MDEV-11197: TrxInInnoDB::is_aborted(const trx_t*): Assertion...

MDEV-11197: TrxInInnoDB::is_aborted(const trx_t*): Assertion `srv_read_only_mode || trx->in_depth > 0' failed

TrxInInnoDB should be constructed to track if a transaction is executing
inside InnoDB code i.e. it is like a gate between Server and InnoDB
::rnd_next() is called from Server and thus construct TrxInInnoDB
also there.

Applied suggested clean-up to TrxInInnoDB class functions enter()
and exit(). Note that exactly original did not work for enter().

storage/innobase/handler/ha_innodb.cc

@@ -10574,6 +10574,8 @@ ha_innobase::rnd_next(
 
 	DBUG_ENTER("rnd_next");
 
+	TrxInInnoDB	trx_in_innodb(m_prebuilt->trx);
+
 	if (m_start_of_scan) {
 		error = index_first(buf);
 

storage/innobase/include/trx0trx.h

@@ -1508,17 +1508,15 @@ class TrxInInnoDB {
 		}
 
 		/* Avoid excessive mutex acquire/release */
-		++trx->in_depth;
-
-		/* If trx->in_depth is greater than 1 then
-		transaction is already in InnoDB. */
-		if (trx->in_depth > 1) {
-
+		if (++trx->in_depth > 1) {
+			/* The transaction is already inside InnoDB. */
+			ut_ad(trx->in_depth > 1);
 			return;
 		}
 
 		/* Only the owning thread should release the latch. */
 
+		ut_ad(trx->in_depth == 1);
 		trx_assert_no_search_latch(trx);
 
 		trx_mutex_enter(trx);
@@ -1545,15 +1543,14 @@ class TrxInInnoDB {
 
 		ut_ad(trx->in_depth > 0);
 
-		--trx->in_depth;
-
-		if (trx->in_depth > 0) {
-
+		if (--trx->in_depth > 0) {
+			ut_ad(trx->in_depth);
 			return;
 		}
 
 		/* Only the owning thread should release the latch. */
 
+		ut_ad(trx->in_depth == 0);
 		trx_assert_no_search_latch(trx);
 
 		trx_mutex_enter(trx);