generic: truncate heavily reflinked file

In btrfs, there is a bug about btrfs' truncate codes, it'll leak
some fs space as the truncate operation proceeds. If this truncate
operation is very large, later metadata request in this truncate
operation may fail for enospc error. I also have sent a kernel
patch fot btrfs to fix this issue.

Signed-off-by: Wang Xiaoguang <wangxg.fnst@cn.fujitsu.com>
Reviewed-by: Eryu Guan <eguan@redhat.com>
Signed-off-by: Eryu Guan <eguan@redhat.com>

tests/generic/387

@@ -0,0 +1,81 @@
+#! /bin/bash
+# FS QA Test 387
+#
+# Create a heavily reflinked file, then check whether we can truncate
+# it correctly.
+#
+#-----------------------------------------------------------------------
+# Copyright (c) 2016 Fujitsu.  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
+. ./common/reflink
+
+# remove previous $seqres.full before test
+rm -f $seqres.full
+
+# Modify as appropriate.
+_supported_fs generic
+_supported_os Linux
+_require_scratch_reflink
+
+_scratch_mkfs_sized $((32 * 1024 * 1024)) >> $seqres.full 2>&1
+_scratch_mount
+
+testfile=$SCRATCH_MNT/testfile
+dummyfile=$SCRATCH_MNT/dummyfile
+blocksize=$((128 * 1024))
+
+# create a dummy file, which is used to occupy some fs space first.
+_pwrite_byte 0xcdcdcdcd 0 $((1 * 1024 * 1024)) $dummyfile > /dev/null
+_pwrite_byte 0xcdcdcdcd 0 $blocksize  $testfile > /dev/null
+
+echo "Silence is golden"
+for ((i = 0; i < 16384; i++)); do
+	_reflink_range $testfile 0 $testfile $(($i * $blocksize)) \
+		$blocksize > /dev/null 2>&1
+done
+
+# consume all remaining free space
+dd if=/dev/zero of=$SCRATCH_MNT/space >/dev/null 2>&1
+sync
+
+# fs is full now and fs internal operations may need some free space, for
+# example, in btrfs, transaction will need to reserve space first, so here free
+# 1MB space.
+rm -f $dummyfile
+$XFS_IO_PROG -f -c "truncate 0" $testfile
+
+status=0
+exit

tests/generic/387.out

@@ -0,0 +1,2 @@
+QA output created by 387
+Silence is golden

tests/generic/group

@@ -389,3 +389,4 @@
 384 quota auto quick
 385 quota auto quick
 386 auto quick quota
+387 auto clone