automatically update the database with Linux inotify

This patch implements a light-weight inotify library, and watches all
directories below the music directory.  It updates all directories
where files changed after a delay of 5 seconds.

7 files changed, 792 insertions, 0 deletions

diff --git a/src/inotify_queue.c b/src/inotify_queue.c
new file mode 100644
index 000000000..da5a215f8
--- /dev/null
+++ b/src/inotify_queue.c
@@ -0,0 +1,134 @@
+/*
+ * Copyright (C) 2003-2009 The Music Player Daemon Project
+ * http://www.musicpd.org
+ *
+ * This program is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by
+ * the Free Software Foundation; either version 2 of the License, or
+ * (at your option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License along
+ * with this program; if not, write to the Free Software Foundation, Inc.,
+ * 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA.
+ */
+
+#include "inotify_queue.h"
+#include "update.h"
+
+#include <glib.h>
+
+#include <string.h>
+
+#undef G_LOG_DOMAIN
+#define G_LOG_DOMAIN "inotify"
+
+enum {
+	/**
+	 * Wait this long after the last change before calling
+	 * update_enqueue().  This increases the probability that
+	 * updates can be bundled.
+	 */
+	INOTIFY_UPDATE_DELAY_MS = 5000,
+};
+
+static GSList *inotify_queue;
+static guint queue_source_id;
+
+void
+mpd_inotify_queue_init(void)
+{
+}
+
+static void
+free_callback(gpointer data, G_GNUC_UNUSED gpointer user_data)
+{
+	g_free(data);
+}
+
+void
+mpd_inotify_queue_finish(void)
+{
+	if (queue_source_id != 0)
+		g_source_remove(queue_source_id);
+
+	g_slist_foreach(inotify_queue, free_callback, NULL);
+	g_slist_free(inotify_queue);
+}
+
+static gboolean
+mpd_inotify_run_update(G_GNUC_UNUSED gpointer data)
+{
+	unsigned id;
+
+	while (inotify_queue != NULL) {
+		char *uri_utf8 = inotify_queue->data;
+
+		id = update_enqueue(uri_utf8, false);
+		if (id == 0)
+			/* retry later */
+			return true;
+
+		g_debug("updating '%s' job=%u", uri_utf8, id);
+
+		g_free(uri_utf8);
+		inotify_queue = g_slist_delete_link(inotify_queue,
+						    inotify_queue);
+	}
+
+	/* done, remove the timer event by returning false */
+	queue_source_id = 0;
+	return false;
+}
+
+static bool
+path_in(const char *path, const char *possible_parent)
+{
+	size_t length = strlen(possible_parent);
+
+	return path[0] == 0 ||
+		(memcmp(possible_parent, path, length) == 0 &&
+		 (path[length] == 0 || path[length] == '/'));
+}
+
+void
+mpd_inotify_enqueue(char *uri_utf8)
+{
+	GSList *old_queue = inotify_queue;
+
+	if (queue_source_id != 0)
+		g_source_remove(queue_source_id);
+	queue_source_id = g_timeout_add(INOTIFY_UPDATE_DELAY_MS,
+					mpd_inotify_run_update, NULL);
+
+	inotify_queue = NULL;
+	while (old_queue != NULL) {
+		char *current_uri = old_queue->data;
+
+		if (path_in(uri_utf8, current_uri)) {
+			/* already enqueued */
+			g_free(uri_utf8);
+			inotify_queue = g_slist_concat(inotify_queue,
+						       old_queue);
+			return;
+		}
+
+		old_queue = g_slist_delete_link(old_queue, old_queue);
+
+		if (path_in(current_uri, uri_utf8))
+			/* existing path is a sub-path of the new
+			   path; we can dequeue the existing path and
+			   update the new path instead */
+			g_free(current_uri);
+		else
+			/* move the existing path to the new queue */
+			inotify_queue = g_slist_prepend(inotify_queue,
+							current_uri);
+	}
+
+	inotify_queue = g_slist_prepend(inotify_queue, uri_utf8);
+}
diff --git a/src/inotify_queue.h b/src/inotify_queue.h
new file mode 100644
index 000000000..6e12e9bda
--- /dev/null
+++ b/src/inotify_queue.h
@@ -0,0 +1,32 @@
+/*
+ * Copyright (C) 2003-2009 The Music Player Daemon Project
+ * http://www.musicpd.org
+ *
+ * This program is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by
+ * the Free Software Foundation; either version 2 of the License, or
+ * (at your option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License along
+ * with this program; if not, write to the Free Software Foundation, Inc.,
+ * 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA.
