[PATCH] sequential mode

[axet]

HDD significantly reduce performance if booth scanning and csum calculating done at the same time. Reducing IO/hash treahds to 1 does not help, since scanning done in main thread. Following patch will let use duperemove on HDD

diff --git a/file_scan.c b/file_scan.c
index 0760b9c..d0859db 100644
--- a/file_scan.c
+++ b/file_scan.c
@@ -1239,12 +1239,18 @@ int add_exclude_pattern(const char *pattern)
 void filescan_init(void)
 {
 	abort_on(scan_pool.pool);
-	setup_pool(&scan_pool, csum_whole_file, NULL, options.io_threads);
+	setup_pool(&scan_pool, csum_whole_file, NULL, 0);
 	abort_on(!scan_pool.pool);
 }
 
 void filescan_free(void)
 {
+	GError *err = NULL;
+	if (!g_thread_pool_set_max_threads(scan_pool.pool, options.io_threads, &err )) {
+		eprintf("g_thread_pool_set_max_threads: %s\n", err->message);
+		g_error_free(err);
+		err = NULL;
+	}
 	free_pool(&scan_pool);
 }