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Re: [Qemu-devel] [RFC 2/3] virtiofsd: add DBus server to handle log leve
From: |
Dr. David Alan Gilbert |
Subject: |
Re: [Qemu-devel] [RFC 2/3] virtiofsd: add DBus server to handle log level changes |
Date: |
Thu, 5 Sep 2019 18:27:32 +0100 |
User-agent: |
Mutt/1.12.1 (2019-06-15) |
* Stefan Hajnoczi (address@hidden) wrote:
> Introduce a DBus server thread that runs alongside the other virtiofsd
> threads. It processes changes to the /org/qemu/virtiofsd object which
> can be accessed at the org.qemu.virtiofsd location on the bus.
>
> This code does not use locking because we are the only writer to the
> int current_log_level variable. More advanced management commands would
> require locking to prevent race conditions with the other threads.
>
> Signed-off-by: Stefan Hajnoczi <address@hidden>
OK, that is less complex than I'd feared.
I guess there's something probably nice to do with name/integer mapping
for warning levels that we could use from one of the libraries.
Dave
> ---
> contrib/virtiofsd/Makefile.objs | 3 +-
> contrib/virtiofsd/dbus.h | 9 ++
> contrib/virtiofsd/dbus.c | 162 +++++++++++++++++++++++++++++
> contrib/virtiofsd/passthrough_ll.c | 8 +-
> 4 files changed, 180 insertions(+), 2 deletions(-)
> create mode 100644 contrib/virtiofsd/dbus.h
> create mode 100644 contrib/virtiofsd/dbus.c
>
> diff --git a/contrib/virtiofsd/Makefile.objs b/contrib/virtiofsd/Makefile.objs
> index 9b2af1bc23..d59ab60f3d 100644
> --- a/contrib/virtiofsd/Makefile.objs
> +++ b/contrib/virtiofsd/Makefile.objs
> @@ -8,7 +8,8 @@ virtiofsd-obj-y = buffer.o \
> helper.o \
> passthrough_ll.o \
> seccomp.o \
> - gdbus_generated.o
> + gdbus_generated.o \
> + dbus.o
>
> seccomp.o-cflags := $(SECCOMP_CFLAGS)
> seccomp.o-libs := $(SECCOMP_LIBS)
> diff --git a/contrib/virtiofsd/dbus.h b/contrib/virtiofsd/dbus.h
> new file mode 100644
> index 0000000000..aa18e47408
> --- /dev/null
> +++ b/contrib/virtiofsd/dbus.h
> @@ -0,0 +1,9 @@
> +#ifndef DBUS_H
> +#define DBUS_H
> +
> +#include <stdbool.h>
> +
> +bool setup_dbus(void);
> +void cleanup_dbus(void);
> +
> +#endif /* DBUS_H */
> diff --git a/contrib/virtiofsd/dbus.c b/contrib/virtiofsd/dbus.c
> new file mode 100644
> index 0000000000..bc2308e34b
> --- /dev/null
> +++ b/contrib/virtiofsd/dbus.c
> @@ -0,0 +1,162 @@
> +#include <assert.h>
> +#include <stdio.h>
> +#include <glib.h>
> +#include "fuse_log.h"
> +#include "dbus.h"
> +#include "gdbus_generated.h"
> +
> +static GThread *the_dbus_thread;
> +static GMainContext *the_dbus_context;
> +static GMainLoop *the_dbus_loop;
> +
> +/* Set the string property based on the current log level */
> +static void refresh_log_level(Virtiofsd *virtiofsd)
> +{
> + switch (current_log_level) {
> + case LOG_ERR:
> + virtiofsd_set_log_level(virtiofsd, "err");
> + break;
> + case LOG_WARNING:
> + virtiofsd_set_log_level(virtiofsd, "warning");
> + break;
> + case LOG_INFO:
> + virtiofsd_set_log_level(virtiofsd, "info");
> + break;
> + case LOG_DEBUG:
> + virtiofsd_set_log_level(virtiofsd, "debug");
> + break;
> + }
> +}
> +
> +/* Handle changes to Virtiofsd object properties */
> +static void notify(GObject *object, GParamSpec *pspec)
> +{
> + Virtiofsd *virtiofsd = VIRTIOFSD(object);
> +
> + fprintf(stderr, "%s %s\n", __func__, pspec->name);
> +
> + if (strcmp(pspec->name, "log-level") == 0) {
> + const char *s = virtiofsd_get_log_level(virtiofsd);
> +
> + if (strcmp(s, "err") == 0) {
> + current_log_level = LOG_ERR;
> + } else if (strcmp(s, "warning") == 0) {
> + current_log_level = LOG_WARNING;
> + } else if (strcmp(s, "info") == 0) {
> + current_log_level = LOG_INFO;
> + } else if (strcmp(s, "debug") == 0) {
> + current_log_level = LOG_DEBUG;
> + } else {
> + /* Invalid, reset the log level property */
> + refresh_log_level(virtiofsd);
> + }
> + }
> +}
> +
> +typedef struct {
> + Virtiofsd *virtiofsd;
> + pthread_barrier_t *started;
> +} GBusOwnNameData;
> +
