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 errcode_t retval = 0;
68
69 #ifdef BLKFLSBUF
70 if (ioctl (fd, BLKFLSBUF, 0) == 0)
71 return 0;
72 retval = errno;
73 #elif defined(__linux__)
74 #warning BLKFLSBUF not defined
75 #endif
76 #ifdef FDFLUSH
77 /* In case this is a floppy */
78 if (ioctl(fd, FDFLUSH, 0) == 0)
79 return 0;
80 if (retval == 0)
81 retval = errno;
82 #elif defined(__linux__)
83 #warning FDFLUSH not defined
84 #endif
85 return retval;
86 }
87 return 0;
88 }
89