#! /bin/bash
# SPDX-License-Identifier: GPL-2.0
# Copyright (c) Meta Platforms, Inc. and affiliates.
#
# FS QA Test No. 604
#
# Regression test for patch "xfs: fix internal error from AGFL exhaustion".
#
. ./common/preamble
_begin_fstest auto prealloc punch

. ./common/filter

_supported_fs xfs
_require_scratch
_require_xfs_io_command "falloc"
_require_xfs_io_command "fpunch"
_require_test_program punch-alternating
_fixed_by_kernel_commit f63a5b3769ad "xfs: fix internal error from AGFL exhaustion"

# Disable the rmapbt so we only need to worry about splitting the bnobt and
# cntbt at the same time.
opts=
if $MKFS_XFS_PROG |& grep -q rmapbt; then
	opts="-m rmapbt=0"
fi
_scratch_mkfs $opts | _filter_mkfs > /dev/null 2> "$tmp.mkfs"
. "$tmp.mkfs"
_scratch_mount

alloc_block_len=$((_fs_has_crcs ? 56 : 16))
allocbt_leaf_maxrecs=$(((dbsize - alloc_block_len) / 8))
allocbt_node_maxrecs=$(((dbsize - alloc_block_len) / 12))

# Create a big file with a size such that the punches below create the exact
# free extents we want.
num_holes=$((allocbt_leaf_maxrecs * allocbt_node_maxrecs - 1))
falloc_size=$((9 * dbsize + num_holes * dbsize * 2))
$XFS_IO_PROG -c "falloc 0 $falloc_size" -f "$SCRATCH_MNT/big" ||
       _notrun "Not enough space on device for falloc_size=$(echo "scale=2; $falloc_size / 1073741824" | $BC -q)GB and bs=$dbsize"

# Fill in any small free extents in AG 0. After this, there should be only one,
# large free extent.
_scratch_unmount
mapfile -t gaps < <(_scratch_xfs_db -c 'agf 0' -c 'addr cntroot' -c btdump |
	$SED_PROG -rn 's/^[0-9]+:\[[0-9]+,([0-9]+)\].*/\1/p' |
	tac | tail -n +2)
_scratch_mount
for gap_i in "${!gaps[@]}"; do
	gap=${gaps[$gap_i]}
	$XFS_IO_PROG -c "falloc 0 $((gap * dbsize))" -f "$SCRATCH_MNT/gap$gap_i"
done

# Create enough free space records to make the bnobt and cntbt both full,
# 2-level trees, plus one more record to make them split all the way to the
# root and become 3-level trees. After this, there is a 7-block free extent in
# the rightmost leaf of the cntbt, and all of the leaves of the cntbt other
# than the rightmost two are full. Without the fix, the free list is also
# empty.
$XFS_IO_PROG -c "fpunch $dbsize $((7 * dbsize))" "$SCRATCH_MNT/big"
"$here/src/punch-alternating" -o 9 "$SCRATCH_MNT/big"

# Do an arbitrary operation that refills the free list. Without the fix, this
# will allocate 6 blocks from the 7-block free extent in the rightmost leaf of
# the cntbt, then try to insert the remaining 1 block free extent in the
# leftmost leaf of the cntbt. But that leaf is full, so this tries to split the
# leaf and fails because the free list is empty, returning EFSCORRUPTED.
$XFS_IO_PROG -c "fpunch 0 $dbsize" "$SCRATCH_MNT/big"

echo "Silence is golden"
status=0
exit