+ */
+
+#ifndef MPD_INOTIFY_QUEUE_H
+#define MPD_INOTIFY_QUEUE_H
+
+void
+mpd_inotify_queue_init(void);
+
+void
+mpd_inotify_queue_finish(void);
+
+void
+mpd_inotify_enqueue(char *uri_utf8);
+
+#endif
diff --git a/src/inotify_source.c b/src/inotify_source.c
new file mode 100644
index 000000000..d5feec3e0
--- /dev/null
+++ b/src/inotify_source.c
@@ -0,0 +1,163 @@
+/*
+ * Copyright (C) 2003-2009 The Music Player Daemon Project
+ * http://www.musicpd.org
+ *
+ * This program is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by
+ * the Free Software Foundation; either version 2 of the License, or
+ * (at your option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License along
+ * with this program; if not, write to the Free Software Foundation, Inc.,
+ * 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA.
+ */
+
+#include "inotify_source.h"
+#include "fifo_buffer.h"
+
+#include <sys/inotify.h>
+#include <unistd.h>
+#include <errno.h>
+#include <stdbool.h>
+
+#undef G_LOG_DOMAIN
+#define G_LOG_DOMAIN "inotify"
+
+struct mpd_inotify_source {
+	int fd;
+
+	GIOChannel *channel;
+
+	/**
+	 * The channel's source id in the GLib main loop.
+	 */
+	guint id;
+
+	struct fifo_buffer *buffer;
+
+	mpd_inotify_callback_t callback;
+	void *callback_ctx;
+};
+
+/**
+ * A GQuark for GError instances.
+ */
+static inline GQuark
+mpd_inotify_quark(void)
+{
+	return g_quark_from_static_string("inotify");
+}
+
+static gboolean
+mpd_inotify_in_event(G_GNUC_UNUSED GIOChannel *_source,
+		     G_GNUC_UNUSED GIOCondition condition,
+		     gpointer data)
+{
+	struct mpd_inotify_source *source = data;
+	void *dest;
+	size_t length;
+	ssize_t nbytes;
+	const struct inotify_event *event;
+
+	dest = fifo_buffer_write(source->buffer, &length);
+	if (dest == NULL)
+		g_error("buffer full");
+
+	nbytes = read(source->fd, dest, length);
+	if (nbytes < 0)
+		g_error("failed to read from inotify: %s", g_strerror(errno));
+	if (nbytes == 0)
+		g_error("end of file from inotify");
+
+	fifo_buffer_append(source->buffer, nbytes);
+
+	while (true) {
+		const char *name;
+
+		event = fifo_buffer_read(source->buffer, &length);
+		if (event == NULL || length < sizeof(*event) ||
+		    length < sizeof(*event) + event->len)
+			break;
+
+		if (event->len > 0 && event->name[event->len - 1] == 0)
+			name = event->name;
+		else
+			name = NULL;
+
+		source->callback(event->wd, event->mask, name,
+				 source->callback_ctx);
+		fifo_buffer_consume(source->buffer,
+				    sizeof(*event) + event->len);
+	}
+
+	return true;
+}
+
+struct mpd_inotify_source *
+mpd_inotify_source_new(mpd_inotify_callback_t callback, void *callback_ctx,
+		       GError **error_r)
+{
+	struct mpd_inotify_source *source =
+		g_new(struct mpd_inotify_source, 1);
+
+	source->fd = inotify_init();
+	if (source->fd < 0) {
+		g_set_error(error_r, mpd_inotify_quark(), errno,
+			    "inotify_init() has failed: %s",
+			    g_strerror(errno));
+		g_free(source);
+		return NULL;
+	}
+
+	source->buffer = fifo_buffer_new(4096);
+
+	source->channel = g_io_channel_unix_new(source->fd);
+	source->id = g_io_add_watch(source->channel, G_IO_IN,
+				    mpd_inotify_in_event, source);
+
+	source->callback = callback;
+	source->callback_ctx = callback_ctx;
+
