qemu-ga: execute hook to quiesce the guest on fsfreeze-freeze/thaw
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>
diff --git a/qga/commands-posix.c b/qga/commands-posix.c
index 614a421..77f6ee7 100644
--- a/qga/commands-posix.c
+++ b/qga/commands-posix.c
@@ -410,6 +410,66 @@
#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 @@
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 @@
ga_unset_frozen(ga_state);
free_fs_mount_list(&mounts);
+
+ execute_fsfreeze_hook(FSFREEZE_HOOK_THAW, err);
+
return i;
}
