[Qemu-devel] [PATCH v2 0/2] qemu-ga: add hook to quiesce the guest on fsfreeze-freeze/thaw

[Qemu-devel] [PATCH v2 0/2] qemu-ga: add hook to quiesce the guest on fsfreeze-freeze/thaw

[Tomoki Sekiyama]

Hi,

This is version 2 of the qemu-ga fsfreeze hook patchset.

*Changes from v1: ( http://lists.gnu.org/archive/html/qemu-devel/2012-11/msg00685.html )
  - Fixed bugs in handling file path which contains spaces.
  - Improved error checkings.
  - Changed the default hook name to fsfreeze-hook.
    This also fixes errors in `make clean'.

---

Tomoki Sekiyama (2):
      qemu-ga: execute hook to quiesce the guest on fsfreeze-freeze/thaw
      qemu-ga: sample fsfreeze hooks


 docs/qemu-guest-agent/fsfreeze-hook                |   31 +++++++++++++
 .../fsfreeze-hook.d.sample/mysql-flush.sh          |   47 ++++++++++++++++++++
 qemu-ga.c                                          |   42 +++++++++++++++++-
 qga/commands-posix.c                               |   44 +++++++++++++++++++
 qga/guest-agent-core.h                             |    1 
 5 files changed, 164 insertions(+), 1 deletion(-)
 create mode 100755 docs/qemu-guest-agent/fsfreeze-hook
 create mode 100755 docs/qemu-guest-agent/fsfreeze-hook.d.sample/mysql-flush.sh


Thanks,
-- 
Tomoki Sekiyama <tomoki.sekiyama.qu@hitachi.com>
Linux Technology Center
Hitachi, Ltd., Yokohama Research Laboratory

Re: [Qemu-devel] [PATCH v2 1/2] qemu-ga: execute hook 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 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.qu@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"
+"                    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 <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 +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;
 }
 
+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");
+
     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);

Re: [Qemu-devel] [PATCH v2 2/2] qemu-ga: sample fsfreeze hooks

[Tomoki Sekiyama]

Adds sample hook scripts for --fsfreeze-hook option of qemu-ga.
  - fsfreeze-hook : execute scripts in fsfreeze-hook.d/
  - fsfreeze-hook.d.sample/mysql-flush.sh : quiesce MySQL before snapshot

Signed-off-by: Tomoki Sekiyama <tomoki.sekiyama.qu@hitachi.com>
---
 docs/qemu-guest-agent/fsfreeze-hook                |   31 +++++++++++++
 .../fsfreeze-hook.d.sample/mysql-flush.sh          |   47 ++++++++++++++++++++
 2 files changed, 78 insertions(+)
 create mode 100755 docs/qemu-guest-agent/fsfreeze-hook
 create mode 100755 docs/qemu-guest-agent/fsfreeze-hook.d.sample/mysql-flush.sh

diff --git a/docs/qemu-guest-agent/fsfreeze-hook b/docs/qemu-guest-agent/fsfreeze-hook
new file mode 100755
index 0000000..efc9bf2
--- /dev/null
+++ b/docs/qemu-guest-agent/fsfreeze-hook
@@ -0,0 +1,31 @@
+#!/bin/sh
+
+# This script is executed when a guest agent receives fsfreeze-freeze and
+# fsfreeze-thaw command, if it is specified in --fsfreeze-hook (-F)
+# option of qemu-ga or placed in default path (/etc/qemu/fsfreeze-hook).
+# When the agent receives fsfreeze-freeze request, this script is issued with
+# "freeze" argument before the filesystem is freezed. And for fsfreeze-thaw
+# request, it is issued with "thaw" argument after filesystem is thawed.
+
+LOGFILE=/var/log/qga-fsreeze-hook.log
+FSFREEZE_D=$(dirname -- "$0")/fsfreeze-hook.d
+
+# Check whether file $1 is a backup or rpm-generated file and should be ignored
+is_ignored_file() {
+    case "$1" in
+        *~ | *.bak | *.orig | *.rpmnew | *.rpmorig | *.rpmsave)
+            return 0 ;;
+    esac
+    return 1
+}
+
+# Iterate executables in directory "fsfreeze-hook.d" with the specified args
+[ ! -d "$FSFREEZE_D" ] && exit 1
+for file in "$FSFREEZE_D"/* ; do
+    is_ignored_file "$file" && continue
+    [ -x "$file" ] || continue
+    echo $(date) ": execute $file $@" >>$LOGFILE
+    "$file" "$@" >>$LOGFILE 2>&1
+    STATUS=$?
+    echo $(date) ": $file finished with status=$STATUS" >>$LOGFILE
+done
diff --git a/docs/qemu-guest-agent/fsfreeze-hook.d.sample/mysql-flush.sh b/docs/qemu-guest-agent/fsfreeze-hook.d.sample/mysql-flush.sh
new file mode 100755
index 0000000..705002e
--- /dev/null
+++ b/docs/qemu-guest-agent/fsfreeze-hook.d.sample/mysql-flush.sh
@@ -0,0 +1,47 @@
+#!/bin/sh
+
+# Flush MySQL tables to the disk before the filesystem is freezed.
+# At the same time, this keeps a read lock while the filesystem is freezed
+# in order to avoid write accesses by the other clients.
+
+MYSQL="mysql -uroot" #"-prootpassword"
+FIFO=/tmp/mysql-flush.fifo
+
+flush_and_wait() {
+    echo 'FLUSH TABLES WITH READ LOCK \G'
+    read < $FIFO
+    echo 'UNLOCK TABLES \G'
+}
+
+case "$1" in
+    freeze)
+        mkfifo $FIFO || exit 1
+        flush_and_wait | $MYSQL &
+        # wait until every block is flushed
+        while [ "$(echo 'SHOW STATUS LIKE "Key_blocks_not_flushed"' |\
+                 $MYSQL | tail -1 | cut -f 2)" -gt 0 ]; do
+            sleep 1
+        done
+        # for InnoDB, wait until every log is flushed
+        INNODB_STATUS=$(mktemp /tmp/mysql-flush.XXXXXX)
+        [ $? -ne 0 ] && exit 2
+        trap "rm -f $INNODB_STATUS" SIGINT
+        while :; do
+            echo 'SHOW ENGINE INNODB STATUS \G' | $MYSQL > $INNODB_STATUS
+            LOG_CURRENT=$(grep 'Log sequence number' $INNODB_STATUS |\
+                          tr -s ' ' | cut -d' ' -f4)
+            LOG_FLUSHED=$(grep 'Log flushed up to' $INNODB_STATUS |\
+                          tr -s ' ' | cut -d' ' -f5)
+            [ "$LOG_CURRENT" = "$LOG_FLUSHED" ] && break
+            sleep 1
+        done
+        rm -f $INNODB_STATUS
+        ;;
+
+    thaw)
+        [ ! -p $FIFO ] && exit 1
+        echo > $FIFO
+        rm $FIFO
+        ;;
+esac
+

