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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  */
ext2fs_sync_device(int fd,int flushb)53 errcode_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