[Qemu-devel] [PULL 0/3] qemu-ga: fsfreeze fix and guest-info extensions

[Qemu-devel] [PULL 0/3] qemu-ga: fsfreeze fix and guest-info extensions

[Michael Roth]

Hi Anthony,

The following patches add support for indicating whether a guest
agent command returns a response, as well as a fix to unfreeze
filesystems LIFO order to avoid deadlocks in some cases where
images are loopback-mounted to frozen filesystem.

The following changes since commit f2c6bcfc2e15e1dc5c69c3e579ff2063068ecb85:

  Merge remote-tracking branch 'sstabellini/xen-2013-10-10' into staging (2013-10-10 10:03:38 -0700)

are available in the git repository at:


  git://github.com/mdroth/qemu.git qga-pull-2013-10-10

for you to fetch changes up to 0106dc4f05231b44f54fae5d0ee42031298588bd:

  qemu-ga: Extend 'guest-info' command to expose flag 'success-response' (2013-10-10 14:52:37 -0500)

----------------------------------------------------------------
Mark Wu (2):
      qemu-ga: Add interface to traverse the qmp command list by QmpCommand
      qemu-ga: Extend 'guest-info' command to expose flag 'success-response'

Tomoki Sekiyama (1):
      qemu-ga: execute fsfreeze-freeze in reverse order of mounts

 include/qapi/qmp/dispatch.h |    7 ++--
 qapi/qmp-registry.c         |   33 +++++++------------
 qga/commands-posix.c        |    4 +--
 qga/commands.c              |   39 +++++++++-------------
 qga/main.c                  |   75 +++++++++++++++++--------------------------
 qga/qapi-schema.json        |    5 ++-
 6 files changed, 69 insertions(+), 94 deletions(-)

[Qemu-devel] [PATCH 1/3] qemu-ga: execute fsfreeze-freeze in reverse order of mounts

[Michael Roth]

From: Tomoki Sekiyama <tomoki.sekiyama@hds.com>

Currently, fsfreeze-freeze may cause deadlock if a guest has loopback mounts
of image files in its disk; e.g.:

    # mount | grep ^/
    /dev/vda1 / type ext4 (rw,noatime,seclabel,data=ordered)
    /tmp/disk.img on /mnt type ext4 (rw,relatime,seclabel)

To avoid the deadlock, this freezes filesystems in reverse order of mounts.

Signed-off-by: Tomoki Sekiyama <tomoki.sekiyama@hds.com>
Reviewed-by: Eric Blake <eblake@redhat.com>
*fix up commit msg
Signed-off-by: Michael Roth <mdroth@linux.vnet.ibm.com>
---
 qga/commands-posix.c |    4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/qga/commands-posix.c b/qga/commands-posix.c
index e199738..f453132 100644
--- a/qga/commands-posix.c
+++ b/qga/commands-posix.c
@@ -566,7 +566,7 @@ typedef struct FsMount {
     QTAILQ_ENTRY(FsMount) next;
 } FsMount;
 
-typedef QTAILQ_HEAD(, FsMount) FsMountList;
+typedef QTAILQ_HEAD(FsMountList, FsMount) FsMountList;
 
 static void free_fs_mount_list(FsMountList *mounts)
 {
@@ -728,7 +728,7 @@ int64_t qmp_guest_fsfreeze_freeze(Error **err)
     /* cannot risk guest agent blocking itself on a write in this state */
     ga_set_frozen(ga_state);
 
-    QTAILQ_FOREACH(mount, &mounts, next) {
+    QTAILQ_FOREACH_REVERSE(mount, &mounts, FsMountList, next) {
         fd = qemu_open(mount->dirname, O_RDONLY);
         if (fd == -1) {
             error_setg_errno(err, errno, "failed to open %s", mount->dirname);
-- 
1.7.9.5

[Qemu-devel] [PATCH 2/3] qemu-ga: Add interface to traverse the qmp command list by QmpCommand

[Michael Roth]

From: Mark Wu <wudxw@linux.vnet.ibm.com>

In the original code, qmp_get_command_list is used to construct
a list of all commands' name. To get the information of all qga
commands, it traverses the name list and search the command info
with its name.  So it can cause O(n^2) in the number of commands.

This patch adds an interface to traverse the qmp command list by
QmpCommand to replace qmp_get_command_list. It can decrease the
complexity from O(n^2) to O(n).

