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+#! /bin/bash
+# SPDX-License-Identifier: GPL-2.0
+# Copyright (c) 2025 Chao Yu. All Rights Reserved.
+#
+# FS QA Test No. f2fs/012
+#
+# This testcase checks whether linear lookup fallback works well
+# or not as below:
+# 1.create file w/ red heart as its filename
+# 2.inject wrong hash code to the file
+# 3.disable linear lookup, expect lookup failure
+# 4.enable linear lookup, expect lookup succeed
+#
+. ./common/preamble
+_begin_fstest auto quick casefold
+
+_fixed_by_kernel_commit 91b587ba79e1 \
+ "f2fs: Introduce linear search for dentries"
+
+export LC_ALL=C.UTF-8
+_require_scratch
+_require_command "$F2FS_IO_PROG" f2fs_io
+_require_command "$F2FS_INJECT_PROG" inject.f2fs
+
+check_lookup()
+{
+ local nolinear_lookup=$1
+ local dir=$SCRATCH_MNT/dir
+ # red heart charactor in unicode format
+ local redheart=$dir/$'\u2764\ufe0f'
+
+ _scratch_mkfs -O casefold -C utf8 >> $seqres.full
+ _scratch_mount
+
+ mkdir $dir
+ $F2FS_IO_PROG setflags casefold $dir >> $seqres.full
+ touch $redheart
+ ino=`stat -c '%i' $redheart`
+ _scratch_unmount
+
+ # should tune nolinear_lookup feature before fault injection
+ $F2FS_FSCK_PROG --nolinear-lookup=$nolinear_lookup $SCRATCH_DEV >> $seqres.full
+
+ # check whether linear_lookup is changed as expected
+ if [ $nolinear_lookup == "1" ]; then
+ $F2FS_FSCK_PROG $SCRATCH_DEV | grep -q "linear_lookup \[disable\]" || \
+ _fail "linear_lookup is not disabled"
+ else
+ $F2FS_FSCK_PROG $SCRATCH_DEV | grep -q "linear_lookup \[enable\]" || \
+ _fail "linear_lookup is not enabled"
+ fi
+
+ $F2FS_INJECT_PROG --dent --mb d_hash --nid $ino --val 0x9a2ea068 $SCRATCH_DEV >> $seqres.full
+
+ _scratch_mount
+ if [ $nolinear_lookup == "1" ]; then
+ [ -f $redheart ] && _fail "red heart file should not exist"
+ else
+ [ -f $redheart ] || _fail "red heart file should exist"
+ fi
+ _scratch_unmount
+
+ # to avoid _check_filesystems failure in the end of test
+ _repair_scratch_fs >> $seqres.full
+}
+
+check_lookup 1
+check_lookup 0
+
+echo "Silence is golden"
+
+status=0
+exit
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+QA output created by 012
+Silence is golden
As Han Qi reported in bugzilla [1], commit 5c26d2f1d3f5 ("unicode: Don't special case ignorable code points") changes logic to handle ignorable code points, when we handle filename which has special unicode charactor like red heart ❤️, utf8_casefold() may return different length than in the past, result in that f2fs cacluates hash code incorreclty, eventually, filename w/ special unicode charactor will not be found w/ the wrong hash code. f2fs has introduces a linear lookup fallback w/ commit 91b587ba79e1 ("f2fs: Introduce linear search for dentries"), once hash-based lookup fails, it tries linear lookup as a fallback. This patch can help to check whether linear lookup fallback works well or not. Firstly, we use below testcase to check how hash code changes: mkfs.f2fs -f -O casefold -C utf8 /dev/vda mount /dev/vda /mnt/f2fs mkdir /mnt/f2fs/dir/ f2fs_io setflags casefold /mnt/f2fs/dir touch /mnt/f2fs/dir/$'\u2764\ufe0f' umount /mnt/f2fs dump.f2fs -i 4 -d 3 /dev/vda dump.f2fs -b $blkaddr_of_dir -d 3 /dev/vda w/o ("unicode: Don't special case ignorable code points") [dump_dirent: 991] bitmap pos[0x2] name[❤️] len[0x6] hash[0x19dd7132] ino[0x5] type[0x1] [dump_dirent: 998] name(hex)[0xe2 0x9d 0xa4 0xef 0xb8 0x8f 0x0] w/ ("unicode: Don't special case ignorable code points") [dump_dirent: 991] bitmap pos[0x2] name[❤️] len[0x6] hash[0x9a2ea068] ino[0x5] type[0x1] [dump_dirent: 998] name(hex)[0xe2 0x9d 0xa4 0xef 0xb8 0x8f 0x0] Correct hash code: 0x19dd7132 Wrong hash code: 0x9a2ea068 So, we can test as below: 1. create file w/ red heart as its filename 2. inject wrong hash code to the file 3. disable linear lookup, expect lookup failure 4. enable linear lookup, expect lookup succeed [1] https://bugzilla.kernel.org/show_bug.cgi?id=219586 Cc: Jaegeuk Kim <jaegeuk@kernel.org> Cc: Daniel Lee <chullee@google.com> Signed-off-by: Chao Yu <chao@kernel.org> --- v2: - tune linear_lookup feature before fault injection - check status after tuning linear_lookup feature - clean up codes tests/f2fs/012 | 73 ++++++++++++++++++++++++++++++++++++++++++++++ tests/f2fs/012.out | 2 ++ 2 files changed, 75 insertions(+) create mode 100755 tests/f2fs/012 create mode 100644 tests/f2fs/012.out