Merge pull request #12340 from athanatos/wip-18127

osd/PGLog::proc_replica_log,merge_log: fix bound for last_update

Reviewed-by: Sage Weil <sage@redhat.com>

src/osd/PGLog.cc

@@ -176,16 +176,21 @@ void PGLog::proc_replica_log(
   }
 
   /* Because olog.head >= log.tail, we know that both pgs must at least have
-   * the event represented by log.tail.  Thus, lower_bound >= log.tail.  It's
+   * the event represented by log.tail.  Similarly, because log.head >= olog.tail,
+   * we know that the even represented by olog.tail must be common to both logs.
+   * Furthermore, the event represented by a log tail was necessarily trimmed,
+   * thus neither olog.tail nor log.tail can be divergent. It's
    * possible that olog/log contain no actual events between olog.head and
-   * log.tail, however, since they might have been split out.  Thus, if
-   * we cannot find an event e such that log.tail <= e.version <= log.head,
-   * the last_update must actually be log.tail.
+   * MAX(log.tail, olog.tail), however, since they might have been split out.
+   * Thus, if we cannot find an event e such that
+   * log.tail <= e.version <= log.head, the last_update must actually be
+   * MAX(log.tail, olog.tail).
    */
+  eversion_t limit = MAX(olog.tail, log.tail);
   eversion_t lu =
     (first_non_divergent == log.log.rend() ||
-     first_non_divergent->version < log.tail) ?
-    log.tail :
+     first_non_divergent->version < limit) ?
+    limit :
     first_non_divergent->version;
 
   IndexedLog folog(olog);
@@ -290,6 +295,7 @@ void PGLog::merge_log(ObjectStore::Transaction& t,
   //  this is just filling in history.  it does not affect our
   //  missing set, as that should already be consistent with our
   //  current log.
+  eversion_t orig_tail = log.tail;
   if (olog.tail < log.tail) {
     dout(10) << "merge_log extending tail to " << olog.tail << dendl;
     list<pg_log_entry_t>::iterator from = olog.log.begin();
@@ -336,19 +342,20 @@ void PGLog::merge_log(ObjectStore::Transaction& t,
     // find start point in olog
     list<pg_log_entry_t>::iterator to = olog.log.end();
     list<pg_log_entry_t>::iterator from = olog.log.end();
-    eversion_t lower_bound = olog.tail;
+    eversion_t lower_bound = MAX(olog.tail, orig_tail);
     while (1) {
       if (from == olog.log.begin())
 	break;
       --from;
       dout(20) << "  ? " << *from << dendl;
       if (from->version <= log.head) {
-	dout(20) << "merge_log cut point (usually last shared) is " << *from << dendl;
-	lower_bound = from->version;
+	lower_bound = MAX(lower_bound, from->version);
 	++from;
 	break;
       }
     }
+    dout(20) << "merge_log cut point (usually last shared) is "
+	     << lower_bound << dendl;
     mark_dirty_from(lower_bound);
 
     auto divergent = log.rewind_from_head(lower_bound);

src/test/osd/TestPGLog.cc

@@ -260,7 +260,8 @@ class PGLogTest : public ::testing::Test, protected PGLog {
     for (list<pg_log_entry_t>::const_iterator i = tcase.auth.begin();
 	 i != tcase.auth.end();
 	 ++i) {
-      omissing.add_next_event(*i);
+      if (i->version > oinfo.last_update)
+	omissing.add_next_event(*i);
     }
     verify_missing(tcase, omissing);
   }
@@ -1947,6 +1948,34 @@ TEST_F(PGLogTest, merge_log_split_missing_entries_at_head) {
   run_test_case(t);
 }
 
+TEST_F(PGLogTest, olog_tail_gt_log_tail_split) {
+  TestCase t;
+  t.auth.push_back(mk_ple_mod(mk_obj(1), mk_evt(10, 100), mk_evt(8, 70)));
+  t.auth.push_back(mk_ple_mod(mk_obj(1), mk_evt(15, 150), mk_evt(10, 100)));
+  t.auth.push_back(mk_ple_mod(mk_obj(1), mk_evt(15, 155), mk_evt(15, 150)));
+
+  t.setup();
+  t.set_div_bounds(mk_evt(15, 153), mk_evt(15, 151));
+  t.set_auth_bounds(mk_evt(15, 156), mk_evt(10, 99));
+  t.final.add(mk_obj(1), mk_evt(15, 155), mk_evt(15, 150));
+  run_test_case(t);
+}
+
+TEST_F(PGLogTest, olog_tail_gt_log_tail_split2) {
+  TestCase t;
+  t.auth.push_back(mk_ple_mod(mk_obj(1), mk_evt(10, 100), mk_evt(8, 70)));
+  t.auth.push_back(mk_ple_mod(mk_obj(1), mk_evt(15, 150), mk_evt(10, 100)));
+  t.auth.push_back(mk_ple_mod(mk_obj(1), mk_evt(16, 155), mk_evt(15, 150)));
+  t.div.push_back(mk_ple_mod(mk_obj(1), mk_evt(15, 153), mk_evt(15, 150)));
+
+  t.setup();
+  t.set_div_bounds(mk_evt(15, 153), mk_evt(15, 151));
+  t.set_auth_bounds(mk_evt(16, 156), mk_evt(10, 99));
+  t.final.add(mk_obj(1), mk_evt(16, 155), mk_evt(0, 0));
+  t.toremove.insert(mk_obj(1));
+  run_test_case(t);
+}
+
 TEST_F(PGLogTest, filter_log_1) {
   {
     clear();