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

[Luiz Capitulino]

On Wed, 9 Jan 2013 21:02:37 +0000
Blue Swirl <address@hidden> wrote:

> 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

This has already been merged. It's quite of a minor change anyway.

> 
> > +    "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
> >
> >
>