Fix removal of orphaned snapshots.
[dss.git] / dss.c
diff --git a/dss.c b/dss.c
index c0597f3af32e4586d6fbb98f78aea9b59f338aff..b9afbc4a8505d1886420d1355bd742dbdd73c756 100644 (file)
--- a/dss.c
+++ b/dss.c
@@ -185,8 +185,8 @@ static int next_snapshot_is_due(void)
                goto out;
        }
 
-       tv_divide(wanted, &diff, &tmp); /* sleep time betweeen two snapshots */
-       diff.tv_sec = s->completion_time; /* completion time of the the latest snaphot */
+       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;
@@ -218,11 +218,13 @@ static int pre_create_hook(void)
        return ret;
 }
 
-static int pre_remove_hook(struct snapshot *s, char *why)
+static int pre_remove_hook(struct snapshot *s, const char *why)
 {
        int ret, fds[3] = {0, 0, 0};
        char *cmd;
 
+       if (!s)
+               return 0;
        DSS_DEBUG_LOG("%s snapshot %s\n", why, s->name);
        assert(snapshot_removal_status == HS_READY);
        assert(remove_pid == 0);
@@ -277,12 +279,46 @@ 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;
+}
+
 /*
  * 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;
 
@@ -329,20 +365,14 @@ 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",
@@ -352,29 +382,21 @@ static int remove_outdated_snapshot(struct snapshot_list *sl)
                        continue;
                if (s->interval <= conf.num_intervals_arg)
                        continue;
-               if (conf.dry_run_given) {
-                       dss_msg("%s would be removed (interval = %i)\n",
-                               s->name, s->interval);
-                       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)
 {
        struct snapshot *s = get_oldest_snapshot(sl);
 
        if (!s) /* no snapshot found */
-               return 0;
+               return NULL;
        DSS_INFO_LOG("oldest snapshot: %s\n", s->name);
        if (snapshot_is_being_created(s))
-               return 0;
-       return pre_remove_hook(s, "oldest");
+               return NULL;
+       return s;
 }
 
 static int rename_incomplete_snapshot(int64_t start)
@@ -400,7 +422,9 @@ static int try_to_free_disk_space(int low_disk_space)
 {
        int ret;
        struct snapshot_list sl;
+       struct snapshot *victim;
        struct timeval now;
+       const char *why;
 
        gettimeofday(&now, NULL);
        if (tv_diff(&next_removal_check, &now, NULL) > 0)
@@ -408,22 +432,31 @@ static int try_to_free_disk_space(int low_disk_space)
        if (!low_disk_space && conf.keep_redundant_given)
                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;
+       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 */
        ret = 0;
        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;
+       victim = find_oldest_removable_snapshot(&sl);
+       if (victim)
+               goto remove;
        DSS_CRIT_LOG("uhuhu: not enough disk space for a single snapshot\n");
        ret = -ERRNO_TO_DSS_ERROR(ENOSPC);
+       goto out;
+remove:
+       ret = pre_remove_hook(victim, why);
 out:
        free_snapshot_list(&sl);
        return ret;
@@ -637,7 +670,12 @@ static int handle_rsync_exit(int status)
                goto out;
        }
        es = WEXITSTATUS(status);
-       if (es == 13) { /* Errors with program diagnostics */
+       /*
+        * Restart rsync on non-fatal errors:
+        * 12: Error in rsync protocol data stream
+        * 13: Errors with program diagnostics
+        */
+       if (es == 12 || es == 13) {
                DSS_WARNING_LOG("rsync process %d returned %d -- restarting\n",
                        (int)create_pid, es);
                snapshot_creation_status = HS_NEEDS_RESTART;
@@ -1059,26 +1097,35 @@ 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;
+       }
+       ret = pre_remove_hook(victim, why);
+       if (ret < 0)
+               goto out;
        if (snapshot_removal_status == HS_PRE_RUNNING) {
                ret = wait_for_remove_process();
                if (ret < 0)