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qemu-ga: execute hook to quiesce the guest on fsfreeze-freeze/thaw

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To use the online disk snapshot for online-backup, application-level
consistency of the snapshot image is required. However, currently the
guest agent can provide only filesystem-level consistency, and the
snapshot may contain dirty data, for example, incomplete transactions.
This patch provides the opportunity to quiesce applications before
snapshot is taken.

If --fsfreeze-hook option is specified, the hook is executed with
"freeze" argument before the filesystem is frozen by fsfreeze-freeze
command. As for fsfreeze-thaw command, the hook is executed with "thaw"
argument after the filesystem is thawed.

This patch depends on patchset to improve error reporting by Luiz Capitulino:
  http://lists.gnu.org/archive/html/qemu-devel/2012-11/msg03016.html

Signed-off-by: Tomoki Sekiyama <tomoki.sekiyama.qu@hitachi.com>
Reviewed-by: Luiz Capitulino <lcapitulino@redhat.com>

*clarified usage in help output

Signed-off-by: Michael Roth <mdroth@linux.vnet.ibm.com>
This commit is contained in:
Tomoki Sekiyama 2012-12-12 12:55:55 +09:00 committed by Michael Roth
parent 7b3760879b
commit ec0f694c11
3 changed files with 117 additions and 1 deletions
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69
qga/commands-posix.c
View File

@ -410,6 +410,66 @@ static void build_fs_mount_list(FsMountList *mounts, Error **err)
#if defined(CONFIG_FSFREEZE)
typedef enum {
FSFREEZE_HOOK_THAW = 0,
FSFREEZE_HOOK_FREEZE,
} FsfreezeHookArg;
const char *fsfreeze_hook_arg_string[] = {
"thaw",
"freeze",
};
static void execute_fsfreeze_hook(FsfreezeHookArg arg, Error **err)
{
int status;
pid_t pid;
const char *hook;
const char *arg_str = fsfreeze_hook_arg_string[arg];
Error *local_err = NULL;
hook = ga_fsfreeze_hook(ga_state);
if (!hook) {
return;
}
if (access(hook, X_OK) != 0) {
error_setg_errno(err, errno, "can't access fsfreeze hook '%s'", hook);
return;
}
slog("executing fsfreeze hook with arg '%s'", arg_str);
pid = fork();
if (pid == 0) {
setsid();
reopen_fd_to_null(0);
reopen_fd_to_null(1);
reopen_fd_to_null(2);
execle(hook, hook, arg_str, NULL, environ);
_exit(EXIT_FAILURE);
} else if (pid < 0) {
error_setg_errno(err, errno, "failed to create child process");
return;
}
ga_wait_child(pid, &status, &local_err);
if (error_is_set(&local_err)) {
error_propagate(err, local_err);
return;
}
if (!WIFEXITED(status)) {
error_setg(err, "fsfreeze hook has terminated abnormally");
return;
}
status = WEXITSTATUS(status);
if (status) {
error_setg(err, "fsfreeze hook has failed with status %d", status);
return;
}
}
/*
* Return status of freeze/thaw
*/
@ -436,6 +496,12 @@ int64_t qmp_guest_fsfreeze_freeze(Error **err)
slog("guest-fsfreeze called");
execute_fsfreeze_hook(FSFREEZE_HOOK_FREEZE, &local_err);
if (error_is_set(&local_err)) {
error_propagate(err, local_err);
return -1;
}
QTAILQ_INIT(&mounts);
build_fs_mount_list(&mounts, &local_err);
if (error_is_set(&local_err)) {
@ -537,6 +603,9 @@ int64_t qmp_guest_fsfreeze_thaw(Error **err)
ga_unset_frozen(ga_state);
free_fs_mount_list(&mounts);
execute_fsfreeze_hook(FSFREEZE_HOOK_THAW, err);
return i;
}

1
qga/guest-agent-core.h
View File

@ -34,6 +34,7 @@ void ga_set_response_delimited(GAState *s);
bool ga_is_frozen(GAState *s);
void ga_set_frozen(GAState *s);
void ga_unset_frozen(GAState *s);
const char *ga_fsfreeze_hook(GAState *s);
#ifndef _WIN32
void reopen_fd_to_null(int fd);

