From 2687c237367779c3a52c642b8147a5a33f2fa941 Mon Sep 17 00:00:00 2001
From: mmacy <mmacy@FreeBSD.org>
Date: Tue, 3 Sep 2019 18:35:55 +0000
Subject: [PATCH] Add conv=fsync flag to dd

The fsync flag performs an fsync(2) on the output file before closing it.
This will be useful for the ZFS test suite.

Submitted by:	ryan@ixsystems.com
Reviewed by:	jilles@, imp@
MFC after:	1 week
Sponsored by:	iXsystems, Inc.
---
 bin/dd/args.c | 1 +
 bin/dd/dd.1   | 4 ++++
 bin/dd/dd.c   | 7 +++++++
 bin/dd/dd.h   | 1 +
 4 files changed, 13 insertions(+)

diff --git a/bin/dd/args.c b/bin/dd/args.c
index f58551dec6a..8e83c6cc608 100644
--- a/bin/dd/args.c
+++ b/bin/dd/args.c
@@ -320,6 +320,7 @@ static const struct conv {
 	{ "ascii",	C_ASCII,	C_EBCDIC,	e2a_POSIX },
 	{ "block",	C_BLOCK,	C_UNBLOCK,	NULL },
 	{ "ebcdic",	C_EBCDIC,	C_ASCII,	a2e_POSIX },
+	{ "fsync",	C_FSYNC,	0,		NULL },
 	{ "ibm",	C_EBCDIC,	C_ASCII,	a2ibm_POSIX },
 	{ "lcase",	C_LCASE,	C_UCASE,	NULL },
 	{ "noerror",	C_NOERROR,	0,		NULL },
diff --git a/bin/dd/dd.1 b/bin/dd/dd.1
index 352c85072d3..539e448b28b 100644
--- a/bin/dd/dd.1
+++ b/bin/dd/dd.1
@@ -252,6 +252,10 @@ are maps used in historic
 and
 .No pre- Ns Bx 4.3 reno
 systems.
+.It Cm fsync
+Perform an
+.Xr fsync 2
+on the output file before closing it.
 .It Cm lcase
 Transform uppercase characters into lowercase characters.
 .It Cm pareven , parnone , parodd , parset
diff --git a/bin/dd/dd.c b/bin/dd/dd.c
index 46175fa4c8f..3db678b8500 100644
--- a/bin/dd/dd.c
+++ b/bin/dd/dd.c
@@ -164,6 +164,8 @@ setup(void)
 		errx(1, "files is not supported for non-tape devices");
 
 	cap_rights_set(&rights, CAP_FTRUNCATE, CAP_IOCTL, CAP_WRITE);
+	if (ddflags & C_FSYNC)
+		cap_rights_set(&rights, CAP_FSYNC);
 	if (out.name == NULL) {
 		/* No way to check for read access here. */
 		out.fd = STDOUT_FILENO;
@@ -505,6 +507,11 @@ dd_close(void)
 		if (ftruncate(out.fd, out.seek_offset) == -1)
 			err(1, "truncating %s", out.name);
 	}
+
+	if (ddflags & C_FSYNC) {
+		if (fsync(out.fd) == -1)
+			err(1, "fsyncing %s", out.name);
+	}
 }
 
 void
diff --git a/bin/dd/dd.h b/bin/dd/dd.h
index 8090252923f..8c01cb4d17c 100644
--- a/bin/dd/dd.h
+++ b/bin/dd/dd.h
@@ -101,6 +101,7 @@ typedef struct {
 #define	C_NOXFER	0x10000000
 #define	C_NOINFO	0x20000000
 #define	C_PROGRESS	0x40000000
+#define	C_FSYNC		0x80000000
 
 #define	C_PARITY	(C_PAREVEN | C_PARODD | C_PARNONE | C_PARSET)
 
-- 
2.39.5