On Tue, Nov 13, 2012 at 01:56:56PM +0900, Tomoki Sekiyama wrote:
> 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.
>
> When the qemu-ga receives fsfreeze-freeze command, the hook script
> specified in --fsfreeze-hook option is executed with "freeze" argument
> before the filesystem is frozen. For fsfreeze-thaw command, the hook
> script is executed with "thaw" argument after the filesystem is thawed.
>
> Signed-off-by: Tomoki Sekiyama <tomoki.sekiyama...@hitachi.com>
> ---
> qemu-ga.c | 42 +++++++++++++++++++++++++++++++++++++++++-
> qga/commands-posix.c | 44 ++++++++++++++++++++++++++++++++++++++++++++
> qga/guest-agent-core.h | 1 +
> 3 files changed, 86 insertions(+), 1 deletion(-)
>
> diff --git a/qemu-ga.c b/qemu-ga.c
> index 9b59a52..d1d9b89 100644
> --- a/qemu-ga.c
> +++ b/qemu-ga.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 +165,10 @@ 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"
Small nit, but can we change this to --fsfreeze-hook?
> +" specify fsfreeze hook (default is %s)\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 +183,9 @@ static void usage(const char *cmd)
> "\n"
> "Report bugs to <mdr...@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 +420,13 @@ 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 +704,13 @@ 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 = QGA_FSFREEZE_HOOK_DEFAULT;
> +#endif
> const char *state_dir = QGA_STATEDIR_DEFAULT;
> #ifdef _WIN32
> const char *service = NULL;
> @@ -691,6 +720,9 @@ int main(int argc, char **argv)
> { "version", 0, NULL, 'V' },
> { "logfile", 1, NULL, 'l' },
> { "pidfile", 1, NULL, 'f' },
> +#ifdef CONFIG_FSFREEZE
> + { "fsfreeze-hook", 1, NULL, 'F' },
> +#endif
> { "verbose", 0, NULL, 'v' },
> { "method", 1, NULL, 'm' },
> { "path", 1, NULL, 'p' },
> @@ -723,6 +755,11 @@ int main(int argc, char **argv)
> case 'f':
> pid_filepath = optarg;
> break;
> +#ifdef CONFIG_FSFREEZE
> + case 'F':
> + fsfreeze_hook = optarg;
> + break;
> +#endif
> case 't':
> state_dir = optarg;
> break;
> @@ -786,6 +823,9 @@ 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);
> diff --git a/qga/commands-posix.c b/qga/commands-posix.c
> index 726930a..8c3e341 100644
> --- a/qga/commands-posix.c
> +++ b/qga/commands-posix.c
> @@ -396,6 +396,45 @@ GuestFsfreezeStatus qmp_guest_fsfreeze_status(Error
> **err)
> return GUEST_FSFREEZE_STATUS_THAWED;
> }
>
Rather than passing freeze/thaw in as a string, I think an enum
parameter of the form:
typedef enum {
FSFREEZE_HOOK_THAW,
FSFREEZE_HOOK_FREEZE,
} FsfreezeHook;
would be better in terms of documenting the interface.
> +static void execute_fsfreeze_hook(const char *arg)
> +{
> + int status;
> + pid_t pid, rpid;
> + const char *hook;
> +
> + hook = ga_fsfreeze_hook(ga_state);
> + if (!hook || access(hook, X_OK) != 0) {
> + return;
> + }
> +
> + slog("executing fsfreeze hook with arg `%s'", arg);
> + 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, NULL, environ);
> + _exit(EXIT_FAILURE);
> + } else if (pid < 0) {
> + slog("execution of fsfreeze hook failed: %s", strerror(errno));
> + return;
> + }
> +
> + do {
> + rpid = waitpid(pid, &status, 0);
> + } while (rpid == -1 && errno == EINTR);
> + if (rpid == pid && WIFEXITED(status)) {
> + int st = WEXITSTATUS(status);
> + if (st) {
> + slog("fsfreeze hook failed with status %d", st);
> + }
> + } else if (rpid == pid && WIFSIGNALED(status)) {
> + slog("fsfreeze hook killed by signal %d", WTERMSIG(status));
> + }
> +}
> +
> /*
> * Walk list of mounted file systems in the guest, and freeze the ones which
> * are real local file systems.
> @@ -410,6 +449,8 @@ int64_t qmp_guest_fsfreeze_freeze(Error **err)
>
> slog("guest-fsfreeze called");
>
> + execute_fsfreeze_hook("freeze");
> +
I think if a user configures a pre-freeze hook, it's failure should be
treated as a failure of the fsfreeze call in general, otherwise we risk
moving forward based on false assumptions that can lead to data loss or
other issues. I think the thaw hook is okay the way it is though, they
can review the logs for any issues arising after the VM is
unfrozen.
> QTAILQ_INIT(&mounts);
> ret = build_fs_mount_list(&mounts);
> if (ret < 0) {
> @@ -513,6 +554,9 @@ int64_t qmp_guest_fsfreeze_thaw(Error **err)
>
> ga_unset_frozen(ga_state);
> free_fs_mount_list(&mounts);
> +
> + execute_fsfreeze_hook("thaw");
> +
> return i;
> }
>
> diff --git a/qga/guest-agent-core.h b/qga/guest-agent-core.h
> index 49a7abe..c6e8de0 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);
>
