[tracker] TrackerCrawler: Do not iterate through folders parallelly.

[Carlos Garnacho <carlosg src gnome org>]

commit df7861f68f46890445e3adb7025e6d97bc76bbd2
Author: Carlos Garnacho <carlos lanedo com>
Date:   Thu Sep 10 15:33:02 2009 +0200

    TrackerCrawler: Do not iterate through folders parallelly.
    
    Previously to this change, the process_func() idle function would be always
    running, starting iteration through folders as soon as the could be processed,
    regardless of having other folders already being iterated. This could lead
    to an scenario where all file descriptors were used under some conditions.
    
    Now, all processing is fully sequential, so process_func() waits until a
    folder is iterated before going on to the next item.

 src/libtracker-miner/tracker-crawler.c |   78 +++++++++++++++++++-------------
 1 files changed, 47 insertions(+), 31 deletions(-)
---
diff --git a/src/libtracker-miner/tracker-crawler.c b/src/libtracker-miner/tracker-crawler.c
index d84352b..0330242 100644
--- a/src/libtracker-miner/tracker-crawler.c
+++ b/src/libtracker-miner/tracker-crawler.c
@@ -55,7 +55,6 @@ struct TrackerCrawlerPrivate {
 
 	/* Statistics */
 	GTimer	       *timer;
-	guint		enumerations;
 	guint		directories_found;
 	guint		directories_ignored;
 	guint		files_found;
@@ -314,18 +313,17 @@ process_func (gpointer data)
 	if (file) {
 		if (check_directory (crawler, file)) {
 			g_queue_push_tail (priv->found, file);
+
+			/* directory is being iterated, this idle function
+			 * will be re-enabled right after it finishes.
+			 */
+			priv->idle_id = 0;
+
+			return FALSE;
 		} else {
 			g_object_unref (file);
+			return TRUE;
 		}
-
-		return TRUE;
-	}
-
-	/* If we still have some async operations in progress, wait
-	 * for them to finish, if not, we are truly done.
-	 */
-	if (priv->enumerations > 0) {
-		return TRUE;
 	}
 
 	priv->idle_id = 0;
@@ -336,6 +334,33 @@ process_func (gpointer data)
 	return FALSE;
 }
 
+static gboolean
+process_func_start (TrackerCrawler *crawler)
+{
+	if (crawler->private->is_paused) {
+		return FALSE;
+	}
+
+	if (crawler->private->is_finished) {
+		return FALSE;
+	}
+
+	if (crawler->private->idle_id == 0) {
+		crawler->private->idle_id = g_idle_add (process_func, crawler);
+	}
+
+	return TRUE;
+}
+
+static void
+process_func_stop (TrackerCrawler *crawler)
+{
+	if (crawler->private->idle_id != 0) {
+		g_source_remove (crawler->private->idle_id);
+		crawler->private->idle_id = 0;
+	}
+}
+
 static EnumeratorChildData *
 enumerator_child_data_new (GFile    *child,
 			   gboolean  is_dir)
@@ -442,7 +467,6 @@ file_enumerator_close_cb (GObject      *enumerator,
 	GError *error = NULL;
 
 	crawler = TRACKER_CRAWLER (user_data);
-	crawler->private->enumerations--;
 
 	if (!g_file_enumerator_close_finish (G_FILE_ENUMERATOR (enumerator),
 					     result,
@@ -452,6 +476,11 @@ file_enumerator_close_cb (GObject      *enumerator,
 
 		g_clear_error (&error);
 	}
+
+	/* Processing of directory is now finished,
+	 * continue with queued files/directories.
+	 */
+	process_func_start (crawler);
 }
 
 static void
@@ -573,7 +602,8 @@ file_enumerate_children_cb (GObject	 *file,
 			g_free (path);
 		}
 
-		crawler->private->enumerations--;
+		enumerator_data_free (ed);
+		process_func_start (crawler);
 		return;
 	}
 
@@ -587,14 +617,12 @@ file_enumerate_children (TrackerCrawler *crawler,
 {
 	EnumeratorData *ed;
 
-	crawler->private->enumerations++;
-
 	ed = enumerator_data_new (crawler, file);
 
 	g_file_enumerate_children_async (file,
 					 FILE_ATTRIBUTES,
 					 G_FILE_QUERY_INFO_NOFOLLOW_SYMLINKS,
-					 G_PRIORITY_DEFAULT,
+					 G_PRIORITY_LOW,
 					 crawler->private->cancellable,
 					 file_enumerate_children_cb,
 					 ed);
@@ -644,11 +672,9 @@ tracker_crawler_start (TrackerCrawler *crawler,
 	priv->files_found = 0;
 	priv->files_ignored = 0;
 
-	/* Set idle handler to process directories and files found */
-	priv->idle_id = g_idle_add (process_func, crawler);
-
 	/* Start things off */
 	add_directory (crawler, file, TRUE);
+	process_func_start (crawler);
 
 	return TRUE;
 }
@@ -665,10 +691,7 @@ tracker_crawler_stop (TrackerCrawler *crawler)
 	priv->is_running = FALSE;
 	g_cancellable_cancel (priv->cancellable);
 
-	if (priv->idle_id) {
-		g_source_remove (priv->idle_id);
-		priv->idle_id = 0;
-	}
+	process_func_stop (crawler);
 
 	if (priv->timer) {
 		g_timer_destroy (priv->timer);
@@ -701,11 +724,7 @@ tracker_crawler_pause (TrackerCrawler *crawler)
 
 	if (crawler->private->is_running) {
 		g_timer_stop (crawler->private->timer);
-		
-		if (crawler->private->idle_id != 0) {
-			g_source_remove (crawler->private->idle_id);
-			crawler->private->idle_id = 0;
-		}
+		process_func_stop (crawler);
 	}
 
 	g_message ("Crawler is paused, %s", 
@@ -721,10 +740,7 @@ tracker_crawler_resume (TrackerCrawler *crawler)
 
 	if (crawler->private->is_running) {
 		g_timer_continue (crawler->private->timer);
-
-		if (crawler->private->idle_id == 0) {
-			crawler->private->idle_id = g_idle_add (process_func, crawler);
-		}
+		process_func_start (crawler);
 	}
 
 	g_message ("Crawler is resuming, %s",