osd/OSD: introduce reset_purged_snaps_last

When the OSD preboots it sends a MMonGetPurgedSnaps message to
the monitor (`_get_purged_snaps`).
The monitor will reply with all the purged snapshots that their purged_epoch_ is in the
range of superblock.purged_snaps_last + 1 up to the last superblock.current_epoch + 1.
When the OSD will handle the reply from the mon (`handle_get_purged_snaps_reply`)
it will call `record_purged_snaps` to write those purged snapshots in the
OSD store as well (PSN_ keys).

Once purged_snaps_last is reset, in the following OSD reboot, the snapshots that were marked as
purged (purged_snaps_ keys) in the mon's store will be also marked,
correspondingly, in the OSD store.
That way `scrub_purged_snaps` will be able to re-trim the snapshots that weren't
marked as purged in the OSD side (for some reason)

Fixes: https://tracker.ceph.com/issues/62981
Signed-off-by: Matan Breizman <mbreizma@redhat.com>

diff --git a/src/osd/OSD.cc b/src/osd/OSD.cc
index 83c49a08a48db37e0367800aa7c654ddf23886be..e978487e4eb1377df25e08110c20016695757999 100644 (file)
--- a/src/osd/OSD.cc
+++ b/src/osd/OSD.cc
@@ -3126,6 +3126,19 @@ will start to track new ops received afterwards.";
     scrub_purged_snaps();
   }
 
+  else if (prefix == "reset_purged_snaps_last") {
+    lock_guard l(osd_lock);
+    superblock.purged_snaps_last = 0;
+    ObjectStore::Transaction t;
+    dout(10) << __func__ << " updating superblock" << dendl;
+    write_superblock(cct, superblock, t);
+    ret = store->queue_transaction(service.meta_ch, std::move(t), nullptr);
+    if (ret < 0) {
+      ss << "Error writing superblock: " << cpp_strerror(ret);
+      goto out;
+    }
+  }
+
   else if (prefix == "dump_osd_network") {
     lock_guard l(osd_lock);
     int64_t value = 0;
@@ -4304,6 +4317,11 @@ void OSD::final_init()
     asok_hook,
     "Scrub purged_snaps vs snapmapper index");
   ceph_assert(r == 0);
+  r = admin_socket->register_command(
+    "reset_purged_snaps_last",
+    asok_hook,
+    "Reset the superblock's purged_snaps_last");
+  ceph_assert(r == 0);
   r = admin_socket->register_command(
     "scrubdebug "                                              \
     "name=pgid,type=CephPgid "                                 \