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qga: Move Linux-specific FS freeze/thaw code to a separate file

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In the next patches we are going to add FreeBSD support for QEMU Guest
Agent. In the result, code in commands-posix.c will be too cumbersome.

Move Linux-specific FS freeze/thaw code to a separate file commands-linux.c
keeping common POSIX code in commands-posix.c.

Reviewed-by: Konstantin Kostiuk <kkostiuk@redhat.com>
Reviewed-by: Marc-André Lureau <marcandre.lureau@redhat.com>
Signed-off-by: Alexander Ivanov <alexander.ivanov@virtuozzo.com>
Signed-off-by: Konstantin Kostiuk <kkostiuk@redhat.com>
This commit is contained in:
Alexander Ivanov 2022-10-17 09:28:20 +02:00 committed by Konstantin Kostiuk
parent c6cd588bb3
commit 518b0d800b
4 changed files with 338 additions and 272 deletions
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34
qga/commands-common.h
View file

@ -10,6 +10,40 @@
#define QGA_COMMANDS_COMMON_H
#include "qga-qapi-types.h"
#include "guest-agent-core.h"
#include "qemu/queue.h"
#if defined(__linux__)
#include <linux/fs.h>
#ifdef FIFREEZE
#define CONFIG_FSFREEZE
#endif
#ifdef FITRIM
#define CONFIG_FSTRIM
#endif
#endif /* __linux__ */
#if defined(CONFIG_FSFREEZE) || defined(CONFIG_FSTRIM)
typedef struct FsMount {
char *dirname;
char *devtype;
unsigned int devmajor, devminor;
QTAILQ_ENTRY(FsMount) next;
} FsMount;
typedef QTAILQ_HEAD(FsMountList, FsMount) FsMountList;
bool build_fs_mount_list(FsMountList *mounts, Error **errp);
void free_fs_mount_list(FsMountList *mounts);
#endif /* CONFIG_FSFREEZE || CONFIG_FSTRIM */
#if defined(CONFIG_FSFREEZE)
int64_t qmp_guest_fsfreeze_do_freeze_list(bool has_mountpoints,
strList *mountpoints,
FsMountList mounts,
Error **errp);
int qmp_guest_fsfreeze_do_thaw(Error **errp);
#endif /* CONFIG_FSFREEZE */
typedef struct GuestFileHandle GuestFileHandle;

