From: Samuel Just <sjust@redhat.com>
Date: Thu, 17 Sep 2020 22:45:56 +0000 (-0700)
Subject: os/seastore/journal: replay_segment: skip replay on deltas to released segments
X-Git-Tag: v16.1.0~807^2~12
X-Git-Url: http://git-server-git.apps.pok.os.sepia.ceph.com/?a=commitdiff_plain;h=c300ec9630abd7bee2fb530dd5364ced6aa9de80;p=ceph.git

os/seastore/journal: replay_segment: skip replay on deltas to released segments

See comment.

Signed-off-by: Samuel Just <sjust@redhat.com>
---

diff --git a/src/crimson/os/seastore/journal.cc b/src/crimson/os/seastore/journal.cc
index 95aad57d67fe..7b228445a32b 100644
--- a/src/crimson/os/seastore/journal.cc
+++ b/src/crimson/os/seastore/journal.cc
@@ -398,11 +398,25 @@ Journal::replay_segment(
   logger().debug("replay_segment: starting at {}", seq);
   return seastar::do_with(
     delta_scan_handler_t(
-      [&handler, seq](auto addr, auto base, const auto &delta) {
-	return handler(
-	  journal_seq_t{seq.segment_seq, addr},
-	  base,
-	  delta);
+      [=, &handler](auto addr, auto base, const auto &delta) {
+	/* The journal may validly contain deltas for extents in since released
+	 * segments.  We can detect those cases by whether the segment in question
+	 * currently has a sequence number > the current journal segment seq.
+	 * We can safely skip these deltas because the extent must already have
+	 * been rewritten.
+	 *
+	 * Note, this comparison exploits the fact that SEGMENT_SEQ_NULL is
+	 * a large number.
+	 */
+	if (delta.paddr != P_ADDR_NULL &&
+	    segment_provider->get_seq(delta.paddr.segment) > seq.segment_seq) {
+	  return replay_ertr::now();
+	} else {
+	  return handler(
+	    journal_seq_t{seq.segment_seq, addr},
+	    base,
+	    delta);
+	}
       }),
     [this, seq](auto &dhandler) {
       return scan_segment(
diff --git a/src/crimson/os/seastore/journal.h b/src/crimson/os/seastore/journal.h
index 805d1f408bc7..5ca090ac4ee8 100644
--- a/src/crimson/os/seastore/journal.h
+++ b/src/crimson/os/seastore/journal.h
@@ -102,6 +102,8 @@ public:
   virtual void init_mark_segment_closed(
     segment_id_t segment, segment_seq_t seq) {}
 
+  virtual segment_seq_t get_seq(segment_id_t id) { return 0; }
+
   virtual ~JournalSegmentProvider() {}
 };