X-Git-Url: http://git.tuebingen.mpg.de/?p=dss.git;a=blobdiff_plain;f=dss.c;h=7c8b54fc6a0502d0a2ab983b5bc8ff3d33e0bda2;hp=3bcf60d4ba39d083f27bd26cb85998bb7a6eff69;hb=9528cf1dad242f2f41757fb1c7cb93acdba2370d;hpb=9967e30b97ef5fb90f31ceb06ac34b974e1788a8

diff --git a/dss.c b/dss.c
index 3bcf60d..7c8b54f 100644
--- a/dss.c
+++ b/dss.c
@@ -1,5 +1,5 @@
 /*
- * Copyright (C) 2008 Andre Noll <maan@systemlinux.org>
+ * Copyright (C) 2008-2011 Andre Noll <maan@systemlinux.org>
  *
  * Licensed under the GPL v2. For licencing details see COPYING.
  */
@@ -47,15 +47,16 @@ static int create_process_stopped;
 /** Process id of current pre-remove/rm/post-remove process. */
 static pid_t remove_pid;
 /** When the next snapshot is due. */
-static struct timeval next_snapshot_time;
+static int64_t next_snapshot_time;
 /** When to try to remove something. */
 static struct timeval next_removal_check;
 /** Creation time of the snapshot currently being created. */
 static int64_t current_snapshot_creation_time;
-/* The snapshot currently being removed. */
+/** The snapshot currently being removed. */
 struct snapshot *snapshot_currently_being_removed;
 /** Needed by the post-create hook. */
 static char *path_to_last_complete_snapshot;
+static char *name_of_reference_snapshot;
 /** \sa \ref snap.h for details. */
 enum hook_status snapshot_creation_status;
 /** \sa \ref snap.h for details. */
@@ -63,7 +64,106 @@ enum hook_status snapshot_removal_status;
 
 
 DEFINE_DSS_ERRLIST;
+static const char *hook_status_description[] = {HOOK_STATUS_ARRAY};
 
+/* may be called with ds == NULL. */
+static int disk_space_low(struct disk_space *ds)
+{
+	struct disk_space ds_struct;
+
+	if (!ds) {
+		int ret = get_disk_space(".", &ds_struct);
+		if (ret < 0)
+			return ret;
+		ds = &ds_struct;
+	}
+	if (conf.min_free_mb_arg)
+		if (ds->free_mb < conf.min_free_mb_arg)
+			return 1;
+	if (conf.min_free_percent_arg)
+		if (ds->percent_free < conf.min_free_percent_arg)
+			return 1;
+	if (conf.min_free_percent_inodes_arg)
+		if (ds->percent_free_inodes < conf.min_free_percent_inodes_arg)
+			return 1;
+	return 0;
+}
+
+static void dump_dss_config(const char *msg)
+{
+	const char dash[] = "-----------------------------";
+	int ret;
+	FILE *log = logfile? logfile : stderr;
+	struct disk_space ds;
+	int64_t now = get_current_time();
+
+	if (conf.loglevel_arg > INFO)
+		return;
+
+	fprintf(log, "%s <%s config> %s\n", dash, msg, dash);
+	fprintf(log, "\n*** disk space ***\n\n");
+	ret = get_disk_space(".", &ds);
+	if (ret >= 0) {
+		DSS_INFO_LOG("disk space low: %s\n", disk_space_low(&ds)?
+			"yes" : "no");
+		log_disk_space(&ds);
+	} else
+		DSS_ERROR_LOG("can not get free disk space: %s\n",
+			dss_strerror(-ret));
+
+	/* we continue on errors from get_disk_space */
+
+	fprintf(log, "\n*** command line and config file options ***\n\n");
+	cmdline_parser_dump(log, &conf);
+	fprintf(log, "\n*** internal state ***\n\n");
+	fprintf(log,
+		"pid: %d\n"
+		"logile: %s\n"
+		"snapshot_currently_being_removed: %s\n"
+		"path_to_last_complete_snapshot: %s\n"
+		"reference_snapshot: %s\n"
+		"snapshot_creation_status: %s\n"
+		"snapshot_removal_status: %s\n"
+		,
+		(int) getpid(),
+		logfile? conf.logfile_arg : "stderr",
+		snapshot_currently_being_removed?
+			snapshot_currently_being_removed->name : "(none)",
+		path_to_last_complete_snapshot?
+			path_to_last_complete_snapshot : "(none)",
+		name_of_reference_snapshot?
+			name_of_reference_snapshot : "(none)",
+		hook_status_description[snapshot_creation_status],
+		hook_status_description[snapshot_removal_status]
+	);
+	if (create_pid != 0)
+		fprintf(log,
+			"create_pid: %" PRId32 "\n"
+			"create process is %sstopped\n"
+			,
+			create_pid,
+			create_process_stopped? "" : "not "
+		);
+	if (remove_pid != 0)
+		fprintf(log, "remove_pid: %" PRId32 "\n", remove_pid);
+	if (next_snapshot_time != 0)
+		fprintf(log, "next snapshot due in %" PRId64 " seconds\n",
+			next_snapshot_time - now);
+	if (current_snapshot_creation_time != 0)
+		fprintf(log, "current_snapshot_creation_time: %"
+			PRId64 " (%" PRId64 " seconds ago)\n",
+			current_snapshot_creation_time,
+			now - current_snapshot_creation_time
+		);
+	if (next_removal_check.tv_sec != 0) {
+		fprintf(log, "next removal check: %llu (%llu seconds ago)\n",
+			(long long unsigned)next_removal_check.tv_sec,
+			now - (long long unsigned)next_removal_check.tv_sec
+		);
+
+	}
+	fprintf(log, "%s </%s config> %s\n", dash, msg, dash);
+}
 
