add a new test for racing AIO COW writes

[Christoph Hellwig <hch@lst.de>]

This can be used to trigger an assert in the current XFS code because it
can't handle the case where there are COW extents on a file, but none
at or below the range converted by the AIO completion handler.

Note that it doesn't trigger the assert 100% but fairly reliably.
    
Signed-off-by: Christoph Hellwig <hch@lst.de>

diff --git a/src/aio-dio-regress/aio-dio-cow-race.c b/src/aio-dio-regress/aio-dio-cow-race.c
new file mode 100755
index 0000000..c7f8e89
--- /dev/null
+++ b/src/aio-dio-regress/aio-dio-cow-race.c
@@ -0,0 +1,119 @@
+/*
+ * Copyright (c) Christoph Hellwig.  All Rights Reserved.
+ *
+ * This program is free software; you can redistribute it and/or
+ * modify it under the terms of the GNU General Public License as
+ * published by the Free Software Foundation.
+ *
+ * This program is distributed in the hope that it would be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with this program; if not, write the Free Software Foundation,
+ * Inc.,  51 Franklin St, Fifth Floor, Boston, MA  02110-1301  USA
+ */
+#include <sys/stat.h>
+#include <sys/types.h>
+#include <errno.h>
+#include <libgen.h>
+#include <fcntl.h>
+#include <stdio.h>
+#include <stdlib.h>
+#include <unistd.h>
+#include <ctype.h>
+#include <sys/ioctl.h>
+#include <linux/fs.h>
+
+#include <libaio.h>
+
+#ifndef FICLONE
+#define FICLONE		_IOW(0x94, 9, int)
+#endif
+
+#define IO_PATTERN	0xab
+
+int main(int argc, char *argv[])
+{
+	struct io_context *ctx = NULL;
+	struct io_event evs[4];
+	struct iocb iocb1, iocb2, iocb3, iocb4;
+	struct iocb *iocbs[] = { &iocb1, &iocb2, &iocb3, &iocb4 };
+	void *buf;
+	int fd, clone, err = 0;
+	unsigned long buf_size = getpagesize() * 2;
+	char *filename, *clonename;
+
+	if (argc != 3) {
+		fprintf(stderr, "usage: %s filename clonename\n", argv[0]);
+		exit(1);
+	}
+
+	err = posix_memalign(&buf, getpagesize(), buf_size);
+	if (err) {
+		fprintf(stderr, "error %s during %s\n",
+			strerror(err), "posix_memalign");
+		return 1;
+	}
+	memset(buf, IO_PATTERN, buf_size);
+
+	filename = argv[1];
+	fd = open(filename, O_DIRECT | O_CREAT | O_TRUNC | O_RDWR, 0600);
+	if (fd == -1) {
+		perror("open");
+		return 1;
+	}
+
+	if (write(fd, buf, buf_size) != buf_size) {
+		perror("write");
+		return 1;
+	}
+
+	clonename = argv[2];
+	clone = open(clonename, O_DIRECT | O_CREAT | O_TRUNC | O_RDWR, 0600);
+	if (clone == -1) {
+		perror("open clone");
+		return 1;
+	}
+
+	if (ioctl(clone, FICLONE, fd)) {
+		perror("FICLONE");
+		return 1;
+	}
+
+	err = io_setup(4, &ctx);
+	if (err) {
+		fprintf(stderr, "error %s during %s\n",
+			strerror(err),
+			"io_setup");
+		return 1;
+	}
+
+	/*
+	 * Test overlapping aio writes, where an earlier one clears the whole
+	 * range of a later aio, thus leaving nothing to do for the I/O
+	 * completion to do.  To make things harder also make sure there is
+	 * other outstanding COW I/O.
+	 */
+	io_prep_pwrite(&iocb1, fd, buf, buf_size, 0);
+	io_prep_pwrite(&iocb2, fd, buf, buf_size / 2, 0);
+	io_prep_pwrite(&iocb3, fd, buf, buf_size / 2, buf_size);
+	io_prep_pwrite(&iocb4, fd, buf, buf_size, 0);
+
+	err = io_submit(ctx, 4, iocbs);
+	if (err != 4) {
+		fprintf(stderr, "error %s during %s\n",
+			strerror(err), "io_submit");
+		return 1;
+	}
+
+	err = io_getevents(ctx, 4, 4, evs, NULL);
+	if (err != 4) {
+		fprintf(stderr, "error %s during %s\n",
+			strerror(err), "io_getevents");
+		return 1;
+	}
+
+	return 0;
+}
diff --git a/tests/generic/463 b/tests/generic/463
new file mode 100755
index 0000000..b3afbb0
--- /dev/null
+++ b/tests/generic/463
@@ -0,0 +1,60 @@
+#! /bin/bash
+# FS QA Test 463
+#
+# Test racy COW AIO write completions.
+#
+#-----------------------------------------------------------------------
+# Copyright (c) 2017 Christoph Hellwig.  All Rights Reserved.
+#
+# This program is free software; you can redistribute it and/or
+# modify it under the terms of the GNU General Public License as
+# published by the Free Software Foundation.
+#
+# This program is distributed in the hope that it would be useful,
+# but WITHOUT ANY WARRANTY; without even the implied warranty of
+# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+# GNU General Public License for more details.
+#
+# You should have received a copy of the GNU General Public License
+# along with this program; if not, write the Free Software Foundation,
+# Inc.,  51 Franklin St, Fifth Floor, Boston, MA  02110-1301  USA
+#-----------------------------------------------------------------------
+#
+
+seq=`basename $0`
+seqres=$RESULT_DIR/$seq
+echo "QA output created by $seq"
+
+here=`pwd`
+tmp=/tmp/$$
+status=1	# failure is the default!
+trap "_cleanup; exit \$status" 0 1 2 3 15
+
+_cleanup()
+{
+	cd /
+	rm -f $tmp.*
+	rm -f $TEST_DIR/file $TEST_DIR/clone
+}
+
+# get standard environment, filters and checks
+. ./common/rc
+. ./common/filter
+. ./common/reflink
+
+# remove previous $seqres.full before test
+rm -f $seqres.full
+
+_supported_fs generic
+_supported_os Linux
+
+_require_test
+_require_test_reflink
+_require_aio
+_require_odirect
+
+$here/src/aio-dio-regress/aio-dio-cow-race $TEST_DIR/file $TEST_DIR/clone
+
+echo "Silence is golden"
+status=0
+exit
diff --git a/tests/generic/group b/tests/generic/group
index f2a6cda..014d6ea 100644
--- a/tests/generic/group
+++ b/tests/generic/group
@@ -465,3 +465,4 @@
 460 auto quick rw
 461 auto shutdown stress
 462 auto quick dax
+463 auto quick reflink dangerous