MDEV-16045: Replace log_group_t with log_t::files

There is only one log_sys and only one log_sys.log.

log_t::files::create(): Replaces log_init().

log_t::files::close(): Replaces log_group_close(), log_group_close_all().

fil_close_log_files(): if (free) log_sys.log_close();
The callers that passed free=true used to call log_group_close_all().

log_header_read(): Replaces log_group_header_read().

log_t::files::file_header_bufs_ptr: Use a single allocation.

log_t::files::file_header_bufs[]: Statically allocate the pointers.

log_t::files::set_fields(): Replaces log_group_set_fields().

log_t::files::calc_lsn_offset(): Replaces log_group_calc_lsn_offset().
Simplify the computation by using fewer variables.

log_t::files::read_log_seg(): Replaces log_group_read_log_seg().

log_sys_t::complete_checkpoint(): Replaces log_io_complete_checkpoint().

fil_aio_wait(): Move the logic from log_io_complete().

2 files changed, 114 insertions, 363 deletions

diff --git a/storage/innobase/log/log0log.cc b/storage/innobase/log/log0log.cc
index 5db40967ab4..f59248cab49 100644
--- a/storage/innobase/log/log0log.cc
+++ b/storage/innobase/log/log0log.cc
@@ -134,13 +134,6 @@ extern "C" UNIV_INTERN
 os_thread_ret_t
 DECLARE_THREAD(log_scrub_thread)(void*);
 
-/******************************************************//**
-Completes a checkpoint write i/o to a log file. */
-static
-void
-log_io_complete_checkpoint(void);
-/*============================*/
-
 /****************************************************************//**
 Returns the oldest modified block lsn in the pool, or log_sys.lsn if none
 exists.
@@ -541,108 +534,6 @@ function_exit:
 	return(lsn);
 }
 
-/******************************************************//**
-Calculates the offset within a log group, when the log file headers are not
-included.
-@return size offset (<= offset) */
-UNIV_INLINE
-lsn_t
-log_group_calc_size_offset(
-/*=======================*/
-	lsn_t			offset,	/*!< in: real offset within the
-					log group */
-	const log_group_t*	group)	/*!< in: log group */
-{
-	/* The lsn parameters are updated while holding both the mutexes
-	and it is ok to have either of them while reading */
-	ut_ad(log_mutex_own() || log_write_mutex_own());
-
-	return(offset - LOG_FILE_HDR_SIZE * (1 + offset / group->file_size));
-}
-
-/******************************************************//**
-Calculates the offset within a log group, when the log file headers are
-included.
-@return real offset (>= offset) */
-UNIV_INLINE
-lsn_t
-log_group_calc_real_offset(
-/*=======================*/
-	lsn_t			offset,	/*!< in: size offset within the
-					log group */
-	const log_group_t*	group)	/*!< in: log group */
-{
-	/* The lsn parameters are updated while holding both the mutexes
-	and it is ok to have either of them while reading */
-	ut_ad(log_mutex_own() || log_write_mutex_own());
-
-	return(offset + LOG_FILE_HDR_SIZE
-	       * (1 + offset / (group->file_size - LOG_FILE_HDR_SIZE)));
-}
-
-/** Calculate the offset of an lsn within a log group.
-@param[in]	lsn	log sequence number
-@param[in]	group	log group
-@return offset within the log group */
-lsn_t
-log_group_calc_lsn_offset(
-	lsn_t			lsn,
-	const log_group_t*	group)
-{
-	lsn_t	gr_lsn;
-	lsn_t	gr_lsn_size_offset;
-	lsn_t	difference;
-	lsn_t	group_size;
-	lsn_t	offset;
-
-	/* The lsn parameters are updated while holding both the mutexes
-	and it is ok to have either of them while reading */
-	ut_ad(log_mutex_own() || log_write_mutex_own());
-
-	gr_lsn = group->lsn;
-
-	gr_lsn_size_offset = log_group_calc_size_offset(
-		group->lsn_offset, group);
-
-	group_size = group->capacity();
-
-	if (lsn >= gr_lsn) {
-
-		difference = lsn - gr_lsn;
-	} else {
-		difference = gr_lsn - lsn;
-
-		difference = difference % group_size;
-
-		difference = group_size - difference;
-	}
-
-	offset = (gr_lsn_size_offset + difference) % group_size;
-
-	/* fprintf(stderr,
-	"Offset is " LSN_PF " gr_lsn_offset is " LSN_PF
-	" difference is " LSN_PF "\n",
-	offset, gr_lsn_size_offset, difference);
-	*/
-
-	return(log_group_calc_real_offset(offset, group));
-}
-
-/********************************************************//**
-Sets the field values in group to correspond to a given lsn. For this function
-to work, the values must already be correctly initialized to correspond to
-some lsn, for instance, a checkpoint lsn. */
-void
-log_group_set_fields(
-/*=================*/
-	log_group_t*	group,	/*!< in/out: group */
-	lsn_t		lsn)	/*!< in: lsn for which the values should be
-				set */
-{
-	group->lsn_offset = log_group_calc_lsn_offset(lsn, group);
-	group->lsn = lsn;
-}
-
 /** Calculate the recommended highest values for lsn - last_checkpoint_lsn
 and lsn - buf_get_oldest_modification().
 @param[in]	file_size	requested innodb_log_file_size
@@ -767,87 +658,38 @@ void log_t::create()
 
