MDEV-21826 Recovery failure : loop of Read redo log up to LSN

- This issue is caused by MDEV-19176
(bba59abb).
- Problem is that there is miscalculation of available memory during
recovery if innodb_buffer_pool_instances > 1.
- Ignore the buffer pool instance while calculating available_memory
- Removed recv_n_pool_free_frames variable and use buf_pool_get_n_pages()
instead.

storage/innobase/buf/buf0rea.cc

 /*****************************************************************************
 
 Copyright (c) 1995, 2017, Oracle and/or its affiliates. All Rights Reserved.
-Copyright (c) 2015, 2019, MariaDB Corporation.
+Copyright (c) 2015, 2020, MariaDB Corporation.
 
 This program is free software; you can redistribute it and/or modify it under
 the terms of the GNU General Public License as published by the Free Software
@@ -925,8 +925,12 @@ buf_read_recv_pages(
 		ulint			count = 0;
 
 		buf_pool = buf_pool_get(cur_page_id);
-		while (buf_pool->n_pend_reads >= recv_n_pool_free_frames / 2) {
+		ulint limit = 0;
+		for (ulint j = 0; j < buf_pool->n_chunks; j++) {
+			limit += buf_pool->chunks[j].size / 2;
+		}
 
+		while (buf_pool->n_pend_reads >= limit) {
 			os_aio_simulated_wake_handler_threads();
 			os_thread_sleep(10000);
 

storage/innobase/include/log0recv.h

 /*****************************************************************************
 
 Copyright (c) 1997, 2016, Oracle and/or its affiliates. All Rights Reserved.
-Copyright (c) 2017, 2019, MariaDB Corporation.
+Copyright (c) 2017, 2020, MariaDB Corporation.
 
 This program is free software; you can redistribute it and/or modify it under
 the terms of the GNU General Public License as published by the Free Software
@@ -342,10 +342,4 @@ times! */
 roll-forward */
 #define RECV_SCAN_SIZE		(4 * UNIV_PAGE_SIZE)
 
-/** This many frames must be left free in the buffer pool when we scan
-the log and store the scanned log records in the buffer pool: we will
-use these free frames to read in pages when we start applying the
-log records to the database. */
-extern ulint	recv_n_pool_free_frames;
-
 #endif

storage/innobase/log/log0recv.cc

@@ -2,7 +2,7 @@
 
 Copyright (c) 1997, 2017, Oracle and/or its affiliates. All Rights Reserved.
 Copyright (c) 2012, Facebook Inc.
-Copyright (c) 2013, 2019, MariaDB Corporation.
+Copyright (c) 2013, 2020, MariaDB Corporation.
 
 This program is free software; you can redistribute it and/or modify it under
 the terms of the GNU General Public License as published by the Free Software
@@ -103,14 +103,6 @@ static ulint	recv_previous_parsed_rec_offset;
 /** The 'multi' flag of the previous parsed redo log record */
 static ulint	recv_previous_parsed_rec_is_multi;
 
-/** This many frames must be left free in the buffer pool when we scan
-the log and store the scanned log records in the buffer pool: we will
-use these free frames to read in pages when we start applying the
-log records to the database.
-This is the default value. If the actual size of the buffer pool is
-larger than 10 MB we'll set this value to 512. */
-ulint	recv_n_pool_free_frames;
-
 /** The maximum lsn we see for a page during the recovery process. If this
 is bigger than the lsn we are able to scan up to, that is an indication that
 the recovery failed and the database may be corrupt. */
@@ -840,9 +832,6 @@ recv_sys_init()
 		recv_sys->flush_end = os_event_create(0);
 	}
 
-	recv_n_pool_free_frames =
-		buf_pool_get_n_pages() / 3;
-
 	recv_sys->buf = static_cast<byte*>(
 		ut_malloc_nokey(RECV_PARSING_BUF_SIZE));
 
@@ -3456,9 +3445,8 @@ recv_group_scan_log_recs(
 	lsn_t	end_lsn;
 	store_t	store_to_hash	= recv_sys->mlog_checkpoint_lsn == 0
 		? STORE_NO : (last_phase ? STORE_IF_EXISTS : STORE_YES);
-	ulint	available_mem	= UNIV_PAGE_SIZE
-		* (buf_pool_get_n_pages()
-		   - (recv_n_pool_free_frames * srv_buf_pool_instances));
+	ulint	available_mem = (buf_pool_get_n_pages() * 2 / 3)
+				<< srv_page_size_shift;
 
 	group->scanned_lsn = end_lsn = *contiguous_lsn = ut_uint64_align_down(
 		*contiguous_lsn, OS_FILE_LOG_BLOCK_SIZE);