+#! /bin/bash
+# FS QA Test No. 311
+#
+# Test to reproduce an XFS unmount crash due to races with directory readahead.
+# XFS had a bug in which unmount would proceed with a readahead I/O in flight.
+# If the unmount deconstructed the log by the time I/O completion occurs,
+# certain metadata read verifier checks could access invalid memory and cause a
+# panic.
+#
+#-----------------------------------------------------------------------
+# Copyright (c) 2016 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.*
+ _scratch_unmount > /dev/null 2>&1
+ _cleanup_delay > /dev/null 2>&1
+}
+
+# get standard environment, filters and checks
+. ./common/rc
+. ./common/dmdelay
+
+# Modify as appropriate.
+_supported_fs xfs
+_supported_os Linux
+
+_require_scratch
+_require_dm_target delay
+
+rm -f $seqres.full
+
+echo "Silence is golden."
+
+_scratch_mkfs_xfs >> $seqres.full 2>&1
+
+_init_delay
+_mount_delay
+
+# insert entries to grow the directory to at least one extent, which is what
+# triggers readahead on dir open
+mkdir $SCRATCH_MNT/dir
+for i in $(seq 0 999); do
+ echo > $SCRATCH_MNT/dir/$i
+done
+
+# remount to clear the buffer cache
+_unmount_delay
+_mount_delay
+
+# introduce a read I/O delay
+_load_delay_table $DELAY_READ
+
+# Map the directory and immediately unmount. This should invoke an asynchronous
+# readahead on the first block of the directory. The readahead is delayed by
+# dm-delay. If the unmount doesn't properly wait for the readahead completion,
+# the read verifier can run after core data structures have been freed and lead
+# to a crash/panic.
+$XFS_IO_PROG -c "bmap -v" $SCRATCH_MNT/dir >> $seqres.full 2>&1
+_unmount_delay
+
+_cleanup_delay
+
+# success, all done
+status=0
+exit