fsck.f2fs: honor --linear-lookup=X for Android case

Behavior summary:
			Android		Distro
By default		disabled	enabled

Android case:

1) enabled -> disabled
- mkfs.f2fs -f -g android -O casefold -C utf8:nohashonly /dev/vdb
- dump.f2fs -d3 /dev/vdb |grep s_encoding_flags
s_encoding_flags                        [0x       0 : 0]
- fsck.f2fs -g android --nolinear-lookup=1 /dev/vdb
- dump.f2fs -d3 /dev/vdb |grep s_encoding_flags
s_encoding_flags                        [0x       2 : 2]

- mkfs.f2fs -f -g android -O casefold -C utf8:nohashonly /dev/vdb
- dump.f2fs -d3 /dev/vdb |grep s_encoding_flags
s_encoding_flags                        [0x       0 : 0]
- fsck.f2fs -g android /dev/vdb
- dump.f2fs -d3 /dev/vdb |grep s_encoding_flags
s_encoding_flags                        [0x       2 : 2]

2) disabled -> enabled
- mkfs.f2fs -f -g android -O casefold -C utf8:hashonly /dev/vdb
- dump.f2fs -d3 /dev/vdb |grep s_encoding_flags
s_encoding_flags                        [0x       2 : 2]
- fsck.f2fs -g android --nolinear-lookup=0 /dev/vdb
- dump.f2fs -d3 /dev/vdb |grep s_encoding_flags
s_encoding_flags                        [0x       0 : 0]

Distro case:

1) enabled -> disabled
- mkfs.f2fs -f -O casefold -C utf8:nohashonly /dev/vdb
- dump.f2fs -d3 /dev/vdb |grep s_encoding_flags
s_encoding_flags                        [0x       0 : 0]
- fsck.f2fs --nolinear-lookup=1 /dev/vdb
- dump.f2fs -d3 /dev/vdb |grep s_encoding_flags
s_encoding_flags                        [0x       2 : 2]

2) disabled -> enabled
- mkfs.f2fs -f -O casefold -C utf8:hashonly /dev/vdb
- dump.f2fs -d3 /dev/vdb |grep s_encoding_flags
s_encoding_flags                        [0x       2 : 2]
- fsck.f2fs --nolinear-lookup=0 /dev/vdb
- dump.f2fs -d3 /dev/vdb |grep s_encoding_flags
s_encoding_flags                        [0x       0 : 0]

3) default
- mkfs.f2fs -f -O casefold -C utf8:hashonly /dev/vdb
- dump.f2fs -d3 /dev/vdb |grep s_encoding_flags
s_encoding_flags                        [0x       2 : 2]
- fsck.f2fs /dev/vdb
- dump.f2fs -d3 /dev/vdb |grep s_encoding_flags
s_encoding_flags                        [0x       2 : 2]

- mkfs.f2fs -f -O casefold -C utf8:nohashonly /dev/vdb
- dump.f2fs -d3 /dev/vdb |grep s_encoding_flags
s_encoding_flags                        [0x       0 : 0]
- fsck.f2fs /dev/vdb
- dump.f2fs -d3 /dev/vdb |grep s_encoding_flags
s_encoding_flags                        [0x       0 : 0]

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

Author: chaseyu

fsck/fsck.c

@@ -2425,6 +2425,15 @@ void fsck_update_sb_flags(struct f2fs_sb_info *sbi)
 	struct f2fs_super_block *sb = F2FS_RAW_SUPER(sbi);
 	u16 flags = get_sb(s_encoding_flags);
 
+	/* handle default option for Android case */
+	if ((c.nolinear_lookup == LINEAR_LOOKUP_DEFAULT) &&
+		c.disabled_feature & F2FS_FEATURE_LINEAR_LOOKUP) {
+		c.nolinear_lookup = LINEAR_LOOKUP_DISABLE;
+		MSG(0, "Info: set default linear_lookup option: %s\n",
+			c.nolinear_lookup == LINEAR_LOOKUP_DISABLE ?
+			"disable" : "enable");
+	}
+
 	if (c.nolinear_lookup == LINEAR_LOOKUP_DEFAULT) {
 		MSG(0, "Info: Casefold: linear_lookup [%s]\n",
 			get_sb(s_encoding_flags) & F2FS_ENC_NO_COMPAT_FALLBACK_FL ?

fsck/main.c

@@ -226,7 +226,7 @@ static void add_default_options(void)
 			c.auto_fix = 1;
 
 			/* disable linear lookup by default */
-			c.nolinear_lookup = LINEAR_LOOKUP_DISABLE;
+			c.disabled_feature |= F2FS_FEATURE_LINEAR_LOOKUP;
 		} else if (c.func == RESIZE) {
 			c.force = 1;
 		}