Set FIL_PAGE_TYPE for every page, so that the field can be relied on in

new tablespaces created from now on.

btr_store_big_rec_extern_fields(): Set FIL_PAGE_TYPE to FIL_PAGE_TYPE_BLOB.

buf_page_print(): Decode FIL_PAGE_TYPE.  Replace if-else with switch().

buf_page_create(): Set FIL_PAGE_PREV, FIL_PAGE_NEXT and FIL_PAGE_TYPE.

trx_sysf_create(): Set FIL_PAGE_TYPE to FIL_PAGE_TYPE_TRX_SYS.
Initialize TRX_SYS_RSEG_SPACE.

FIL_PAGE_TYPE: Document that the field cannot be relied on in older
versions of MySQL/InnoDB.  Add new type codes.

ibuf_bitmap_page_init(): Document that the rest of the page is uninitialized.

ibuf_add_free_page(): Log the setting of FIL_PAGE_TYPE.

fsp_header_init(): Set FIL_PAGE_TYPE to FIL_PAGE_TYPE_FSP_HDR.
Initialize FSP_NOT_USED.

fsp_fill_free_list(): Set FIL_PAGE_TYPE to FIL_PAGE_TYPE_XDES.

fsp_alloc_seg_inode_page(): Set FIL_PAGE_TYPE to FIL_PAGE_INODE.

fseg_create_general(): Set FIL_PAGE_TYPE to FIL_PAGE_TYPE_SYS.

btr/btr0cur.c

@@ -3392,6 +3392,9 @@ btr_store_big_rec_extern_fields(
 				return(DB_OUT_OF_FILE_SPACE);
 			}
 
+			mlog_write_ulint(page + FIL_PAGE_TYPE,
+					FIL_PAGE_TYPE_BLOB, MLOG_2BYTES, &mtr);
+
 			page_no = buf_frame_get_page_no(page);
 
 			if (prev_page_no != FIL_NULL) {

buf/buf0buf.c

@@ -427,7 +427,8 @@ buf_page_print(
 			"InnoDB: Page may be an update undo log page\n");
 	}
 
-	if (fil_page_get_type(read_buf) == FIL_PAGE_INDEX) {
+	switch (fil_page_get_type(read_buf)) {
+	case FIL_PAGE_INDEX:
 	    	fprintf(stderr,
 "InnoDB: Page may be an index page where index id is %lu %lu\n",
 			(ulong) ut_dulint_get_high(btr_page_get_index_id(read_buf)),
@@ -446,11 +447,42 @@ buf_page_print(
 				fputs(")\n", stderr);
 			}
 		}
-	} else if (fil_page_get_type(read_buf) == FIL_PAGE_INODE) {
+		break;
+	case FIL_PAGE_INODE:
 		fputs("InnoDB: Page may be an 'inode' page\n", stderr);
-	} else if (fil_page_get_type(read_buf) == FIL_PAGE_IBUF_FREE_LIST) {
+		break;
+	case FIL_PAGE_IBUF_FREE_LIST:
 		fputs("InnoDB: Page may be an insert buffer free list page\n",
 			stderr);
+		break;
+	case FIL_PAGE_TYPE_ALLOCATED:
+		fputs("InnoDB: Page may be a freshly allocated page\n",
+			stderr);
+		break;
+	case FIL_PAGE_IBUF_BITMAP:
+		fputs("InnoDB: Page may be an insert buffer bitmap page\n",
+			stderr);
+		break;
+	case FIL_PAGE_TYPE_SYS:
+		fputs("InnoDB: Page may be a system page\n",
+			stderr);
+		break;
+	case FIL_PAGE_TYPE_TRX_SYS:
+		fputs("InnoDB: Page may be a transaction system page\n",
+			stderr);
+		break;
+	case FIL_PAGE_TYPE_FSP_HDR:
+		fputs("InnoDB: Page may be a file space header page\n",
+			stderr);
+		break;
+	case FIL_PAGE_TYPE_XDES:
+		fputs("InnoDB: Page may be an extent descriptor page\n",
+			stderr);
+		break;
+	case FIL_PAGE_TYPE_BLOB:
+		fputs("InnoDB: Page may be a BLOB page\n",
+			stderr);
+		break;
 	}
 }
 
@@ -1784,6 +1816,10 @@ buf_page_create(
 
 	frame = block->frame;
 