+	return source;
+}
+
+void
+mpd_inotify_source_free(struct mpd_inotify_source *source)
+{
+	g_source_remove(source->id);
+	g_io_channel_unref(source->channel);
+	fifo_buffer_free(source->buffer);
+	close(source->fd);
+	g_free(source);
+}
+
+int
+mpd_inotify_source_add(struct mpd_inotify_source *source,
+		       const char *path_fs, unsigned mask,
+		       GError **error_r)
+{
+	int wd = inotify_add_watch(source->fd, path_fs, mask);
+	if (wd < 0)
+		g_set_error(error_r, mpd_inotify_quark(), errno,
+			    "inotify_add_watch() has failed: %s",
+			    g_strerror(errno));
+
+	return wd;
+}
+
+void
+mpd_inotify_source_rm(struct mpd_inotify_source *source, unsigned wd)
+{
+	int ret = inotify_rm_watch(source->fd, wd);
+	if (ret < 0 && errno != EINVAL)
+		g_warning("inotify_rm_watch() has failed: %s",
+			  g_strerror(errno));
+
+	/* EINVAL may happen here when the file has been deleted; the
+	   kernel seems to auto-unregister deleted files */
+}
diff --git a/src/inotify_source.h b/src/inotify_source.h
new file mode 100644
index 000000000..eb609ccfc
--- /dev/null
+++ b/src/inotify_source.h
@@ -0,0 +1,61 @@
+/*
+ * Copyright (C) 2003-2009 The Music Player Daemon Project
+ * http://www.musicpd.org
+ *
+ * This program is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by
+ * the Free Software Foundation; either version 2 of the License, or
+ * (at your option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License along
+ * with this program; if not, write to the Free Software Foundation, Inc.,
+ * 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA.
+ */
+
+#ifndef MPD_INOTIFY_SOURCE_H
+#define MPD_INOTIFY_SOURCE_H
+
+#include <glib.h>
+
+typedef void (*mpd_inotify_callback_t)(int wd, unsigned mask,
+				       const char *name, void *ctx);
+
+struct mpd_inotify_source;
+
+/**
+ * Creates a new inotify source and registers it in the GLib main
+ * loop.
+ *
+ * @param a callback invoked for events received from the kernel
+ */
+struct mpd_inotify_source *
+mpd_inotify_source_new(mpd_inotify_callback_t callback, void *callback_ctx,
+		       GError **error_r);
+
+void
+mpd_inotify_source_free(struct mpd_inotify_source *source);
+
+/**
+ * Adds a path to the notify list.
+ *
+ * @return a watch descriptor or -1 on error
+ */
+int
+mpd_inotify_source_add(struct mpd_inotify_source *source,
+		       const char *path_fs, unsigned mask,
+		       GError **error_r);
+
+/**
+ * Removes a path from the notify list.
+ *
+ * @param wd the watch descriptor returned by mpd_inotify_source_add()
+ */
+void
+mpd_inotify_source_rm(struct mpd_inotify_source *source, unsigned wd);
+
+#endif
diff --git a/src/inotify_update.c b/src/inotify_update.c
new file mode 100644
index 000000000..996afb0aa
--- /dev/null
+++ b/src/inotify_update.c
@@ -0,0 +1,349 @@
+/*
+ * Copyright (C) 2003-2009 The Music Player Daemon Project
+ * http://www.musicpd.org
+ *
+ * This program is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by
+ * the Free Software Foundation; either version 2 of the License, or
+ * (at your option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License along
+ * with this program; if not, write to the Free Software Foundation, Inc.,
+ * 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA.
