[PATCH v5 08/10] libxl: call hotplug scripts for disk devices from libxl

Roger Pau Monne
Wed, 30 May 2012 13:07:53 -0000

Since most of the needed work is already done in previous patches,
this patch only contains the necessary code to call hotplug scripts
for disk devices, that should be called when the device is added or
removed from a guest.

We will chain the launch of the disk hotplug scripts after the
device_backend_callback callback, or directly from
libxl__initiate_device_{add,remove} if the device is already in the
desired state.

Changes since v4:

 * Init args and env to NULL.

 * Correctly propagate errors from libxl__get_hotplug_script_info.

 * Replaced if in libxl__ev_child_inuse with asserts.

 * Renamed fork_cb to child_death_cb.

 * Move deregistration of device_hotplug_timeout_cb to the top of the
   function.

 * Removed "pid" field from libxl__ao_device struct.

 * Moved arraysize declaration.

 * Fixed diff complain about no newline at the end of libxl_netbsd.c.

Changes since v2:

 * Added array size check with assert.

 * Added NetBSD code (so compilation is not broken).

 * Removed a check for null in device_hotplug_timeout_cb.

Changes since v1:

 * Moved all the event related code that was inside libxl_linux.c into
   libxl_device.c, so the flow of the device addition/removal event is
   all in the same file.

Cc: Ian Jackson <ian.jackson@eu.citrix.com>
Signed-off-by: Roger Pau Monne <roger.pau@citrix.com>
---
 tools/hotplug/Linux/xen-backend.rules     |    6 +-
 tools/hotplug/Linux/xen-hotplug-common.sh |    6 ++
 tools/libxl/libxl.c                       |   10 +++
 tools/libxl/libxl_device.c                |  115 +++++++++++++++++++++++++++++
 tools/libxl/libxl_internal.h              |   19 +++++
 tools/libxl/libxl_linux.c                 |  100 +++++++++++++++++++++++++
 tools/libxl/libxl_netbsd.c                |    9 ++
 7 files changed, 262 insertions(+), 3 deletions(-)

diff --git a/tools/hotplug/Linux/xen-backend.rules
b/tools/hotplug/Linux/xen-backend.rules
index 405387f..d55ff11 100644
--- a/tools/hotplug/Linux/xen-backend.rules
+++ b/tools/hotplug/Linux/xen-backend.rules
@@ -1,11 +1,11 @@
-SUBSYSTEM=="xen-backend", KERNEL=="tap*",
RUN+="/etc/xen/scripts/blktap $env{ACTION}"
-SUBSYSTEM=="xen-backend", KERNEL=="vbd*",
RUN+="/etc/xen/scripts/block $env{ACTION}"
+SUBSYSTEM=="xen-backend", KERNEL=="tap*",
ENV{UDEV_CALL}="1", RUN+="/etc/xen/scripts/blktap
$env{ACTION}"
+SUBSYSTEM=="xen-backend", KERNEL=="vbd*",
ENV{UDEV_CALL}="1", RUN+="/etc/xen/scripts/block
$env{ACTION}"
 SUBSYSTEM=="xen-backend", KERNEL=="vtpm*",
RUN+="/etc/xen/scripts/vtpm $env{ACTION}"
 SUBSYSTEM=="xen-backend", KERNEL=="vif2-*",
RUN+="/etc/xen/scripts/vif2 $env{ACTION}"
 SUBSYSTEM=="xen-backend", KERNEL=="vif-*",
ACTION=="online", RUN+="/etc/xen/scripts/vif-setup online
type_if=vif"
 SUBSYSTEM=="xen-backend", KERNEL=="vif-*",
ACTION=="offline", RUN+="/etc/xen/scripts/vif-setup offline
type_if=vif"
 SUBSYSTEM=="xen-backend", KERNEL=="vscsi*",
RUN+="/etc/xen/scripts/vscsi $env{ACTION}"
-SUBSYSTEM=="xen-backend", ACTION=="remove",
RUN+="/etc/xen/scripts/xen-hotplug-cleanup"
+SUBSYSTEM=="xen-backend", ACTION=="remove",
ENV{UDEV_CALL}="1",
RUN+="/etc/xen/scripts/xen-hotplug-cleanup"
 KERNEL=="evtchn", NAME="xen/%k"
 SUBSYSTEM=="xen", KERNEL=="blktap[0-9]*",
NAME="xen/%k", MODE="0600"
 SUBSYSTEM=="blktap2", KERNEL=="blktap[0-9]*",
NAME="xen/blktap-2/%k", MODE="0600"
diff --git a/tools/hotplug/Linux/xen-hotplug-common.sh
b/tools/hotplug/Linux/xen-hotplug-common.sh
index 8f6557d..4a7bc73 100644
--- a/tools/hotplug/Linux/xen-hotplug-common.sh
+++ b/tools/hotplug/Linux/xen-hotplug-common.sh
@@ -15,6 +15,12 @@
 # Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA  02111-1307  USA
 #