 /* a litte cpp magic helps to DRY */
 #define COMMANDS \
@@ -126,46 +226,21 @@ static __printf_1_2 void dss_msg(const char* fmt,...)
 	va_end(argp);
 }
 
-static int disk_space_low(void)
-{
-	struct disk_space ds;
-	int ret = get_disk_space(".", &ds);
-
-	if (ret < 0)
-		return ret;
-	if (conf.min_free_mb_arg)
-		if (ds.free_mb < conf.min_free_mb_arg)
-			return 1;
-	if (conf.min_free_percent_arg)
-		if (ds.percent_free < conf.min_free_percent_arg)
-			return 1;
-	if (conf.min_free_percent_inodes_arg)
-		if (ds.percent_free_inodes < conf.min_free_percent_inodes_arg)
-			return 1;
-	return 0;
-}
-
 static void dss_get_snapshot_list(struct snapshot_list *sl)
 {
 	get_snapshot_list(sl, conf.unit_interval_arg, conf.num_intervals_arg);
 }
 
-static int next_snapshot_is_due(void)
+static int64_t compute_next_snapshot_time(void)
 {
-	struct timeval now, unit_interval = {.tv_sec = 24 * 3600 * conf.unit_interval_arg},
-		tmp, diff;
-	int64_t x = 0;
+	int64_t x = 0, now = get_current_time(), unit_interval
+		= 24 * 3600 * conf.unit_interval_arg, ret;
 	unsigned wanted = desired_number_of_snapshots(0, conf.num_intervals_arg),
 		num_complete_snapshots = 0;
-	int i, ret;
+	int i;
 	struct snapshot *s = NULL;
 	struct snapshot_list sl;
 
-	gettimeofday(&now, NULL);
-	if (tv_diff(&next_snapshot_time, &now, NULL) > 0)
-		return 0;
-	assert(snapshot_creation_status == HS_READY);
-	current_snapshot_creation_time = 0;
 	dss_get_snapshot_list(&sl);
 	FOR_EACH_SNAPSHOT(s, i, &sl) {
 		if (!(s->flags & SS_COMPLETE))
@@ -174,55 +249,60 @@ static int next_snapshot_is_due(void)
 		x += s->completion_time - s->creation_time;
 	}
 	assert(x >= 0);
-	if (num_complete_snapshots)
-		x /= num_complete_snapshots; /* avg time to create one snapshot */
-	x *= wanted; /* time to create all snapshots in interval 0 */
-	tmp.tv_sec = x;
-	tmp.tv_usec = 0;
-	ret = tv_diff(&unit_interval, &tmp, &diff); /* total sleep time per unit interval */
-	if (ret < 0 || !s) { /* unit_interval < tmp or no snapshot */
-		ret = 1;
-		goto out;
-	}
 
-	tv_divide(wanted, &diff, &tmp); /* sleep time between two snapshots */
-	diff.tv_sec = s->completion_time; /* completion time of the latest snapshot */
-	diff.tv_usec = 0;
-	tv_add(&diff, &tmp, &next_snapshot_time);
-	ret = (tv_diff(&now, &next_snapshot_time, &diff) < 0)? 0 : 1;
+	ret = now;
+	if (num_complete_snapshots == 0)
+		goto out;
+	x /= num_complete_snapshots; /* avg time to create one snapshot */
+	if (unit_interval < x * wanted) /* oops, no sleep at all */
+		goto out;
+	ret = s->completion_time + unit_interval / wanted - x;
 out:
 	free_snapshot_list(&sl);
-	if (ret == 0)
-		DSS_DEBUG_LOG("next snapshot due in %lu seconds\n",
-			tv2ms(&diff) / 1000);
-	else
-		DSS_DEBUG_LOG("next snapshot: now\n");
 	return ret;
 }
 
-static int pre_create_hook(void)
+static inline void invalidate_next_snapshot_time(void)
+{
+	next_snapshot_time = 0;
+}
+
+static inline int next_snapshot_time_is_valid(void)
 {
-	int ret, fds[3] = {0, 0, 0};
+	return next_snapshot_time != 0;
+}
 
