osd: fix check for whether to recalculate past_intervals

We may not recalculate all the way back to last_interval_clean due to
the oldest_map floor.  Figure out what we want and could calculate before
deciding whether what we have is insufficient.

Also, print something if we discard and recalculate so it is clear what is
happening and why.

Signed-off-by: Sage Weil <sage@newdream.net>

1 files changed, 12 insertions, 11 deletions

diff --git a/src/osd/PG.cc b/src/osd/PG.cc
index 813f992786b..2bba57d1b67 100644
--- a/src/osd/PG.cc
+++ b/src/osd/PG.cc
@@ -678,17 +678,6 @@ bool PG::needs_recovery() const
 
 void PG::generate_past_intervals()
 {
-  // Do we already have the intervals we want?
-  map<epoch_t,pg_interval_t>::const_iterator pif = past_intervals.begin();
-  if (pif != past_intervals.end()) {
-    if (pif->first <= info.history.last_epoch_clean) {
-      dout(10) << __func__ << ": already have past intervals back to "
-	       << info.history.last_epoch_clean << dendl;
-      return;
-    }
-    past_intervals.clear();
-  }
-
   epoch_t first_epoch = 0;
   epoch_t stop = MAX(info.history.epoch_created, info.history.last_epoch_clean);
   if (stop < osd->superblock.oldest_map)
@@ -701,6 +690,18 @@ void PG::generate_past_intervals()
     return;
   }
 
+  // Do we already have the intervals we want?
+  map<epoch_t,pg_interval_t>::const_iterator pif = past_intervals.begin();
+  if (pif != past_intervals.end()) {
+    if (pif->first <= stop) {
+      dout(10) << __func__ << " already have past intervals back to "
+	       << stop << dendl;
+      return;
+    }
+    dout(10) << __func__ << " only have past intervals back to " << pif->first << ", recalculating" << dendl;
+    past_intervals.clear();
+  }
+
   dout(10) << __func__ << " over epochs " << stop << "-" << last_epoch << dendl;
 
   OSDMapRef nextmap = osd->get_map(last_epoch);