mon: OSDMonitor: do not write full_latest during trim

On commit 81983bab we patched OSDMonitor::update_from_paxos() such that we
write the latest full map version to 'full_latest' each time the latest
full map was built from the incremental versions.

This change however clashed with OSDMonitor::encode_trim_extra(), which
also wrote to 'full_latest' on each trim, writing instead the version of
the *oldest* full map.  This duality of behaviors could lead the store
to an inconsistent state across the monitors (although there's no sign of
it actually imposing any issues besides rebuilding already existing full
maps on some monitors).

We now stop OSDMonitor::encode_trim_extra() from writing to 'full_latest'.
This function will still write out the oldest full map it has in the store,
but it will no longer write to full_latest, instead leaving it up to
OSDMonitor::update_from_paxos() to figure it out -- and it already does.

Fixes: #6378
Backport: dumpling

Signed-off-by: Joao Eduardo Luis <joao.luis@inktank.com>
Reviewed-by: Sage Weil <sage@inktank.com>
(cherry picked from commit bd0f29a2c28cca496ec830eac932477ebf3182ba)

diff --git a/src/mon/OSDMonitor.cc b/src/mon/OSDMonitor.cc
index 68dab0a59d541d94612f2cb6b07b785663b2449e..850bee05d275f5b43ca3557deb6705e0a35124a9 100644 (file)
--- a/src/mon/OSDMonitor.cc
+++ b/src/mon/OSDMonitor.cc
@@ -120,7 +120,12 @@ void OSDMonitor::update_from_paxos(bool *need_bootstrap)
    * We will possibly have a stashed latest that *we* wrote, and we will
    * always be sure to have the oldest full map in the first..last range
    * due to encode_trim_extra(), which includes the oldest full map in the trim
-   * transaction.  Start with whichever is newer.
+   * transaction.
+   *
+   * encode_trim_extra() does not however write the full map's
+   * version to 'full_latest'.  This is only done when we are building the
+   * full maps from the incremental versions.  But don't panic!  We make sure
+   * that the following conditions find whichever full map version is newer.
    */
   version_t latest_full = get_version_latest_full();
   if (latest_full == 0 && get_first_committed() > 1)
@@ -637,7 +642,6 @@ void OSDMonitor::encode_trim_extra(MonitorDBStore::Transaction *tx, version_t fi
   bufferlist bl;
   get_version_full(first, bl);
   put_version_full(tx, first, bl);
-  put_version_latest_full(tx, first);
 }
 
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