-	assert(snapshot_creation_status == HS_READY);
-	if (!conf.pre_create_hook_given) {
-		snapshot_creation_status = HS_PRE_SUCCESS;
-		return 0;
+static int next_snapshot_is_due(void)
+{
+	int64_t now = get_current_time();
+
+	if (!next_snapshot_time_is_valid())
+		next_snapshot_time = compute_next_snapshot_time();
+	if (next_snapshot_time <= now) {
+		DSS_DEBUG_LOG("next snapshot: now\n");
+		return 1;
 	}
+	DSS_DEBUG_LOG("next snapshot due in %" PRId64 " seconds\n",
+		next_snapshot_time - now);
+	return 0;
+}
+
+static void pre_create_hook(void)
+{
+	assert(snapshot_creation_status == HS_READY);
+	/* make sure that the next snapshot time will be recomputed */
+	invalidate_next_snapshot_time();
 	DSS_DEBUG_LOG("executing %s\n", conf.pre_create_hook_arg);
-	ret = dss_exec_cmdline_pid(&create_pid,
-		conf.pre_create_hook_arg, fds);
-	if (ret < 0)
-		return ret;
+	dss_exec_cmdline_pid(&create_pid, conf.pre_create_hook_arg);
 	snapshot_creation_status = HS_PRE_RUNNING;
-	return ret;
 }
 
-static int pre_remove_hook(struct snapshot *s, char *why)
+static void pre_remove_hook(struct snapshot *s, const char *why)
 {
-	int ret, fds[3] = {0, 0, 0};
 	char *cmd;
 
+	if (!s)
+		return;
 	DSS_DEBUG_LOG("%s snapshot %s\n", why, s->name);
 	assert(snapshot_removal_status == HS_READY);
 	assert(remove_pid == 0);
@@ -232,30 +312,26 @@ static int pre_remove_hook(struct snapshot *s, char *why)
 	*snapshot_currently_being_removed = *s;
 	snapshot_currently_being_removed->name = dss_strdup(s->name);
 
-	if (!conf.pre_remove_hook_given) {
-		snapshot_removal_status = HS_PRE_SUCCESS;
-		return 0;
-	}
 	cmd = make_message("%s %s/%s", conf.pre_remove_hook_arg,
 		conf.dest_dir_arg, s->name);
 	DSS_DEBUG_LOG("executing %s\n", cmd);
-	ret = dss_exec_cmdline_pid(&remove_pid,
-		conf.pre_remove_hook_arg, fds);
+	dss_exec_cmdline_pid(&remove_pid, cmd);
 	free(cmd);
-	if (ret < 0)
-		return ret;
 	snapshot_removal_status = HS_PRE_RUNNING;
-	return ret;
 }
 
 static int exec_rm(void)
 {
 	struct snapshot *s = snapshot_currently_being_removed;
-	int fds[3] = {0, 0, 0};
 	char *new_name = being_deleted_name(s);
-	char *argv[] = {"rm", "-rf", new_name, NULL};
+	char *argv[4];
 	int ret;
 
+	argv[0] = "rm";
+	argv[1] = "-rf";
+	argv[2] = new_name;
+	argv[3] = NULL;
+
 	assert(snapshot_removal_status == HS_PRE_SUCCESS);
 	assert(remove_pid == 0);
 
@@ -263,9 +339,7 @@ static int exec_rm(void)
 	ret = dss_rename(s->name, new_name);
 	if (ret < 0)
 		goto out;
-	ret = dss_exec(&remove_pid, argv[0], argv, fds);
-	if (ret < 0)
-		goto out;
+	dss_exec(&remove_pid, argv[0], argv);
 	snapshot_removal_status = HS_RUNNING;
 out:
 	free(new_name);
@@ -277,12 +351,53 @@ static int snapshot_is_being_created(struct snapshot *s)
 	return s->creation_time == current_snapshot_creation_time;
 }
 
+static struct snapshot *find_orphaned_snapshot(struct snapshot_list *sl)
+{
+	struct snapshot *s;
+	int i;
+
+	DSS_DEBUG_LOG("looking for orphaned snapshots\n");
+	FOR_EACH_SNAPSHOT(s, i, sl) {
+		if (snapshot_is_being_created(s))
+			continue;
+		/*
+		 * We know that no rm is currently running, so if s is marked
+		 * as being deleted, a previously started rm must have failed.
+		 */
+		if (s->flags & SS_BEING_DELETED)
+			return s;
+
+		if (s->flags & SS_COMPLETE) /* good snapshot */
+			continue;
+		/*
+		 * This snapshot is incomplete and it is not the snapshot
+		 * currently being created. However, we must not remove it if
+		 * rsync is about to be restarted. As only the newest snapshot
+		 * can be restarted, this snapshot is orphaned if it is not the
+		 * newest snapshot or if we are not about to restart rsync.
+		 */
+		if (get_newest_snapshot(sl) != s)
+			return s;
+		if (snapshot_creation_status != HS_NEEDS_RESTART)
+			return s;
+	}
+	/* no orphaned snapshots */
+	return NULL;
+}
+
+static int is_reference_snapshot(struct snapshot *s)
+{
+	if (!name_of_reference_snapshot)
+		return 0;
+	return strcmp(s->name, name_of_reference_snapshot)? 0 : 1;
+}
+
 /*
  * return: 0: no redundant snapshots, 1: rm process started, negative: error
  */
-static int remove_redundant_snapshot(struct snapshot_list *sl)
+static struct snapshot *find_redundant_snapshot(struct snapshot_list *sl)
 {
-	int ret, i, interval;
+	int i, interval;
 	struct snapshot *s;
 	unsigned missing = 0;
 
