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 */
ext2fs_sync_device(int fd,int flushb)52 errcode_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 #elif defined(__linux__)
69 #warning BLKFLSBUF not defined
70 #endif
71 #ifdef FDFLUSH
72 return ioctl(fd, FDFLUSH, 0); /* In case this is a floppy */
73 #elif defined(__linux__)
74 #warning FDFLUSH not defined
75 #endif
76 }
77 return 0;
78 }
79