[Qemu-devel] [PATCH 1/2] qemu-ga: execute script to quiesce the guest on fsfreeze-freeze/thaw

[Tomoki Sekiyama]

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 script specified
in --fsfreeze-script option is executed with "freeze" argument before the
filesystem is frozen. For fsfreeze-thaw command, the script is executed
with "thaw" argument after the filesystem is thawed.

Signed-off-by: Tomoki Sekiyama <address@hidden>
---
 qemu-ga.c              | 42 +++++++++++++++++++++++++++++++++++++++++-
 qga/commands-posix.c   | 34 ++++++++++++++++++++++++++++++++++
 qga/guest-agent-core.h |  2 ++
 3 files changed, 77 insertions(+), 1 deletion(-)

diff --git a/qemu-ga.c b/qemu-ga.c
index 9b59a52..7cb682e 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_SCRIPT_DEFAULT CONFIG_QEMU_CONFDIR "/fsfreeze.sh"
+#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_script;
+#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_script\n"
+"                    specify fsfreeze script (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 <address@hidden>\n"
     , cmd, QEMU_VERSION, QGA_VIRTIO_PATH_DEFAULT, QGA_PIDFILE_DEFAULT,
+#ifdef CONFIG_FSFREEZE
+    QGA_FSFREEZE_SCRIPT_DEFAULT,
+#endif
     QGA_STATEDIR_DEFAULT);
 }
 
@@ -401,6 +420,13 @@ void ga_unset_frozen(GAState *s)
     }
 }
 
+#ifdef CONFIG_FSFREEZE
+const char *ga_fsfreeze_script(GAState *s)
+{
+    return s->fsfreeze_script;
+}
+#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_script = QGA_FSFREEZE_SCRIPT_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-script", 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_script = 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_script = fsfreeze_script;
+#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..007c0a3 100644
--- a/qga/commands-posix.c
+++ b/qga/commands-posix.c
@@ -13,6 +13,7 @@
 
 #include <glib.h>
 #include <sys/types.h>
+#include <sys/stat.h>
 #include <sys/ioctl.h>
 #include <sys/wait.h>
 #include "qga/guest-agent-core.h"
@@ -396,6 +397,34 @@ GuestFsfreezeStatus qmp_guest_fsfreeze_status(Error **err)
     return GUEST_FSFREEZE_STATUS_THAWED;
 }
 
+int execute_fsfreeze_script(const char *arg)
+{
+    int ret = -1;
+    const char *fsfreeze_script;
+    char *cmdline;
+    struct stat st;
+
+    fsfreeze_script = ga_fsfreeze_script(ga_state);
+    if (fsfreeze_script && stat(fsfreeze_script, &st) == 0) {
+        if (S_ISREG(st.st_mode) && (st.st_mode & S_IXUSR)) {
+            slog("executing fsfreeze script with arg `%s'", arg);
+            cmdline = malloc(strlen(fsfreeze_script) + strlen(arg) + 2);
+            if (cmdline) {
+                sprintf(cmdline, "%s %s", fsfreeze_script, arg);
+                ret = system(cmdline);
+                free(cmdline);
+            }
+            if (ret > 0) {
+                g_warning("fsfreeze script failed with status=%d", ret);
+            } else if (ret == -1) {
+                g_warning("execution of fsfreeze script failed: %s",
+                          strerror(errno));
+            }
+        }
+    }
+    return ret;
+}
+
 /*
  * Walk list of mounted file systems in the guest, and freeze the ones which
  * are real local file systems.
@@ -410,6 +439,8 @@ int64_t qmp_guest_fsfreeze_freeze(Error **err)
 
     slog("guest-fsfreeze called");
 
+    execute_fsfreeze_script("freeze");
+
     QTAILQ_INIT(&mounts);
     ret = build_fs_mount_list(&mounts);
     if (ret < 0) {
@@ -513,6 +544,9 @@ int64_t qmp_guest_fsfreeze_thaw(Error **err)
 
     ga_unset_frozen(ga_state);
     free_fs_mount_list(&mounts);
+
+    execute_fsfreeze_script("thaw");
+
     return i;
 }
 
diff --git a/qga/guest-agent-core.h b/qga/guest-agent-core.h
index 49a7abe..b466bfd 100644
--- a/qga/guest-agent-core.h
+++ b/qga/guest-agent-core.h
@@ -34,6 +34,8 @@ 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_script(GAState *s);
+int execute_fsfreeze_script(const char *arg);
 
 #ifndef _WIN32
 void reopen_fd_to_null(int fd);
-- 
1.7.11.7