@@ -305,6 +420,8 @@ static int remove_redundant_snapshot(struct snapshot_list *sl)
 
 			if (snapshot_is_being_created(s))
 				continue;
+			if (is_reference_snapshot(s))
+				continue;
 			//DSS_DEBUG_LOG("checking %s\n", s->name);
 			if (s->interval > interval) {
 				prev = s;
@@ -329,56 +446,43 @@ static int remove_redundant_snapshot(struct snapshot_list *sl)
 			prev = s;
 		}
 		assert(victim);
-		if (conf.dry_run_given) {
-			dss_msg("%s would be removed (interval = %i)\n",
-				victim->name, victim->interval);
-			continue;
-		}
-		ret = pre_remove_hook(victim, "redundant");
-		return ret < 0? ret : 1;
+		return victim;
 	}
-	return 0;
+	return NULL;
 }
 
-static int remove_outdated_snapshot(struct snapshot_list *sl)
+static struct snapshot *find_outdated_snapshot(struct snapshot_list *sl)
 {
-	int i, ret;
+	int i;
 	struct snapshot *s;
 
-	DSS_DEBUG_LOG("looking for snapshots belonging to intervals greater than %d\n",
+	DSS_DEBUG_LOG("looking for snapshots belonging to intervals >= %d\n",
 		conf.num_intervals_arg);
 	FOR_EACH_SNAPSHOT(s, i, sl) {
 		if (snapshot_is_being_created(s))
 			continue;
-		if (s->interval <= conf.num_intervals_arg)
+		if (is_reference_snapshot(s))
 			continue;
-		if (conf.dry_run_given) {
-			dss_msg("%s would be removed (interval = %i)\n",
-				s->name, s->interval);
+		if (s->interval < conf.num_intervals_arg)
 			continue;
-		}
-		ret = pre_remove_hook(s, "outdated");
-		if (ret < 0)
-			return ret;
-		return 1;
+		return s;
 	}
-	return 0;
+	return NULL;
 }
 
-static int remove_oldest_snapshot(struct snapshot_list *sl)
+struct snapshot *find_oldest_removable_snapshot(struct snapshot_list *sl)
 {
-	int ret;
-	struct snapshot *s = get_oldest_snapshot(sl);
-
-	if (!s) /* no snapshot found */
-		return 0;
-	DSS_INFO_LOG("oldest snapshot: %s\n", s->name);
-	if (snapshot_is_being_created(s))
-		return 0;
-	ret = pre_remove_hook(s, "oldest");
-	if (ret < 0)
-		return ret;
-	return 1;
+	int i;
+	struct snapshot *s;
+	FOR_EACH_SNAPSHOT(s, i, sl) {
+		if (snapshot_is_being_created(s))
+			continue;
+		if (is_reference_snapshot(s))
+			continue;
+		DSS_INFO_LOG("oldest removable snapshot: %s\n", s->name);
+		return s;
+	}
+	return NULL;
 }
 
 static int rename_incomplete_snapshot(int64_t start)
@@ -400,103 +504,130 @@ static int rename_incomplete_snapshot(int64_t start)
 	return ret;
 }
 
-static int try_to_free_disk_space(int low_disk_space)
+static int try_to_free_disk_space(void)
 {
 	int ret;
 	struct snapshot_list sl;
+	struct snapshot *victim;
 	struct timeval now;
+	const char *why;
+	int low_disk_space;
 
+	ret = disk_space_low(NULL);
+	if (ret < 0)
+		return ret;
+	low_disk_space = ret;
 	gettimeofday(&now, NULL);
 	if (tv_diff(&next_removal_check, &now, NULL) > 0)
 		return 0;
-	if (!low_disk_space && conf.keep_redundant_given)
-		return 0;
+	if (!low_disk_space) {
+		if (conf.keep_redundant_given)
+			return 0;
+		if (snapshot_creation_status != HS_READY)
+			return 0;
+		if (next_snapshot_is_due())
+			return 0;
+	}
 	dss_get_snapshot_list(&sl);
-	ret = remove_outdated_snapshot(&sl);
-	if (ret) /* error, or we are removing something */
-		goto out;
-	/* no outdated snapshot */
-	ret = remove_redundant_snapshot(&sl);
-	if (ret)
-		goto out;
 	ret = 0;
+	if (!low_disk_space && sl.num_snapshots <= 1)
+		goto out;
+	why = "outdated";
+	victim = find_outdated_snapshot(&sl);
+	if (victim)
+		goto remove;
+	why = "redundant";
+	victim = find_redundant_snapshot(&sl);
+	if (victim)
+		goto remove;
+	/* try harder only if disk space is low */
 	if (!low_disk_space)
 		goto out;
+	why = "orphaned";
+	victim = find_orphaned_snapshot(&sl);
+	if (victim)
+		goto remove;
 	DSS_WARNING_LOG("disk space low and nothing obvious to remove\n");
-	ret = remove_oldest_snapshot(&sl);
-	if (ret)
-		goto out;
-	DSS_CRIT_LOG("uhuhu: not enough disk space for a single snapshot\n");
+	victim = find_oldest_removable_snapshot(&sl);
+	if (victim)
+		goto remove;
+	DSS_CRIT_LOG("uhuhu: disk space low and nothing to remove\n");
 	ret = -ERRNO_TO_DSS_ERROR(ENOSPC);
+	goto out;
+remove:
+	pre_remove_hook(victim, why);
 out:
 	free_snapshot_list(&sl);
 	return ret;
 }
 
