MDEV-11782 preparation: Remove recv_sys_t::last_block.

We can use log_sys->buf instead of recv_sys->last_block during crash recovery. Remove the redundant buffer.

Author: dr-m

storage/innobase/include/log0recv.h

@@ -214,12 +214,6 @@ struct recv_sys_t{
 ibool	apply_batch_on;
 /*!< this is TRUE when a log rec application
 batch is running */
-byte*	last_block;
-/*!< possible incomplete last recovered log
-block */
-byte*	last_block_buf_start;
-/*!< the nonaligned start address of the
-preceding buffer */
 byte*	buf;/*!< buffer for parsing log records */
 ulint	len;/*!< amount of data in buf */
 lsn_tparse_start_lsn;

storage/innobase/log/log0recv.cc

@@ -474,7 +474,6 @@ recv_sys_close(void)
 }
 
 ut_free(recv_sys->buf);
-ut_free(recv_sys->last_block_buf_start);
 
 ut_ad(!recv_writer_thread_active);
 mutex_free(&recv_sys->writer_mutex);
@@ -512,7 +511,6 @@ recv_sys_mem_free(void)
 }
 
 ut_free(recv_sys->buf);
-ut_free(recv_sys->last_block_buf_start);
 ut_free(recv_sys);
 recv_sys = NULL;
 }
@@ -631,12 +629,6 @@ recv_sys_init(
 recv_sys->apply_log_recs = FALSE;
 recv_sys->apply_batch_on = FALSE;
 
-recv_sys->last_block_buf_start = static_cast<byte*>(
-ut_malloc_nokey(2 * OS_FILE_LOG_BLOCK_SIZE));
-
-recv_sys->last_block = static_cast<byte*>(ut_align(
-recv_sys->last_block_buf_start, OS_FILE_LOG_BLOCK_SIZE));
-
 recv_sys->found_corrupt_log = false;
 recv_sys->found_corrupt_fs = false;
 recv_sys->mlog_checkpoint_lsn = 0;
@@ -680,12 +672,10 @@ recv_sys_debug_free(void)
 hash_table_free(recv_sys->addr_hash);
 mem_heap_free(recv_sys->heap);
 ut_free(recv_sys->buf);
-ut_free(recv_sys->last_block_buf_start);
 
 recv_sys->buf = NULL;
 recv_sys->heap = NULL;
 recv_sys->addr_hash = NULL;
-recv_sys->last_block_buf_start = NULL;
 
 /* wake page cleaner up to progress */
 if (!srv_read_only_mode) {
@@ -708,25 +698,24 @@ void
 recv_synchronize_groups(void)
 /*=========================*/
 {
-lsn_tstart_lsn;
-lsn_tend_lsn;
-lsn_trecovered_lsn;
-
-recovered_lsn = recv_sys->recovered_lsn;
+const lsn_t recovered_lsn = recv_sys->recovered_lsn;
 
 /* Read the last recovered log block to the recovery system buffer:
 the block is always incomplete */
 
-start_lsn = ut_uint64_align_down(recovered_lsn,
- OS_FILE_LOG_BLOCK_SIZE);
-end_lsn = ut_uint64_align_up(recovered_lsn, OS_FILE_LOG_BLOCK_SIZE);
+const lsn_t start_lsn = ut_uint64_align_down(recovered_lsn,
+ OS_FILE_LOG_BLOCK_SIZE);
+const lsn_t end_lsn = ut_uint64_align_up(recovered_lsn,
+ OS_FILE_LOG_BLOCK_SIZE);
 
-ut_a(start_lsn != end_lsn);
+ut_ad(start_lsn != end_lsn);
 
-log_group_read_log_seg(recv_sys->last_block,
+log_group_read_log_seg(log_sys->buf,
  UT_LIST_GET_FIRST(log_sys->log_groups),
  start_lsn, end_lsn);
 
+ut_ad(UT_LIST_GET_LEN(log_sys->log_groups) == 1);
+
 for (log_group_t* group = UT_LIST_GET_FIRST(log_sys->log_groups);
  group;
  group = UT_LIST_GET_NEXT(log_groups, group)) {
@@ -3404,8 +3393,6 @@ recv_recovery_from_checkpoint_start(
 srv_start_lsn = recv_sys->recovered_lsn;
 }
 
-ut_memcpy(log_sys->buf, recv_sys->last_block, OS_FILE_LOG_BLOCK_SIZE);
-
 log_sys->buf_free = (ulint) log_sys->lsn % OS_FILE_LOG_BLOCK_SIZE;
 log_sys->buf_next_to_write = log_sys->buf_free;
 log_sys->write_lsn = log_sys->lsn;