generic: test data corruption on ext4 caused by written/delayed extent

This test exercises the problem with unwritten and delayed extents
in ext4 extent status tree where we might in some cases lose a block
worth of data. Even though this was a ext4 specific problem the
reproducer can be easily run on any file system so let's do that just
in case.

This test exercises the problem fixed in kernel with commit
"ext4: Fix data corruption caused by unwritten and delayed extents"

Signed-off-by: Lukas Czerner <lczerner@redhat.com>
Reviewed-by: Eryu Guan <eguan@redhat.com>
Signed-off-by: Dave Chinner <david@fromorbit.com>

tests/generic/086

@@ -0,0 +1,85 @@
+#! /bin/bash
+# FS QA Test 086
+#
+# This test excercises the problem with unwritten and delayed extents
+# in ext4 extent status tree where we might in some cases lose a block
+# worth of data. Even though this was a ext4 specific problem the
+# reproducer can be easily tun on any file system so let's do that just
+# in case.
+#
+# This tests excercises the problem fixed in kernel with commit
+# "ext4: Fix data corruption caused by unwritten and delayed extents"
+#
+#-----------------------------------------------------------------------
+# Copyright (c) 2015 Red Hat, Inc., Lukas Czerner <lczerner@redhat.com>
+#
+# 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 $tmp.*
+}
+
+# get standard environment, filters and checks
+. ./common/rc
+. ./common/filter
+
+# real QA test starts here
+
+# Modify as appropriate.
+_supported_fs generic
+_supported_os IRIX Linux
+_require_test
+_require_xfs_io_command "falloc"
+
+test_file=${TEST_DIR}/testfile-$seq
+
+rm -f $test_file
+
+# The first write creates a delayed extent, fallocate creates
+# unwritten extent which will be marked as delayed in ext4
+# extent status tree. Second write will convert unwritten/delayed
+# block into written/delayed.
+$XFS_IO_PROG -f -c "pwrite -S 0xaa 4096 2048" \
+		-c "falloc 0 131072" \
+		-c "pwrite -S 0xbb 65536 2048" \
+		-c "fsync"  $test_file > $seqres.full 2>&1
+
+# Drop the caches to evict dirty buffers from memory
+echo 3 > /proc/sys/vm/drop_caches
+
+# Write into the second part of the block with 0xbb write from before
+# will create new empty! buffer because the block is still marked as
+# delayed even though it's already written - resulting in
+# overwriting previous data.
+$XFS_IO_PROG -c "pwrite -S 0xdd 67584 2048" $test_file >> $seqres.full 2>&1
+
+# On a faulty ext4 oxbb data will be missing, overwritten by zeroes.
+hexdump -C $test_file
+
+# success, all done
+status=0
+exit

tests/generic/086.out

@@ -0,0 +1,14 @@
+QA output created by 086
+00000000  00 00 00 00 00 00 00 00  00 00 00 00 00 00 00 00  |................|
+*
+00001000  aa aa aa aa aa aa aa aa  aa aa aa aa aa aa aa aa  |................|
+*
+00001800  00 00 00 00 00 00 00 00  00 00 00 00 00 00 00 00  |................|
+*
+00010000  bb bb bb bb bb bb bb bb  bb bb bb bb bb bb bb bb  |................|
+*
+00010800  dd dd dd dd dd dd dd dd  dd dd dd dd dd dd dd dd  |................|
+*
+00011000  00 00 00 00 00 00 00 00  00 00 00 00 00 00 00 00  |................|
+*
+00020000

tests/generic/group

@@ -88,6 +88,7 @@
 083 rw auto enospc stress
 084 auto metadata quick
 085 auto freeze mount
+086 auto prealloc preallocrw quick
 088 perms auto quick
 089 metadata auto
 091 rw auto quick