MDEV-36868: Inconsistency when shrinking innodb_buffer_pool_size

buf_pool_t::resize(): After successfully shrinking the buffer pool,
announce the success. The size had already been updated in shrunk().
After failing to shrink the buffer pool, re-enable the adaptive
hash index if it had been enabled.

Reviewed by: Debarun Banerjee

Author: dr-m

mysql-test/suite/innodb/r/innodb_buffer_pool_resize.result

@@ -14,6 +14,15 @@ create table t1 (id int primary key, val int not null)
 ENGINE=InnoDB ROW_FORMAT=COMPRESSED;
 SET STATEMENT foreign_key_checks=0, unique_checks=0 FOR
 INSERT INTO t1 SELECT seq*4,seq*4 FROM seq_1_to_262144;
+SELECT @@GLOBAL.innodb_adaptive_hash_index;
+@@GLOBAL.innodb_adaptive_hash_index
+1
+SET STATEMENT max_statement_time=1e-9 FOR
+SET GLOBAL innodb_buffer_pool_size = 7340032;
+SELECT @@GLOBAL.innodb_adaptive_hash_index;
+@@GLOBAL.innodb_adaptive_hash_index
+1
+FOUND 1 /innodb_buffer_pool_size=7m.*resized from|innodb_buffer_pool_size change aborted/ in mysqld.1.err
 set global innodb_buffer_pool_size = 7340032;
 select count(val) from t1;
 count(val)

mysql-test/suite/innodb/r/innodb_buffer_pool_resize_temporary.result

@@ -2,6 +2,16 @@ SET @save_limit=@@GLOBAL.innodb_limit_optimistic_insert_debug;
 SET @save_size=@@GLOBAL.innodb_buffer_pool_size;
 SET GLOBAL innodb_limit_optimistic_insert_debug=2;
 SET GLOBAL innodb_buffer_pool_size=16777216;
+call mtr.add_suppression("innodb_buffer_pool_size change aborted");
+SET @old_innodb_adaptive_hash_index = @@innodb_adaptive_hash_index;
+SET GLOBAL innodb_adaptive_hash_index = ON;
+SET STATEMENT debug_dbug='+d,buf_shrink_fail' FOR
+SET GLOBAL innodb_buffer_pool_size=8388608;
+ERROR HY000: innodb_buffer_pool_size change aborted
+SELECT @@GLOBAL.innodb_adaptive_hash_index,@@GLOBAL.innodb_buffer_pool_size;
+@@GLOBAL.innodb_adaptive_hash_index	@@GLOBAL.innodb_buffer_pool_size
+1	16777216
+SET GLOBAL innodb_adaptive_hash_index = @old_innodb_adaptive_hash_index;
 CREATE TEMPORARY TABLE t1 (a INT PRIMARY KEY) ENGINE=InnoDB;
 INSERT INTO t1 SELECT seq FROM seq_1_to_200;
 SET GLOBAL innodb_max_purge_lag_wait=0;

mysql-test/suite/innodb/t/innodb_buffer_pool_resize.test

@@ -1,5 +1,6 @@
 --source include/have_innodb.inc
 --source include/have_sequence.inc
+--source include/not_embedded.inc # there are no messages in mysqld.1.err
 
 --echo #
 --echo # MDEV-29445: Reorganize buffer pool (and remove chunks)
@@ -37,6 +38,17 @@ INSERT INTO t1 SELECT seq*4,seq*4 FROM seq_1_to_262144;
 SET GLOBAL innodb_read_only_compressed=@save_innodb_read_only_compressed;
 --enable_query_log
 