-static int post_create_hook(void)
+static void post_create_hook(void)
 {
-	int ret, fds[3] = {0, 0, 0};
-	char *cmd;
-
-	if (!conf.post_create_hook_given) {
-		snapshot_creation_status = HS_READY;
-		return 0;
-	}
-	cmd = make_message("%s %s/%s", conf.post_create_hook_arg,
+	char *cmd = make_message("%s %s/%s", conf.post_create_hook_arg,
 		conf.dest_dir_arg, path_to_last_complete_snapshot);
 	DSS_NOTICE_LOG("executing %s\n", cmd);
-	ret = dss_exec_cmdline_pid(&create_pid, cmd, fds);
+	dss_exec_cmdline_pid(&create_pid, cmd);
 	free(cmd);
-	if (ret < 0)
-		return ret;
 	snapshot_creation_status = HS_POST_RUNNING;
-	return ret;
 }
 
-static int post_remove_hook(void)
+static void post_remove_hook(void)
 {
-	int ret, fds[3] = {0, 0, 0};
 	char *cmd;
 	struct snapshot *s = snapshot_currently_being_removed;
 
 	assert(s);
 
-	if (!conf.post_remove_hook_given) {
-		snapshot_removal_status = HS_READY;
-		return 0;
-	}
 	cmd = make_message("%s %s/%s", conf.post_remove_hook_arg,
 		conf.dest_dir_arg, s->name);
 	DSS_NOTICE_LOG("executing %s\n", cmd);
-	ret = dss_exec_cmdline_pid(&remove_pid, cmd, fds);
+	dss_exec_cmdline_pid(&remove_pid, cmd);
 	free(cmd);
-	if (ret < 0)
-		return ret;
 	snapshot_removal_status = HS_POST_RUNNING;
-	return ret;
 }
 
-static void kill_process(pid_t pid)
+static void dss_kill(pid_t pid, int sig, const char *msg)
 {
-	if (!pid)
+	const char *signame, *process_name;
+
+	if (pid == 0)
+		return;
+	switch (sig) {
+	case SIGTERM: signame = "TERM"; break;
+	case SIGSTOP: signame = "STOP"; break;
+	case SIGCONT: signame = "CONT"; break;
+	default: signame = "????";
+	}
+
+	if (pid == create_pid)
+		process_name = "create";
+	else if (pid == remove_pid)
+		process_name = "remove";
+	else process_name = "??????";
+
+	if (msg)
+		DSS_INFO_LOG("%s\n", msg);
+	DSS_DEBUG_LOG("sending signal %d (%s) to pid %d (%s process)\n",
+		sig, signame, (int)pid, process_name);
+	if (kill(pid, sig) >= 0)
 		return;
-	DSS_WARNING_LOG("sending SIGTERM to pid %d\n", (int)pid);
-	kill(pid, SIGTERM);
+	DSS_INFO_LOG("failed to send signal %d (%s) to pid %d (%s process)\n",
+		sig, signame, (int)pid, process_name);
 }
 
 static void stop_create_process(void)
 {
-	if (!create_pid || create_process_stopped)
+	if (create_process_stopped)
 		return;
-	kill(SIGSTOP, create_pid);
+	dss_kill(create_pid, SIGSTOP, "suspending create process");
 	create_process_stopped = 1;
 }
 
 static void restart_create_process(void)
 {
-	if (!create_pid || !create_process_stopped)
+	if (!create_process_stopped)
 		return;
-	kill (SIGCONT, create_pid);
+	dss_kill(create_pid, SIGCONT, "resuming create process");
 	create_process_stopped = 0;
 }
 
@@ -541,8 +672,7 @@ static int wait_for_process(pid_t pid, int *status)
 			}
 		}
 		/* SIGINT or SIGTERM */
-		DSS_WARNING_LOG("sending SIGTERM to pid %d\n", (int)pid);
-		kill(pid, SIGTERM);
+		dss_kill(pid, SIGTERM, "killing child process");
 	}
 	if (ret < 0)
 		DSS_ERROR_LOG("failed to wait for process %d\n", (int)pid);
@@ -572,10 +702,7 @@ static int handle_rm_exit(int status)
 		snapshot_removal_status = HS_READY;
 		return -E_BAD_EXIT_CODE;
 	}
-	if (conf.post_remove_hook_given)
-		snapshot_removal_status = HS_SUCCESS;
-	else
-		snapshot_removal_status = HS_READY;
+	snapshot_removal_status = HS_SUCCESS;
 	return 1;
 }
 
