f2fs: sysfs: add encoding_flags entry

This patch adds a new sysfs entry /sys/fs/f2fs/<disk>/encoding_flags,
it is a read-only entry to show the value of sb.s_encoding_flags, the
value is hexadecimal.

============================     ==========
Flag_Name                        Flag_Value
============================     ==========
SB_ENC_STRICT_MODE_FL            0x00000001
SB_ENC_NO_COMPAT_FALLBACK_FL     0x00000002
============================     ==========

case#1
mkfs.f2fs -f -O casefold -C utf8:strict /dev/vda
mount /dev/vda /mnt/f2fs
cat /sys/fs/f2fs/vda/encoding_flags
1

case#2
mkfs.f2fs -f -O casefold -C utf8 /dev/vda
fsck.f2fs --nolinear-lookup=1 /dev/vda
mount /dev/vda /mnt/f2fs
cat /sys/fs/f2fs/vda/encoding_flags
2

Signed-off-by: Chao Yu <chao@kernel.org>
Signed-off-by: Jaegeuk Kim <jaegeuk@kernel.org>

Author: chaseyu

Documentation/ABI/testing/sysfs-fs-f2fs

@@ -846,3 +846,16 @@ Description:	For several zoned storage devices, vendors will provide extra space
 		reserved_blocks. However, it is not enough, since this extra space should
 		not be shown to users. So, with this new sysfs node, we can hide the space
 		by substracting reserved_blocks from total bytes.
+
+What:		/sys/fs/f2fs/<disk>/encoding_flags
+Date:		April 2025
+Contact:	"Chao Yu" <chao@kernel.org>
+Description:	This is a read-only entry to show the value of sb.s_encoding_flags, the
+		value is hexadecimal.
+
+		============================     ==========
+		Flag_Name                        Flag_Value
+		============================     ==========
+		SB_ENC_STRICT_MODE_FL            0x00000001
+		SB_ENC_NO_COMPAT_FALLBACK_FL     0x00000002
+		============================     ==========

fs/f2fs/sysfs.c

@@ -274,6 +274,13 @@ static ssize_t encoding_show(struct f2fs_attr *a,
 	return sysfs_emit(buf, "(none)\n");
 }
 
+static ssize_t encoding_flags_show(struct f2fs_attr *a,
+		struct f2fs_sb_info *sbi, char *buf)
+{
+	return sysfs_emit(buf, "%x\n",
+		le16_to_cpu(F2FS_RAW_SUPER(sbi)->s_encoding_flags));
+}
+
 static ssize_t mounted_time_sec_show(struct f2fs_attr *a,
 		struct f2fs_sb_info *sbi, char *buf)
 {
@@ -1158,6 +1165,7 @@ F2FS_GENERAL_RO_ATTR(features);
 F2FS_GENERAL_RO_ATTR(current_reserved_blocks);
 F2FS_GENERAL_RO_ATTR(unusable);
 F2FS_GENERAL_RO_ATTR(encoding);
+F2FS_GENERAL_RO_ATTR(encoding_flags);
 F2FS_GENERAL_RO_ATTR(mounted_time_sec);
 F2FS_GENERAL_RO_ATTR(main_blkaddr);
 F2FS_GENERAL_RO_ATTR(pending_discard);
@@ -1270,6 +1278,7 @@ static struct attribute *f2fs_attrs[] = {
 	ATTR_LIST(reserved_blocks),
 	ATTR_LIST(current_reserved_blocks),
 	ATTR_LIST(encoding),
+	ATTR_LIST(encoding_flags),
 	ATTR_LIST(mounted_time_sec),
 #ifdef CONFIG_F2FS_STAT_FS
 	ATTR_LIST(cp_foreground_calls),