osd: Optimized EC don't try to trim past crt

If there is an exceptionally long sequence of partial writes
that did not update a shard that is followed by a full write
then it is possible that the log trim point is ahead of the
previous write to the shard (and hence crt). We cannot trim
beyond crt. In this scenario its fine to limit the trim to crt
because the shard doesn't have any of the log entries for the
partial writes so there is nothing more to trim.

Signed-off-by: Bill Scales <[email protected]>

Author: bill-scales

src/osd/PeeringState.cc

@@ -4549,8 +4549,16 @@ bool PeeringState::append_log_entries_update_missing(
 
   psdout(20) << "trim_to bool = " << bool(trim_to)
 	     << " trim_to = " << (trim_to ? *trim_to : eversion_t()) << dendl;
-  if (trim_to)
-    pg_log.trim(*trim_to, info);
+  if (trim_to) {
+    eversion_t trim = *trim_to;
+    if (pool.info.allows_ecoptimizations() &&
+	(trim > pg_log.get_can_rollback_to())) {
+      // An exceptionally long sequence of partial writes followed by a full
+      // write can result in trim_to being ahead of crt
+      trim = pg_log.get_can_rollback_to();
+    }
+    pg_log.trim(trim, info);
+  }
   dirty_info = true;
   write_if_dirty(t);
   return invalidate_stats;
@@ -4722,6 +4730,12 @@ void PeeringState::append_log(
   if (!transaction_applied || async)
     psdout(10) << pg_whoami
 	       << " is async_recovery or backfill target" << dendl;
+  if (pool.info.allows_ecoptimizations() &&
+      (trim_to > pg_log.get_can_rollback_to())) {
+    // An exceptionally long sequence of partial writes followed by a full
+    // write can result in trim_to being ahead of crt
+    trim_to = pg_log.get_can_rollback_to();
+  }
   pg_log.trim(trim_to, info, transaction_applied, async);
 
   // update the local pg, pg log
@@ -7028,6 +7042,13 @@ boost::statechart::result PeeringState::ReplicaActive::react(const MTrim& trim)
 {
   DECLARE_LOCALS;
   // primary is instructing us to trim
+  eversion_t trim_to = trim.trim_to;
+  if (ps->pool.info.allows_ecoptimizations() &&
+      (trim_to > ps->pg_log.get_can_rollback_to())) {
+    // An exceptionally long sequence of partial writes followed by a full
+    // write can result in trim_to being ahead of crt
+    trim_to = ps->pg_log.get_can_rollback_to();
+  }
   ps->pg_log.trim(trim.trim_to, ps->info);
   ps->dirty_info = true;
   return discard_event();