Port r529 of branches/5.0: Port r27 of innodb-4.1/trunk: Check the page

trailers also after writing to disk.
This improves the chances of diagnosing Bug #18886.

os_file_check_page_trailers(): New function for checking that the two
copies of the LSN stamped on the pages match.

os_aio_simulated_handle(): Call os_file_check_page_trailers() before
and after os_file_write().

os/os0file.c

@@ -3679,6 +3679,37 @@ os_aio_posix_handle(
 }
 #endif
 
+/**************************************************************************
+Do a 'last millisecond' check that the page end is sensible;
+reported page checksum errors from Linux seem to wipe over the page end. */
+static
+void
+os_file_check_page_trailers(
+/*========================*/
+	byte*	combined_buf,	/* in: combined write buffer */
+	ulint	total_len)	/* in: size of combined_buf, in bytes
+				(a multiple of UNIV_PAGE_SIZE) */
+{
+	ulint	len;
+
+	for (len = 0; len + UNIV_PAGE_SIZE <= total_len;
+			len += UNIV_PAGE_SIZE) {
+		byte*	buf = combined_buf + len;
+
+		if (memcmp(buf + (FIL_PAGE_LSN + 4), buf + (UNIV_PAGE_SIZE
+				- FIL_PAGE_END_LSN_OLD_CHKSUM + 4), 4)) {
+		    	ut_print_timestamp(stderr);
+		    	fprintf(stderr,
+"  InnoDB: ERROR: The page to be written seems corrupt!\n"
+"InnoDB: Writing a block of %lu bytes, currently at offset %lu\n",
+			(ulong)total_len, (ulong)len);
+			buf_page_print(buf);
+		    	fprintf(stderr,
+"InnoDB: ERROR: The page to be written seems corrupt!\n");
+		}
+	}
+}
+
 /**************************************************************************
 Does simulated aio. This function should be called by an i/o-handler
 thread. */
@@ -3716,7 +3747,6 @@ os_aio_simulated_handle(
 	ibool		ret;
 	ulint		n;
 	ulint		i;
-	ulint		len2;
 
 	segment = os_aio_get_array_and_local_segment(&array, global_segment);
 
@@ -3924,32 +3954,15 @@ os_aio_simulated_handle(
 				ut_error;
 			}
 
-			/* Do a 'last millisecond' check that the page end
-			is sensible; reported page checksum errors from
-			Linux seem to wipe over the page end */
-
-			for (len2 = 0; len2 + UNIV_PAGE_SIZE <= total_len;
-						len2 += UNIV_PAGE_SIZE) {
-				if (mach_read_from_4(combined_buf + len2
-						+ FIL_PAGE_LSN + 4)
-					!= mach_read_from_4(combined_buf + len2
-						+ UNIV_PAGE_SIZE
-					- FIL_PAGE_END_LSN_OLD_CHKSUM + 4)) {
-					ut_print_timestamp(stderr);
-					fprintf(stderr,
-"  InnoDB: ERROR: The page to be written seems corrupt!\n");
-					fprintf(stderr,
-"InnoDB: Writing a block of %lu bytes, currently writing at offset %lu\n",
-					(ulong)total_len, (ulong)len2);
-					buf_page_print(combined_buf + len2);
-					fprintf(stderr,
-"InnoDB: ERROR: The page to be written seems corrupt!\n");
-				}
-			}
+			os_file_check_page_trailers(combined_buf, total_len);
 		}
 
 		ret = os_file_write(slot->name, slot->file, combined_buf,
 				slot->offset, slot->offset_high, total_len);
+
+		if (array == os_aio_write_array) {
+			os_file_check_page_trailers(combined_buf, total_len);
+		}
 	} else {
 		ret = os_file_read(slot->file, combined_buf,
 				slot->offset, slot->offset_high, total_len);