[PATCH] f2fs/012: adapt lookup_mode=x mount option

[Chao Yu <chao@kernel.org>]

w/ below change [1], f2fs will enable lookup_mode=perf by default, it
will change f2fs dirent lookup method from linear based lookup to hash
based lookup.

So that, f2fs will ignore sb.s_encoding_flags by default, which is not
compatible w/ f2fs/012 testcase, in where it will control lookup method
by configuring this flag w/ fsck.f2fs.

To avoid failure of f2fs/012, let's check whether f2fs has supported
"lookup_mode=auto" mount option, mount w/ the option if it can,
otherwise, don't.

[1] https://lore.kernel.org/linux-f2fs-devel/20250805065228.1473089-1-chullee@google.com

Cc: Daniel Lee <chullee@google.com>
Signed-off-by: Chao Yu <chao@kernel.org>
---
 tests/f2fs/012 | 13 +++++++++++--
 1 file changed, 11 insertions(+), 2 deletions(-)

diff --git a/tests/f2fs/012 b/tests/f2fs/012
index b3df9a8f..15fc8f0c 100755
--- a/tests/f2fs/012
+++ b/tests/f2fs/012
@@ -22,6 +22,15 @@ _require_scratch_nocheck
 _require_command "$F2FS_IO_PROG" f2fs_io
 _require_command "$F2FS_INJECT_PROG" inject.f2fs
 
+#check whether f2fs supports "lookup_mode=x" mount option
+mntopt=""
+_scratch_mkfs -O casefold -C utf8 >> $seqres.full
+_try_scratch_mount "-o lookup_mode=auto"
+if [ $? == 0 ]; then
+	mntopt="-o lookup_mode=auto"
+	_scratch_unmount
+fi
+
 check_lookup()
 {
 	local nolinear_lookup=$1
@@ -30,7 +39,7 @@ check_lookup()
 	local redheart=$dir/$'\u2764\ufe0f'
 
 	_scratch_mkfs -O casefold -C utf8 >> $seqres.full
-	_scratch_mount
+	_scratch_mount $mntopt
 
 	mkdir $dir
 	$F2FS_IO_PROG setflags casefold $dir >> $seqres.full
@@ -52,7 +61,7 @@ check_lookup()
 
 	$F2FS_INJECT_PROG --dent --mb d_hash --nid $ino --val 0x9a2ea068 $SCRATCH_DEV >> $seqres.full
 
-	_scratch_mount
+	_scratch_mount $mntopt
 	if [ $nolinear_lookup == "1" ]; then
 		[ -f $redheart ] && _fail "red heart file should not exist"
 	else
-- 
2.40.1