286
qga/commands-linux.c Normal file
View file

@ -0,0 +1,286 @@
/*
* QEMU Guest Agent Linux-specific command implementations
*
* Copyright IBM Corp. 2011
*
* Authors:
* Michael Roth <mdroth@linux.vnet.ibm.com>
* Michal Privoznik <mprivozn@redhat.com>
*
* This work is licensed under the terms of the GNU GPL, version 2 or later.
* See the COPYING file in the top-level directory.
*/
#include "qemu/osdep.h"
#include "qapi/error.h"
#include "commands-common.h"
#include "cutils.h"
#include <mntent.h>
#include <sys/ioctl.h>
#if defined(CONFIG_FSFREEZE) || defined(CONFIG_FSTRIM)
static int dev_major_minor(const char *devpath,
unsigned int *devmajor, unsigned int *devminor)
{
struct stat st;
*devmajor = 0;
*devminor = 0;
if (stat(devpath, &st) < 0) {
slog("failed to stat device file '%s': %s", devpath, strerror(errno));
return -1;
}
if (S_ISDIR(st.st_mode)) {
/* It is bind mount */
return -2;
}
if (S_ISBLK(st.st_mode)) {
*devmajor = major(st.st_rdev);
*devminor = minor(st.st_rdev);
return 0;
}
return -1;
}
static bool build_fs_mount_list_from_mtab(FsMountList *mounts, Error **errp)
{
struct mntent *ment;
FsMount *mount;
char const *mtab = "/proc/self/mounts";
FILE *fp;
unsigned int devmajor, devminor;
fp = setmntent(mtab, "r");
if (!fp) {
error_setg(errp, "failed to open mtab file: '%s'", mtab);
return false;
}
while ((ment = getmntent(fp))) {
/*
* An entry which device name doesn't start with a '/' is
* either a dummy file system or a network file system.
* Add special handling for smbfs and cifs as is done by
* coreutils as well.
*/
if ((ment->mnt_fsname[0] != '/') ||
(strcmp(ment->mnt_type, "smbfs") == 0) ||
(strcmp(ment->mnt_type, "cifs") == 0)) {
continue;
}
if (dev_major_minor(ment->mnt_fsname, &devmajor, &devminor) == -2) {
/* Skip bind mounts */
continue;
}
mount = g_new0(FsMount, 1);
mount->dirname = g_strdup(ment->mnt_dir);
mount->devtype = g_strdup(ment->mnt_type);
mount->devmajor = devmajor;
mount->devminor = devminor;
QTAILQ_INSERT_TAIL(mounts, mount, next);
}
endmntent(fp);
return true;
}
static void decode_mntname(char *name, int len)
{
int i, j = 0;
for (i = 0; i <= len; i++) {
if (name[i] != '\\') {
name[j++] = name[i];
} else if (name[i + 1] == '\\') {
name[j++] = '\\';
i++;
} else if (name[i + 1] >= '0' && name[i + 1] <= '3' &&
name[i + 2] >= '0' && name[i + 2] <= '7' &&
name[i + 3] >= '0' && name[i + 3] <= '7') {
name[j++] = (name[i + 1] - '0') * 64 +
(name[i + 2] - '0') * 8 +
(name[i + 3] - '0');
i += 3;
} else {
name[j++] = name[i];
}
}
}
/*
* Walk the mount table and build a list of local file systems
*/
bool build_fs_mount_list(FsMountList *mounts, Error **errp)
{
FsMount *mount;
char const *mountinfo = "/proc/self/mountinfo";
FILE *fp;
char *line = NULL, *dash;
size_t n;
char check;
unsigned int devmajor, devminor;
int ret, dir_s, dir_e, type_s, type_e, dev_s, dev_e;
fp = fopen(mountinfo, "r");
if (!fp) {
return build_fs_mount_list_from_mtab(mounts, errp);
}
while (getline(&line, &n, fp) != -1) {
ret = sscanf(line, "%*u %*u %u:%u %*s %n%*s%n%c",
&devmajor, &devminor, &dir_s, &dir_e, &check);
if (ret < 3) {
continue;
}
dash = strstr(line + dir_e, " - ");
if (!dash) {
continue;
}
ret = sscanf(dash, " - %n%*s%n %n%*s%n%c",
&type_s, &type_e, &dev_s, &dev_e, &check);
if (ret < 1) {
continue;
}
line[dir_e] = 0;
dash[type_e] = 0;
dash[dev_e] = 0;
decode_mntname(line + dir_s, dir_e - dir_s);
decode_mntname(dash + dev_s, dev_e - dev_s);
if (devmajor == 0) {