@@ -650,8 +777,7 @@ static int handle_rsync_exit(int status)
 		DSS_WARNING_LOG("rsync process %d returned %d -- restarting\n",
 			(int)create_pid, es);
 		snapshot_creation_status = HS_NEEDS_RESTART;
-		gettimeofday(&next_snapshot_time, NULL);
-		next_snapshot_time.tv_sec += 60;
+		next_snapshot_time = get_current_time() + 60;
 		ret = 1;
 		goto out;
 	}
@@ -665,8 +791,9 @@ static int handle_rsync_exit(int status)
 	if (ret < 0)
 		goto out;
 	snapshot_creation_status = HS_SUCCESS;
+	free(name_of_reference_snapshot);
+	name_of_reference_snapshot = NULL;
 out:
-	create_pid = 0;
 	create_process_stopped = 0;
 	return ret;
 }
@@ -689,6 +816,7 @@ static int handle_pre_create_hook_exit(int status)
 			DSS_NOTICE_LOG("deferring snapshot creation...\n");
 			warn_count = 60; /* warn only once per hour */
 		}
+		next_snapshot_time = get_current_time() + 60;
 		snapshot_creation_status = HS_READY;
 		ret = 0;
 		goto out;
@@ -697,7 +825,6 @@ static int handle_pre_create_hook_exit(int status)
 	snapshot_creation_status = HS_PRE_SUCCESS;
 	ret = 1;
 out:
-	create_pid = 0;
 	return ret;
 }
 
@@ -712,17 +839,22 @@ static int handle_sigchld(void)
 	if (pid == create_pid) {
 		switch (snapshot_creation_status) {
 		case HS_PRE_RUNNING:
-			return handle_pre_create_hook_exit(status);
+			ret = handle_pre_create_hook_exit(status);
+			break;
 		case HS_RUNNING:
-			return handle_rsync_exit(status);
+			ret = handle_rsync_exit(status);
+			break;
 		case HS_POST_RUNNING:
 			snapshot_creation_status = HS_READY;
-			return 1;
+			ret = 1;
+			break;
 		default:
 			DSS_EMERG_LOG("BUG: create can't die in status %d\n",
 				snapshot_creation_status);
 			return -E_BUG;
 		}
+		create_pid = 0;
+		return ret;
 	}
 	if (pid == remove_pid) {
 		ret = handle_remove_exit(status);
@@ -749,9 +881,13 @@ static int check_config(void)
 	return 1;
 }
 
+/*
+ * Returns < 0 on errors, 0 if no config file is given and > 0 if the config
+ * file was read successfully.
+ */
 static int parse_config_file(int override)
 {
-	int ret;
+	int ret, config_file_exists;
 	char *config_file;
 	struct stat statbuf;
 	char *old_logfile_arg = NULL;
@@ -770,13 +906,13 @@ static int parse_config_file(int override)
 		old_daemon_given = conf.daemon_given;
 	}
 
-	ret = stat(config_file, &statbuf);
-	if (ret && conf.config_file_given) {
+	config_file_exists = !stat(config_file, &statbuf);
+	if (!config_file_exists && conf.config_file_given) {
 		ret = -ERRNO_TO_DSS_ERROR(errno);
 		DSS_ERROR_LOG("failed to stat config file %s\n", config_file);
 		goto out;
 	}
-	if (!ret) {
+	if (config_file_exists) {
 		struct cmdline_parser_params params = {
 			.override = override,
 			.initialize = 0,
@@ -810,12 +946,12 @@ static int parse_config_file(int override)
 			conf.logfile_given = 1;
 		}
 	}
-	if (conf.logfile_given) {
+	if (conf.logfile_given && conf.run_given && conf.daemon_given) {
 		logfile = open_log(conf.logfile_arg);
 		log_welcome(conf.loglevel_arg);
 	}
 	DSS_DEBUG_LOG("loglevel: %d\n", conf.loglevel_arg);
-//	cmdline_parser_dump(logfile? logfile : stdout, &conf);
+	ret = config_file_exists;
 out:
 	free(config_file);
 	if (ret < 0)
@@ -833,10 +969,13 @@ static int handle_sighup(void)
 {
 	int ret;
 
-	DSS_NOTICE_LOG("SIGHUP\n");
+	DSS_NOTICE_LOG("SIGHUP, re-reading config\n");
+	dump_dss_config("old");
 	ret = parse_config_file(1);
 	if (ret < 0)
 		return ret;
+	dump_dss_config("reloaded");
+	invalidate_next_snapshot_time();
 	return change_to_dest_dir();
 }
 
@@ -851,8 +990,8 @@ static int handle_signal(void)
 	case SIGINT:
 	case SIGTERM:
 		restart_create_process();
-		kill_process(create_pid);
-		kill_process(remove_pid);
+		dss_kill(create_pid, SIGTERM, NULL);
+		dss_kill(remove_pid, SIGTERM, NULL);
 		ret = -E_SIGNAL;
 		break;
 	case SIGHUP:
@@ -883,14 +1022,67 @@ static int use_rsync_locally(char *logname)
 	return 1;
 }
 
