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 $blkaddr_of_dir -d 3 /dev/vda
w/o ("unicode: Don't special case ignorable code points")
[dump_dirent: 991] bitmap pos[0x2] name[❤️] len[0x6] hash[0x19dd7132] ino[0x5]
type[0x1]
[dump_dirent: 998] name(hex)[0xe2 0x9d 0xa4 0xef 0xb8 0x8f 0x0]
w/ ("unicode: Don't special case ignorable code points")
[dump_dirent: 991] bitmap pos[0x2] name[❤️] len[0x6] hash[0x9a2ea068] ino[0x5]
type[0x1]
[dump_dirent: 998] name(hex)[0xe2 0x9d 0xa4 0xef 0xb8 0x8f 0x0]
Correct hash code: 0x19dd7132
Wrong hash code: 0x9a2ea068
So, we can test as below:
1. create file w/ red heart as its filename
2. inject wrong hash code to the file
3. disable linear lookup, expect lookup failure
4. enable linear lookup, expect lookup succeed
[1] https://bugzilla.kernel.org/show_bug.cgi?id=219586
Cc: Jaegeuk Kim <jaeg...@kernel.org>
Cc: Daniel Lee <chul...@google.com>
Signed-off-by: Chao Yu <c...@kernel.org>
---
tests/f2fs/012 | 54 ++++++++++++++++++++++++++++++++++++++++++++++
tests/f2fs/012.out | 2 ++
2 files changed, 56 insertions(+)
create mode 100755 tests/f2fs/012
create mode 100644 tests/f2fs/012.out
diff --git a/tests/f2fs/012 b/tests/f2fs/012
new file mode 100755
index 00000000..fdc30bea
--- /dev/null
+++ b/tests/f2fs/012
@@ -0,0 +1,54 @@
+#! /bin/bash
+# SPDX-License-Identifier: GPL-2.0
+# Copyright (c) 2025 Chao Yu. All Rights Reserved.
+#
+# FS QA Test No. f2fs/012
+#
+# This testcase checks whether linear lookup fallback works well
+# or not as below:
+# 1.create file w/ red heart as its filename
+# 2.inject wrong hash code to the file
+# 3.disable linear lookup, expect lookup failure
+# 4.enable linear lookup, expect lookup succeed
+#
+. ./common/preamble
+_begin_fstest auto quick casefold
+
+_fixed_by_kernel_commit 91b587ba79e1 \
+ "f2fs: Introduce linear search for dentries"
+
+export LC_ALL=C.UTF-8
+_require_scratch
+_require_command "$F2FS_IO_PROG" f2fs_io
+_require_command "$F2FS_INJECT_PROG" inject.f2fs
+
+_scratch_mkfs -f -O casefold -C utf8 >> $seqres.full
+_scratch_mount
+
+dir=$SCRATCH_MNT/dir
+
+# red heart charactor in unicode format
+redheart=$dir/$'\u2764\ufe0f'
+
+mkdir $dir
+$F2FS_IO_PROG setflags casefold $dir >> $seqres.full
+touch $redheart
+ino=`stat -c '%i' $redheart`
+_scratch_unmount
+
+$F2FS_INJECT_PROG --dent --mb d_hash --nid $ino --val 0x9a2ea068 $SCRATCH_DEV
>> $seqres.full
+
+$F2FS_FSCK_PROG --nolinear-lookup=1 $SCRATCH_DEV >> $seqres.full
+_scratch_mount
+[ -f $redheart ] && _fail "red heart file should not exist"
+_scratch_unmount
+
+$F2FS_FSCK_PROG --nolinear-lookup=0 $SCRATCH_DEV >> $seqres.full
+_scratch_mount
+[ -f $redheart ] || _fail "red heart file should exist"
+_scratch_unmount
+
+echo "Silence is golden"
+
+status=0
+exit
diff --git a/tests/f2fs/012.out b/tests/f2fs/012.out
new file mode 100644
index 00000000..3afeca2f
--- /dev/null
+++ b/tests/f2fs/012.out
@@ -0,0 +1,2 @@
+QA output created by 012
+Silence is golden
--
2.49.0
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