfunc = "(directory) fsync";
+			goto err;
+		}
+		if (closedir(dir) < 0) {
+			errfunc = "closedir";
+			goto err;
+		}
+		free(dpath);
+	}
+
+	return 0;
+err:
+	fprintf(stderr, "%s: %s(): %s\n", path, errfunc, strerror(errno));
+	return -1;
+}
+
+int main(int argc, char * const argv[])
+{
+	int data_only = 0;
+	int directory = 0;
+	int opt;
+	int argi = 1;
+
+	while ((opt = getopt(argc, argv, "dD")) != -1) {
+		++argi;
+		switch(opt) {
+		case 'd':
+			data_only = 1;
+			break;
+		case 'D':
+			directory = 1;
+			break;
+		default:
+			return usage(argv[0]);
+		}
+	}
+
+	if (argi >= argc)
+		return usage(argv[0]);
+
+	for (; argi < argc; ++argi) {
+		if (do_sync(argv[argi], data_only, directory) < 0)
+			return 1;
+	}
+
+	return 0;
+}
-- 
2.11.4.GIT