MDEV-21171 InnoDB is unnecessarily resetting FIL_PAGE_TYPE for full_crc32 files

Before commit c0f47a4a (MDEV-12026)
introduced the innodb_checksum_algorithm=full_crc32 format,
it was impossible to tell if InnoDB data files contained garbage in
the FIL_PAGE_TYPE header field (and possibly other fields).
This is because before commit 3926673c
in MySQL 5.1.48, InnoDB would write uninitialized data to some fields,
and because there was no way to tell with which InnoDB version a data
file was created.

If fil_space_t::full_crc32() holds, the data file cannot contain
uninitialized garbage or invalid FIL_PAGE_TYPE, and thus
fil_block_check_type() should not be invoked to correct anything.

storage/innobase/fsp/fsp0fsp.cc

@@ -1012,7 +1012,7 @@ fsp_fill_free_list(
 		buf_block_t*	desc_block = NULL;
 		descr = xdes_get_descriptor_with_space_hdr(
 			header, space, i, mtr, init_space, &desc_block);
-		if (desc_block != NULL) {
+		if (desc_block && !space->full_crc32()) {
 			fil_block_check_type(
 				*desc_block, FIL_PAGE_TYPE_XDES, mtr);
 		}
@@ -1070,7 +1070,7 @@ fsp_alloc_free_extent(
 	descr = xdes_get_descriptor_with_space_hdr(
 		header, space, hint, mtr, false, &desc_block);
 
-	if (desc_block != NULL) {
+	if (desc_block && !space->full_crc32()) {
 		fil_block_check_type(*desc_block, FIL_PAGE_TYPE_XDES, mtr);
 	}
 
@@ -1597,7 +1597,9 @@ fsp_alloc_seg_inode(
 
 	block = buf_page_get(page_id, space->zip_size(), RW_SX_LATCH, mtr);
 	buf_block_dbg_add_level(block, SYNC_FSP_PAGE);
-	fil_block_check_type(*block, FIL_PAGE_INODE, mtr);
+	if (!space->full_crc32()) {
+		fil_block_check_type(*block, FIL_PAGE_INODE, mtr);
+	}
 
 	page = buf_block_get_frame(block);
 
@@ -1898,12 +1900,13 @@ fseg_create(
 
 		header = byte_offset + buf_block_get_frame(block);
 
-		const ulint	type = space->id == TRX_SYS_SPACE
-			&& page == TRX_SYS_PAGE_NO
-			? FIL_PAGE_TYPE_TRX_SYS
-			: FIL_PAGE_TYPE_SYS;
-
-		fil_block_check_type(*block, type, mtr);
+		if (!space->full_crc32()) {
+			fil_block_check_type(*block, space->id == TRX_SYS_SPACE
+					     && page == TRX_SYS_PAGE_NO
+					     ? FIL_PAGE_TYPE_TRX_SYS
+					     : FIL_PAGE_TYPE_SYS,
+					     mtr);
+		}
 	}
 
 	if (!has_done_reservation
@@ -2452,7 +2455,9 @@ fseg_alloc_free_page_general(
 	space = mtr_x_lock_space(space_id, mtr);
 	inode = fseg_inode_get(seg_header, space_id, space->zip_size(),
 			       mtr, &iblock);
-	fil_block_check_type(*iblock, FIL_PAGE_INODE, mtr);
+	if (!space->full_crc32()) {
+		fil_block_check_type(*iblock, FIL_PAGE_INODE, mtr);
+	}
 
 	if (!has_done_reservation
 	    && !fsp_reserve_free_extents(&n_reserved, space, 2,
@@ -2872,7 +2877,9 @@ fseg_free_page_func(
 	seg_inode = fseg_inode_get(seg_header, space->id, space->zip_size(),
 				   mtr,
 				   &iblock);
-	fil_block_check_type(*iblock, FIL_PAGE_INODE, mtr);
+	if (!space->full_crc32()) {
+		fil_block_check_type(*iblock, FIL_PAGE_INODE, mtr);
+	}
 
 	fseg_free_page_low(seg_inode, space, offset, ahi, log, mtr);
 