Signed-off-by: Mark Wu <wudxw@linux.vnet.ibm.com>
Reviewed-by: Eric Blake <eblake@redhat.com>
*fix up commit subject
Signed-off-by: Michael Roth <mdroth@linux.vnet.ibm.com>
---
 include/qapi/qmp/dispatch.h |    6 ++--
 qapi/qmp-registry.c         |   30 +++++------------
 qga/commands.c              |   38 +++++++++-------------
 qga/main.c                  |   75 +++++++++++++++++--------------------------
 4 files changed, 57 insertions(+), 92 deletions(-)

diff --git a/include/qapi/qmp/dispatch.h b/include/qapi/qmp/dispatch.h
index 1ce11f5..7d759ef 100644
--- a/include/qapi/qmp/dispatch.h
+++ b/include/qapi/qmp/dispatch.h
@@ -47,9 +47,11 @@ QmpCommand *qmp_find_command(const char *name);
 QObject *qmp_dispatch(QObject *request);
 void qmp_disable_command(const char *name);
 void qmp_enable_command(const char *name);
-bool qmp_command_is_enabled(const char *name);
-char **qmp_get_command_list(void);
+bool qmp_command_is_enabled(const QmpCommand *cmd);
+const char *qmp_command_name(const QmpCommand *cmd);
 QObject *qmp_build_error_object(Error *errp);
+typedef void (*qmp_cmd_callback_fn)(QmpCommand *cmd, void *opaque);
+void qmp_for_each_command(qmp_cmd_callback_fn fn, void *opaque);
 
 #endif
 
diff --git a/qapi/qmp-registry.c b/qapi/qmp-registry.c
index 28bbbe8..5e26710 100644
--- a/qapi/qmp-registry.c
+++ b/qapi/qmp-registry.c
@@ -66,35 +66,21 @@ void qmp_enable_command(const char *name)
     qmp_toggle_command(name, true);
 }
 
-bool qmp_command_is_enabled(const char *name)
+bool qmp_command_is_enabled(const QmpCommand *cmd)
 {
-    QmpCommand *cmd;
-
-    QTAILQ_FOREACH(cmd, &qmp_commands, node) {
-        if (strcmp(cmd->name, name) == 0) {
-            return cmd->enabled;
-        }
-    }
+    return cmd->enabled;
+}
 
-    return false;
+const char *qmp_command_name(const QmpCommand *cmd)
+{
+    return cmd->name;
 }
 
-char **qmp_get_command_list(void)
+void qmp_for_each_command(qmp_cmd_callback_fn fn, void *opaque)
 {
     QmpCommand *cmd;
-    int count = 1;
-    char **list_head, **list;
-
-    QTAILQ_FOREACH(cmd, &qmp_commands, node) {
-        count++;
-    }
-
-    list_head = list = g_malloc0(count * sizeof(char *));
 
     QTAILQ_FOREACH(cmd, &qmp_commands, node) {
-        *list = g_strdup(cmd->name);
-        list++;
+        fn(cmd, opaque);
     }
-
-    return list_head;
 }
diff --git a/qga/commands.c b/qga/commands.c
index 528b082..e87cbf8 100644
--- a/qga/commands.c
+++ b/qga/commands.c
@@ -45,35 +45,27 @@ void qmp_guest_ping(Error **err)
     slog("guest-ping called");
 }
 
-struct GuestAgentInfo *qmp_guest_info(Error **err)
+static void qmp_command_info(QmpCommand *cmd, void *opaque)
 {
-    GuestAgentInfo *info = g_malloc0(sizeof(GuestAgentInfo));
+    GuestAgentInfo *info = opaque;
     GuestAgentCommandInfo *cmd_info;
     GuestAgentCommandInfoList *cmd_info_list;
-    char **cmd_list_head, **cmd_list;
-
-    info->version = g_strdup(QEMU_VERSION);
-
-    cmd_list_head = cmd_list = qmp_get_command_list();
-    if (*cmd_list_head == NULL) {
-        goto out;
-    }
 
-    while (*cmd_list) {
-        cmd_info = g_malloc0(sizeof(GuestAgentCommandInfo));
-        cmd_info->name = g_strdup(*cmd_list);
-        cmd_info->enabled = qmp_command_is_enabled(cmd_info->name);
+    cmd_info = g_malloc0(sizeof(GuestAgentCommandInfo));
+    cmd_info->name = g_strdup(qmp_command_name(cmd));
+    cmd_info->enabled = qmp_command_is_enabled(cmd);
 
-        cmd_info_list = g_malloc0(sizeof(GuestAgentCommandInfoList));
-        cmd_info_list->value = cmd_info;
-        cmd_info_list->next = info->supported_commands;
-        info->supported_commands = cmd_info_list;
+    cmd_info_list = g_malloc0(sizeof(GuestAgentCommandInfoList));
+    cmd_info_list->value = cmd_info;
+    cmd_info_list->next = info->supported_commands;
+    info->supported_commands = cmd_info_list;
+}
 
