[PATCH] fstests: test a regression with btrfs extent reference collisions

[Josef Bacik <josef@toxicpanda.com>]

This is a regression test for a problem where we would flip read only if
we reflink'ed enough extents to generate key'ed references, and then got
a hash collision with those references.  This is a test for the fix

	btrfs: do not error out if the extent ref hash doesn't match

and is relatively straightforward, simply generate such a file and
watch for fireworks.

Signed-off-by: Josef Bacik <josef@toxicpanda.com>
---
 tests/btrfs/231     | 81 +++++++++++++++++++++++++++++++++++++++++++++
 tests/btrfs/231.out | 11 ++++++
 tests/btrfs/group   |  1 +
 3 files changed, 93 insertions(+)
 create mode 100755 tests/btrfs/231
 create mode 100644 tests/btrfs/231.out

diff --git a/tests/btrfs/231 b/tests/btrfs/231
new file mode 100755
index 00000000..b4787f9f
--- /dev/null
+++ b/tests/btrfs/231
@@ -0,0 +1,81 @@
+#! /bin/bash
+# SPDX-License-Identifier: GPL-2.0
+# Copyright (c) 2021 Josef Bacik.  All Rights Reserved.
+#
+# FS QA Test 231
+#
+# This is a regression test for a problem fixed by
+#
+#    btrfs: do not error out if the extent ref hash doesn't match
+#
+# Simply generate a file with a lot of extent references, then reflink in a few
+# offsets that will generate hash collisions, sync and validate we can still
+# write to the file system.
+
+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/reflink
+
+# remove previous $seqres.full before test
+rm -f $seqres.full
+
+# real QA test starts here
+_supported_fs btrfs
+_require_test
+_require_scratch_reflink
+
+_scratch_mkfs >>$seqres.full 2>&1
+_scratch_mount
+
+FILE=$SCRATCH_MNT/file
+
+# Create a 1m extent to reflink
+$XFS_IO_PROG -f -c "pwrite 0 1M" -c "fsync" $FILE | _filter_xfs_io
+
+# Generate a bunch of extent references so we're forced to use key'ed extent
+# references.
+offset=2
+for i in {0..10000}
+do
+	$XFS_IO_PROG -c "reflink ${FILE} 0 ${offset}M 1M" $FILE \
+		> /dev/null 2>&1
+	offset=$(( offset + 2 ))
+done
+
+# Our key is
+#
+# key.objectid = bytenr
+# key.type = BTRFS_EXTENT_DATA_REF_KEY
+# key.offset = hash(tree, inode, offset)
+#
+# The tree id is 5, the inode is 257, and the reflink'ed offset is 0, the below
+# offsets generate a hash collision with that offset.  We only need two to
+# collide, but if it's worth doing it's worth overdoing.
+$XFS_IO_PROG -c "reflink ${FILE} 0 17999258914816 1M" $FILE | _filter_xfs_io
+$XFS_IO_PROG -c "reflink ${FILE} 0 35998517829632 1M" $FILE | _filter_xfs_io
+$XFS_IO_PROG -c "reflink ${FILE} 0 53752752058368 1M" $FILE | _filter_xfs_io
+
+# Sync to make sure this works, it'll error out if we abort the transaction, but
+# write a file just to make sure
+$BTRFS_UTIL_PROG filesystem sync $SCRATCH_MNT
+$XFS_IO_PROG -f -c "pwrite 0 1M" $SCRATCH_MNT/write | _filter_xfs_io
+
+# success, all done
+status=0
+exit
diff --git a/tests/btrfs/231.out b/tests/btrfs/231.out
new file mode 100644
index 00000000..f52c71ac
--- /dev/null
+++ b/tests/btrfs/231.out
@@ -0,0 +1,11 @@
+QA output created by 231
+wrote 1048576/1048576 bytes at offset 0
+XXX Bytes, X ops; XX:XX:XX.X (XXX YYY/sec and XXX ops/sec)
+linked 1048576/1048576 bytes at offset 17999258914816
+XXX Bytes, X ops; XX:XX:XX.X (XXX YYY/sec and XXX ops/sec)
+linked 1048576/1048576 bytes at offset 35998517829632
+XXX Bytes, X ops; XX:XX:XX.X (XXX YYY/sec and XXX ops/sec)
+linked 1048576/1048576 bytes at offset 53752752058368
+XXX Bytes, X ops; XX:XX:XX.X (XXX YYY/sec and XXX ops/sec)
+wrote 1048576/1048576 bytes at offset 0
+XXX Bytes, X ops; XX:XX:XX.X (XXX YYY/sec and XXX ops/sec)
diff --git a/tests/btrfs/group b/tests/btrfs/group
index a7c65983..65cedf7f 100644
--- a/tests/btrfs/group
+++ b/tests/btrfs/group
@@ -233,3 +233,4 @@
 228 auto quick volume
 229 auto quick send clone
 230 auto quick qgroup limit
+231 auto
-- 
2.26.2