@@ -3047,7 +3054,9 @@ fseg_free_step_func(
 		DBUG_RETURN(TRUE);
 	}
 
-	fil_block_check_type(*iblock, FIL_PAGE_INODE, mtr);
+	if (!space->full_crc32()) {
+		fil_block_check_type(*iblock, FIL_PAGE_INODE, mtr);
+	}
 	descr = fseg_get_first_extent(inode, space, mtr);
 
 	if (descr != NULL) {
@@ -3113,7 +3122,9 @@ fseg_free_step_not_header_func(
 
 	inode = fseg_inode_get(header, space_id, space->zip_size(), mtr,
 			       &iblock);
-	fil_block_check_type(*iblock, FIL_PAGE_INODE, mtr);
+	if (!space->full_crc32()) {
+		fil_block_check_type(*iblock, FIL_PAGE_INODE, mtr);
+	}
 
 	descr = fseg_get_first_extent(inode, space, mtr);
 

storage/innobase/include/trx0sys.h

@@ -68,17 +68,13 @@ trx_sys_rseg_find_free(const buf_block_t* sys_header);
 @param[in]	rw	whether to lock the page for writing
 @return the TRX_SYS page
 @retval	NULL	if the page cannot be read */
-inline
-buf_block_t*
-trx_sysf_get(mtr_t* mtr, bool rw = true)
+inline buf_block_t *trx_sysf_get(mtr_t* mtr, bool rw= true)
 {
-	buf_block_t* block = buf_page_get(
-		page_id_t(TRX_SYS_SPACE, TRX_SYS_PAGE_NO),
-		0, rw ? RW_X_LATCH : RW_S_LATCH, mtr);
-	if (block) {
-		buf_block_dbg_add_level(block, SYNC_TRX_SYS_HEADER);
-	}
-	return block;
+  buf_block_t* block = buf_page_get(page_id_t(TRX_SYS_SPACE, TRX_SYS_PAGE_NO),
+				    0, rw ? RW_X_LATCH : RW_S_LATCH, mtr);
+  if (block)
+    buf_block_dbg_add_level(block, SYNC_TRX_SYS_HEADER);
+  return block;
 }
 
 #ifdef UNIV_DEBUG
@@ -200,14 +196,13 @@ trx_sysf_rseg_get_space(const buf_block_t* sys_header, ulint rseg_id)
 @param[in]	sys_header	TRX_SYS page
 @param[in]	rseg_id		rollback segment identifier
 @return	undo page number */
-inline
-uint32_t
-trx_sysf_rseg_get_page_no(const buf_block_t* sys_header, ulint rseg_id)
+inline uint32_t
+trx_sysf_rseg_get_page_no(const buf_block_t *sys_header, ulint rseg_id)
 {
-	ut_ad(rseg_id < TRX_SYS_N_RSEGS);
-	return mach_read_from_4(TRX_SYS + TRX_SYS_RSEGS + TRX_SYS_RSEG_PAGE_NO
-				+ rseg_id * TRX_SYS_RSEG_SLOT_SIZE
-				+ sys_header->frame);
+  ut_ad(rseg_id < TRX_SYS_N_RSEGS);
+  return mach_read_from_4(TRX_SYS + TRX_SYS_RSEGS + TRX_SYS_RSEG_PAGE_NO +
+			  rseg_id * TRX_SYS_RSEG_SLOT_SIZE +
+			  sys_header->frame);
 }
 
 /** Maximum length of MySQL binlog file name, in bytes.

storage/innobase/srv/srv0start.cc

@@ -2104,8 +2104,9 @@ dberr_t srv_start(bool create_new_db)
 		}
 
 		/* Validate a few system page types that were left
-		uninitialized by older versions of MySQL. */
-		if (!high_level_read_only) {
+		uninitialized before MySQL or MariaDB 5.5. */
+		if (!high_level_read_only
+		    && !fil_system.sys_space->full_crc32()) {
 			buf_block_t*	block;
 			mtr.start();
 			/* Bitmap page types will be reset in