/* btrfs reports major number = 0 */
if (strcmp("btrfs", dash + type_s) != 0 ||
dev_major_minor(dash + dev_s, &devmajor, &devminor) < 0) {
continue;
}
}
mount = g_new0(FsMount, 1);
mount->dirname = g_strdup(line + dir_s);
mount->devtype = g_strdup(dash + type_s);
mount->devmajor = devmajor;
mount->devminor = devminor;
QTAILQ_INSERT_TAIL(mounts, mount, next);
}
free(line);
fclose(fp);
return true;
}
#endif /* CONFIG_FSFREEZE || CONFIG_FSTRIM */
#ifdef CONFIG_FSFREEZE
/*
* Walk list of mounted file systems in the guest, and freeze the ones which
* are real local file systems.
*/
int64_t qmp_guest_fsfreeze_do_freeze_list(bool has_mountpoints,
strList *mountpoints,
FsMountList mounts,
Error **errp)
{
struct FsMount *mount;
strList *list;
int fd, ret, i = 0;
QTAILQ_FOREACH_REVERSE(mount, &mounts, next) {
/* To issue fsfreeze in the reverse order of mounts, check if the
* mount is listed in the list here */
if (has_mountpoints) {
for (list = mountpoints; list; list = list->next) {
if (strcmp(list->value, mount->dirname) == 0) {
break;
}
}
if (!list) {
continue;
}
}
fd = qga_open_cloexec(mount->dirname, O_RDONLY, 0);
if (fd == -1) {
error_setg_errno(errp, errno, "failed to open %s", mount->dirname);
return -1;
}
/* we try to cull filesystems we know won't work in advance, but other
* filesystems may not implement fsfreeze for less obvious reasons.
* these will report EOPNOTSUPP. we simply ignore these when tallying
* the number of frozen filesystems.
* if a filesystem is mounted more than once (aka bind mount) a
* consecutive attempt to freeze an already frozen filesystem will
* return EBUSY.
*
* any other error means a failure to freeze a filesystem we
* expect to be freezable, so return an error in those cases
* and return system to thawed state.
*/
ret = ioctl(fd, FIFREEZE);
if (ret == -1) {
if (errno != EOPNOTSUPP && errno != EBUSY) {
error_setg_errno(errp, errno, "failed to freeze %s",
mount->dirname);
close(fd);
return -1;
}
} else {
i++;
}
close(fd);
}
return i;
}
int qmp_guest_fsfreeze_do_thaw(Error **errp)
{
int ret;
FsMountList mounts;
FsMount *mount;
int fd, i = 0, logged;
Error *local_err = NULL;
QTAILQ_INIT(&mounts);
if (!build_fs_mount_list(&mounts, &local_err)) {
error_propagate(errp, local_err);
return -1;
}
QTAILQ_FOREACH(mount, &mounts, next) {
logged = false;
fd = qga_open_cloexec(mount->dirname, O_RDONLY, 0);
if (fd == -1) {
continue;
}
/* we have no way of knowing whether a filesystem was actually unfrozen
* as a result of a successful call to FITHAW, only that if an error
* was returned the filesystem was *not* unfrozen by that particular
* call.
*
* since multiple preceding FIFREEZEs require multiple calls to FITHAW
* to unfreeze, continuing issuing FITHAW until an error is returned,
* in which case either the filesystem is in an unfreezable state, or,
* more likely, it was thawed previously (and remains so afterward).
*
* also, since the most recent successful call is the one that did
* the actual unfreeze, we can use this to provide an accurate count
* of the number of filesystems unfrozen by guest-fsfreeze-thaw, which
* may * be useful for determining whether a filesystem was unfrozen
* during the freeze/thaw phase by a process other than qemu-ga.
*/
do {
ret = ioctl(fd, FITHAW);
if (ret == 0 && !logged) {
i++;
logged = true;
}
} while (ret == 0);
close(fd);
}
free_fs_mount_list(&mounts);
return i;
}
#endif /* CONFIG_FSFREEZE */

