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/*
This program is free software: you can redistribute it and/or modify
it under the terms of the GNU General Public License as published by
the Free Software Foundation, either version 3 of the License, or
(at your option) any later version.
This program is distributed in the hope that it will be useful,
but WITHOUT ANY WARRANTY; without even the implied warranty of
MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
GNU General Public License for more details.
You should have received a copy of the GNU General Public License
along with this program. If not, see <http://www.gnu.org/licenses/>.
*/
/*
#define CHECK_FILE "/tmp/eatmydata"
*/
#ifndef RTLD_NEXT
# define _GNU_SOURCE
#endif
#include <sys/types.h>
#include <unistd.h>
#include <errno.h>
#include <sys/stat.h>
#include <fcntl.h>
#include <dlfcn.h>
#include <stdarg.h>
int errno;
static int (*libc_open)(const char*, int, ...)= NULL;
static int (*libc_fsync)(int)= NULL;
static int (*libc_sync)()= NULL;
static int (*libc_fdatasync)(int)= NULL;
static int (*libc_msync)(void*, size_t, int)= NULL;
#define ASSIGN_DLSYM_OR_DIE(name) \
libc_##name = dlsym(RTLD_NEXT, #name); \
if (!libc_##name || dlerror()) \
_exit(1);
void __attribute__ ((constructor)) eatmydata_init(void)
{
ASSIGN_DLSYM_OR_DIE(open);
ASSIGN_DLSYM_OR_DIE(fsync);
ASSIGN_DLSYM_OR_DIE(sync);
ASSIGN_DLSYM_OR_DIE(fdatasync);
ASSIGN_DLSYM_OR_DIE(msync);
}
int eatmydata_is_hungry(void)
{
/* Init here, as it is called before any libc functions */
if(!libc_open)
eatmydata_init();
#ifdef CHECK_FILE
static struct stat buf;
int old_errno, stat_ret;
old_errno= errno;
stat_ret= stat(CHECK_FILE, &buf);
errno= old_errno;
/* Treat any error as if file doesn't exist, for safety */
return !stat_ret;
#else
/* Always hungry! */
return 1;
#endif
}
int fsync(int fd)
{
if (eatmydata_is_hungry()) {
errno= 0;
return 0;
}
return (*libc_fsync)(fd);
}
/* no errors are defined for this function */
void sync(void)
{
if (eatmydata_is_hungry())
return;
(*libc_sync)();
}
int open(const char* pathname, int flags, ...)
{
va_list ap;
mode_t mode;
va_start(ap, flags);
mode= va_arg(ap, mode_t);
va_end(ap);
/* In pthread environments the dlsym() may call our open(). */
/* We simply ignore it because libc is already loaded */
if (!libc_open) {
errno = EFAULT;
return -1;
}
if (eatmydata_is_hungry())
flags &= ~(O_SYNC|O_DSYNC);
return (*libc_open)(pathname,flags,mode);
}
int fdatasync(int fd)
{
if (eatmydata_is_hungry()) {
errno= 0;
return 0;
}
return (*libc_fdatasync)(fd);
}
int msync(void *addr, size_t length, int flags)
{
if (eatmydata_is_hungry()) {
errno= 0;
return 0;
}
return (*libc_msync)(addr, length, flags);
}
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