 /** Initialize the redo log.
 @param[in]	n_files		number of files */
-void
-log_init(ulint n_files)
-{
-	ulint	i;
-	log_group_t*	group = &log_sys.log;
-
-	group->n_files = n_files;
-	group->format = srv_encrypt_log
-		? LOG_HEADER_FORMAT_CURRENT | LOG_HEADER_FORMAT_ENCRYPTED
-		: LOG_HEADER_FORMAT_CURRENT;
-	group->file_size = srv_log_file_size;
-	group->state = LOG_GROUP_OK;
-	group->lsn = LOG_START_LSN;
-	group->lsn_offset = LOG_FILE_HDR_SIZE;
-
-	group->file_header_bufs_ptr = static_cast<byte**>(
-		ut_zalloc_nokey(sizeof(byte*) * n_files));
-
-	group->file_header_bufs = static_cast<byte**>(
-		ut_zalloc_nokey(sizeof(byte**) * n_files));
-
-	for (i = 0; i < n_files; i++) {
-		group->file_header_bufs_ptr[i] = static_cast<byte*>(
-			ut_zalloc_nokey(LOG_FILE_HDR_SIZE
-					+ OS_FILE_LOG_BLOCK_SIZE));
-
-		group->file_header_bufs[i] = static_cast<byte*>(
-			ut_align(group->file_header_bufs_ptr[i],
-				 OS_FILE_LOG_BLOCK_SIZE));
-	}
-
-	group->checkpoint_buf_ptr = static_cast<byte*>(
-		ut_zalloc_nokey(2 * OS_FILE_LOG_BLOCK_SIZE));
-
-	group->checkpoint_buf = static_cast<byte*>(
-		ut_align(group->checkpoint_buf_ptr,OS_FILE_LOG_BLOCK_SIZE));
-}
-
-/******************************************************//**
-Completes an i/o to a log file. */
-void
-log_io_complete(
-/*============*/
-	log_group_t*	group)	/*!< in: log group or a dummy pointer */
+void log_t::files::create(ulint n_files)
 {
-	if ((ulint) group & 0x1UL) {
-		/* It was a checkpoint write */
-		group = (log_group_t*)((ulint) group - 1);
-
-		switch (srv_file_flush_method) {
-		case SRV_O_DSYNC:
-		case SRV_NOSYNC:
-			break;
-		case SRV_FSYNC:
-		case SRV_LITTLESYNC:
-		case SRV_O_DIRECT:
-		case SRV_O_DIRECT_NO_FSYNC:
-#ifdef _WIN32
-		case SRV_ALL_O_DIRECT_FSYNC:
-#endif
-			fil_flush(SRV_LOG_SPACE_FIRST_ID);
-		}
-
+  ut_ad(n_files <= SRV_N_LOG_FILES_MAX);
+  ut_ad(this == &log_sys.log);
+  ut_ad(log_sys.is_initialised());
+
+  this->n_files= n_files;
+  format= srv_encrypt_log
+    ? LOG_HEADER_FORMAT_CURRENT | LOG_HEADER_FORMAT_ENCRYPTED
+    : LOG_HEADER_FORMAT_CURRENT;
+  file_size= srv_log_file_size;
+  state= LOG_GROUP_OK;
+  lsn= LOG_START_LSN;
+  lsn_offset= LOG_FILE_HDR_SIZE;
 
-		DBUG_PRINT("ib_log", ("checkpoint info written"));
-		log_io_complete_checkpoint();
+  byte* ptr= static_cast<byte*>(ut_zalloc_nokey(LOG_FILE_HDR_SIZE
+						+ OS_FILE_LOG_BLOCK_SIZE
+						* n_files));
+  file_header_bufs_ptr= ptr;
+  ptr= static_cast<byte*>(ut_align(ptr, OS_FILE_LOG_BLOCK_SIZE));
 
-		return;
-	}
+  memset(file_header_bufs, 0, sizeof file_header_bufs);
 
-	ut_error;	/*!< We currently use synchronous writing of the
-			logs and cannot end up here! */
+  for (ulint i = 0; i < n_files; i++, ptr += LOG_FILE_HDR_SIZE)
+    file_header_bufs[i] = ptr;
 }
 
 /******************************************************//**
 Writes a log file header to a log file space. */
 static
 void
-log_group_file_header_flush(
-/*========================*/
-	log_group_t*	group,		/*!< in: log group */
+log_file_header_flush(
 	ulint		nth_file,	/*!< in: header to the nth file in the
 					log file space */
 	lsn_t		start_lsn)	/*!< in: log file data starts at this
@@ -858,14 +700,14 @@ log_group_file_header_flush(
 
 	ut_ad(log_write_mutex_own());
 	ut_ad(!recv_no_log_write);
-	ut_a(nth_file < group->n_files);
-	ut_ad((group->format & ~LOG_HEADER_FORMAT_ENCRYPTED)
+	ut_a(nth_file < log_sys.log.n_files);
+	ut_ad((log_sys.log.format & ~LOG_HEADER_FORMAT_ENCRYPTED)
 	      == LOG_HEADER_FORMAT_CURRENT);
 