48
qga/main.c
View File

@ -34,6 +34,12 @@
#include "qga/service-win32.h"
#include <windows.h>
#endif
#ifdef __linux__
#include <linux/fs.h>
#ifdef FIFREEZE
#define CONFIG_FSFREEZE
#endif
#endif
#ifndef _WIN32
#define QGA_VIRTIO_PATH_DEFAULT "/dev/virtio-ports/org.qemu.guest_agent.0"
@ -42,6 +48,9 @@
#endif
#define QGA_STATEDIR_DEFAULT CONFIG_QEMU_LOCALSTATEDIR "/run"
#define QGA_PIDFILE_DEFAULT QGA_STATEDIR_DEFAULT "/qemu-ga.pid"
#ifdef CONFIG_FSFREEZE
#define QGA_FSFREEZE_HOOK_DEFAULT CONFIG_QEMU_CONFDIR "/fsfreeze-hook"
#endif
#define QGA_SENTINEL_BYTE 0xFF
struct GAState {
@ -64,6 +73,9 @@ struct GAState {
const char *log_filepath;
const char *pid_filepath;
} deferred_options;
#ifdef CONFIG_FSFREEZE
const char *fsfreeze_hook;
#endif
};
struct GAState *ga_state;
@ -153,6 +165,16 @@ static void usage(const char *cmd)
" %s)\n"
" -l, --logfile set logfile path, logs to stderr by default\n"
" -f, --pidfile specify pidfile (default is %s)\n"
#ifdef CONFIG_FSFREEZE
" -F, --fsfreeze-hook\n"
" enable fsfreeze hook. Accepts an optional argument that\n"
" specifies script to run on freeze/thaw. Script will be\n"
" called with 'freeze'/'thaw' arguments accordingly.\n"
" (default is %s)\n"
" If using -F with an argument, do not follow -F with a\n"
" space.\n"
" (for example: -F/var/run/fsfreezehook.sh)\n"
#endif
" -t, --statedir specify dir to store state information (absolute paths\n"
" only, default is %s)\n"
" -v, --verbose log extra debugging information\n"
@ -167,6 +189,9 @@ static void usage(const char *cmd)
"\n"
"Report bugs to <mdroth@linux.vnet.ibm.com>\n"
, cmd, QEMU_VERSION, QGA_VIRTIO_PATH_DEFAULT, QGA_PIDFILE_DEFAULT,
#ifdef CONFIG_FSFREEZE
QGA_FSFREEZE_HOOK_DEFAULT,
#endif
QGA_STATEDIR_DEFAULT);
}
@ -401,6 +426,13 @@ void ga_unset_frozen(GAState *s)
}
}
#ifdef CONFIG_FSFREEZE
const char *ga_fsfreeze_hook(GAState *s)
{
return s->fsfreeze_hook;
}
#endif
static void become_daemon(const char *pidfile)
{
#ifndef _WIN32
@ -678,10 +710,13 @@ VOID WINAPI service_main(DWORD argc, TCHAR *argv[])
int main(int argc, char **argv)
{
const char *sopt = "hVvdm:p:l:f:b:s:t:";
const char *sopt = "hVvdm:p:l:f:F::b:s:t:";
const char *method = NULL, *path = NULL;
const char *log_filepath = NULL;
const char *pid_filepath = QGA_PIDFILE_DEFAULT;
#ifdef CONFIG_FSFREEZE
const char *fsfreeze_hook = NULL;
#endif
const char *state_dir = QGA_STATEDIR_DEFAULT;
#ifdef _WIN32
const char *service = NULL;
@ -691,6 +726,9 @@ int main(int argc, char **argv)
{ "version", 0, NULL, 'V' },
{ "logfile", 1, NULL, 'l' },
{ "pidfile", 1, NULL, 'f' },
#ifdef CONFIG_FSFREEZE
{ "fsfreeze-hook", 2, NULL, 'F' },
#endif
{ "verbose", 0, NULL, 'v' },
{ "method", 1, NULL, 'm' },
{ "path", 1, NULL, 'p' },
@ -723,6 +761,11 @@ int main(int argc, char **argv)
case 'f':
pid_filepath = optarg;
break;
#ifdef CONFIG_FSFREEZE
case 'F':
fsfreeze_hook = optarg ? optarg : QGA_FSFREEZE_HOOK_DEFAULT;
break;
#endif
case 't':
state_dir = optarg;
break;
@ -786,6 +829,9 @@ int main(int argc, char **argv)
s = g_malloc0(sizeof(GAState));
s->log_level = log_level;
s->log_file = stderr;
#ifdef CONFIG_FSFREEZE
s->fsfreeze_hook = fsfreeze_hook;
#endif
g_log_set_default_handler(ga_log, s);
g_log_set_fatal_mask(NULL, G_LOG_LEVEL_ERROR);
ga_enable_logging(s);