1/*
2 * flushb.c --- Hides system-dependent information for both syncing a
3 * 	device to disk and to flush any buffers from disk cache.
4 *
5 * Copyright (C) 2000 Theodore Ts'o.
6 *
7 * %Begin-Header%
8 * This file may be redistributed under the terms of the GNU Library
9 * General Public License, version 2.
10 * %End-Header%
11 */
12
13#include "config.h"
14#include <stdio.h>
15#if HAVE_ERRNO_H
16#include <errno.h>
17#endif
18#if HAVE_UNISTD_H
19#include <unistd.h>
20#endif
21#if HAVE_SYS_IOCTL_H
22#include <sys/ioctl.h>
23#endif
24#if HAVE_SYS_MOUNT_H
25#include <sys/param.h>
26#include <sys/mount.h>		/* This may define BLKFLSBUF */
27#endif
28
29#include "ext2_fs.h"
30#include "ext2fs.h"
31
32/*
33 * For Linux, define BLKFLSBUF and FDFLUSH if necessary, since
34 * not all portable header file does so for us.  This really should be
35 * fixed in the glibc header files.  (Recent glibcs appear to define
36 * BLKFLSBUF in sys/mount.h, but FDFLUSH still doesn't seem to be
37 * defined anywhere portable.)  Until then....
38 */
39#ifdef __linux__
40#ifndef BLKFLSBUF
41#define BLKFLSBUF	_IO(0x12,97)	/* flush buffer cache */
42#endif
43#ifndef FDFLUSH
44#define FDFLUSH		_IO(2,0x4b)	/* flush floppy disk */
45#endif
46#endif
47
48/*
49 * This function will sync a device/file, and optionally attempt to
50 * flush the buffer cache.  The latter is basically only useful for
51 * system benchmarks and for torturing systems in burn-in tests.  :)
52 */
53errcode_t ext2fs_sync_device(int fd, int flushb)
54{
55	/*
56	 * We always sync the device in case we're running on old
57	 * kernels for which we can lose data if we don't.  (There
58	 * still is a race condition for those kernels, but this
59	 * reduces it greatly.)
60	 */
61#if defined(HAVE_FSYNC)
62	if (fsync (fd) == -1)
63		return errno;
64#endif
65
66	if (flushb) {
67
68#ifdef BLKFLSBUF
69		if (ioctl (fd, BLKFLSBUF, 0) == 0)
70			return 0;
71#elif defined(__linux__)
72#warning BLKFLSBUF not defined
73#endif
74#ifdef FDFLUSH
75		return ioctl(fd, FDFLUSH, 0);   /* In case this is a floppy */
76#elif defined(__linux__)
77#warning FDFLUSH not defined
78#endif
79	}
80	return 0;
81}
82