287
qga/commands-posix.c
View file

@ -16,11 +16,9 @@
#include <sys/utsname.h>
#include <sys/wait.h>
#include <dirent.h>
#include "guest-agent-core.h"
#include "qga-qapi-commands.h"
#include "qapi/error.h"
#include "qapi/qmp/qerror.h"
#include "qemu/queue.h"
#include "qemu/host-utils.h"
#include "qemu/sockets.h"
#include "qemu/base64.h"
@ -629,16 +627,7 @@ void qmp_guest_file_flush(int64_t handle, Error **errp)
#if defined(__linux__)
#if defined(CONFIG_FSFREEZE) || defined(CONFIG_FSTRIM)
typedef struct FsMount {
char *dirname;
char *devtype;
unsigned int devmajor, devminor;
QTAILQ_ENTRY(FsMount) next;
} FsMount;
typedef QTAILQ_HEAD(FsMountList, FsMount) FsMountList;
static void free_fs_mount_list(FsMountList *mounts)
void free_fs_mount_list(FsMountList *mounts)
{
FsMount *mount, *temp;
@ -653,157 +642,6 @@ static void free_fs_mount_list(FsMountList *mounts)
g_free(mount);
}
}
static int dev_major_minor(const char *devpath,
unsigned int *devmajor, unsigned int *devminor)
{
struct stat st;
*devmajor = 0;
*devminor = 0;
if (stat(devpath, &st) < 0) {
slog("failed to stat device file '%s': %s", devpath, strerror(errno));
return -1;
}
if (S_ISDIR(st.st_mode)) {
/* It is bind mount */
return -2;
}
if (S_ISBLK(st.st_mode)) {
*devmajor = major(st.st_rdev);
*devminor = minor(st.st_rdev);
return 0;
}
return -1;
}
/*
* Walk the mount table and build a list of local file systems
*/
static bool build_fs_mount_list_from_mtab(FsMountList *mounts, Error **errp)
{
struct mntent *ment;
FsMount *mount;
char const *mtab = "/proc/self/mounts";
FILE *fp;
unsigned int devmajor, devminor;
fp = setmntent(mtab, "r");
if (!fp) {
error_setg(errp, "failed to open mtab file: '%s'", mtab);
return false;
}
while ((ment = getmntent(fp))) {
/*
* An entry which device name doesn't start with a '/' is
* either a dummy file system or a network file system.
* Add special handling for smbfs and cifs as is done by
* coreutils as well.
*/
if ((ment->mnt_fsname[0] != '/') ||
(strcmp(ment->mnt_type, "smbfs") == 0) ||
(strcmp(ment->mnt_type, "cifs") == 0)) {
continue;
}
if (dev_major_minor(ment->mnt_fsname, &devmajor, &devminor) == -2) {
/* Skip bind mounts */
continue;
}
mount = g_new0(FsMount, 1);
mount->dirname = g_strdup(ment->mnt_dir);
mount->devtype = g_strdup(ment->mnt_type);
mount->devmajor = devmajor;
mount->devminor = devminor;
QTAILQ_INSERT_TAIL(mounts, mount, next);
}
endmntent(fp);
return true;
}
static void decode_mntname(char *name, int len)
{
int i, j = 0;
for (i = 0; i <= len; i++) {
if (name[i] != '\\') {
name[j++] = name[i];
} else if (name[i + 1] == '\\') {
name[j++] = '\\';
i++;
} else if (name[i + 1] >= '0' && name[i + 1] <= '3' &&
name[i + 2] >= '0' && name[i + 2] <= '7' &&
name[i + 3] >= '0' && name[i + 3] <= '7') {
name[j++] = (name[i + 1] - '0') * 64 +
(name[i + 2] - '0') * 8 +
(name[i + 3] - '0');
i += 3;
} else {
name[j++] = name[i];
}
}
}
static bool build_fs_mount_list(FsMountList *mounts, Error **errp)
{
FsMount *mount;
char const *mountinfo = "/proc/self/mountinfo";
FILE *fp;
char *line = NULL, *dash;
size_t n;
char check;
unsigned int devmajor, devminor;
int ret, dir_s, dir_e, type_s, type_e, dev_s, dev_e;
fp = fopen(mountinfo, "r");
if (!fp) {
return build_fs_mount_list_from_mtab(mounts, errp);
}
while (getline(&line, &n, fp) != -1) {
ret = sscanf(line, "%*u %*u %u:%u %*s %n%*s%n%c",
&devmajor, &devminor, &dir_s, &dir_e, &check);
if (ret < 3) {
continue;
}
dash = strstr(line + dir_e, " - ");
if (!dash) {
continue;
}
ret = sscanf(dash, " - %n%*s%n %n%*s%n%c",
&type_s, &type_e, &dev_s, &dev_e, &check);
if (ret < 1) {
continue;
}
line[dir_e] = 0;
dash[type_e] = 0;
dash[dev_e] = 0;
decode_mntname(line + dir_s, dir_e - dir_s);
decode_mntname(dash + dev_s, dev_e - dev_s);
if (devmajor == 0) {
/* btrfs reports major number = 0 */
if (strcmp("btrfs", dash + type_s) != 0 ||
dev_major_minor(dash + dev_s, &devmajor, &devminor) < 0) {
continue;
}
}
mount = g_new0(FsMount, 1);
mount->dirname = g_strdup(line + dir_s);
mount->devtype = g_strdup(dash + type_s);
mount->devmajor = devmajor;
mount->devminor = devminor;
QTAILQ_INSERT_TAIL(mounts, mount, next);
}
free(line);
fclose(fp);
return true;
}
#endif
#if defined(CONFIG_FSFREEZE)
@ -1708,20 +1546,13 @@ int64_t qmp_guest_fsfreeze_freeze(Error **errp)
