flushb.c revision a6ce1349539f866334ef3d5758bc2ee44a454acd 
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 <stdio.h>
14#if HAVE_ERRNO_H
15#include <errno.h>
16#endif
17#if HAVE_UNISTD_H
18#include <unistd.h>
19#endif
20#if HAVE_SYS_IOCTL_H
21#include <sys/ioctl.h>
22#endif
23#if HAVE_SYS_MOUNT_H
24#include <sys/param.h>
25#include <sys/mount.h>		/* This may define BLKFLSBUF */
26#endif
27
28#include "ext2_fs.h"
29#include "ext2fs.h"
30
31/*
32 * For Linux, define BLKFLSBUF and FDFLUSH if necessary, since
33 * not all portable header file does so for us.  This really should be
34 * fixed in the glibc header files.  (Recent glibcs appear to define
35 * BLKFLSBUF in sys/mount.h, but FDFLUSH still doesn't seem to be
36 * defined anywhere portable.)  Until then....
37 */
38#ifdef __linux__
39#ifndef BLKFLSBUF
40#define BLKFLSBUF	_IO(0x12,97)	/* flush buffer cache */
41#endif
42#ifndef FDFLUSH
43#define FDFLUSH		_IO(2,0x4b)	/* flush floppy disk */
44#endif
45#endif
46
47/*
48 * This function will sync a device/file, and optionally attempt to
49 * flush the buffer cache.  The latter is basically only useful for
50 * system benchmarks and for torturing systems in burn-in tests.  :)
51 */
52errcode_t ext2fs_sync_device(int fd, int flushb)
53{
54	/*
55	 * We always sync the device in case we're running on old
56	 * kernels for which we can lose data if we don't.  (There
57	 * still is a race condition for those kernels, but this
58	 * reduces it greatly.)
59	 */
60	if (fsync (fd) == -1)
61		return errno;
62
63	if (flushb) {
64
65#ifdef BLKFLSBUF
66		if (ioctl (fd, BLKFLSBUF, 0) == 0)
67			return 0;
68#else
69#ifdef __GNUC__
70 #warning BLKFLSBUF not defined
71#endif /* __GNUC__ */
72#endif
73#ifdef FDFLUSH
74		ioctl (fd, FDFLUSH, 0);   /* In case this is a floppy */
75#else
76#ifdef __GNUC__
77 #warning FDFLUSH not defined
78#endif /* __GNUC__ */
79#endif
80	}
81	return 0;
82}
83