-        g_free(*cmd_list);
-        cmd_list++;
-    }
+struct GuestAgentInfo *qmp_guest_info(Error **err)
+{
+    GuestAgentInfo *info = g_malloc0(sizeof(GuestAgentInfo));
 
-out:
-    g_free(cmd_list_head);
+    info->version = g_strdup(QEMU_VERSION);
+    qmp_for_each_command(qmp_command_info, info);
     return info;
 }
diff --git a/qga/main.c b/qga/main.c
index 6c746c8..c58b26a 100644
--- a/qga/main.c
+++ b/qga/main.c
@@ -347,48 +347,35 @@ static gint ga_strcmp(gconstpointer str1, gconstpointer str2)
 }
 
 /* disable commands that aren't safe for fsfreeze */
-static void ga_disable_non_whitelisted(void)
+static void ga_disable_non_whitelisted(QmpCommand *cmd, void *opaque)
 {
-    char **list_head, **list;
-    bool whitelisted;
-    int i;
-
-    list_head = list = qmp_get_command_list();
-    while (*list != NULL) {
-        whitelisted = false;
-        i = 0;
-        while (ga_freeze_whitelist[i] != NULL) {
-            if (strcmp(*list, ga_freeze_whitelist[i]) == 0) {
-                whitelisted = true;
-            }
-            i++;
-        }
-        if (!whitelisted) {
-            g_debug("disabling command: %s", *list);
-            qmp_disable_command(*list);
+    bool whitelisted = false;
+    int i = 0;
+    const char *name = qmp_command_name(cmd);
+
+    while (ga_freeze_whitelist[i] != NULL) {
+        if (strcmp(name, ga_freeze_whitelist[i]) == 0) {
+            whitelisted = true;
         }
-        g_free(*list);
-        list++;
+        i++;
+    }
+    if (!whitelisted) {
+        g_debug("disabling command: %s", name);
+        qmp_disable_command(name);
     }
-    g_free(list_head);
 }
 
 /* [re-]enable all commands, except those explicitly blacklisted by user */
-static void ga_enable_non_blacklisted(GList *blacklist)
+static void ga_enable_non_blacklisted(QmpCommand *cmd, void *opaque)
 {
-    char **list_head, **list;
-
-    list_head = list = qmp_get_command_list();
-    while (*list != NULL) {
-        if (g_list_find_custom(blacklist, *list, ga_strcmp) == NULL &&
-            !qmp_command_is_enabled(*list)) {
-            g_debug("enabling command: %s", *list);
-            qmp_enable_command(*list);
-        }
-        g_free(*list);
-        list++;
+    GList *blacklist = opaque;
+    const char *name = qmp_command_name(cmd);
+
+    if (g_list_find_custom(blacklist, name, ga_strcmp) == NULL &&
+        !qmp_command_is_enabled(cmd)) {
+        g_debug("enabling command: %s", name);
+        qmp_enable_command(name);
     }
-    g_free(list_head);
 }
 
 static bool ga_create_file(const char *path)
@@ -424,7 +411,7 @@ void ga_set_frozen(GAState *s)
         return;
     }
     /* disable all non-whitelisted (for frozen state) commands */
-    ga_disable_non_whitelisted();
+    qmp_for_each_command(ga_disable_non_whitelisted, NULL);
     g_warning("disabling logging due to filesystem freeze");
     ga_disable_logging(s);
     s->frozen = true;
@@ -460,7 +447,7 @@ void ga_unset_frozen(GAState *s)
     }
 
     /* enable all disabled, non-blacklisted commands */
-    ga_enable_non_blacklisted(s->blacklist);
+    qmp_for_each_command(ga_enable_non_blacklisted, s->blacklist);
     s->frozen = false;
     if (!ga_delete_file(s->state_filepath_isfrozen)) {
         g_warning("unable to delete %s, fsfreeze may not function properly",
@@ -920,6 +907,11 @@ int64_t ga_get_fd_handle(GAState *s, Error **errp)
     return handle;
 }
 
