MDEV-17843 Assertion `page_rec_is_leaf(rec)' failed in lock_rec_queue_validate...

MDEV-17843 Assertion `page_rec_is_leaf(rec)' failed in lock_rec_queue_validate upon SHOW ENGINE INNODB STATUS

lock_validate() accumulates page ids under locked lock_sys->mutex, then
releases the latch, and invokes lock_rec_block_validate() for each page.
Some other thread has ability to add/remove locks and change pages
between releasing the latch in lock_validate() and acquiring it in
lock_rec_validate_page().

lock_rec_validate_page() can invoke lock_rec_queue_validate() for
non-locked supremum, what can cause ut_ad(page_rec_is_leaf(rec)) failure
in lock_rec_queue_validate().

The fix is to invoke lock_rec_queue_validate() only for locked records
in lock_rec_validate_page().

The error message in lock_rec_block_validate() is not necessary as
BUF_GET_POSSIBLY_FREED mode is used to get block from buffer pool, and
this is not error if a block was evicted.

The test case would require new debug sync point. I think it's not
necessary as the fixed code is debug-only.

storage/innobase/lock/lock0lock.cc

@@ -5050,25 +5050,25 @@ lock_rec_validate_page(
 	holding a space->latch. */
 	if (!sync_check_find(SYNC_FSP))
 	for (i = nth_bit; i < lock_rec_get_n_bits(lock); i++) {
-
-		if (i == PAGE_HEAP_NO_SUPREMUM
-		    || lock_rec_get_nth_bit(lock, i)) {
+		bool locked = lock_rec_get_nth_bit(lock, i);
+		if (locked || i == PAGE_HEAP_NO_SUPREMUM) {
 
 			rec = page_find_rec_with_heap_no(block->frame, i);
 			ut_a(rec);
-			ut_ad(!lock_rec_get_nth_bit(lock, i)
-			      || page_rec_is_leaf(rec));
-			offsets = rec_get_offsets(rec, lock->index, offsets,
-						  lock->index->n_core_fields,
-						  ULINT_UNDEFINED, &heap);
+			ut_ad(!locked || page_rec_is_leaf(rec));
 
 			/* If this thread is holding the file space
 			latch (fil_space_t::latch), the following
 			check WILL break the latching order and may
 			cause a deadlock of threads. */
 
-			lock_rec_queue_validate(
-				TRUE, block, rec, lock->index, offsets);
+			if (locked) {
+				offsets = rec_get_offsets(rec, lock->index,
+					offsets, lock->index->n_core_fields,
+					ULINT_UNDEFINED, &heap);
+				lock_rec_queue_validate(TRUE, block, rec,
+					lock->index, offsets);
+			}
 
 			nth_bit = i + 1;
 
@@ -5161,13 +5161,6 @@ lock_rec_block_validate(
 			BUF_GET_POSSIBLY_FREED,
 			__FILE__, __LINE__, &mtr, &err);
 
-		if (err != DB_SUCCESS) {
-			ib::error() << "Lock rec block validate failed for tablespace "
-				   << space->name
-				   << " space_id " << space_id
-				   << " page_no " << page_no << " err " << err;
-		}
-
 		if (block) {
 			buf_block_dbg_add_level(block, SYNC_NO_ORDER_CHECK);