Patchwork [11/12] qemu-ga: execute hook to quiesce the guest on fsfreeze-freeze/thaw

login
register
mail settings
Submitter Michael Roth
Date Jan. 8, 2013, 11 p.m.
Message ID <1357686009-13139-12-git-send-email-mdroth@linux.vnet.ibm.com>
Download mbox | patch
Permalink /patch/210583/
State New
Headers show

Comments

Michael Roth - Jan. 8, 2013, 11 p.m.
From: Tomoki Sekiyama <tomoki.sekiyama.qu@hitachi.com>

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>
---
 qga/commands-posix.c   |   69 ++++++++++++++++++++++++++++++++++++++++++++++++
 qga/guest-agent-core.h |    1 +
 qga/main.c             |   48 ++++++++++++++++++++++++++++++++-
 3 files changed, 117 insertions(+), 1 deletion(-)
Blue Swirl - Jan. 9, 2013, 9:02 p.m.
On Tue, Jan 8, 2013 at 11:00 PM, Michael Roth <mdroth@linux.vnet.ibm.com> wrote:
> From: Tomoki Sekiyama <tomoki.sekiyama.qu@hitachi.com>
>
> 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>
> ---
>  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 <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);
> --
> 1.7.9.5
>
>
Luiz Capitulino - Jan. 10, 2013, 11:17 a.m.
On Wed, 9 Jan 2013 21:02:37 +0000
Blue Swirl <blauwirbel@gmail.com> wrote:

> On Tue, Jan 8, 2013 at 11:00 PM, Michael Roth <mdroth@linux.vnet.ibm.com> wrote:
> > From: Tomoki Sekiyama <tomoki.sekiyama.qu@hitachi.com>
> >
> > 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>
> > ---
> >  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 <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);
> > --
> > 1.7.9.5
> >
> >
>

Patch

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[] = {
+    "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 <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);