return qmp_guest_fsfreeze_freeze_list(false, NULL, errp);
}
/*
* Walk list of mounted file systems in the guest, and freeze the ones which
* are real local file systems.
*/
int64_t qmp_guest_fsfreeze_freeze_list(bool has_mountpoints,
strList *mountpoints,
Error **errp)
{
int ret = 0, i = 0;
strList *list;
int ret;
FsMountList mounts;
struct FsMount *mount;
Error *local_err = NULL;
int fd;
slog("guest-fsfreeze called");
@ -1740,122 +1571,34 @@ int64_t qmp_guest_fsfreeze_freeze_list(bool has_mountpoints,
/* cannot risk guest agent blocking itself on a write in this state */
ga_set_frozen(ga_state);
QTAILQ_FOREACH_REVERSE(mount, &mounts, next) {
/* To issue fsfreeze in the reverse order of mounts, check if the
* mount is listed in the list here */
if (has_mountpoints) {
for (list = mountpoints; list; list = list->next) {
if (strcmp(list->value, mount->dirname) == 0) {
break;
}
}
if (!list) {
continue;
}
}
fd = qga_open_cloexec(mount->dirname, O_RDONLY, 0);
if (fd == -1) {
error_setg_errno(errp, errno, "failed to open %s", mount->dirname);
goto error;
}
/* we try to cull filesystems we know won't work in advance, but other
* filesystems may not implement fsfreeze for less obvious reasons.
* these will report EOPNOTSUPP. we simply ignore these when tallying
* the number of frozen filesystems.
* if a filesystem is mounted more than once (aka bind mount) a
* consecutive attempt to freeze an already frozen filesystem will
* return EBUSY.
*
* any other error means a failure to freeze a filesystem we
* expect to be freezable, so return an error in those cases
* and return system to thawed state.
*/
ret = ioctl(fd, FIFREEZE);
if (ret == -1) {
if (errno != EOPNOTSUPP && errno != EBUSY) {
error_setg_errno(errp, errno, "failed to freeze %s",
mount->dirname);
close(fd);
goto error;
}
} else {
i++;
}
close(fd);
}
ret = qmp_guest_fsfreeze_do_freeze_list(has_mountpoints, mountpoints,
mounts, errp);
free_fs_mount_list(&mounts);
/* We may not issue any FIFREEZE here.
* Just unset ga_state here and ready for the next call.
*/
if (i == 0) {
if (ret == 0) {
ga_unset_frozen(ga_state);
} else if (ret < 0) {
qmp_guest_fsfreeze_thaw(NULL);
}
return i;
error:
free_fs_mount_list(&mounts);
qmp_guest_fsfreeze_thaw(NULL);
return 0;
return ret;
}
/*
* Walk list of frozen file systems in the guest, and thaw them.
*/
int64_t qmp_guest_fsfreeze_thaw(Error **errp)
{
int ret;
FsMountList mounts;
FsMount *mount;
int fd, i = 0, logged;
Error *local_err = NULL;
QTAILQ_INIT(&mounts);
if (!build_fs_mount_list(&mounts, &local_err)) {
error_propagate(errp, local_err);
return 0;
ret = qmp_guest_fsfreeze_do_thaw(errp);
if (ret >= 0) {
ga_unset_frozen(ga_state);
execute_fsfreeze_hook(FSFREEZE_HOOK_THAW, errp);
} else {
ret = 0;
}
QTAILQ_FOREACH(mount, &mounts, next) {
logged = false;
fd = qga_open_cloexec(mount->dirname, O_RDONLY, 0);
if (fd == -1) {
continue;
}
/* we have no way of knowing whether a filesystem was actually unfrozen
* as a result of a successful call to FITHAW, only that if an error
* was returned the filesystem was *not* unfrozen by that particular
* call.
*
* since multiple preceding FIFREEZEs require multiple calls to FITHAW
* to unfreeze, continuing issuing FITHAW until an error is returned,
* in which case either the filesystem is in an unfreezable state, or,
* more likely, it was thawed previously (and remains so afterward).
*
* also, since the most recent successful call is the one that did
* the actual unfreeze, we can use this to provide an accurate count
* of the number of filesystems unfrozen by guest-fsfreeze-thaw, which
* may * be useful for determining whether a filesystem was unfrozen
* during the freeze/thaw phase by a process other than qemu-ga.
*/
do {
ret = ioctl(fd, FITHAW);
if (ret == 0 && !logged) {
i++;
logged = true;
}
} while (ret == 0);
close(fd);
}
ga_unset_frozen(ga_state);
free_fs_mount_list(&mounts);
execute_fsfreeze_hook(FSFREEZE_HOOK_THAW, errp);
return i;
return ret;
}
static void guest_fsfreeze_cleanup(void)

3
qga/meson.build
View file

@ -72,6 +72,9 @@ qga_ss.add(when: 'CONFIG_POSIX', if_true: files(
'commands-posix.c',
'commands-posix-ssh.c',
))
qga_ss.add(when: 'CONFIG_LINUX', if_true: files(
'commands-linux.c',
))
qga_ss.add(when: 'CONFIG_WIN32', if_true: files(
'channel-win32.c',
'commands-win32.c',