aio: test closing the fd before destroying the ioctx

By closing the file descriptor before calling io_destroy, you pretty
much guarantee that the last put on the ioctx will be done in interrupt
context (during I/O completion).  This behavior has unearthed bugs in
the kernel in several different kernel versions, so let's add a test to
poke at it.

The original test case was provided by Matt Cross.  He has graciously
relicensed it under the GPL v2 or later so that it can be included in
xfstests.  I've modified the test a bit so that it would generate a
stable output format and to run for a fixed amount of time.

Signed-off-by: Jeff Moyer <jmoyer@redhat.com>
Reviewed-by: Brian Foster <bfoster@redhat.com>
Signed-off-by: Dave Chinner <david@fromorbit.com>

tests/generic/323

@@ -0,0 +1,67 @@
+#! /bin/bash
+# FS QA Test No. 323
+#
+# Run aio-last-ref-held-by-io - last put of ioctx not in process
+# context. We've had a couple of instances in the past where having the
+# last reference to an ioctx be held by the IO (instead of the
+# process) would cause problems (hung system, crashes).
+
+#-----------------------------------------------------------------------
+# Copyright (c) 2014 Red Hat, Inc.  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 $tmp.*
+}
+
+# get standard environment, filters and checks
+. ./common/rc
+. ./common/filter
+
+# real QA test starts here
+
+_supported_fs generic
+_supported_os Linux
+
+_require_aiodio aio-last-ref-held-by-io
+
+testfile=$TEST_DIR/aio-testfile
+$XFS_IO_PROG -ftc "pwrite 0 10m" $testfile | _filter_xfs_io
+
+$AIO_TEST 0 100 $testfile
+if [ $? -ne 0 ]; then
+	exit $status
+fi
+
+$AIO_TEST 1 100 $testfile
+if [ $? -ne 0 ]; then
+	exit $status
+fi
+
+status=0
+exit $status