From 637ec3fc4ea7e756ba62a69e7ebe7a15713626b9 Mon Sep 17 00:00:00 2001
From: Thomas Schoebel-Theuer <tst@1und1.de>
Date: Thu, 4 Jul 2013 07:16:38 +0200
Subject: [PATCH] tools: new checking tool write-reboot.c

Use this for testing the power blackout safety.
---
 userspace/write-reboot.c | 162 +++++++++++++++++++++++++++++++++++++++
 1 file changed, 162 insertions(+)
 create mode 100644 userspace/write-reboot.c

diff --git a/userspace/write-reboot.c b/userspace/write-reboot.c
new file mode 100644
index 00000000..1d268b4b
--- /dev/null
+++ b/userspace/write-reboot.c
@@ -0,0 +1,162 @@
+// (c) 2013 Thomas Schoebel-Theuer / 1&1 Internet AG
+
+/* This is a trivial hacker's tool for testing the reboot saftey of MARS
+ * (or other system software).
+ *
+ * The trick is to reboot _immediately_ after the last IO operation.
+ * Will the block layer contain _all_ the data, at least if it had been
+ * sync()ed before?
+ *
+ * Note: the transaction logfiles of MARS may contain an incomplete
+ * log record at the end if there was (additional) IO running _in parallel_
+ * to the reboot operation.
+ * Even then, the transaction logfile must contain all the data which
+ * has been reported as "completed" by O_DIRECT or O_SYNC or by one
+ * of the fsync() / fdatasync() operations.
+ * In addition, MARS must tolerate such incomplete records because they
+ * are unavoidable as such (races between IO and reboot / reset).
+ *
+ * Exception: when /proc/sys/mars/logger_completion_semantics is deliberately
+ * set to 0, some synced IO may get lost. However, even then the _order_ must
+ * be correct.
+ *
+ * Hint: you may also try physical reset via IPMI
+ */
+
+#define _FILE_OFFSET_BITS 64
+#define _LARGEFILE64_SOURCE
+#define _GNU_SOURCE
+
+#include <sys/types.h>
+#include <sys/stat.h>
+#include <fcntl.h>
+#include <unistd.h>
+#include <errno.h>
+#include <string.h>
+
+#include <stdio.h>
+#include <stdlib.h>
+
+#include <linux/reboot.h>
+#include <sys/reboot.h>
+
+#include <time.h>
+
+#define BLK_SIZE 1024
+
+static
+time_t now = 0;
+
+static
+int blk_size = BLK_SIZE;
+
+void write_block(int fd, int nr)
+{
+	char *buf = aligned_alloc(blk_size, blk_size);
+	int status;
+
+	if (!buf) {
+		fprintf(stderr, "no mem\n");
+		exit (-1);
+	}
+
+	/* Hint: you may simply use the tool "strings" to dig for
+	 * the markers produced by this.
+	 * When running multiple times, check the correctness of the
+	 * timestamps.
+	 */
+	memset(buf, 0, blk_size);
+	snprintf(buf, blk_size, "timestamp %lld block %05d\n", (long long)now, nr);
+
+	status = write(fd, buf, blk_size);
+	if (status != blk_size) {
+		fprintf(stderr, "write() #%d failed, status = %d, errno = %d %s\n", nr, status, errno, strerror(errno));
+		exit (-1);
+	}
+
+	free(buf);
+}
+
+int main(int argc, char *argv[])
+{
+	/* smode:
+	 *  0 = only write blocks (see fmode)            [DEFAULT]
+	 *  1 = immedialtely reboot afterwards (no sync, no pause)
+	 *  2 = use fdatasync() before reboot
+	 *  3 = use fsync() before reboot
+	 */
+	int smode = 0;
+
+	/* fmode:
+	 *  0 = buffered write (IO may get lost because of buffering)
+	 *  1 = use O_DIRECT   (IO should not get lost)  [DEFAULT]
+	 *  2 = use O_SYNC     (IO should not get lost)
+	 * [combine the bits like a bitmask]
+	 */
+	int fmode = 1;
+	int flags = O_WRONLY | O_CREAT;
+
+	int count = 1000;
+	int fd;
+	int i;
+
+	if (argc < 2) {
+		fprintf(stderr, "usage: write-reboot <filename> [<smode>] [<fmode>] [<count>] [<blk_size>]\n");
+		exit (-1);
+	}
+	if (argc > 2) {
+		smode = atoi(argv[2]);
+	}
+	if (argc > 3) {
+		fmode = atoi(argv[3]);
+	}
+	if (fmode & 1)
+		flags |= O_DIRECT;
+	if (fmode & 2)
+		flags |= O_SYNC;
+	if (argc > 4) {
+		count = atoi(argv[4]);
+	}
+	if (argc > 5) {
+		blk_size = atoi(argv[5]);
+	}
+
+	time(&now);
+
+	printf("now = %lld file = '%s' fmode = %d smode = %d count = %d blk_size = %d\n",
+	       (long long)now,
+	       argv[1],
+	       fmode,
+	       smode,
+	       count,
+	       blk_size);
+
+	fd = open(argv[1], flags,  0600);
+	if (fd < 0) {
+		fprintf(stderr, "open() with flags %d failed, errno = %d %s\n", flags, errno, strerror(errno));
+		exit (-1);
+	}
+	printf("fd = %d\n", fd);
+
+	for (i = 0; i < count; i++) {
+		write_block(fd, i);
+	}
+	
+	printf("done.\n");
+
+	if (smode > 2) {
+		printf("fsync()\n");
+		fsync(fd);
+	} else
+	if (smode > 1) {
+		printf("fdatasync()\n");
+		fdatasync(fd);
+	}
+
+	if (smode > 0) {
+		printf("reboot...\n");
+		reboot(LINUX_REBOOT_CMD_RESTART);
+	}
+
+	return 0;
+}