[PATCH v3] btrfs: test premature submount unmounting when deleting default subvolume

[Omar Sandoval <osandov@osandov.com>]

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.

Reviewed-by: Eryu Guan <eguan@redhat.com>
Signed-off-by: Omar Sandoval <osandov@osandov.com>
---
v2->v3:
- Update description (thanks, Eryu)
- Remove unneeded touch

v1->v2:
- Simpler test: just depends on umount of the bind mount succeeding
  instead of running find. Without the patch applied, the bind mount
  will disappear so umount will fail.
- Fix Eryu's comments (better subject, copyright, use
  _btrfs_get_subvolid)

 tests/btrfs/089     | 79 +++++++++++++++++++++++++++++++++++++++++++++++++++++
 tests/btrfs/089.out |  2 ++
 tests/btrfs/group   |  1 +
 3 files changed, 82 insertions(+)
 create mode 100755 tests/btrfs/089
 create mode 100644 tests/btrfs/089.out

diff --git a/tests/btrfs/089 b/tests/btrfs/089
new file mode 100755
index 000000000000..537269824b62
--- /dev/null
+++ b/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
diff --git a/tests/btrfs/089.out b/tests/btrfs/089.out
new file mode 100644
index 000000000000..a7fcdee9b767
--- /dev/null
+++ b/tests/btrfs/089.out
@@ -0,0 +1,2 @@
+QA output created by 089
+Silence is golden
diff --git a/tests/btrfs/group b/tests/btrfs/group
index ffe18bff0d21..616d060758c1 100644
--- a/tests/btrfs/group
+++ b/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
-- 
2.4.2