Re: [Qemu-devel] [PATCH v2 2/2] qemu-ga: sample fsfreeze hooks

[Eric Blake]

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On 11/12/2012 02:32 AM, Tomoki Sekiyama wrote:
> Adds sample hook scripts for --fsfreeze-hook option of qemu-ga.
>   - fsfreeze-hook : execute scripts in fsfreeze-hook.d/
>   - fsfreeze-hook.d.sample/mysql-flush.sh : quiesce MySQL before snapshot
> 
> Signed-off-by: Tomoki Sekiyama <tomoki.sekiyama.qu@hitachi.com>
> ---

> +LOGFILE=/var/log/qga-fsreeze-hook.log

s/fsreeze/fsfreeze/

> +# Iterate executables in directory "fsfreeze-hook.d" with the specified args
> +[ ! -d "$FSFREEZE_D" ] && exit 1
> +for file in "$FSFREEZE_D"/* ; do
> +    is_ignored_file "$file" && continue
> +    [ -x "$file" ] || continue
> +    echo $(date) ": execute $file $@" >>$LOGFILE

Put $(date) inside the ""; otherwise, single-digit days will be one
character shorter due to IFS field splitting eating the double-space;
and I don't like unaligned dates in logs.

> +    "$file" "$@" >>$LOGFILE 2>&1
> +    STATUS=$?
> +    echo $(date) ": $file finished with status=$STATUS" >>$LOGFILE

and again.

> +        INNODB_STATUS=$(mktemp /tmp/mysql-flush.XXXXXX)
> +        [ $? -ne 0 ] && exit 2
> +        trap "rm -f $INNODB_STATUS" SIGINT
> +        while :; do
> +            echo 'SHOW ENGINE INNODB STATUS \G' | $MYSQL > $INNODB_STATUS

'echo' cannot portably be used with \.  Use 'printf' instead.

-- 
Eric Blake   eblake@redhat.com    +1-919-301-3266
Libvirt virtualization library http://libvirt.org


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Re: [Qemu-devel] [PATCH v2 2/2] qemu-ga: sample fsfreeze hooks

[Tomoki Sekiyama]

Hi Eric,
thank you for the review again.

On 2012/11/13 7:16, Eric Blake wrote:
> On 11/12/2012 02:32 AM, Tomoki Sekiyama wrote:
>> Adds sample hook scripts for --fsfreeze-hook option of qemu-ga.
>>   - fsfreeze-hook : execute scripts in fsfreeze-hook.d/
>>   - fsfreeze-hook.d.sample/mysql-flush.sh : quiesce MySQL before snapshot
>>
>> Signed-off-by: Tomoki Sekiyama <tomoki.sekiyama.qu@hitachi.com>
>> ---
> 
>> +LOGFILE=/var/log/qga-fsreeze-hook.log
> 
> s/fsreeze/fsfreeze/

Oops...

>> +# Iterate executables in directory "fsfreeze-hook.d" with the specified args
>> +[ ! -d "$FSFREEZE_D" ] && exit 1
>> +for file in "$FSFREEZE_D"/* ; do
>> +    is_ignored_file "$file" && continue
>> +    [ -x "$file" ] || continue
>> +    echo $(date) ": execute $file $@" >>$LOGFILE
> 
> Put $(date) inside the ""; otherwise, single-digit days will be one
> character shorter due to IFS field splitting eating the double-space;
> and I don't like unaligned dates in logs.
> 
>> +    "$file" "$@" >>$LOGFILE 2>&1
>> +    STATUS=$?
>> +    echo $(date) ": $file finished with status=$STATUS" >>$LOGFILE
> 
> and again.

I will fix this.

>> +        INNODB_STATUS=$(mktemp /tmp/mysql-flush.XXXXXX)
>> +        [ $? -ne 0 ] && exit 2
>> +        trap "rm -f $INNODB_STATUS" SIGINT
>> +        while :; do
>> +            echo 'SHOW ENGINE INNODB STATUS \G' | $MYSQL > $INNODB_STATUS
> 
> 'echo' cannot portably be used with \.  Use 'printf' instead.

OK, I replace this with 'printf' (also in 'flush_and_wait' function).

-- 
Tomoki Sekiyama <tomoki.sekiyama.qu@hitachi.com>
Linux Technology Center
Hitachi, Ltd., Yokohama Research Laboratory