tests/btrfs/302

#! /bin/bash
# SPDX-License-Identifier: GPL-2.0
# Copyright (C) 2023 SUSE Linux Products GmbH. All Rights Reserved.
#
# FS QA Test 302
#
# Test that snapshotting a new subvolume (created in the current transaction)
# that has a btree with a height > 1, works and does not result in a filesystem
# corruption.
#
# This exercises a regression introduced in kernel 6.5 by the kernel commit:
#
#    1b53e51a4a8f ("btrfs: don't commit transaction for every subvol create")
#
. ./common/preamble
_begin_fstest auto quick snapshot subvol

. ./common/filter

_require_scratch
_require_fssum

_fixed_by_kernel_commit eb96e221937a \
	"btrfs: fix unwritten extent buffer after snapshotting a new subvolume"

# Use a filesystem with a 64K node size so that we have the same node size on
# every machine regardless of its page size (on x86_64 default node size is 16K
# due to the 4K page size, while on PPC it's 64K by default). This way we can
# make sure we are able to create a btree for the subvolume with a height of 2.
_scratch_mkfs -n 64K >> $seqres.full 2>&1 || _fail "mkfs failed"
_scratch_mount

$BTRFS_UTIL_PROG subvolume create $SCRATCH_MNT/subvol | _filter_scratch

# Create a few empty files on the subvolume, this bumps its btree height to 2
# (root node at level 1 and 2 leaves).
for ((i = 1; i <= 300; i++)); do
	echo -n > $SCRATCH_MNT/subvol/file_$i
done

# Create a checksum of the subvolume's content.
fssum_file="$SCRATCH_MNT/checksum.fssum"
$FSSUM_PROG -A -f -w $fssum_file $SCRATCH_MNT/subvol

# Now create a snapshot of the subvolume and make it accessible from within the
# subvolume.
_btrfs subvolume snapshot -r $SCRATCH_MNT/subvol $SCRATCH_MNT/subvol/snap

# Now unmount and mount again the fs. We want to verify we are able to read all
# metadata for the snapshot from disk (no IO failures, etc).
_scratch_cycle_mount

# The snapshot's content should match the subvolume's content before we created
# the snapshot.
$FSSUM_PROG -r $fssum_file $SCRATCH_MNT/subvol/snap

# success, all done
status=0
exit