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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;
}