+# Hack to prevent the execution of hotplug scripts from udev if the domain
+# has been launched from libxl
+if [ -n "${UDEV_CALL}" ] && \
+   xenstore-read "libxl/disable_udev" >/dev/null 2>&1; then
+    exit 0
+fi

 dir=$(dirname "$0")
 . "$dir/hotplugpath.sh"
diff --git a/tools/libxl/libxl.c b/tools/libxl/libxl.c
index ef99fa6..f7a137f 100644
--- a/tools/libxl/libxl.c
+++ b/tools/libxl/libxl.c
@@ -1607,6 +1607,11 @@ void libxl__device_disk_add(libxl__egc *egc, uint32_t
domid,
             flexarray_append(back, "params");
             flexarray_append(back, dev);

+            flexarray_append(back, "script");
+            flexarray_append(back, GCSPRINTF("%s/%s",
+                                             libxl__xen_script_dir_path(),
+                                             "block"));
+
             assert(device->backend_kind == LIBXL__DEVICE_KIND_VBD);
             break;
         case LIBXL_DISK_BACKEND_TAP:
@@ -1622,6 +1627,11 @@ void libxl__device_disk_add(libxl__egc *egc, uint32_t
domid,
                 libxl__device_disk_string_of_format(disk->format),
                 disk->pdev_path));

+            flexarray_append(back, "script");
+            flexarray_append(back, GCSPRINTF("%s/%s",
+                                             libxl__xen_script_dir_path(),
+                                             "blktap"));
+
             /* now create a phy device to export the device to the guest */
             goto do_backend_phy;
         case LIBXL_DISK_BACKEND_QDISK:
diff --git a/tools/libxl/libxl_device.c b/tools/libxl/libxl_device.c
index de7904a..7db379a 100644
--- a/tools/libxl/libxl_device.c
+++ b/tools/libxl/libxl_device.c
@@ -572,6 +572,15 @@ static void device_backend_callback(libxl__egc *egc,
libxl__ev_devstate *ds,
 static void device_backend_cleanup(libxl__gc *gc,
                                    libxl__ao_device *aodev);

+static void device_hotplug(libxl__egc *egc, libxl__ao_device *aodev);
+
+static void device_hotplug_child_death_cb(libxl__egc *egc,
+                                          libxl__ev_child *child,
+                                          pid_t pid, int status);
+
+static void device_hotplug_timeout_cb(libxl__egc *egc, libxl__ev_time *ev,
+                                      const struct timeval *requested_abs);
+
 void libxl__initiate_device_add(libxl__egc *egc, libxl__ao_device *aodev)
 {
     STATE_AO_GC(aodev->ao);
@@ -679,6 +688,9 @@ static void device_backend_callback(libxl__egc *egc,
libxl__ev_devstate *ds,
         goto out;
     }

+    device_hotplug(egc, aodev);
+    return;
+
 out:
     aodev->rc = rc;
     aodev->callback(egc, aodev);
@@ -691,6 +703,109 @@ static void device_backend_cleanup(libxl__gc *gc,
libxl__ao_device *aodev)
     libxl__ev_devstate_cancel(gc, &aodev->ds);
 }

