MDEV-13080 [ERROR] InnoDB: Missing MLOG_CHECKPOINT between the checkpoint x and the end y

log_buffer_extend(): Do not write to disk. Just allocate new bigger
buffer and copy contents of old one to it. Do not acquire write_mutex.

log_t::is_extending: Removed as unneeded now.

LOG_BUFFER_SIZE: Removed to make the dependence on srv_log_buffer_size
visible.

storage/innobase/include/log0log.h

@@ -411,8 +411,6 @@ extern my_bool	innodb_log_checksums;
 /* The counting of lsn's starts from this value: this must be non-zero */
 #define LOG_START_LSN		((lsn_t) (16 * OS_FILE_LOG_BLOCK_SIZE))
 
-#define LOG_BUFFER_SIZE		(srv_log_buffer_size * UNIV_PAGE_SIZE)
-
 /* Offsets of a log block header */
 #define	LOG_BLOCK_HDR_NO	0	/* block number which must be > 0 and
 					is allowed to wrap around at 2G; the
@@ -644,8 +642,6 @@ struct log_t{
 					later; this is advanced when a flush
 					operation is completed to all the log
 					groups */
-	volatile bool	is_extending;	/*!< this is set to true during extend
-					the log buffer size */
 	lsn_t		write_lsn;	/*!< last written lsn */
 	lsn_t		current_flush_lsn;/*!< end lsn for the current running
 					write + flush operation */

storage/innobase/log/log0log.cc

@@ -169,89 +169,52 @@ void
 log_buffer_extend(
 	ulint	len)
 {
-	ulint	move_start;
-	ulint	move_end;
-	byte	tmp_buf[OS_FILE_LOG_BLOCK_SIZE];
+	const ulint new_log_buffer_size = (len >> srv_page_size_shift) + 1;
+	const ulint new_buf_size = (new_log_buffer_size
+				    << (srv_page_size_shift + 1))
+		+ OS_FILE_LOG_BLOCK_SIZE;
+	byte* new_buf_ptr = static_cast<byte*>(ut_malloc_nokey(new_buf_size));
 
-	log_mutex_enter_all();
-
-	while (log_sys->is_extending) {
-		/* Another thread is trying to extend already.
-		Needs to wait for. */
-		log_mutex_exit_all();
-
-		log_buffer_flush_to_disk();
+	log_mutex_enter();
 
-		log_mutex_enter_all();
+	const ulint size = srv_log_buffer_size << srv_page_size_shift;
 
-		if (srv_log_buffer_size > len / UNIV_PAGE_SIZE) {
+	if (len <= size) {
 		/* Already extended enough by the others */
-			log_mutex_exit_all();
+		log_mutex_exit();
+		ut_free(new_buf_ptr);
 		return;
 	}
-	}
 
-	if (len >= log_sys->buf_size / 2) {
-		DBUG_EXECUTE_IF("ib_log_buffer_is_short_crash",
-				DBUG_SUICIDE(););
-
-		/* log_buffer is too small. try to extend instead of crash. */
 	ib::warn() << "The transaction log size is too large"
-			" for innodb_log_buffer_size (" << len << " >= "
-			<< LOG_BUFFER_SIZE << " / 2). Trying to extend it.";
-	}
+		" for innodb_log_buffer_size (" << len
+		<< " >= " << size << " / 2). Trying to extend it.";
 
-	log_sys->is_extending = true;
+	byte* old_buf_ptr = log_sys->buf_ptr;
+	const byte* begin = log_sys->buf;
+	const byte* end = begin + log_sys->buf_free;
 
-	while ((log_sys->buf_free ^ log_sys->buf_next_to_write)
-	       & (OS_FILE_LOG_BLOCK_SIZE - 1)) {
-		/* Buffer might have >1 blocks to write still. */
-		log_mutex_exit_all();
-
-		log_buffer_flush_to_disk();
+	log_sys->buf_ptr = new_buf_ptr;
+	srv_log_buffer_size = new_log_buffer_size;
+	log_sys->buf_size = size;
+	log_sys->buf
+	    = static_cast<byte*>(ut_align(new_buf_ptr, OS_FILE_LOG_BLOCK_SIZE));
 
