btrfs: add test for quota groups and drop snapshot

Test btrfs quota group consistency operations during snapshot
delete. Btrfs has had long standing issues with drop snapshot
failing to properly account for quota groups. This test crafts
several snapshot trees with shared and exclusive elements. One of
the trees is removed and then quota group consistency is checked.

This issue is fixed by the following linux kernel patches:
   Btrfs: use btrfs_get_fs_root in resolve_indirect_ref
   Btrfs: keep dropped roots in cache until transaciton commit
   btrfs: qgroup: account shared subtree during snapshot delete

Signed-off-by: Mark Fasheh <mfasheh@suse.de>

tests/btrfs/098

@@ -0,0 +1,166 @@
+#! /bin/bash
+# FS QA Test No. btrfs/098
+#
+# Test btrfs quota group consistency operations during snapshot
+# delete. Btrfs has had long standing issues with drop snapshot
+# failing to properly account for quota groups. This test crafts
+# several snapshot trees with shared and exclusive elements. One of
+# the trees is removed and then quota group consistency is checked.
+#
+# This issue is fixed by the following linux kernel patches:
+#
+#    Btrfs: use btrfs_get_fs_root in resolve_indirect_ref
+#    Btrfs: keep dropped roots in cache until transaciton commit
+#    btrfs: qgroup: account shared subtree during snapshot delete
+#
+#-----------------------------------------------------------------------
+# Copyright (C) 2015 SUSE Linux Products GmbH. 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"
+
+tmp=/tmp/$$
+status=1	# failure is the default!
+trap "_cleanup; exit \$status" 0 1 2 3 15
+
+_cleanup()
+{
+	rm -fr $tmp
+}
+
+# get standard environment, filters and checks
+. ./common/rc
+. ./common/filter
+
+# real QA test starts here
+_supported_fs btrfs
+_supported_os Linux
+_require_scratch
+_need_to_be_root
+
+rm -f $seqres.full
+
+# Create an fs tree of a given height at a target location. This is
+# done by agressively creating inline extents to expand the number of
+# nodes required. We also add an traditional extent so that
+# drop_snapshot is forced to walk at least one extent that is not
+# stored in metadata.
+#
+# NOTE: The ability to vary tree height for this test is very useful
+# for debugging problems with drop_snapshot(). As a result we retain
+# that parameter even though the test below always does level 2 trees.
+_explode_fs_tree () {
+    local level=$1;
+    local loc="$2";
+    local bs=4095;
+    local cnt=1;
+    local n;
+
+    if [ -z $loc ]; then
+	echo "specify location for fileset"
+	exit 1;
+    fi
+
+    case $level in
+	1)# this always reproduces level 1 trees	
+	    n=10;
+	    ;;
+	2)# this always reproduces level 2 trees
+	    n=1500
+	    ;;
+	3)# this always reproduces level 3 trees
+	    n=1000000;
+	    ;;
+	*)
+	    echo "Can't make level $level trees";
+	    exit 1;
+	    ;;
+    esac
+
+    mkdir -p $loc
+    for i in `seq -w 1 $n`;
+    do
+	dd status=none if=/dev/zero of=$loc/file$i bs=$bs count=$cnt
+    done
+
+    bs=131072
+    cnt=1
+    dd status=none if=/dev/zero of=$loc/extentfile bs=$bs count=$cnt
+}
+
+# Force the default leaf size as the calculations for making our btree
+# heights are based on that.
+run_check _scratch_mkfs "--nodesize 16384"
+_scratch_mount
+
+# populate the default subvolume and create a snapshot ('snap1')
+_explode_fs_tree 1 $SCRATCH_MNT/files
+_run_btrfs_util_prog subvolume snapshot $SCRATCH_MNT $SCRATCH_MNT/snap1
+
+# create new btree nodes in this snapshot. They will become shared
+# with the next snapshot we create.
+_explode_fs_tree 1 $SCRATCH_MNT/snap1/files-snap1
+
+# create our final snapshot ('snap2'), populate it with
+# exclusively owned nodes.
+#
+# As a result of this action, snap2 will get an implied ref to the
+# 128K extent created in the default subvolume.
+_run_btrfs_util_prog subvolume snapshot $SCRATCH_MNT/snap1 $SCRATCH_MNT/snap2
+_explode_fs_tree 1 $SCRATCH_MNT/snap2/files-snap2
+
+# Enable qgroups now that we have our filesystem prepared. This
+# will kick off a scan which we will have to wait for.
+_run_btrfs_util_prog quota enable $SCRATCH_MNT
+_run_btrfs_util_prog quota rescan -w $SCRATCH_MNT
+
+# Remount to clear cache, force everything to disk
+_scratch_unmount
+_scratch_mount
+
+# Finally, delete snap1 to trigger btrfs_drop_snapshot(). This
+# snapshot is most interesting to delete because it will cause some
+# nodes to go exclusively owned for snap2, while some will stay shared
+# with the default subvolume. That exercises a maximum of the drop
+# snapshot/qgroup interactions.
+#
+# snap2s imlied ref from to the 128K extent in files/ can be lost by
+# the root finding code in qgroup accounting due to snap1 no longer
+# providing a path to it. This was fixed by the first two patches
+# referenced above.
+_run_btrfs_util_prog subvolume delete $SCRATCH_MNT/snap1
+
+# There is no way from userspace to force btrfs_drop_snapshot to run
+# at a given time (even via mount/unmount). We must wait for it to
+# start and complete. This is the shortest time on my tests systems I
+# have found which always allows drop_snapshot to run to completion.
+sleep 45
+
+_scratch_unmount
+
+# generate a qgroup report and look for inconsistent groups
+#  - don't use _run_btrfs_util_prog here as it captures the output and
+#    we need to grep it.
+$BTRFS_UTIL_PROG check --qgroup-report $SCRATCH_DEV 2>&1 | grep -E -q "Counts for qgroup.*are different"
+if [ $? -ne 0 ]; then
+    status=0
+fi
+
+exit

tests/btrfs/group

@@ -100,3 +100,4 @@
 095 auto quick metadata
 096 auto quick clone
 097 auto quick send clone
+098 auto qgroup