btrfs: test premature submount unmounting when deleting default subvolume

Add a regression test for a problem where attempting to delete the
default subvolume would fail (as expected), but not until after all
submounts under the subvolume were unmounted.

Signed-off-by: Omar Sandoval <osandov@osandov.com>
Reviewed-by: Eryu Guan <eguan@redhat.com>
Signed-off-by: Dave Chinner <david@fromorbit.com>

tests/btrfs/089

@@ -0,0 +1,79 @@
+#! /bin/bash
+# FS QA Test 089
+#
+# Test deleting the default subvolume, making sure that submounts under it are
+# not unmounted prematurely. This is a regression test for Linux commit "Btrfs:
+# don't invalidate root dentry when subvolume deletion fails".
+#
+#-----------------------------------------------------------------------
+# Copyright (c) 2015 Omar Sandoval.  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/filter.btrfs
+
+# real QA test starts here
+
+# Modify as appropriate.
+_need_to_be_root
+_supported_fs btrfs
+_supported_os Linux
+_require_scratch
+
+rm -f $seqres.full
+
+_scratch_mkfs >>$seqres.full 2>&1
+_scratch_mount
+
+# Create a new subvolume and make it the default subvolume.
+$BTRFS_UTIL_PROG subvolume create "$SCRATCH_MNT/testvol" >>$seqres.full 2>&1 \
+	|| _fail "couldn't create subvol"
+testvol_id=$(_btrfs_get_subvolid "$SCRATCH_MNT" testvol)
+$BTRFS_UTIL_PROG subvolume set-default $testvol_id "$SCRATCH_MNT" >>$seqres.full 2>&1 \
+	|| _fail "couldn't set default"
+
+# Bind-mount a directory under the default subvolume.
+mkdir "$SCRATCH_MNT/testvol/testdir"
+mkdir "$SCRATCH_MNT/testvol/mnt"
+mount --bind "$SCRATCH_MNT/testvol/testdir" "$SCRATCH_MNT/testvol/mnt"
+
+# Now attempt to delete the default subvolume.
+$BTRFS_UTIL_PROG subvolume delete "$SCRATCH_MNT/testvol" >>$seqres.full 2>&1
+
+# Unmount the bind mount, which should still be alive.
+$UMOUNT_PROG "$SCRATCH_MNT/testvol/mnt"
+
+echo "Silence is golden"
+status=0
+exit

tests/btrfs/089.out

@@ -0,0 +1,2 @@
+QA output created by 089
+Silence is golden

tests/btrfs/group

@@ -91,6 +91,7 @@
 086 auto quick clone
 087 auto quick send
 088 auto quick metadata
+089 auto quick subvol
 090 auto quick metadata
 091 auto quick qgroup
 092 auto quick send