+static int rename_resume_snap(int64_t creation_time)
+{
+	struct snapshot_list sl = {.num_snapshots = 0};
+	struct snapshot *s = NULL;
+	char *new_name = incomplete_name(creation_time);
+	int ret;
+	const char *why;
+
+	ret = 0;
+	if (conf.no_resume_given)
+		goto out;
+	dss_get_snapshot_list(&sl);
+	/*
+	 * Snapshot recycling: We first look at the newest snapshot. If this
+	 * snapshot happens to be incomplete, the last rsync process was
+	 * aborted and we reuse this one. Otherwise we look at snapshots which
+	 * could be removed (outdated and redundant snapshots) as candidates
+	 * for recycling. If no outdated/redundant snapshot exists, we check if
+	 * there is an orphaned snapshot, which likely is useless anyway.
+	 *
+	 * Only if no existing snapshot is suitable for recycling, we bite the
+	 * bullet and create a new one.
+	 */
+	s = get_newest_snapshot(&sl);
+	if (!s) /* no snapshots at all */
+		goto out;
+	/* re-use last snapshot if it is incomplete */
+	why = "aborted";
+	if ((s->flags & SS_COMPLETE) == 0)
+		goto out;
+	why = "outdated";
+	s = find_outdated_snapshot(&sl);
+	if (s)
+		goto out;
+	why = "redundant";
+	s = find_redundant_snapshot(&sl);
+	if (s)
+		goto out;
+	why = "orphaned";
+	s = find_orphaned_snapshot(&sl);
+out:
+	if (s) {
+		DSS_INFO_LOG("reusing %s snapshot %s\n", why, s->name);
+		ret = dss_rename(s->name, new_name);
+	}
+	if (ret >= 0)
+		DSS_NOTICE_LOG("creating new snapshot %s\n", new_name);
+	free(new_name);
+	free_snapshot_list(&sl);
+	return ret;
+}
+
 static void create_rsync_argv(char ***argv, int64_t *num)
 {
-	char *logname, *newest;
+	char *logname;
 	int i = 0, j;
 	struct snapshot_list sl;
 
 	dss_get_snapshot_list(&sl);
-	newest = name_of_newest_complete_snapshot(&sl);
+	assert(!name_of_reference_snapshot);
+	name_of_reference_snapshot = name_of_newest_complete_snapshot(&sl);
 	free_snapshot_list(&sl);
 
 	*argv = dss_malloc((15 + conf.rsync_option_given) * sizeof(char *));
@@ -899,12 +1091,12 @@ static void create_rsync_argv(char ***argv, int64_t *num)
 	(*argv)[i++] = dss_strdup("--delete");
 	for (j = 0; j < conf.rsync_option_given; j++)
 		(*argv)[i++] = dss_strdup(conf.rsync_option_arg[j]);
-	if (newest) {
-		DSS_INFO_LOG("using %s as reference snapshot\n", newest);
-		(*argv)[i++] = make_message("--link-dest=../%s", newest);
-		free(newest);
+	if (name_of_reference_snapshot) {
+		DSS_INFO_LOG("using %s as reference\n", name_of_reference_snapshot);
+		(*argv)[i++] = make_message("--link-dest=../%s",
+			name_of_reference_snapshot);
 	} else
-		DSS_INFO_LOG("no previous snapshot found\n");
+		DSS_INFO_LOG("no suitable reference snapshot found\n");
 	logname = dss_logname();
 	if (use_rsync_locally(logname))
 		(*argv)[i++] = dss_strdup(conf.source_dir_arg);
@@ -933,15 +1125,12 @@ static void free_rsync_argv(char **argv)
 
 static int create_snapshot(char **argv)
 {
-	int ret, fds[3] = {0, 0, 0};
-	char *name;
+	int ret;
 
-	name = incomplete_name(current_snapshot_creation_time);
-	DSS_NOTICE_LOG("creating new snapshot %s\n", name);
-	free(name);
-	ret = dss_exec(&create_pid, argv[0], argv, fds);
+	ret = rename_resume_snap(current_snapshot_creation_time);
 	if (ret < 0)
 		return ret;
+	dss_exec(&create_pid, argv[0], argv);
 	snapshot_creation_status = HS_RUNNING;
 	return ret;
 }
@@ -955,7 +1144,6 @@ static int select_loop(void)
 
 	for (;;) {
 		fd_set rfds;
-		int low_disk_space;
 		struct timeval *tvp;
 