-	buf = *(group->file_header_bufs + nth_file);
+	buf = log_sys.log.file_header_bufs[nth_file];
 
 	memset(buf, 0, OS_FILE_LOG_BLOCK_SIZE);
-	mach_write_to_4(buf + LOG_HEADER_FORMAT, group->format);
+	mach_write_to_4(buf + LOG_HEADER_FORMAT, log_sys.log.format);
 	mach_write_to_8(buf + LOG_HEADER_START_LSN, start_lsn);
 	strcpy(reinterpret_cast<char*>(buf) + LOG_HEADER_CREATOR,
 	       LOG_HEADER_CREATOR_CURRENT);
@@ -873,7 +715,7 @@ log_group_file_header_flush(
 	      >= sizeof LOG_HEADER_CREATOR_CURRENT);
 	log_block_set_checksum(buf, log_block_calc_checksum_crc32(buf));
 
-	dest_offset = nth_file * group->file_size;
+	dest_offset = nth_file * log_sys.log.file_size;
 
 	DBUG_PRINT("ib_log", ("write " LSN_PF
 			      " file " ULINTPF " header",
@@ -891,7 +733,7 @@ log_group_file_header_flush(
 	       page_id_t(SRV_LOG_SPACE_FIRST_ID, page_no),
 	       univ_page_size,
 	       ulint(dest_offset & (srv_page_size - 1)),
-	       OS_FILE_LOG_BLOCK_SIZE, buf, group);
+	       OS_FILE_LOG_BLOCK_SIZE, buf, NULL);
 
 	srv_stats.os_log_pending_writes.dec();
 }
@@ -910,12 +752,10 @@ log_block_store_checksum(
 }
 
 /******************************************************//**
-Writes a buffer to a log file group. */
+Writes a buffer to a log file. */
 static
 void
-log_group_write_buf(
-/*================*/
-	log_group_t*	group,		/*!< in: log group */
+log_write_buf(
 	byte*		buf,		/*!< in: buffer */
 	ulint		len,		/*!< in: buffer len; must be divisible
 					by OS_FILE_LOG_BLOCK_SIZE */
@@ -946,28 +786,27 @@ loop:
 		return;
 	}
 
-	next_offset = log_group_calc_lsn_offset(start_lsn, group);
+	next_offset = log_sys.log.calc_lsn_offset(start_lsn);
 
 	if (write_header
-	    && next_offset % group->file_size == LOG_FILE_HDR_SIZE) {
+	    && next_offset % log_sys.log.file_size == LOG_FILE_HDR_SIZE) {
 		/* We start to write a new log file instance in the group */
 
-		ut_a(next_offset / group->file_size <= ULINT_MAX);
+		ut_a(next_offset / log_sys.log.file_size <= ULINT_MAX);
 
-		log_group_file_header_flush(group, (ulint)
-					    (next_offset / group->file_size),
-					    start_lsn);
+		log_file_header_flush(
+			ulint(next_offset / log_sys.log.file_size), start_lsn);
 		srv_stats.os_log_written.add(OS_FILE_LOG_BLOCK_SIZE);
 
 		srv_stats.log_writes.inc();
 	}
 
-	if ((next_offset % group->file_size) + len > group->file_size) {
-
+	if ((next_offset % log_sys.log.file_size) + len
+	    > log_sys.log.file_size) {
 		/* if the above condition holds, then the below expression
 		is < len which is ulint, so the typecast is ok */
-		write_len = (ulint)
-			(group->file_size - (next_offset % group->file_size));
+		write_len = ulint(log_sys.log.file_size
+				  - (next_offset % log_sys.log.file_size));
 	} else {
 		write_len = len;
 	}
@@ -1012,8 +851,7 @@ loop:
 	fil_io(IORequestLogWrite, true,
 	       page_id_t(SRV_LOG_SPACE_FIRST_ID, page_no),
 	       univ_page_size,
-	       ulint(next_offset & (srv_page_size - 1)), write_len, buf,
-	       group);
+	       ulint(next_offset & (srv_page_size - 1)), write_len, buf, NULL);
 
 	srv_stats.os_log_pending_writes.dec();
 
@@ -1227,7 +1065,7 @@ loop:
 
 	log_buffer_switch();
 
-	log_group_set_fields(&log_sys.log, log_sys.write_lsn);
+	log_sys.log.set_fields(log_sys.write_lsn);
 
 	log_mutex_exit();
 	/* Erase the end of the last log block. */
@@ -1236,12 +1074,9 @@ loop:
 	/* Calculate pad_size if needed. */
 	pad_size = 0;
 	if (write_ahead_size > OS_FILE_LOG_BLOCK_SIZE) {
-		lsn_t	end_offset;
 		ulint	end_offset_in_unit;
-		end_offset = log_group_calc_lsn_offset(
-			ut_uint64_align_up(write_lsn,
-					   OS_FILE_LOG_BLOCK_SIZE),
-			&log_sys.log);
+		lsn_t	end_offset = log_sys.log.calc_lsn_offset(
+			ut_uint64_align_up(write_lsn, OS_FILE_LOG_BLOCK_SIZE));
 		end_offset_in_unit = (ulint) (end_offset % write_ahead_size);
 
