Commit ec0f694c authored by Tomoki Sekiyama's avatar Tomoki Sekiyama Committed by Michael Roth
Browse files

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: default avatarTomoki Sekiyama <tomoki.sekiyama.qu@hitachi.com>
Reviewed-by: default avatarLuiz Capitulino <lcapitulino@redhat.com>

*clarified usage in help output

Signed-off-by: default avatarMichael Roth <mdroth@linux.vnet.ibm.com>
parent 7b376087

qga/commands-posix.c

+69 −0
Original line number Diff line number Diff line
@@ -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;

}

qga/guest-agent-core.h

+1 −0
Original line number Diff line number Diff line
@@ -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);

qga/main.c

+47 −1
Original line number Diff line number Diff line
@@ -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);