+ */
+
+#include "inotify_update.h"
+#include "inotify_source.h"
+#include "inotify_queue.h"
+#include "database.h"
+#include "mapper.h"
+#include "path.h"
+
+#include <assert.h>
+#include <sys/inotify.h>
+#include <sys/stat.h>
+#include <stdbool.h>
+#include <string.h>
+#include <dirent.h>
+#include <errno.h>
+
+#undef G_LOG_DOMAIN
+#define G_LOG_DOMAIN "inotify"
+
+enum {
+	IN_MASK = IN_ATTRIB|IN_CLOSE_WRITE|IN_CREATE|IN_DELETE|IN_DELETE_SELF
+	|IN_MOVE|IN_MOVE_SELF
+#ifdef IN_ONLYDIR
+	|IN_ONLYDIR
+#endif
+};
+
+struct watch_directory {
+	struct watch_directory *parent;
+
+	char *name;
+
+	int descriptor;
+
+	GList *children;
+};
+
+static struct mpd_inotify_source *inotify_source;
+
+static struct watch_directory inotify_root;
+static GTree *inotify_directories;
+
+static gint
+compare(gconstpointer a, gconstpointer b)
+{
+	if (a < b)
+		return -1;
+	else if (a > b)
+		return 1;
+	else
+		return 0;
+}
+
+static void
+tree_add_watch_directory(struct watch_directory *directory)
+{
+	g_tree_insert(inotify_directories,
+		      GINT_TO_POINTER(directory->descriptor), directory);
+}
+
+static void
+tree_remove_watch_directory(struct watch_directory *directory)
+{
+	bool found = g_tree_remove(inotify_directories,
+				   GINT_TO_POINTER(directory->descriptor));
+	assert(found);
+}
+
+static struct watch_directory *
+tree_find_watch_directory(int wd)
+{
+	return g_tree_lookup(inotify_directories, GINT_TO_POINTER(wd));
+}
+
+static void
+remove_watch_directory(struct watch_directory *directory)
+{
+	assert(directory != NULL);
+	assert(directory->parent != NULL);
+	assert(directory->parent->children != NULL);
+
+	tree_remove_watch_directory(directory);
+
+	while (directory->children != NULL)
+		remove_watch_directory(directory->children->data);
+
+	directory->parent->children =
+		g_list_remove(directory->parent->children, directory);
+
+	mpd_inotify_source_rm(inotify_source, directory->descriptor);
+	g_free(directory->name);
+	g_slice_free(struct watch_directory, directory);
+}
+
+static char *
+watch_directory_get_uri_fs(const struct watch_directory *directory)
+{
+	char *parent_uri, *uri;
+
+	if (directory->parent == NULL)
+		return NULL;
+
+	parent_uri = watch_directory_get_uri_fs(directory->parent);
+	if (parent_uri == NULL)
+		return g_strdup(directory->name);
+
+	uri = g_strconcat(parent_uri, "/", directory->name, NULL);
+	g_free(parent_uri);
+
+	return uri;
+}
+
+/* we don't look at "." / ".." nor files with newlines in their name */
+static bool skip_path(const char *path)
+{
+	return (path[0] == '.' && path[1] == 0) ||
+		(path[0] == '.' && path[1] == '.' && path[2] == 0) ||
+		strchr(path, '\n') != NULL;
+}
+
+static void
+recursive_watch_subdirectories(struct watch_directory *directory,
+			       const char *path_fs)
+{
+	GError *error = NULL;
+	DIR *dir;
+	struct dirent *ent;
+
+	assert(directory != NULL);
+	assert(path_fs != NULL);
+
+	dir = opendir(path_fs);
+	if (dir == NULL) {
+		g_warning("Failed to open directory %s: %s",
+			  path_fs, g_strerror(errno));
+		return;