+	memset(frame + FIL_PAGE_PREV, 0xff, 4);
+	memset(frame + FIL_PAGE_NEXT, 0xff, 4);
+	mach_write_to_2(frame + FIL_PAGE_TYPE, FIL_PAGE_TYPE_ALLOCATED);
+
 	/* Reset to zero the file flush lsn field in the page; if the first
 	page of an ibdata file is 'created' in this function into the buffer
 	pool then we lose the original contents of the file flush lsn stamp.

fsp/fsp0fsp.c

@@ -893,9 +893,13 @@ fsp_header_init(
 
 	fsp_init_file_page(page, mtr);
 
+	mlog_write_ulint(page + FIL_PAGE_TYPE, FIL_PAGE_TYPE_FSP_HDR,
+					MLOG_2BYTES, mtr);
+
 	header = FSP_HEADER_OFFSET + page;
 
 	mlog_write_ulint(header + FSP_SPACE_ID, space, MLOG_4BYTES, mtr);
+	mlog_write_ulint(header + FSP_NOT_USED, 0, MLOG_4BYTES, mtr);
 
 	mlog_write_ulint(header + FSP_SIZE, size, MLOG_4BYTES, mtr); 
 	mlog_write_ulint(header + FSP_FREE_LIMIT, 0, MLOG_4BYTES, mtr); 
@@ -1254,6 +1258,8 @@ fsp_fill_free_list(
 								SYNC_FSP_PAGE);
 #endif /* UNIV_SYNC_DEBUG */
 				fsp_init_file_page(descr_page, mtr);
+				mlog_write_ulint(descr_page + FIL_PAGE_TYPE,
+					FIL_PAGE_TYPE_XDES, MLOG_2BYTES, mtr);
 			}
 
 			/* Initialize the ibuf bitmap page in a separate
@@ -1720,7 +1726,8 @@ fsp_alloc_seg_inode_page(
 
 	buf_block_align(page)->check_index_page_at_flush = FALSE;
 
-	fil_page_set_type(page, FIL_PAGE_INODE);
+	mlog_write_ulint(page + FIL_PAGE_TYPE, FIL_PAGE_INODE,
+						MLOG_2BYTES, mtr);
 #ifdef UNIV_SYNC_DEBUG
 	buf_page_dbg_add_level(page, SYNC_FSP_PAGE);
 #endif /* UNIV_SYNC_DEBUG */
@@ -2091,6 +2098,8 @@ fseg_create_general(
 
 		header = byte_offset
 			 + buf_page_get(space, page, RW_X_LATCH, mtr);
+		mlog_write_ulint(header - byte_offset + FIL_PAGE_TYPE,
+					FIL_PAGE_TYPE_SYS, MLOG_2BYTES, mtr);
 	}	
 
 	mlog_write_ulint(header + FSEG_HDR_OFFSET,

ibuf/ibuf0ibuf.c

@@ -574,18 +574,18 @@ ibuf_bitmap_page_init(
 {
 	ulint	bit_offset;
 	ulint	byte_offset;
-	ulint	i;
 
 	/* Write all zeros to the bitmap */
 
 	bit_offset = XDES_DESCRIBED_PER_PAGE * IBUF_BITS_PER_PAGE;
 
-	byte_offset = bit_offset / 8 + 1;
+	byte_offset = bit_offset / 8 + 1; /* better: (bit_offset + 7) / 8 */
 
-	for (i = IBUF_BITMAP; i < IBUF_BITMAP + byte_offset; i++) {
+	fil_page_set_type(page, FIL_PAGE_IBUF_BITMAP);
 
-		*(page + i) = (byte)0;
-	}
+	memset(page + IBUF_BITMAP, 0, byte_offset);
+
+	/* The remaining area (up to the page trailer) is uninitialized. */
 
 	mlog_write_initial_log_record(page, MLOG_IBUF_BITMAP_INIT, mtr);
 }
@@ -1680,7 +1680,8 @@ ibuf_add_free_page(
 	flst_add_last(root + PAGE_HEADER + PAGE_BTR_IBUF_FREE_LIST,
 		      page + PAGE_HEADER + PAGE_BTR_IBUF_FREE_LIST_NODE, &mtr);
 