-		log_mutex_enter_all();
+	if (!log_sys->first_in_use) {
+		log_sys->buf += size;
 	}
 
-	move_start = ut_2pow_round(log_sys->buf_free,
-				   ulint(OS_FILE_LOG_BLOCK_SIZE));
-	move_end = log_sys->buf_free;
-
-	/* store the last log block in buffer */
-	ut_memcpy(tmp_buf, log_sys->buf + move_start,
-		  move_end - move_start);
-
-	log_sys->buf_free -= move_start;
-	log_sys->buf_next_to_write -= move_start;
-
-	/* reallocate log buffer */
-	srv_log_buffer_size = len / UNIV_PAGE_SIZE + 1;
-	ut_free(log_sys->buf_ptr);
-
-	log_sys->buf_size = LOG_BUFFER_SIZE;
-
-	log_sys->buf_ptr = static_cast<byte*>(
-		ut_zalloc_nokey(log_sys->buf_size * 2 + OS_FILE_LOG_BLOCK_SIZE));
-	TRASH_ALLOC(log_sys->buf_ptr,
-		    log_sys->buf_size * 2 + OS_FILE_LOG_BLOCK_SIZE);
-	log_sys->buf = static_cast<byte*>(
-		ut_align(log_sys->buf_ptr, OS_FILE_LOG_BLOCK_SIZE));
-
-	log_sys->first_in_use = true;
+	memcpy(log_sys->buf, begin, end - begin);
 
-	log_sys->max_buf_free = log_sys->buf_size / LOG_BUF_FLUSH_RATIO
+	log_sys->max_buf_free = size / LOG_BUF_FLUSH_RATIO
 		- LOG_BUF_FLUSH_MARGIN;
 
-	/* restore the last log block */
-	ut_memcpy(log_sys->buf, tmp_buf, move_end - move_start);
-
-	ut_ad(log_sys->is_extending);
-	log_sys->is_extending = false;
+	log_mutex_exit();
 
-	log_mutex_exit_all();
+	ut_free(old_buf_ptr);
 
 	ib::info() << "innodb_log_buffer_size was extended to "
-		<< LOG_BUFFER_SIZE << ".";
+		<< size << ".";
 }
 
 /** Calculate actual length in redo buffer and file including
@@ -360,20 +323,6 @@ log_reserve_and_open(
 loop:
 	ut_ad(log_mutex_own());
 
-	if (log_sys->is_extending) {
-		log_mutex_exit();
-
-		/* Log buffer size is extending. Writing up to the next block
-		should wait for the extending finished. */
-
-		os_thread_sleep(100000);
-
-		ut_ad(++count < 50);
-
-		log_mutex_enter();
-		goto loop;
-	}
-
 	/* Calculate an upper limit for the space the string may take in the
 	log buffer */
 
@@ -718,10 +667,9 @@ log_sys_init()
 
 	log_sys->lsn = LOG_START_LSN;
 
-	ut_a(LOG_BUFFER_SIZE >= 16 * OS_FILE_LOG_BLOCK_SIZE);
-	ut_a(LOG_BUFFER_SIZE >= 4 * UNIV_PAGE_SIZE);
+	ut_ad(srv_log_buffer_size >= 4);
 
-	log_sys->buf_size = LOG_BUFFER_SIZE;
+	log_sys->buf_size = srv_log_buffer_size << srv_page_size_shift;
 
 	log_sys->buf_ptr = static_cast<byte*>(
 		ut_zalloc_nokey(log_sys->buf_size * 2 + OS_FILE_LOG_BLOCK_SIZE));