+	}
+
+	while ((ent = readdir(dir))) {
+		char *child_path_fs;
+		struct stat st;
+		int ret;
+		struct watch_directory *child;
+
+		if (skip_path(ent->d_name))
+			continue;
+
+		child_path_fs = g_strconcat(path_fs, "/", ent->d_name, NULL);
+		/* XXX what about symlinks? */
+		ret = lstat(child_path_fs, &st);
+		if (ret < 0) {
+			g_warning("Failed to stat %s: %s",
+				  child_path_fs, g_strerror(errno));
+			g_free(child_path_fs);
+			continue;
+		}
+
+		if (!S_ISDIR(st.st_mode)) {
+			g_free(child_path_fs);
+			continue;
+		}
+
+		ret = mpd_inotify_source_add(inotify_source, child_path_fs,
+					     IN_MASK, &error);
+		if (ret < 0) {
+			g_warning("Failed to register %s: %s",
+				  child_path_fs, error->message);
+			g_error_free(error);
+			error = NULL;
+			g_free(child_path_fs);
+			continue;
+		}
+
+		child = tree_find_watch_directory(ret);
+		if (child != NULL) {
+			/* already being watched */
+			g_free(child_path_fs);
+			continue;
+		}
+
+		child = g_slice_new(struct watch_directory);
+		child->parent = directory;
+		child->name = g_strdup(ent->d_name);
+		child->descriptor = ret;
+		child->children = NULL;
+
+		directory->children = g_list_prepend(directory->children,
+						     child);
+
+		tree_add_watch_directory(child);
+
+		recursive_watch_subdirectories(child, child_path_fs);
+		g_free(child_path_fs);
+	}
+
+	closedir(dir);
+}
+
+static void
+mpd_inotify_callback(int wd, unsigned mask,
+		     G_GNUC_UNUSED const char *name, G_GNUC_UNUSED void *ctx)
+{
+	struct watch_directory *directory;
+	char *uri_fs;
+
+	/*g_debug("wd=%d mask=0x%x name='%s'", wd, mask, name);*/
+
+	directory = tree_find_watch_directory(wd);
+	if (directory == NULL)
+		return;
+
+	uri_fs = watch_directory_get_uri_fs(directory);
+
+	if ((mask & (IN_DELETE_SELF|IN_MOVE_SELF)) != 0) {
+		g_free(uri_fs);
+		remove_watch_directory(directory);
+		return;
+	}
+
+	if ((mask & (IN_ATTRIB|IN_CREATE|IN_MOVE)) != 0 &&
+	    (mask & IN_ISDIR) != 0) {
+		/* a sub directory was changed: register those in
+		   inotify */
+		char *root = map_directory_fs(db_get_root());
+		char *path_fs;
+
+		if (uri_fs != NULL) {
+			path_fs = g_strconcat(root, "/", uri_fs, NULL);
+			g_free(root);
+		} else
+			path_fs = root;
+
+		recursive_watch_subdirectories(directory, path_fs);
+		g_free(path_fs);
+	}
+
+	if ((mask & (IN_CLOSE_WRITE|IN_MOVE|IN_DELETE)) != 0) {
+		/* a file was changed, or a direectory was
+		   moved/deleted: queue a database update */
+		char *uri_utf8 = uri_fs != NULL
+			? fs_charset_to_utf8(uri_fs)
+			: g_strdup("");
+
+		if (uri_utf8 != NULL)
+			/* this function will take care of freeing
+			   uri_utf8 */
+			mpd_inotify_enqueue(uri_utf8);
+	}
+
+	g_free(uri_fs);
+}
+
+void
+mpd_inotify_init(void)
+{
+	struct directory *root;
+	char *path;
+	GError *error = NULL;
+
+	g_debug("initializing inotify");
+
+	root = db_get_root();
+	if (root == NULL) {
+		g_debug("no music directory configured");
+		return;
+	}
+
+	path = map_directory_fs(root);
+	if (path == NULL) {
+		g_warning("mapper has failed");