> +static void bus_acquired(GDBusConnection *connection, const gchar *name,
> + gpointer user_data)
> +{
> + GBusOwnNameData *data = user_data;
> + GError *error = NULL;
> +
> + if (!g_dbus_interface_skeleton_export(
> + G_DBUS_INTERFACE_SKELETON(data->virtiofsd),
> + connection, "/org/qemu/virtiofsd", &error)) {
> + fuse_err("g_dbus_interface_skeleton_export: %s\n", error->message);
> + g_error_free(error);
> + exit(EXIT_FAILURE);
> + }
> +}
> +
> +static void name_acquired(GDBusConnection *connection, const gchar *name,
> + gpointer user_data)
> +{
> + GBusOwnNameData *data = user_data;
> +
> + pthread_barrier_wait(data->started);
> +}
> +
> +static void name_lost(GDBusConnection *connection, const gchar *name,
> + gpointer user_data)
> +{
> + if (connection) {
> + fuse_err("unable to own dbus name\n");
> + } else {
> + fuse_err("unable to connect to dbus\n");
> + }
> + exit(EXIT_FAILURE);
> +}
> +
> +static gpointer dbus_thread(gpointer opaque)
> +{
> + GBusOwnNameData data;
> + Virtiofsd *virtiofsd;
> + guint owner_id;
> +
> + g_main_context_push_thread_default(the_dbus_context);
> +
> + virtiofsd = virtiofsd_skeleton_new();
> + refresh_log_level(virtiofsd);
> + g_signal_connect(virtiofsd, "notify", G_CALLBACK(notify), NULL);
> +
> + data.virtiofsd = virtiofsd;
> + data.started = opaque;
> +
> + owner_id = g_bus_own_name(G_BUS_TYPE_SESSION, "org.qemu.virtiofsd",
> + G_BUS_NAME_OWNER_FLAGS_DO_NOT_QUEUE, bus_acquired, name_acquired,
> + name_lost, &data, NULL);
> +
> + g_main_loop_run(the_dbus_loop);
> + g_bus_unown_name(owner_id);
> + g_object_unref(virtiofsd);
> +
> + g_main_context_pop_thread_default(the_dbus_context);
> + return NULL;
> +}
> +
> +/**
> + * Start DBus server thread.
> + *
> + * Returns: true on success, false on failure
> + */
> +bool setup_dbus(void)
> +{
> + pthread_barrier_t started;
> +
> + assert(!the_dbus_thread);
> +
> + fuse_info("Using dbus address %s\n",
> + getenv("DBUS_SESSION_BUS_ADDRESS") ?: "(null)");
> +
> + pthread_barrier_init(&started, NULL, 2);
> +
> + the_dbus_context = g_main_context_new();
> + the_dbus_loop = g_main_loop_new(the_dbus_context, FALSE);
> + the_dbus_thread = g_thread_new("dbus-thread", dbus_thread, &started);
> +
> + pthread_barrier_wait(&started);
> + pthread_barrier_destroy(&started);
> +
> + return true;
> +}
> +
> +/**
> + * Stop DBus server thread.
> + */
> +void cleanup_dbus(void)
> +{
> + g_main_loop_quit(the_dbus_loop);
> + g_thread_join(the_dbus_thread);
> + the_dbus_thread = NULL;
> +
> + g_main_loop_unref(the_dbus_loop);
> + the_dbus_loop = NULL;
> +
> + g_main_context_unref(the_dbus_context);
> + the_dbus_context = NULL;
> +}
> diff --git a/contrib/virtiofsd/passthrough_ll.c
> b/contrib/virtiofsd/passthrough_ll.c
> index 0ef01b7e3f..0ddd7d280a 100644
> --- a/contrib/virtiofsd/passthrough_ll.c
> +++ b/contrib/virtiofsd/passthrough_ll.c
> @@ -66,6 +66,7 @@
> #include <gmodule.h>
> #include "fuse_log.h"
> #include "seccomp.h"
> +#include "dbus.h"
>
> /* Keep track of inode posix locks for each owner. */
> struct lo_inode_plock {
> @@ -2989,6 +2990,9 @@ int main(int argc, char *argv[])
> if (fuse_session_mount(se) != 0)
> goto err_out3;
>
> + if (!setup_dbus())
> + goto err_out4;
> +
> fuse_daemonize(opts.foreground);
>
> if (lo.ireg_sock != -1) {
> @@ -2998,7 +3002,7 @@ int main(int argc, char *argv[])
> if (ret) {
> warnx("pthread_create: %s", strerror(ret));
> ret = 1;
> - goto err_out4;
> + goto err_out5;
> }
>
> get_shared(&lo, &lo.root);
> @@ -3014,6 +3018,8 @@ int main(int argc, char *argv[])
> /* Block until ctrl+c or fusermount -u */
> ret = virtio_loop(se);
>
> +err_out5:
> + cleanup_dbus();
> err_out4:
> fuse_session_unmount(se);
> err_out3:
> --
> 2.21.0
>
--
Dr. David Alan Gilbert / address@hidden / Manchester, UK
[Qemu-devel] [RFC 3/3] virtiofsd: add virtiofsctl command-line management tool, Stefan Hajnoczi, 2019/09/05
Re: [Qemu-devel] [RFC 0/3] virtiofsd: get/set log level via DBus, Dr. David Alan Gilbert, 2019/09/05