 		if (end_offset_in_unit > 0
@@ -1262,9 +1097,8 @@ loop:
 	}
 
 	/* Do the write to the log files */
-	log_group_write_buf(
-		&log_sys.log, write_buf + area_start,
-		area_end - area_start + pad_size,
+	log_write_buf(
+		write_buf + area_start, area_end - area_start + pad_size,
 #ifdef UNIV_DEBUG
 		pad_size,
 #endif /* UNIV_DEBUG */
@@ -1444,20 +1278,17 @@ log_complete_checkpoint(void)
 	rw_lock_x_unlock_gen(&(log_sys.checkpoint_lock), LOG_CHECKPOINT);
 }
 
-/******************************************************//**
-Completes an asynchronous checkpoint info write i/o to a log file. */
-static
-void
-log_io_complete_checkpoint(void)
-/*============================*/
+/** Complete an asynchronous checkpoint write. */
+void log_t::complete_checkpoint()
 {
+	ut_ad(this == &log_sys);
 	MONITOR_DEC(MONITOR_PENDING_CHECKPOINT_WRITE);
 
 	log_mutex_enter();
 
-	ut_ad(log_sys.n_pending_checkpoint_writes > 0);
+	ut_ad(n_pending_checkpoint_writes > 0);
 
-	if (--log_sys.n_pending_checkpoint_writes == 0) {
+	if (!--n_pending_checkpoint_writes) {
 		log_complete_checkpoint();
 	}
 
@@ -1471,7 +1302,6 @@ void
 log_group_checkpoint(lsn_t end_lsn)
 {
 	lsn_t		lsn_offset;
-	byte*		buf;
 
 	ut_ad(!srv_read_only_mode);
 	ut_ad(log_mutex_own());
@@ -1485,9 +1315,7 @@ log_group_checkpoint(lsn_t end_lsn)
 			      log_sys.next_checkpoint_no,
 			      log_sys.next_checkpoint_lsn));
 
-	log_group_t*	group = &log_sys.log;
-
-	buf = group->checkpoint_buf;
+	byte* buf = log_sys.checkpoint_buf;
 	memset(buf, 0, OS_FILE_LOG_BLOCK_SIZE);
 
 	mach_write_to_8(buf + LOG_CHECKPOINT_NO, log_sys.next_checkpoint_no);
@@ -1497,8 +1325,7 @@ log_group_checkpoint(lsn_t end_lsn)
 		log_crypt_write_checkpoint_buf(buf);
 	}
 
-	lsn_offset = log_group_calc_lsn_offset(log_sys.next_checkpoint_lsn,
-					       group);
+	lsn_offset = log_sys.log.calc_lsn_offset(log_sys.next_checkpoint_lsn);
 	mach_write_to_8(buf + LOG_CHECKPOINT_OFFSET, lsn_offset);
 	mach_write_to_8(buf + LOG_CHECKPOINT_LOG_BUF_SIZE,
 			srv_log_buffer_size);
@@ -1523,28 +1350,18 @@ log_group_checkpoint(lsn_t end_lsn)
 	/* Note: We alternate the physical place of the checkpoint info.
 	See the (next_checkpoint_no & 1) below. */
 
-	/* We send as the last parameter the group machine address
-	added with 1, as we want to distinguish between a normal log
-	file write and a checkpoint field write */
-
 	fil_io(IORequestLogWrite, false,
 	       page_id_t(SRV_LOG_SPACE_FIRST_ID, 0),
 	       univ_page_size,
 	       (log_sys.next_checkpoint_no & 1)
 	       ? LOG_CHECKPOINT_2 : LOG_CHECKPOINT_1,
 	       OS_FILE_LOG_BLOCK_SIZE,
-	       buf, (byte*) group + 1);
-
-	ut_ad(((ulint) group & 0x1UL) == 0);
+	       buf, reinterpret_cast<void*>(1) /* checkpoint write */);
 }
 
 /** Read a log group header page to log_sys.checkpoint_buf.
-@param[in]	group	log group
-@param[in]	header	0 or LOG_CHEKCPOINT_1 or LOG_CHECKPOINT2 */
-void
-log_group_header_read(
-	const log_group_t*	group,
-	ulint			header)
+@param[in]	header	0 or LOG_CHECKPOINT_1 or LOG_CHECKPOINT2 */
+void log_header_read(ulint header)
 {
 	ut_ad(log_mutex_own());
 
@@ -2212,43 +2029,13 @@ log_refresh_stats(void)
 	log_sys.last_printout_time = time(NULL);
 }
 