+		return;
+	}
+
+	inotify_source = mpd_inotify_source_new(mpd_inotify_callback, NULL,
+						&error);
+	if (inotify_source == NULL) {
+		g_warning("%s", error->message);
+		g_error_free(error);
+		g_free(path);
+		return;
+	}
+
+	inotify_root.name = path;
+	inotify_root.descriptor = mpd_inotify_source_add(inotify_source, path,
+							 IN_MASK, &error);
+	if (inotify_root.descriptor < 0) {
+		g_warning("%s", error->message);
+		g_error_free(error);
+		mpd_inotify_source_free(inotify_source);
+		inotify_source = NULL;
+		g_free(path);
+		return;
+	}
+
+	inotify_directories = g_tree_new(compare);
+	tree_add_watch_directory(&inotify_root);
+
+	recursive_watch_subdirectories(&inotify_root, path);
+
+	mpd_inotify_queue_init();
+
+	g_debug("watching music directory");
+}
+
+static gboolean
+free_watch_directory(G_GNUC_UNUSED gpointer key, gpointer value,
+		     G_GNUC_UNUSED gpointer data)
+{
+	struct watch_directory *directory = value;
+
+	g_free(directory->name);
+	g_list_free(directory->children);
+
+	if (directory != &inotify_root)
+		g_slice_free(struct watch_directory, directory);
+
+	return false;
+}
+
+void
+mpd_inotify_finish(void)
+{
+	if (inotify_source == NULL)
+		return;
+
+	mpd_inotify_queue_finish();
+	mpd_inotify_source_free(inotify_source);
+
+	g_tree_foreach(inotify_directories, free_watch_directory, NULL);
+	g_tree_destroy(inotify_directories);
+}
diff --git a/src/inotify_update.h b/src/inotify_update.h
new file mode 100644
index 000000000..45466afae
--- /dev/null
+++ b/src/inotify_update.h
@@ -0,0 +1,47 @@
+/*
+ * Copyright (C) 2003-2009 The Music Player Daemon Project
+ * http://www.musicpd.org
+ *
+ * This program is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by
+ * the Free Software Foundation; either version 2 of the License, or
+ * (at your option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License along
+ * with this program; if not, write to the Free Software Foundation, Inc.,
+ * 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA.
+ */
+
+#ifndef MPD_INOTIFY_UPDATE_H
+#define MPD_INOTIFY_UPDATE_H
+
+#include "config.h"
+
+#ifdef HAVE_INOTIFY_INIT
+
+void
+mpd_inotify_init(void);
+
+void
+mpd_inotify_finish(void);
+
+#else /* !HAVE_INOTIFY_INIT */
+
+static inline void
+mpd_inotify_init(void)
+{
+}
+
+static inline void
+mpd_inotify_finish(void)
+{
+}
+
+#endif /* !HAVE_INOTIFY_INIT */
+
+#endif
diff --git a/src/main.c b/src/main.c
index 56627b665..bb0d09eaf 100644
--- a/src/main.c
+++ b/src/main.c
@@ -55,6 +55,7 @@
 #include "dirvec.h"
 #include "songvec.h"
 #include "tag_pool.h"
+#include "inotify_update.h"
 
 #ifdef ENABLE_SQLITE
 #include "sticker.h"
@@ -369,6 +370,9 @@ int main(int argc, char *argv[])
 
 	glue_state_file_init();
 
+	if (mapper_has_music_directory())
+		mpd_inotify_init();
+
 	config_global_check();
 
 	/* run the main loop */
@@ -379,6 +383,8 @@ int main(int argc, char *argv[])
 
 	g_main_loop_unref(main_loop);
 
+	mpd_inotify_finish();
+
 	state_file_finish();
 	playerKill();
 	finishZeroconf();