generic: reserve correct indirect blocks for delalloc write path

Test that XFS reserves reasonable indirect blocks for delalloc and
speculative allocation, and doesn't cause any fdblocks corruption.

This was inspired by an XFS but that too large 'indlen' was returned by
xfs_bmap_worst_indlen() which can't fit in a 17 bits value
(STARTBLOCKVALBITS is defined as 17), then leaked 1 << 17 blocks in
sb_fdblocks.

This was only seen on XFS with rmapbt feature enabled, but nothing
prevents the test from being a generic test.

Reviewed-by: "Darrick J. Wong" <darrick.wong@oracle.com>
Signed-off-by: Eryu Guan <eguan@redhat.com>

tests/generic/460

@@ -0,0 +1,113 @@
+#! /bin/bash
+# FS QA Test 460
+#
+# Test that XFS reserves reasonable indirect blocks for delalloc and
+# speculative allocation, and doesn't cause any fdblocks corruption.
+#
+# This was inspired by an XFS but that too large 'indlen' was returned by
+# xfs_bmap_worst_indlen() which can't fit in a 17 bits value (STARTBLOCKVALBITS
+# is defined as 17), then leaked 1 << 17 blocks in sb_fdblocks.
+#
+# This was only seen on XFS with rmapbt feature enabled, but nothing prevents
+# the test from being a generic test.
+#
+#-----------------------------------------------------------------------
+# Copyright (c) 2017 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!
+testfile=$SCRATCH_MNT/1G_file.$seq
+file_size=$((1024 * 1024 * 1024))
+trap "_cleanup; exit \$status" 0 1 2 3 15
+
+saved_dirty_background_ratio=0
+saved_dirty_ratio=0
+
+save_dirty_ratio()
+{
+	saved_dirty_background_ratio=`cat /proc/sys/vm/dirty_background_ratio`
+	saved_dirty_ratio=`cat /proc/sys/vm/dirty_ratio`
+}
+
+set_dirty_ratio()
+{
+	echo 100 > /proc/sys/vm/dirty_background_ratio
+	echo 100 > /proc/sys/vm/dirty_ratio
+}
+
+restore_dirty_ratio()
+{
+	if [ $saved_dirty_background_ratio -ne 0 ]; then
+		echo $saved_dirty_background_ratio > /proc/sys/vm/dirty_background_ratio
+	fi
+	if [ $saved_dirty_ratio -ne 0 ]; then
+		echo $saved_dirty_ratio > /proc/sys/vm/dirty_ratio
+	fi
+}
+
+_cleanup()
+{
+	cd /
+	restore_dirty_ratio
+	rm -f $tmp.*
+}
+
+# get standard environment, filters and checks
+. ./common/rc
+. ./common/filter
+
+# remove previous $seqres.full before test
+rm -f $seqres.full
+
+# real QA test starts here
+_supported_fs generic
+_supported_os Linux
+# test with scratch device, because test is known to corrupt fs, we don't want
+# the corruption affect subsequent tests
+_require_scratch
+
+_scratch_mkfs >>$seqres.full 2>&1
+_scratch_mount
+
+# need at least 1G free space
+_require_fs_space $SCRATCH_MNT $((1024 * 1024))
+
+# To reproduce the bug, we need to keep enough dirty data in memory (1G at
+# least), so that a large enough delay allocated extent is kept in memory, then
+# speculative preallocation could allocate large number of blocks based on the
+# existing extent size.
+# So we set dirty_background_ratio and dirty_ratio to 100% uncontitionally,
+# even if the total memory is less than 1G, there's no harm to run a test on a
+# such host.
+save_dirty_ratio
+set_dirty_ratio
+
+# buffer write a 1G file, which is enough to trigger the bug,
+# _check_filesystems will complain about fs corruption after test
+$XFS_IO_PROG -fc "pwrite -b 1m 0 $file_size" $testfile >/dev/null 2>&1
+
+echo "Silence is golden"
+
+# success, all done
+status=0
+exit

tests/generic/460.out

@@ -0,0 +1,2 @@
+QA output created by 460
+Silence is golden

tests/generic/group

@@ -462,3 +462,4 @@
 457 auto log replay clone
 458 auto quick clone
 459 auto dangerous
+460 auto quick rw