btrfs: add regression test for send with extrefs

Regression for btrfs send when an inode only has extended references
associated to it (no regular references present). This used to cause
incorrect access to a b+tree leaf, where an extended reference item
was accessed as if it were a regular reference item, causing unexpected
and unpredictable behaviour such as producing a random/weird path string
or a crash.

This issue is fixed by the following linux kernel btrfs patch:

   Btrfs: send, fix incorrect ref access when using extrefs

Signed-off-by: Filipe David Borba Manana <fdmanana@gmail.com>
Reviewed-by: Dave Chinner <dchinner@redhat.com>
Signed-off-by: Dave Chinner <david@fromorbit.com>

tests/btrfs/050

@@ -0,0 +1,109 @@
+#! /bin/bash
+# FS QA Test No. btrfs/050
+#
+# Regression for btrfs send when an inode only has extended references
+# associated to it (no regular references present). This used to cause
+# incorrect access to a b+tree leaf, where an extended reference item
+# was accessed as if it were a regular reference item, causing unexpected
+# and unpredictable behaviour such as producing a random/weird path string
+# or a crash.
+#
+# This issue is fixed by the following linux kernel btrfs patch:
+#
+#   Btrfs: send, fix incorrect ref access when using extrefs
+#
+#-----------------------------------------------------------------------
+# Copyright (c) 2014 Filipe Manana.  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 $send_files_dir
+    rm -fr $tmp
+}
+
+# get standard environment, filters and checks
+. ./common/rc
+. ./common/filter
+
+# real QA test starts here
+_supported_fs btrfs
+_supported_os Linux
+_require_scratch
+_require_fssum
+_need_to_be_root
+
+send_files_dir=$TEST_DIR/btrfs-test-$seq
+
+rm -f $seqres.full
+rm -fr $send_files_dir
+mkdir $send_files_dir
+
+_scratch_mkfs "-O extref" >/dev/null 2>&1
+_scratch_mount
+
+# 2550 hard links is enough to cause creation of extended references
+# even if the leaf/node size is 64Kb (largest possible).
+NUM_LINKS=2550
+TEST_PATH=$SCRATCH_MNT/home/john/files/series/qwerty
+
+mkdir -p $TEST_PATH
+touch $TEST_PATH/foobar
+
+# Create a bunch of hard links for the file, such that at least one
+# inode extended reference item is created.
+for i in `seq 1 $NUM_LINKS`; do
+	ln $TEST_PATH/foobar $TEST_PATH/foobar_link_`printf "%04d" $i`
+done
+
+# The only link we'll have alive at the end.
+ln $TEST_PATH/foobar $TEST_PATH/final_foobar_name
+
+# Now delete all previous hard links (except the last one). This will
+# remove the regular inode reference item from the b+tree, and will
+# leave only an inode extended reference item, which is the condition
+# necessary to trigger the bug.
+rm -f $TEST_PATH/foobar
+for i in `seq 1 $NUM_LINKS`; do
+	rm -f $TEST_PATH/foobar_link_`printf "%04d" $i`
+done
+
+_run_btrfs_util_prog subvolume snapshot -r $SCRATCH_MNT $SCRATCH_MNT/mysnap1
+run_check $FSSUM_PROG -A -f -w $send_files_dir/1.fssum $SCRATCH_MNT/mysnap1
+_run_btrfs_util_prog send $SCRATCH_MNT/mysnap1 -f $send_files_dir/1.snap
+
+_scratch_unmount
+_check_scratch_fs
+
+_scratch_mkfs >/dev/null 2>&1
+_scratch_mount
+
+_run_btrfs_util_prog receive $SCRATCH_MNT -f $send_files_dir/1.snap
+run_check $FSSUM_PROG -r $send_files_dir/1.fssum $SCRATCH_MNT/mysnap1
+
+_check_scratch_fs
+
+status=0
+exit

tests/btrfs/050.out

@@ -0,0 +1 @@
+QA output created by 050

tests/btrfs/group

@@ -52,3 +52,4 @@
 047 auto quick
 048 auto quick
 049 auto quick
+050 auto