+static void ga_print_cmd(QmpCommand *cmd, void *opaque)
+{
+    printf("%s\n", qmp_command_name(cmd));
+}
+
 int main(int argc, char **argv)
 {
     const char *sopt = "hVvdm:p:l:f:F::b:s:t:";
@@ -996,15 +988,8 @@ int main(int argc, char **argv)
             daemonize = 1;
             break;
         case 'b': {
-            char **list_head, **list;
             if (is_help_option(optarg)) {
-                list_head = list = qmp_get_command_list();
-                while (*list != NULL) {
-                    printf("%s\n", *list);
-                    g_free(*list);
-                    list++;
-                }
-                g_free(list_head);
+                qmp_for_each_command(ga_print_cmd, NULL);
                 return 0;
             }
             for (j = 0, i = 0, len = strlen(optarg); i < len; i++) {
@@ -1126,7 +1111,7 @@ int main(int argc, char **argv)
             s->deferred_options.log_filepath = log_filepath;
         }
         ga_disable_logging(s);
-        ga_disable_non_whitelisted();
+        qmp_for_each_command(ga_disable_non_whitelisted, NULL);
     } else {
         if (daemonize) {
             become_daemon(pid_filepath);
-- 
1.7.9.5

[Qemu-devel] [PATCH 3/3] qemu-ga: Extend 'guest-info' command to expose flag 'success-response'

[Michael Roth]

From: Mark Wu <wudxw@linux.vnet.ibm.com>

Now we have several qemu-ga commands not returning response on success.
It has been documented in qga/qapi-schema.json already. This patch exposes
the 'success-response' flag by extending 'guest-info' command. With this
change, the clients can handle the command response more flexibly.

Signed-off-by: Mark Wu <wudxw@linux.vnet.ibm.com>
Reviewed-by: Eric Blake <eblake@redhat.com>
Reviewed-by: Michael Roth <mdroth@linux.vnet.ibm.com>
*fixed up commit subject
Signed-off-by: Michael Roth <mdroth@linux.vnet.ibm.com>
---
 include/qapi/qmp/dispatch.h |    1 +
 qapi/qmp-registry.c         |    5 +++++
 qga/commands.c              |    1 +
 qga/qapi-schema.json        |    5 ++++-
 4 files changed, 11 insertions(+), 1 deletion(-)

diff --git a/include/qapi/qmp/dispatch.h b/include/qapi/qmp/dispatch.h
index 7d759ef..cea3818 100644
--- a/include/qapi/qmp/dispatch.h
+++ b/include/qapi/qmp/dispatch.h
@@ -49,6 +49,7 @@ void qmp_disable_command(const char *name);
 void qmp_enable_command(const char *name);
 bool qmp_command_is_enabled(const QmpCommand *cmd);
 const char *qmp_command_name(const QmpCommand *cmd);
+bool qmp_has_success_response(const QmpCommand *cmd);
 QObject *qmp_build_error_object(Error *errp);
 typedef void (*qmp_cmd_callback_fn)(QmpCommand *cmd, void *opaque);
 void qmp_for_each_command(qmp_cmd_callback_fn fn, void *opaque);
diff --git a/qapi/qmp-registry.c b/qapi/qmp-registry.c
index 5e26710..3e4498a 100644
--- a/qapi/qmp-registry.c
+++ b/qapi/qmp-registry.c
@@ -76,6 +76,11 @@ const char *qmp_command_name(const QmpCommand *cmd)
     return cmd->name;
 }
 
+bool qmp_has_success_response(const QmpCommand *cmd)
+{
+    return !(cmd->options & QCO_NO_SUCCESS_RESP);
+}
+
 void qmp_for_each_command(qmp_cmd_callback_fn fn, void *opaque)
 {
     QmpCommand *cmd;
diff --git a/qga/commands.c b/qga/commands.c
index e87cbf8..a0c2de0 100644
--- a/qga/commands.c
+++ b/qga/commands.c
@@ -54,6 +54,7 @@ static void qmp_command_info(QmpCommand *cmd, void *opaque)
     cmd_info = g_malloc0(sizeof(GuestAgentCommandInfo));
     cmd_info->name = g_strdup(qmp_command_name(cmd));
     cmd_info->enabled = qmp_command_is_enabled(cmd);
+    cmd_info->success_response = qmp_has_success_response(cmd);
 
     cmd_info_list = g_malloc0(sizeof(GuestAgentCommandInfoList));
     cmd_info_list->value = cmd_info;
diff --git a/qga/qapi-schema.json b/qga/qapi-schema.json
index 7155b7a..245f968 100644
--- a/qga/qapi-schema.json
+++ b/qga/qapi-schema.json
@@ -141,10 +141,13 @@
 #
 # @enabled: whether command is currently enabled by guest admin
 #
+# @success-response: whether command returns a response on success
+#                    (since 1.7)
+#
 # Since 1.1.0
 ##
 { 'type': 'GuestAgentCommandInfo',
-  'data': { 'name': 'str', 'enabled': 'bool' } }
+  'data': { 'name': 'str', 'enabled': 'bool', 'success-response': 'bool' } }
 
 ##
 # @GuestAgentInfo
-- 
1.7.9.5