-/** Close a log group.
-@param[in,out]	group	log group to close */
-static
-void
-log_group_close(log_group_t* group)
-{
-	ulint	i;
-
-	for (i = 0; i < group->n_files; i++) {
-		ut_free(group->file_header_bufs_ptr[i]);
-	}
-
-	ut_free(group->file_header_bufs_ptr);
-	ut_free(group->file_header_bufs);
-	ut_free(group->checkpoint_buf_ptr);
-	group->n_files = 0;
-	group->file_header_bufs_ptr = NULL;
-	group->file_header_bufs = NULL;
-	group->checkpoint_buf_ptr = NULL;
-}
-
-/********************************************************//**
-Closes all log groups. */
-void
-log_group_close_all(void)
-/*=====================*/
-{
-	log_group_close(&log_sys.log);
-}
-
 /** Shut down the redo log subsystem. */
 void log_t::close()
 {
   ut_ad(this == &log_sys);
   if (!is_initialised()) return;
   m_initialised = false;
-  log_group_close_all();
+  log.close();
 
   if (!first_in_use)
     buf -= srv_log_buffer_size;
diff --git a/storage/innobase/log/log0recv.cc b/storage/innobase/log/log0recv.cc
index 223733ccc27..8213aa446d1 100644
--- a/storage/innobase/log/log0recv.cc
+++ b/storage/innobase/log/log0recv.cc
@@ -631,42 +631,32 @@ recv_sys_debug_free(void)
 	mutex_exit(&(recv_sys->mutex));
 }
 
-/** Read a log segment to a buffer.
-@param[out]	buf		buffer
-@param[in]	group		redo log files
-@param[in, out]	start_lsn	in : read area start, out: the last read valid lsn
+/** Read a log segment to log_sys.buf.
+@param[in,out]	start_lsn	in: read area start,
+out: the last read valid lsn
 @param[in]	end_lsn		read area end
-@param[out] invalid_block - invalid, (maybe incompletely written) block encountered
-@return	false, if invalid block encountered (e.g checksum mismatch), true otherwise */
-bool
-log_group_read_log_seg(
-	byte*			buf,
-	const log_group_t*	group,
-	lsn_t			*start_lsn,
-	lsn_t			end_lsn)
+@return	whether no invalid blocks (e.g checksum mismatch) were found */
+bool log_t::files::read_log_seg(lsn_t* start_lsn, lsn_t end_lsn)
 {
 	ulint	len;
-	lsn_t	source_offset;
 	bool success = true;
-	ut_ad(log_mutex_own());
+	ut_ad(log_sys.mutex.is_owned());
 	ut_ad(!(*start_lsn % OS_FILE_LOG_BLOCK_SIZE));
 	ut_ad(!(end_lsn % OS_FILE_LOG_BLOCK_SIZE));
-
+	byte* buf = log_sys.buf;
 loop:
-	source_offset = log_group_calc_lsn_offset(*start_lsn, group);
+	lsn_t source_offset = calc_lsn_offset(*start_lsn);
 
 	ut_a(end_lsn - *start_lsn <= ULINT_MAX);
 	len = (ulint) (end_lsn - *start_lsn);
 
 	ut_ad(len != 0);
 
-	const bool at_eof = (source_offset % group->file_size) + len
-		> group->file_size;
+	const bool at_eof = (source_offset % file_size) + len > file_size;
 	if (at_eof) {
 		/* If the above condition is true then len (which is ulint)
 		is > the expression below, so the typecast is ok */
-		len = (ulint) (group->file_size -
-			(source_offset % group->file_size));
+		len = ulint(file_size - (source_offset % file_size));
 	}
 
 	log_sys.n_log_ios++;
@@ -698,7 +688,7 @@ loop:
 			break;
 		}
 
-		if (innodb_log_checksums || group->is_encrypted()) {
+		if (innodb_log_checksums || is_encrypted()) {
 			ulint crc = log_block_calc_checksum_crc32(buf);
 			ulint cksum = log_block_get_checksum(buf);
 
@@ -721,7 +711,7 @@ loop:
 				break;
 			}
 
-			if (group->is_encrypted()) {
+			if (is_encrypted()) {
 				log_crypt(buf, *start_lsn,
 					  OS_FILE_LOG_BLOCK_SIZE, true);
 			}
@@ -759,14 +749,10 @@ recv_synchronize_groups()
 	the block is always incomplete */
 
 	lsn_t start_lsn = ut_uint64_align_down(recovered_lsn,
-						     OS_FILE_LOG_BLOCK_SIZE);
-	log_group_read_log_seg(log_sys.buf, &log_sys.log,
-			       &start_lsn, start_lsn + OS_FILE_LOG_BLOCK_SIZE);
-
-	/* Update the fields in the group struct to correspond to
-	recovered_lsn */
-
-	log_group_set_fields(&log_sys.log, recovered_lsn);
+					       OS_FILE_LOG_BLOCK_SIZE);
+	log_sys.log.read_log_seg(&start_lsn,
+				 start_lsn + OS_FILE_LOG_BLOCK_SIZE);
+	log_sys.log.set_fields(recovered_lsn);
 
 	/* Copy the checkpoint info to the log; remember that we have
 	incremented checkpoint_no by one, and the info will not be written
@@ -792,19 +778,17 @@ recv_check_log_header_checksum(
 }
 
