| Message ID | 509B9FEF.4040604@hitachi.com |
|---|---|
| State | New |
| Headers | show |
On 11/08/2012 05:05 AM, Tomoki Sekiyama wrote: [Recoding to UTF-8, as ISO-2022-JP is not universally installed these days - you may want to reconsider your mailer's defaults] > 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 <tomoki.sekiyama.qu@hitachi.com> > --- > @@ -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)) { Is it any simpler to use access(fsfreeze_script, X_OK) to check if the script exists and is executable? > + slog("executing fsfreeze script with arg `%s'", arg); > + cmdline = malloc(strlen(fsfreeze_script) + strlen(arg) + 2); Don't we prefer g_malloc over malloc in qemu-ga? > + if (cmdline) { > + sprintf(cmdline, "%s %s", fsfreeze_script, arg); Thankfully, this doesn't overflow, but isn't there a glib function that makes it easier to create a malloc'd concatenated string in one call rather than pairing a malloc and sprintf? That said, why do you even need a single string, given that... > + ret = system(cmdline); ...system() is not required to be thread-safe, but we should assume that qemu-ga is multi-threaded, and therefore we should not use system. Besides executing things via an extra layer of shell opens doors for further problems; for example, if the user starts qemu-ga with --fsfreeze-script '/path/with spaces/script', your command line is horribly broken when passed through the shell. It would be much better to directly fork() and exec() the script ourselves instead of relying on system(). > + free(cmdline); > + } > + if (ret > 0) { > + g_warning("fsfreeze script failed with status=%d", ret); This is a potentially misleading message; you should be using macros such as WEXITSTATUS when interpreting the result of system(), since not all systems return exit status 1 in the same bit position. > + } else if (ret == -1) { > + g_warning("execution of fsfreeze script failed: %s", > + strerror(errno)); free() is allowed to clobber errno, which means you may be reporting the wrong error if system() failed with -1. > + } > + } > + } > + return ret; > +} > + The idea of having the freeze and thaw actions hook out to user-specified actions for additional steps seems nice, but this patch series needs a lot more work.
Hi Eric, thanks for your review. On 2012/11/09 3:38, Eric Blake wrote: > On 11/08/2012 05:05 AM, Tomoki Sekiyama wrote: > > [Recoding to UTF-8, as ISO-2022-JP is not universally installed these > days - you may want to reconsider your mailer's defaults] Now this should be UTF-8, sorry. >> 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 <tomoki.sekiyama.qu@hitachi.com> >> --- > >> @@ -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)) { > > Is it any simpler to use access(fsfreeze_script, X_OK) to check if the > script exists and is executable? OK, I will use access() here. <snip> >> + ret = system(cmdline); > > ...system() is not required to be thread-safe, but we should assume that > qemu-ga is multi-threaded, and therefore we should not use system. > Besides executing things via an extra layer of shell opens doors for > further problems; for example, if the user starts qemu-ga with > --fsfreeze-script '/path/with spaces/script', your command line is > horribly broken when passed through the shell. It would be much better > to directly fork() and exec() the script ourselves instead of relying on > system(). I will use fork()/exec() method instead of system(), as in shutdown, so I can remove malloc/free. >> + if (ret > 0) { >> + g_warning("fsfreeze script failed with status=%d", ret); > > This is a potentially misleading message; you should be using macros > such as WEXITSTATUS when interpreting the result of system(), since not > all systems return exit status 1 in the same bit position. OK. I will refine error messages. > The idea of having the freeze and thaw actions hook out to > user-specified actions for additional steps seems nice, but this patch > series needs a lot more work. Regards,
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 <mdroth@linux.vnet.ibm.com>\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);
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 <tomoki.sekiyama.qu@hitachi.com> --- qemu-ga.c | 42 +++++++++++++++++++++++++++++++++++++++++- qga/commands-posix.c | 34 ++++++++++++++++++++++++++++++++++ qga/guest-agent-core.h | 2 ++ 3 files changed, 77 insertions(+), 1 deletion(-)