-	fil_page_set_type(page, FIL_PAGE_IBUF_FREE_LIST);
+	mlog_write_ulint(page + FIL_PAGE_TYPE, FIL_PAGE_IBUF_FREE_LIST,
+						MLOG_2BYTES, &mtr);
 
 	ibuf_data->seg_size++;
 	ibuf_data->free_list_len++;

include/fil0fil.h

@@ -63,7 +63,20 @@ extern fil_addr_t	fil_addr_null;
 #define FIL_PAGE_LSN		16	/* lsn of the end of the newest
 					modification log record to the page */
 #define	FIL_PAGE_TYPE		24	/* file page type: FIL_PAGE_INDEX,...,
-					2 bytes */
+					2 bytes.
+
+					The contents of this field can only
+					be trusted in the following case:
+					if the page is an uncompressed
+					B-tree index page, then it is
+					guaranteed that the value is
+					FIL_PAGE_INDEX.
+					The opposite does not hold.
+
+					In tablespaces created by
+					MySQL/InnoDB 5.1.19 or later, the
+					contents of this field is valid
+					for all uncompressed pages. */
 #define FIL_PAGE_FILE_FLUSH_LSN	26	/* this is only defined for the
 					first page in a data file: the file
 					has been flushed to disk at least up
@@ -79,11 +92,19 @@ extern fil_addr_t	fil_addr_null;
 					to the last 4 bytes of FIL_PAGE_LSN */
 #define FIL_PAGE_DATA_END	8
 
-/* File page types */
-#define FIL_PAGE_INDEX		17855
-#define FIL_PAGE_UNDO_LOG	2
-#define FIL_PAGE_INODE		3
-#define FIL_PAGE_IBUF_FREE_LIST	4
+/* File page types (values of FIL_PAGE_TYPE) */
+#define FIL_PAGE_INDEX		17855	/* B-tree node */
+#define FIL_PAGE_UNDO_LOG	2	/* Undo log page */
+#define FIL_PAGE_INODE		3	/* Index node */
+#define FIL_PAGE_IBUF_FREE_LIST	4	/* Insert buffer free list */
+/* File page types introduced in MySQL/InnoDB 5.1.19 */
+#define FIL_PAGE_TYPE_ALLOCATED	0	/* Freshly allocated page */
+#define FIL_PAGE_IBUF_BITMAP	5	/* Insert buffer bitmap */
+#define FIL_PAGE_TYPE_SYS	6	/* System page */
+#define FIL_PAGE_TYPE_TRX_SYS	7	/* Transaction system data */
+#define FIL_PAGE_TYPE_FSP_HDR	8	/* File space header */
+#define FIL_PAGE_TYPE_XDES	9	/* Extent descriptor page */
+#define FIL_PAGE_TYPE_BLOB	10	/* Uncompressed BLOB page */
 
 /* Space types */
 #define FIL_TABLESPACE 		501

include/trx0sys.ic

@@ -16,7 +16,9 @@ typedef byte 	trx_sysf_rseg_t;
 /* Rollback segment specification slot offsets */
 /*-------------------------------------------------------------*/
 #define	TRX_SYS_RSEG_SPACE	0	/* space where the the segment
-					header is placed */
+					header is placed; starting with
+					MySQL/InnoDB 5.1.19, this is
+					UNIV_UNDEFINED if the slot is unused */
 #define	TRX_SYS_RSEG_PAGE_NO	4	/*  page number where the the segment
 					header is placed; this is FIL_NULL
 					if the slot is unused */

trx/trx0sys.c

@@ -819,6 +819,9 @@ trx_sysf_create(
 	buf_page_dbg_add_level(page, SYNC_TRX_SYS_HEADER);
 #endif /* UNIV_SYNC_DEBUG */
 
+	mlog_write_ulint(page + FIL_PAGE_TYPE, FIL_PAGE_TYPE_TRX_SYS,
+					MLOG_2BYTES, mtr);
+
 	sys_header = trx_sysf_get(mtr);
 
 	/* Start counting transaction ids from number 1 up */
@@ -828,9 +831,12 @@ trx_sysf_create(
 	/* Reset the rollback segment slots */
 	for (i = 0; i < TRX_SYS_N_RSEGS; i++) {
 
+		trx_sysf_rseg_set_space(sys_header, i, ULINT_UNDEFINED, mtr);
 		trx_sysf_rseg_set_page_no(sys_header, i, FIL_NULL, mtr);
 	}
 
+	/* The remaining area (up to the page trailer) is uninitialized. */
+
 	/* Create the first rollback segment in the SYSTEM tablespace */
 	page_no = trx_rseg_header_create(TRX_SYS_SPACE, ULINT_MAX, &slot_no,
 									mtr);