Re: [Qemu-devel] [PATCH 11/12] qemu-ga: execute hook to quiesce the guest on fsfreeze-freeze/thaw

[Blue Swirl]

On Tue, Jan 8, 2013 at 11:00 PM, Michael Roth <address@hidden> wrote:
> From: Tomoki Sekiyama <address@hidden>
>
> 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 <address@hidden>
> Reviewed-by: Luiz Capitulino <address@hidden>
>
> *clarified usage in help output
>
> Signed-off-by: Michael Roth <address@hidden>
> ---
>  qga/commands-posix.c   |   69 
> ++++++++++++++++++++++++++++++++++++++++++++++++
>  qga/guest-agent-core.h |    1 +
>  qga/main.c             |   48 ++++++++++++++++++++++++++++++++-
>  3 files changed, 117 insertions(+), 1 deletion(-)
>
> 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 @@ 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[] = {

static

> +    "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;
>  }
>
> diff --git a/qga/guest-agent-core.h b/qga/guest-agent-core.h
> index 8934163..3354598 100644
> --- a/qga/guest-agent-core.h
> +++ b/qga/guest-agent-core.h
> @@ -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);
> diff --git a/qga/main.c b/qga/main.c
> index ba5fa1c..a9b968c 100644
> --- a/qga/main.c
> +++ b/qga/main.c
> @@ -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 <address@hidden>\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);
> --
> 1.7.9.5
>
>