 /** Find the latest checkpoint in the format-0 log header.
-@param[out]	max_group	log group, or NULL
 @param[out]	max_field	LOG_CHECKPOINT_1 or LOG_CHECKPOINT_2
 @return error code or DB_SUCCESS */
 static MY_ATTRIBUTE((warn_unused_result))
 dberr_t
-recv_find_max_checkpoint_0(log_group_t** max_group, ulint* max_field)
+recv_find_max_checkpoint_0(ulint* max_field)
 {
-	log_group_t*	group = &log_sys.log;
 	ib_uint64_t	max_no = 0;
 	ib_uint64_t	checkpoint_no;
 	byte*		buf	= log_sys.checkpoint_buf;
 
-	ut_ad(group->format == 0);
+	ut_ad(log_sys.log.format == 0);
 
 	/** Offset of the first checkpoint checksum */
 	static const uint CHECKSUM_1 = 288;
@@ -815,11 +799,11 @@ recv_find_max_checkpoint_0(log_group_t** max_group, ulint* max_field)
 	/** Least significant bits of the checkpoint offset */
 	static const uint OFFSET_LOW32 = 16;
 
-	*max_group = NULL;
+	bool found = false;
 
 	for (ulint field = LOG_CHECKPOINT_1; field <= LOG_CHECKPOINT_2;
 	     field += LOG_CHECKPOINT_2 - LOG_CHECKPOINT_1) {
-		log_group_header_read(group, field);
+		log_header_read(field);
 
 		if (static_cast<uint32_t>(ut_fold_binary(buf, CHECKSUM_1))
 		    != mach_read_from_4(buf + CHECKSUM_1)
@@ -846,21 +830,21 @@ recv_find_max_checkpoint_0(log_group_t** max_group, ulint* max_field)
 			    mach_read_from_8(buf + LOG_CHECKPOINT_LSN)));
 
 		if (checkpoint_no >= max_no) {
-			*max_group = group;
+			found = true;
 			*max_field = field;
 			max_no = checkpoint_no;
 
-			group->state = LOG_GROUP_OK;
+			log_sys.log.state = LOG_GROUP_OK;
 
-			group->lsn = mach_read_from_8(
+			log_sys.log.lsn = mach_read_from_8(
 				buf + LOG_CHECKPOINT_LSN);
-			group->lsn_offset = static_cast<ib_uint64_t>(
+			log_sys.log.lsn_offset = static_cast<ib_uint64_t>(
 				mach_read_from_4(buf + OFFSET_HIGH32)) << 32
 				| mach_read_from_4(buf + OFFSET_LOW32);
 		}
 	}
 
-	if (*max_group != NULL) {
+	if (found) {
 		return(DB_SUCCESS);
 	}
 
@@ -882,9 +866,7 @@ dberr_t
 recv_log_format_0_recover(lsn_t lsn)
 {
 	log_mutex_enter();
-	log_group_t*	group = &log_sys.log;
-	const lsn_t	source_offset
-		= log_group_calc_lsn_offset(lsn, group);
+	const lsn_t	source_offset = log_sys.log.calc_lsn_offset(lsn);
 	log_mutex_exit();
 	const ulint	page_no = ulint(source_offset >> srv_page_size_shift);
 	byte*		buf = log_sys.buf;
@@ -933,26 +915,23 @@ recv_log_format_0_recover(lsn_t lsn)
 dberr_t
 recv_find_max_checkpoint(ulint* max_field)
 {
-	log_group_t*	group;
 	ib_uint64_t	max_no;
 	ib_uint64_t	checkpoint_no;
 	ulint		field;
 	byte*		buf;
 
-	group = &log_sys.log;
-
 	max_no = 0;
 	*max_field = 0;
 
 	buf = log_sys.checkpoint_buf;
 
-	group->state = LOG_GROUP_CORRUPTED;
+	log_sys.log.state = LOG_GROUP_CORRUPTED;
 
-	log_group_header_read(group, 0);
+	log_header_read(0);
 	/* Check the header page checksum. There was no
 	checksum in the first redo log format (version 0). */
-	group->format = mach_read_from_4(buf + LOG_HEADER_FORMAT);
-	if (group->format != LOG_HEADER_FORMAT_3_23
+	log_sys.log.format = mach_read_from_4(buf + LOG_HEADER_FORMAT);
+	if (log_sys.log.format != LOG_HEADER_FORMAT_3_23
 	    && !recv_check_log_header_checksum(buf)) {
 		ib::error() << "Invalid redo log header checksum.";
 		return(DB_CORRUPTION);
@@ -964,9 +943,9 @@ recv_find_max_checkpoint(ulint* max_field)
 	/* Ensure that the string is NUL-terminated. */
 	creator[LOG_HEADER_CREATOR_END - LOG_HEADER_CREATOR] = 0;
 
-	switch (group->format) {
+	switch (log_sys.log.format) {
 	case LOG_HEADER_FORMAT_3_23:
-		return(recv_find_max_checkpoint_0(&group, max_field));
+		return(recv_find_max_checkpoint_0(max_field));
 	case LOG_HEADER_FORMAT_10_2:
 	case LOG_HEADER_FORMAT_10_2 | LOG_HEADER_FORMAT_ENCRYPTED:
 	case LOG_HEADER_FORMAT_CURRENT:
@@ -981,7 +960,7 @@ recv_find_max_checkpoint(ulint* max_field)
 	for (field = LOG_CHECKPOINT_1; field <= LOG_CHECKPOINT_2;
 	     field += LOG_CHECKPOINT_2 - LOG_CHECKPOINT_1) {
 