 		if (remove_pid)
@@ -967,7 +1155,6 @@ static int select_loop(void)
 		}
 		FD_ZERO(&rfds);
 		FD_SET(signal_pipe, &rfds);
-		DSS_DEBUG_LOG("tvp: %p, tv_sec : %lu\n", tvp, (long unsigned) tv.tv_sec);
 		ret = dss_select(signal_pipe + 1, &rfds, NULL, tvp);
 		if (ret < 0)
 			goto out;
@@ -985,16 +1172,10 @@ static int select_loop(void)
 			continue;
 		}
 		if (snapshot_removal_status == HS_SUCCESS) {
-			ret = post_remove_hook();
-			if (ret < 0)
-				goto out;
+			post_remove_hook();
 			continue;
 		}
-		ret = disk_space_low();
-		if (ret < 0)
-			goto out;
-		low_disk_space = ret;
-		ret = try_to_free_disk_space(low_disk_space);
+		ret = try_to_free_disk_space();
 		if (ret < 0)
 			goto out;
 		if (snapshot_removal_status != HS_READY) {
@@ -1006,28 +1187,31 @@ static int select_loop(void)
 		case HS_READY:
 			if (!next_snapshot_is_due())
 				continue;
-			ret = pre_create_hook();
-			if (ret < 0)
-				goto out;
+			pre_create_hook();
 			continue;
 		case HS_PRE_RUNNING:
 		case HS_RUNNING:
 		case HS_POST_RUNNING:
 			continue;
 		case HS_PRE_SUCCESS:
-			free_rsync_argv(rsync_argv);
-			create_rsync_argv(&rsync_argv, &current_snapshot_creation_time);
-			/* fall through */
-		case HS_NEEDS_RESTART:
+			if (!name_of_reference_snapshot) {
+				free_rsync_argv(rsync_argv);
+				create_rsync_argv(&rsync_argv, &current_snapshot_creation_time);
+			}
 			ret = create_snapshot(rsync_argv);
 			if (ret < 0)
 				goto out;
 			continue;
-		case HS_SUCCESS:
-			ret = post_create_hook();
+		case HS_NEEDS_RESTART:
+			if (!next_snapshot_is_due())
+				continue;
+			ret = create_snapshot(rsync_argv);
 			if (ret < 0)
 				goto out;
 			continue;
+		case HS_SUCCESS:
+			post_create_hook();
+			continue;
 		}
 	}
 out:
@@ -1036,14 +1220,15 @@ out:
 
 static void exit_hook(int exit_code)
 {
-	int fds[3] = {0, 0, 0};
-	char *argv[] = {conf.exit_hook_arg, dss_strerror(-exit_code), NULL};
+	char *argv[3];
 	pid_t pid;
 
-	if (!conf.exit_hook_given)
-		return;
+	argv[0] = conf.exit_hook_arg;
+	argv[1] = dss_strerror(-exit_code);
+	argv[2] = NULL;
+
 	DSS_NOTICE_LOG("executing %s %s\n", argv[0], argv[1]);
-	dss_exec(&pid, conf.exit_hook_arg, argv, fds);
+	dss_exec(&pid, conf.exit_hook_arg, argv);
 }
 
 static int com_run(void)
@@ -1068,26 +1253,33 @@ static int com_prune(void)
 {
 	int ret;
 	struct snapshot_list sl;
+	struct snapshot *victim;
 	struct disk_space ds;
+	const char *why;
 
 	ret = get_disk_space(".", &ds);
 	if (ret < 0)
 		return ret;
 	log_disk_space(&ds);
 	dss_get_snapshot_list(&sl);
-	ret = remove_outdated_snapshot(&sl);
-	if (ret < 0)
-		goto out;
-	if (ret > 0)
+	why = "outdated";
+	victim = find_outdated_snapshot(&sl);
+	if (victim)
 		goto rm;
-	ret = remove_redundant_snapshot(&sl);
-	if (ret < 0)
-		goto out;
-	if (ret > 0)
+	why = "redundant";
+	victim = find_redundant_snapshot(&sl);
+	if (victim)
 		goto rm;
 	ret = 0;
 	goto out;
 rm:
+	if (conf.dry_run_given) {
+		dss_msg("%s snapshot %s (interval = %i)\n",
+			why, victim->name, victim->interval);
+		ret = 0;
+		goto out;
+	}
+	pre_remove_hook(victim, why);
 	if (snapshot_removal_status == HS_PRE_RUNNING) {
 		ret = wait_for_remove_process();
 		if (ret < 0)
@@ -1103,9 +1295,7 @@ rm:
 		goto out;
 	if (snapshot_removal_status != HS_SUCCESS)
 		goto out;
-	ret = post_remove_hook();
-	if (ret < 0)
-		goto out;
+	post_remove_hook();
 	if (snapshot_removal_status != HS_POST_RUNNING)
 		goto out;
 	ret = wait_for_remove_process();
@@ -1137,9 +1327,7 @@ static int com_create(void)
 		free(msg);
 		return 1;
 	}
-	ret = pre_create_hook();
-	if (ret < 0)
-		return ret;
+	pre_create_hook();
 	if (create_pid) {
 		ret = wait_for_process(create_pid, &status);
 		if (ret < 0)
@@ -1219,11 +1407,26 @@ int main(int argc, char **argv)
 	ret = parse_config_file(0);
 	if (ret < 0)
 		goto out;
+	if (ret == 0) { /* no config file given */
+		/*
+		 * Parse the command line options again, but this time check
+		 * that all required options are given.
+		 */
+		params = (struct cmdline_parser_params) {
+			.override = 1,
+			.initialize = 1,
+			.check_required = 1,
+			.check_ambiguity = 1,
+			.print_errors = 1
+		};
+		cmdline_parser_ext(argc, argv, &conf, &params); /* aborts on errors */
+	}
 	if (conf.daemon_given)
 		daemon_init();
 	ret = change_to_dest_dir();
 	if (ret < 0)
 		goto out;
+	dump_dss_config("startup");
 	ret = setup_signal_handling();
 	if (ret < 0)
 		goto out;