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/*********************************************************
* Copyright (C) 2011-2015 VMware, Inc. All rights reserved.
*
* This program is free software; you can redistribute it and/or modify it
* under the terms of the GNU Lesser General Public License as published
* by the Free Software Foundation version 2.1 and no 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 Lesser GNU General Public
* License for more details.
*
* You should have received a copy of the GNU Lesser General Public License
* along with this program; if not, write to the Free Software Foundation, Inc.,
* 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
*
*********************************************************/
/**
* @file syncDriverLinux.c
*
* A sync driver backend that uses the Linux "FIFREEZE" and "FITHAW" ioctls
* to freeze and thaw file systems.
*/
#include <errno.h>
#include <fcntl.h>
#include <stdlib.h>
#include <string.h>
#include <unistd.h>
#include <linux/fs.h>
#include <sys/ioctl.h>
#include "debug.h"
#include "dynbuf.h"
#include "strutil.h"
#include "syncDriverInt.h"
/* Out toolchain headers are somewhat outdated and don't define these. */
#if !defined(FIFREEZE)
# define FIFREEZE _IOWR('X', 119, int) /* Freeze */
# define FITHAW _IOWR('X', 120, int) /* Thaw */
#endif
typedef struct LinuxDriver {
SyncHandle driver;
size_t fdCnt;
int *fds;
} LinuxDriver;
/*
*******************************************************************************
* LinuxFiThaw -- */ /**
*
* Thaws the file systems monitored by the given handle. Tries to thaw all the
* file systems even if an error occurs in one of them.
*
* @param[in] handle Handle returned by the freeze call.
*
* @return A SyncDriverErr.
*
*******************************************************************************
*/
static SyncDriverErr
LinuxFiThaw(const SyncDriverHandle handle)
{
size_t i;
LinuxDriver *sync = (LinuxDriver *) handle;
SyncDriverErr err = SD_SUCCESS;
for (i = 0; i < sync->fdCnt; i++) {
if (ioctl(sync->fds[i], FITHAW) == -1) {
err = SD_ERROR;
}
}
return err;
}
/*
*******************************************************************************
* LinuxFiClose -- */ /**
*
* Closes the file descriptors used for freezing, and frees memory associated
* with the handle.
*
* @param[in] handle Handle to close.
*
*******************************************************************************
*/
static void
LinuxFiClose(SyncDriverHandle handle)
{
LinuxDriver *sync = (LinuxDriver *) handle;
size_t i;
for (i = 0; i < sync->fdCnt; i++) {
close(sync->fds[i]);
}
free(sync->fds);
free(sync);
}
/*
*******************************************************************************
* LinuxDriver_Freeze -- */ /**
*
* Tries to freeze the filesystems using the Linux kernel's FIFREEZE ioctl.
*
* If the first attempt at using the ioctl fails, assume that it doesn't exist
* and return SD_UNAVAILABLE, so that other means of freezing are tried.
*
* @param[in] paths Paths to freeze (colon-separated).
* @param[out] handle Handle to use for thawing.
*
* @return A SyncDriverErr.
*
*******************************************************************************
*/
SyncDriverErr
LinuxDriver_Freeze(const char *paths,
SyncDriverHandle *handle)
{
char *path;
int fd;
size_t count = 0;
unsigned int index = 0;
Bool first = TRUE;
DynBuf fds;
LinuxDriver *sync = NULL;
SyncDriverErr err = SD_SUCCESS;
DynBuf_Init(&fds);
Debug(LGPFX "Freezing using Linux ioctls...\n");
sync = calloc(1, sizeof *sync);
if (sync == NULL) {
return SD_ERROR;
}
sync->driver.thaw = LinuxFiThaw;
sync->driver.close = LinuxFiClose;
/*
* Iterate through the requested paths. If we get an error for the first
* path, and it's not EPERM, assume that the ioctls are not available in
* the current kernel.
*/
while ((path = StrUtil_GetNextToken(&index, paths, ":")) != NULL) {
fd = open(path, O_RDONLY);
if (fd == -1) {
switch (errno) {
case EACCES:
/*
* We sometimes get access errors to virtual filesystems mounted
* as users with permission 700, so just ignore these.
*/
Debug(LGPFX "cannot access mounted directory '%s'.\n", path);
free(path);
continue;
case EIO:
/*
* A mounted HGFS filesystem with the backend disabled will give
* us these; probably could use a better way to detect HFGS, but
* this should be enough. Just skip.
*/
Debug(LGPFX "I/O error reading directory '%s'.\n", path);
free(path);
continue;
default:
Debug(LGPFX "failed to open '%s': %d (%s)\n",
path, errno, strerror(errno));
err = SD_ERROR;
free(path);
goto exit;
}
}
if (ioctl(fd, FIFREEZE) == -1) {
int ioctlerr = errno;
/*
* If the ioctl does not exist, Linux will return ENOTTY. If it's not
* supported on the device, we get EOPNOTSUPP. Ignore the latter,
* since freezing does not make sense for all fs types, and some
* Linux fs drivers may not have been hooked up in the running kernel.
*
* Also ignore EBUSY since we may try to freeze the same superblock
* more than once depending on the OS configuration (e.g., usage of
* bind mounts).
*/
close(fd);
if (ioctlerr != EBUSY && ioctlerr != EOPNOTSUPP) {
Debug(LGPFX "failed to freeze '%s': %d (%s)\n",
path, ioctlerr, strerror(ioctlerr));
err = first && ioctlerr == ENOTTY ? SD_UNAVAILABLE : SD_ERROR;
free(path);
break;
}
} else {
Debug(LGPFX "successfully froze '%s'.\n", path);
if (!DynBuf_Append(&fds, &fd, sizeof fd)) {
if (ioctl(fd, FITHAW) == -1) {
Warning(LGPFX "failed to thaw '%s': %d (%s)\n",
path, errno, strerror(errno));
}
free(path);
close(fd);
err = SD_ERROR;
break;
}
count++;
}
free(path);
first = FALSE;
}
exit:
sync->fds = DynBuf_Detach(&fds);
sync->fdCnt = count;
if (err != SD_SUCCESS) {
LinuxFiThaw(&sync->driver);
LinuxFiClose(&sync->driver);
} else {
*handle = &sync->driver;
}
return err;
}
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