+SELECT @@GLOBAL.innodb_adaptive_hash_index;
+--error 0,ER_WRONG_USAGE
+SET STATEMENT max_statement_time=1e-9 FOR
+SET GLOBAL innodb_buffer_pool_size = 7340032;
+SELECT @@GLOBAL.innodb_adaptive_hash_index;
+
+--let SEARCH_FILE= $MYSQLTEST_VARDIR/log/mysqld.1.err
+--let SEARCH_PATTERN= InnoDB: Trying to shrink innodb_buffer_pool_size=7m
+--let SEARCH_PATTERN= innodb_buffer_pool_size=7m.*resized from|innodb_buffer_pool_size change aborted
+--source include/search_pattern_in_file.inc
+
 # Attempt to shrink the buffer pool. This may occasionally fail.
 --error 0,ER_WRONG_USAGE
 set global innodb_buffer_pool_size = 7340032;

mysql-test/suite/innodb/t/innodb_buffer_pool_resize_temporary.test

@@ -8,6 +8,16 @@ SET @save_size=@@GLOBAL.innodb_buffer_pool_size;
 SET GLOBAL innodb_limit_optimistic_insert_debug=2;
 SET GLOBAL innodb_buffer_pool_size=16777216;
 
+call mtr.add_suppression("innodb_buffer_pool_size change aborted");
+
+SET @old_innodb_adaptive_hash_index = @@innodb_adaptive_hash_index;
+SET GLOBAL innodb_adaptive_hash_index = ON;
+--error ER_WRONG_USAGE
+SET STATEMENT debug_dbug='+d,buf_shrink_fail' FOR
+SET GLOBAL innodb_buffer_pool_size=8388608;
+SELECT @@GLOBAL.innodb_adaptive_hash_index,@@GLOBAL.innodb_buffer_pool_size;
+SET GLOBAL innodb_adaptive_hash_index = @old_innodb_adaptive_hash_index;
+
 CREATE TEMPORARY TABLE t1 (a INT PRIMARY KEY) ENGINE=InnoDB;
 INSERT INTO t1 SELECT seq FROM seq_1_to_200;
 

storage/innobase/buf/buf0buf.cc

@@ -1614,6 +1614,7 @@ ATTRIBUTE_COLD buf_pool_t::shrink_status buf_pool_t::shrink(size_t size)
   noexcept
 {
   mysql_mutex_assert_owner(&mutex);
+  DBUG_EXECUTE_IF("buf_shrink_fail", return SHRINK_ABORT;);
   buf_load_abort();
 
   if (!n_blocks_to_withdraw)
@@ -2014,25 +2015,12 @@ ATTRIBUTE_COLD void buf_pool_t::resize(size_t size, THD *thd) noexcept
     if (ahi_disabled)
       btr_search.enable(true);
 #endif
-    mysql_mutex_lock(&LOCK_global_system_variables);
-    bool resized= n_blocks_removed < 0;
-    if (n_blocks_removed > 0)
-    {
-      mysql_mutex_lock(&mutex);
-      resized= size_in_bytes == old_size;
-      if (resized)
-      {
-        size_in_bytes_requested= size;
-        size_in_bytes= size;
-      }
-      mysql_mutex_unlock(&mutex);
-    }
-
-    if (resized)
+    if (n_blocks_removed)
       sql_print_information("InnoDB: innodb_buffer_pool_size=%zum (%zu pages)"
                             " resized from %zum (%zu pages)",
                             size >> 20, n_blocks_new, old_size >> 20,
                             old_blocks);
+    mysql_mutex_lock(&LOCK_global_system_variables);
   }
   else
   {
@@ -2095,6 +2083,10 @@ ATTRIBUTE_COLD void buf_pool_t::resize(size_t size, THD *thd) noexcept
     mysql_mutex_unlock(&mutex);
     my_printf_error(ER_WRONG_USAGE, "innodb_buffer_pool_size change aborted",
                     MYF(ME_ERROR_LOG));
+#ifdef BTR_CUR_HASH_ADAPT
+    if (ahi_disabled)
+      btr_search.enable(true);
+#endif
     mysql_mutex_lock(&LOCK_global_system_variables);
   }