log_t::persist(): Assertion is_opened() == archive failed

I encountered a debug assertion while working on MDEV-14992. The scenario involves crash recovery with innodb_log_file_mmap=ON and a startup with innodb_log_archive=OFF while a log file in the innodb_log_archive=ON format exists (ib_0000000000003000.log).

The assertion would fail when crash recovery is writing back recovered data pages. It invokes log_file_up_to(), which in this case would be a no-op, because the log_sys.flushed_to_disk_lsn would have been recovered from the log. Yet, a debug assertion would fail because we are asserting right before checking that if a write is actually needed. The patch below fixes the issue:

diff --git a/storage/innobase/log/log0log.cc b/storage/innobase/log/log0log.cc

index 6364f9fc496..aad4f768f08 100644

--- a/storage/innobase/log/log0log.cc

+++ b/storage/innobase/log/log0log.cc

@@ -1544,13 +1544,14 @@ void log_t::persist(lsn_t lsn) noexcept

   ut_ad(!write_lock.is_owner());

   ut_ad(!flush_lock.is_owner());

   ut_ad(latch_have_wr());

-  ut_ad(is_opened() == archive);

   lsn_t old= flushed_to_disk_lsn.load(std::memory_order_relaxed);

   if (old > lsn)

     return;

+  ut_ad(is_mmap_writeable());

+  ut_ad(is_opened() == archive);

   const size_t start(calc_lsn_offset(old));

   const size_t end(calc_lsn_offset(lsn));