-		log_group_header_read(group, field);
+		log_header_read(field);
 
 		const ulint crc32 = log_block_calc_checksum_crc32(buf);
 		const ulint cksum = log_block_get_checksum(buf);
@@ -996,7 +975,7 @@ recv_find_max_checkpoint(ulint* max_field)
 			continue;
 		}
 
-		if (group->is_encrypted()
+		if (log_sys.is_encrypted()
 		    && !log_crypt_read_checkpoint_buf(buf)) {
 			ib::error() << "Reading checkpoint"
 				" encryption info failed.";
@@ -1014,10 +993,10 @@ recv_find_max_checkpoint(ulint* max_field)
 		if (checkpoint_no >= max_no) {
 			*max_field = field;
 			max_no = checkpoint_no;
-			group->state = LOG_GROUP_OK;
-			group->lsn = mach_read_from_8(
+			log_sys.log.state = LOG_GROUP_OK;
+			log_sys.log.lsn = mach_read_from_8(
 				buf + LOG_CHECKPOINT_LSN);
-			group->lsn_offset = mach_read_from_8(
+			log_sys.log.lsn_offset = mach_read_from_8(
 				buf + LOG_CHECKPOINT_OFFSET);
 			log_sys.next_checkpoint_no = checkpoint_no;
 		}
@@ -2867,7 +2846,6 @@ recv_scan_log_recs(
 
 /** Scans log from a buffer and stores new log data to the parsing buffer.
 Parses and hashes the log records if new data found.
-@param[in,out]	group			log group
 @param[in]	checkpoint_lsn		latest checkpoint log sequence number
 @param[in,out]	contiguous_lsn		log sequence number
 until which all redo log has been scanned
@@ -2877,7 +2855,6 @@ can be applied to the tablespaces
 static
 bool
 recv_group_scan_log_recs(
-	log_group_t*	group,
 	lsn_t		checkpoint_lsn,
 	lsn_t*		contiguous_lsn,
 	bool		last_phase)
@@ -2910,8 +2887,8 @@ recv_group_scan_log_recs(
 		* (buf_pool_get_n_pages()
 		   - (recv_n_pool_free_frames * srv_buf_pool_instances));
 
-	group->scanned_lsn = end_lsn = *contiguous_lsn = ut_uint64_align_down(
-		*contiguous_lsn, OS_FILE_LOG_BLOCK_SIZE);
+	log_sys.log.scanned_lsn = end_lsn = *contiguous_lsn =
+		ut_uint64_align_down(*contiguous_lsn, OS_FILE_LOG_BLOCK_SIZE);
 
 	do {
 		if (last_phase && store_to_hash == STORE_NO) {
@@ -2926,15 +2903,13 @@ recv_group_scan_log_recs(
 		start_lsn = ut_uint64_align_down(end_lsn,
 						 OS_FILE_LOG_BLOCK_SIZE);
 		end_lsn = start_lsn;
-		log_group_read_log_seg(
-			log_sys.buf, group, &end_lsn,
-			start_lsn + RECV_SCAN_SIZE);
+		log_sys.log.read_log_seg(&end_lsn, start_lsn + RECV_SCAN_SIZE);
 	} while (end_lsn != start_lsn
 		 && !recv_scan_log_recs(
 			 available_mem, &store_to_hash, log_sys.buf,
 			 checkpoint_lsn,
 			 start_lsn, end_lsn,
-			 contiguous_lsn, &group->scanned_lsn));
+			 contiguous_lsn, &log_sys.log.scanned_lsn));
 
 	if (recv_sys->found_corrupt_log || recv_sys->found_corrupt_fs) {
 		DBUG_RETURN(false);
@@ -2942,7 +2917,7 @@ recv_group_scan_log_recs(
 
 	DBUG_PRINT("ib_log", ("%s " LSN_PF " completed",
 			      last_phase ? "rescan" : "scan",
-			      group->scanned_lsn));
+			      log_sys.log.scanned_lsn));
 
 	DBUG_RETURN(store_to_hash == STORE_NO);
 }
@@ -3123,7 +3098,6 @@ of first system tablespace page
 dberr_t
 recv_recovery_from_checkpoint_start(lsn_t flush_lsn)
 {
-	log_group_t*	group;
 	ulint		max_cp_field;
 	lsn_t		checkpoint_lsn;
 	bool		rescan;
@@ -3151,8 +3125,6 @@ recv_recovery_from_checkpoint_start(lsn_t flush_lsn)
 
 	log_mutex_enter();
 
-	/* Look for the latest checkpoint from any of the log groups */
-
 	err = recv_find_max_checkpoint(&max_cp_field);
 
 	if (err != DB_SUCCESS) {
@@ -3162,28 +3134,26 @@ recv_recovery_from_checkpoint_start(lsn_t flush_lsn)
 		return(err);
 	}
 
-	log_group_header_read(&log_sys.log, max_cp_field);
+	log_header_read(max_cp_field);
 
 	buf = log_sys.checkpoint_buf;
 
 	checkpoint_lsn = mach_read_from_8(buf + LOG_CHECKPOINT_LSN);
 	checkpoint_no = mach_read_from_8(buf + LOG_CHECKPOINT_NO);
 