+static void device_hotplug(libxl__egc *egc, libxl__ao_device *aodev)
+{
+    STATE_AO_GC(aodev->ao);
+    char *be_path = libxl__device_backend_path(gc, aodev->dev);
+    char **args = NULL, **env = NULL;
+    int rc = 0;
+    int hotplug;
+    pid_t pid;
+
+    /* Check if we have to execute hotplug scripts for this device
+     * and return the necessary args/env vars for execution */
+    hotplug = libxl__get_hotplug_script_info(gc, aodev->dev, &args,
&env,
+                                             aodev->action);
+    switch (hotplug) {
+    case 0:
+        /* no hotplug script to execute */
+        goto out;
+    case 1:
+        /* execute hotplug script */
+        break;
+    default:
+        /* everything else is an error */
+        LOG(ERROR, "unable to get args/env to execute hotplug script for
"
+                   "device %s", libxl__device_backend_path(gc,
aodev->dev));
+        rc = hotplug;
+        goto out;
+    }
+
+    /* Set hotplug timeout */
+    libxl__ev_time_init(&aodev->ev);
+    rc = libxl__ev_time_register_rel(gc, &aodev->ev,
device_hotplug_timeout_cb,
+                                     LIBXL_HOTPLUG_TIMEOUT * 1000);
+    if (rc) {
+        LOG(ERROR, "unable to register timeout for hotplug device
%s", be_path);
+        goto out;
+    }
+
+    aodev->what = GCSPRINTF("%s %s", args[0], args[1]);
+    LOG(DEBUG, "calling hotplug script: %s %s", args[0], args[1]);
+    libxl__ev_child_init(&aodev->child);
+
+    /* fork and execute hotplug script */
+    pid = libxl__ev_child_fork(gc, &aodev->child,
device_hotplug_child_death_cb);
+    if (pid == -1) {
+        LOG(ERROR, "unable to fork");
+        rc = ERROR_FAIL;
+        goto out;
+    }
+
+    if (!pid) {
+        /* child */
+        libxl__exec(gc, -1, -1, -1, args[0], args, env);
+        /* notreached */
+        abort();
+    }
+
+    assert(libxl__ev_child_inuse(&aodev->child));
+
+    return;
+
+out:
+    libxl__ev_time_deregister(gc, &aodev->ev);
+    aodev->rc = rc;
+    aodev->callback(egc, aodev);
+    return;
+}
+
+static void device_hotplug_child_death_cb(libxl__egc *egc,
+                                          libxl__ev_child *child,
+                                          pid_t pid, int status)
+{
+    libxl__ao_device *aodev = CONTAINER_OF(child, *aodev, child);
+    STATE_AO_GC(aodev->ao);
+
+    libxl__ev_time_deregister(gc, &aodev->ev);
+
+    if (status) {
+        libxl_report_child_exitstatus(CTX, aodev->rc ? LIBXL__LOG_ERROR
+                                                     : LIBXL__LOG_WARNING,
+                                      aodev->what, pid, status);
+        aodev->rc = ERROR_FAIL;
+    }
+    aodev->callback(egc, aodev);
+}
+
+static void device_hotplug_timeout_cb(libxl__egc *egc, libxl__ev_time *ev,
+                                      const struct timeval *requested_abs)
+{
+    libxl__ao_device *aodev = CONTAINER_OF(ev, *aodev, ev);
+    STATE_AO_GC(aodev->ao);
+
+    libxl__ev_time_deregister(gc, &aodev->ev);
+
+    assert(libxl__ev_child_inuse(&aodev->child));
+    LOG(DEBUG, "killing hotplug script %s because of timeout",
aodev->what);
+    if (kill(aodev->child.pid, SIGKILL)) {
+        LOGEV(ERROR, errno, "unable to kill hotplug script %s [%ld]",
+                            aodev->what, (unsigned
long)aodev->child.pid);
+    }
+
+    return;
+}
+
 static void device_remove_callback(libxl__egc *egc, libxl__ao_device *aodev)
 {
     STATE_AO_GC(aodev->ao);
diff --git a/tools/libxl/libxl_internal.h b/tools/libxl/libxl_internal.h
index 5a2a87a..9dd2404 100644
--- a/tools/libxl/libxl_internal.h
+++ b/tools/libxl/libxl_internal.h
@@ -72,6 +72,7 @@

 #define LIBXL_INIT_TIMEOUT 10
 #define LIBXL_DESTROY_TIMEOUT 10
+#define LIBXL_HOTPLUG_TIMEOUT 10
 #define LIBXL_DEVICE_MODEL_START_TIMEOUT 10
 #define LIBXL_XENCONSOLE_LIMIT 1048576
 #define LIBXL_XENCONSOLE_PROTOCOL "vt100"
@@ -1846,6 +1847,10 @@ struct libxl__ao_device {
     int rc;
     libxl__ev_devstate ds;
     void *base;
+    /* device hotplug execution */
+    char *what;
+    libxl__ev_time ev;
+    libxl__ev_child child;
 };

 /* Internal AO operation to connect a disk device, called by
@@ -1880,6 +1885,20 @@ _hidden void libxl__initiate_device_add(libxl__egc*,
libxl__ao_device *aodev);
 _hidden void libxl__initiate_device_remove(libxl__egc *egc,
                                            libxl__ao_device *aodev);

+/*
+ * libxl__get_hotplug_script_info returns the args and env that should
+ * be passed to the hotplug script for the requested device.
+ *
+ * Since a device might not need to execute any hotplug script, this function
+ * can return the following values:
+ * < 0: Error
+ * 0: No need to execute hotplug script
+ * 1: Execute hotplug script
+ */
+_hidden int libxl__get_hotplug_script_info(libxl__gc *gc, libxl__device *dev,
+                                           char ***args, char ***env,
+                                           libxl__device_action action);
+
 /*----- Domain destruction -----*/

