src/osd/PG.cc: remove redundant call to trim_log()

This change is motived by the failure tracked in
https://tracker.ceph.com/issues/25198. The failure highlights a case, when a
call to trim_log() after the PG has recovered, races with the previous op,
on a replica OSD. Since the previous operation has not completed, the
last_complete value for that OSD is not valid, when we try to trim the
log. It is also worth noting that the race is due to MOSDPGTrim going through
the strict queue as a peering message vs regular ops going through the
non-strict queue.

During the investigation of this bug, we noticed that, with
https://tracker.ceph.com/issues/23979, we allow pg log trimming to
happen on the primary and replicas, whenever we cross the upper bound of
the pg log. This also ensures that pg log trimming happens while processing
any new op.

Therefore, the function trim_log(), which earlier served the purpose of
trimming logs on the primary and replicas, just before the PG went into
the Recovered state, is no more required. This acted like a last line of
defense to trim logs, when we did not need the logs any more. But, this call
seems redundant now, because, we are limiting the pg log length at all times.

Signed-off-by: Neha Ojha <nojha@redhat.com>
(cherry picked from commit 283b0bde4a52128c1590afe8e5011b266a2e334b)

Conflicts:
	src/osd/PG.cc: We do not need the trim_log() call any longer,
        due to the explanation provided in the commit message.

diff --git a/src/osd/PG.cc b/src/osd/PG.cc
index 443d8c4860e59720771812cd8a9fdd17e915e0df..7965757d7bd461a3d110d96c750d4ed3987ca64a 100644 (file)
--- a/src/osd/PG.cc
+++ b/src/osd/PG.cc
@@ -3348,33 +3348,6 @@ void PG::write_if_dirty(ObjectStore::Transaction& t)
     t.omap_setkeys(coll, pgmeta_oid, km);
 }
 
-void PG::trim_log()
-{
-  assert(is_primary());
-  calc_trim_to();
-  dout(10) << __func__ << " to " << pg_trim_to << dendl;
-  if (pg_trim_to != eversion_t()) {
-    // inform peers to trim log
-    assert(!actingbackfill.empty());
-    for (set<pg_shard_t>::iterator i = actingbackfill.begin();
-        i != actingbackfill.end();
-        ++i) {
-      if (*i == pg_whoami) continue;
-      osd->send_message_osd_cluster(
-       i->osd,
-       new MOSDPGTrim(
-         get_osdmap()->get_epoch(),
-         spg_t(info.pgid.pgid, i->shard),
-         pg_trim_to),
-       get_osdmap()->get_epoch());
-    }
-
-    // trim primary as well
-    pg_log.trim(pg_trim_to, info);
-    dirty_info = true;
-  }
-}
-
 void PG::add_log_entry(const pg_log_entry_t& e, bool applied)
 {
   // raise last_complete only if we were previously up to date
@@ -7565,9 +7538,6 @@ PG::RecoveryState::Recovered::Recovered(my_context ctx)
     pg->publish_stats_to_osd();
   }
 
-  // trim pglog on recovered
-  pg->trim_log();
-
   // adjust acting set?  (e.g. because backfill completed...)
   bool history_les_bound = false;
   if (pg->acting != pg->up && !pg->choose_acting(auth_log_shard,

diff --git a/src/osd/PG.h b/src/osd/PG.h
index 11bf5fc8d4fd2900a3b20143730672f4ebd51997..212da4d7ed386bebfccaf7b19ac7d68870ec33cc 100644 (file)
--- a/src/osd/PG.h
+++ b/src/osd/PG.h
@@ -2653,7 +2653,6 @@ public:
     ObjectStore::Transaction &t,
     bool transaction_applied = true);
   bool check_log_for_corruption(ObjectStore *store);
-  void trim_log();
 
   std::string get_corrupt_pg_log_name() const;
   static int read_info(