flushb.c revision d90f3494b219f9fe327eaa561faf75582f65ad9e 
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 Public
9 * License.
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/mount.h>		/* This may define BLKFLSBUF */
25#endif
26
27#include "ext2_fs.h"
28#include "ext2fs.h"
29
30/*
31 * For Linux, define BLKFLSBUF and FDFLUSH if necessary, since
32 * not all portable header file does so for us.  This really should be
33 * fixed in the glibc header files.  (Recent glibcs appear to define
34 * BLKFLSBUF in sys/mount.h, but FDFLUSH still doesn't seem to be
35 * defined anywhere portable.)  Until then....
36 */
37#ifdef __linux__
38#ifndef BLKFLSBUF
39#define BLKFLSBUF	_IO(0x12,97)	/* flush buffer cache */
40#endif
41#ifndef FDFLUSH
42#define FDFLUSH		_IO(2,0x4b)	/* flush floppy disk */
43#endif
44#endif
45
46/*
47 * This function will sync a device/file, and optionally attempt to
48 * flush the buffer cache.  The latter is basically only useful for
49 * system benchmarks and for torturing systems in burn-in tests.  :)
50 */
51errcode_t ext2fs_sync_device(int fd, int flushb)
52{
53	/*
54	 * We always sync the device in case we're running on old
55	 * kernels for which we can lose data if we don't.  (There
56	 * still is a race condition for those kernels, but this
57	 * reduces it greatly.)
58	 */
59	if (fsync (fd) == -1)
60		return errno;
61
62	if (flushb) {
63
64#ifdef BLKFLSBUF
65		ioctl (fd, BLKFLSBUF, 0);   /* In case this is a HD */
66#else
67 #warning BLKFLSBUF not defined
68#endif
69#ifdef FDFLUSH
70		ioctl (fd, FDFLUSH, 0);   /* In case this is floppy */
71#else
72 #warning FDFLUSH not defined
73#endif
74	}
75	return 0;
76}
77