-	/* Start reading the log groups from the checkpoint lsn up. The
-	variable contiguous_lsn contains an lsn up to which the log is
-	known to be contiguously written to all log groups. */
-
+	/* Start reading the log from the checkpoint lsn. The variable
+	contiguous_lsn contains an lsn up to which the log is known to
+	be contiguously written. */
 	recv_sys->mlog_checkpoint_lsn = 0;
 
 	ut_ad(RECV_SCAN_SIZE <= srv_log_buffer_size);
 
-	group = &log_sys.log;
 	const lsn_t	end_lsn = mach_read_from_8(
 		buf + LOG_CHECKPOINT_END_LSN);
 
 	ut_ad(recv_sys->n_addrs == 0);
 	contiguous_lsn = checkpoint_lsn;
-	switch (group->format) {
+	switch (log_sys.log.format) {
 	case 0:
 		log_mutex_exit();
 		return(recv_log_format_0_recover(checkpoint_lsn));
@@ -3201,8 +3171,7 @@ recv_recovery_from_checkpoint_start(lsn_t flush_lsn)
 	}
 
 	/* Look for MLOG_CHECKPOINT. */
-	recv_group_scan_log_recs(group, checkpoint_lsn, &contiguous_lsn,
-				 false);
+	recv_group_scan_log_recs(checkpoint_lsn, &contiguous_lsn, false);
 	/* The first scan should not have stored or applied any records. */
 	ut_ad(recv_sys->n_addrs == 0);
 	ut_ad(!recv_sys->found_corrupt_fs);
@@ -3219,7 +3188,7 @@ recv_recovery_from_checkpoint_start(lsn_t flush_lsn)
 	}
 
 	if (recv_sys->mlog_checkpoint_lsn == 0) {
-		lsn_t scan_lsn = group->scanned_lsn;
+		lsn_t scan_lsn = log_sys.log.scanned_lsn;
 		if (!srv_read_only_mode && scan_lsn != checkpoint_lsn) {
 			log_mutex_exit();
 			ib::error err;
@@ -3232,12 +3201,12 @@ recv_recovery_from_checkpoint_start(lsn_t flush_lsn)
 			return(DB_ERROR);
 		}
 
-		group->scanned_lsn = checkpoint_lsn;
+		log_sys.log.scanned_lsn = checkpoint_lsn;
 		rescan = false;
 	} else {
 		contiguous_lsn = checkpoint_lsn;
 		rescan = recv_group_scan_log_recs(
-			group, checkpoint_lsn, &contiguous_lsn, false);
+			checkpoint_lsn, &contiguous_lsn, false);
 
 		if ((recv_sys->found_corrupt_log && !srv_force_recovery)
 		    || recv_sys->found_corrupt_fs) {
@@ -3308,8 +3277,7 @@ recv_recovery_from_checkpoint_start(lsn_t flush_lsn)
 
 			lsn_t recent_stored_lsn = recv_sys->last_stored_lsn;
 			rescan = recv_group_scan_log_recs(
-				group, checkpoint_lsn,
-				&recent_stored_lsn, false);
+				checkpoint_lsn, &recent_stored_lsn, false);
 
 			ut_ad(!recv_sys->found_corrupt_fs);
 
@@ -3340,8 +3308,8 @@ recv_recovery_from_checkpoint_start(lsn_t flush_lsn)
 		if (rescan) {
 			contiguous_lsn = checkpoint_lsn;
 
-			recv_group_scan_log_recs(group, checkpoint_lsn,
-						 &contiguous_lsn, true);
+			recv_group_scan_log_recs(
+				checkpoint_lsn, &contiguous_lsn, true);
 
 			if ((recv_sys->found_corrupt_log
 			     && !srv_force_recovery)
@@ -3354,12 +3322,11 @@ recv_recovery_from_checkpoint_start(lsn_t flush_lsn)
 		ut_ad(!rescan || recv_sys->n_addrs == 0);
 	}
 
-	/* We currently have only one log group */
+	if (log_sys.log.scanned_lsn < checkpoint_lsn
+	    || log_sys.log.scanned_lsn < recv_max_page_lsn) {
 
-	if (group->scanned_lsn < checkpoint_lsn
-	    || group->scanned_lsn < recv_max_page_lsn) {
-
-		ib::error() << "We scanned the log up to " << group->scanned_lsn
+		ib::error() << "We scanned the log up to "
+			<< log_sys.log.scanned_lsn
 			<< ". A checkpoint was at " << checkpoint_lsn << " and"
 			" the maximum LSN on a database page was "
 			<< recv_max_page_lsn << ". It is possible that the"
@@ -3375,9 +3342,6 @@ recv_recovery_from_checkpoint_start(lsn_t flush_lsn)
 		return(DB_ERROR);
 	}
 
-	/* Synchronize the uncorrupted log groups to the most up-to-date log
-	group; we also copy checkpoint info to groups */
-
 	log_sys.next_checkpoint_lsn = checkpoint_lsn;
 	log_sys.next_checkpoint_no = checkpoint_no + 1;