Home | History | Annotate | Download | only in ext2fs
      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  */
     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