 /* Domain destruction has been split into two functions:
diff --git a/tools/libxl/libxl_linux.c b/tools/libxl/libxl_linux.c
index 925248b..60a966f 100644
--- a/tools/libxl/libxl_linux.c
+++ b/tools/libxl/libxl_linux.c
@@ -25,3 +25,103 @@ int libxl__try_phy_backend(mode_t st_mode)

     return 1;
 }
+
+/* Hotplug scripts helpers */
+
+static char **get_hotplug_env(libxl__gc *gc, libxl__device *dev)
+{
+    char *be_path = libxl__device_backend_path(gc, dev);
+    char *script;
+    const char *type = libxl__device_kind_to_string(dev->backend_kind);
+    char **env;
+    int nr = 0;
+
+    script = libxl__xs_read(gc, XBT_NULL,
+                            GCSPRINTF("%s/%s", be_path,
"script"));
+    if (!script) {
+        LOGEV(ERROR, errno, "unable to read script from %s",
be_path);
+        return NULL;
+    }
+
+    const int arraysize = 9;
+    GCNEW_ARRAY(env, arraysize);
+    env[nr++] = "script";
+    env[nr++] = script;
+    env[nr++] = "XENBUS_TYPE";
+    env[nr++] = libxl__strdup(gc, type);
+    env[nr++] = "XENBUS_PATH";
+    env[nr++] = GCSPRINTF("backend/%s/%u/%d", type, dev->domid,
dev->devid);
+    env[nr++] = "XENBUS_BASE_PATH";
+    env[nr++] = "backend";
+    env[nr++] = NULL;
+    assert(nr == arraysize);
+
+    return env;
+}
+
+/* Hotplug scripts caller functions */
+
+static int libxl__hotplug_disk(libxl__gc *gc, libxl__device *dev,
+                               char ***args, char ***env,
+                               libxl__device_action action)
+{
+    char *be_path = libxl__device_backend_path(gc, dev);
+    char *script;
+    int nr = 0, rc = 0;
+
+    script = libxl__xs_read(gc, XBT_NULL,
+                            GCSPRINTF("%s/%s", be_path,
"script"));
+    if (!script) {
+        LOGEV(ERROR, errno, "unable to read script from %s",
be_path);
+        rc = ERROR_FAIL;
+        goto error;
+    }
+
+    *env = get_hotplug_env(gc, dev);
+    if (!*env) {
+        rc = ERROR_FAIL;
+        goto error;
+    }
+
+    const int arraysize = 3;
+    GCNEW_ARRAY(*args, arraysize);
+    (*args)[nr++] = script;
+    (*args)[nr++] = action == DEVICE_CONNECT ? "add" :
"remove";
+    (*args)[nr++] = NULL;
+    assert(nr == arraysize);
+
+    rc = 0;
+
+error:
+    return rc;
+}
+
+int libxl__get_hotplug_script_info(libxl__gc *gc, libxl__device *dev,
+                                   char ***args, char ***env,
+                                   libxl__device_action action)
+{
+    char *disable_udev = libxl__xs_read(gc, XBT_NULL, DISABLE_UDEV_PATH);
+    int rc;
+
+    /* Check if we have to run hotplug scripts */
+    if (!disable_udev) {
+        rc = 0;
+        goto out;
+    }
+
+    switch (dev->backend_kind) {
+    case LIBXL__DEVICE_KIND_VBD:
+        rc = libxl__hotplug_disk(gc, dev, args, env, action);
+        if (!rc) rc = 1;
+        break;
+    default:
+        /* If no need to execute any hotplug scripts,
+         * call the callback manually
+         */
+        rc = 0;
+        break;
+    }
+
+out:
+    return rc;
+}
diff --git a/tools/libxl/libxl_netbsd.c b/tools/libxl/libxl_netbsd.c
index 9e0ed6d..d41a046 100644
--- a/tools/libxl/libxl_netbsd.c
+++ b/tools/libxl/libxl_netbsd.c
@@ -24,3 +24,12 @@ int libxl__try_phy_backend(mode_t st_mode)

     return 0;
 }
+
+/* Hotplug scripts caller functions */
+
+int libxl__get_hotplug_script_info(libxl__gc *gc, libxl__device *dev,
+                                   char ***args, char ***env,
+                                   libxl__device_action action)
+{
+    return 0;
+}
--
1.7.7.5 (Apple Git-26)