[PATCH v4 19/23] ext4: Reserve superblock fields for encoding information

[Gabriel Krisman Bertazi <krisman@collabora.com>]

From: Gabriel Krisman Bertazi <krisman@collabora.co.uk>

The s_encoding field stores a magic number indicating the encoding
format and version used globally by file and directory names in the
filesystem.

The s_encoding_flags defines policies for using the charset encoding,
like how to handle invalid sequences and what kind of normalization to
use.

Signed-off-by: Gabriel Krisman Bertazi <krisman@collabora.co.uk>
---
 fs/ext4/ext4.h | 7 ++++++-
 1 file changed, 6 insertions(+), 1 deletion(-)

diff --git a/fs/ext4/ext4.h b/fs/ext4/ext4.h
index 3f89d0ab08fc..52c9e8b948a0 100644
--- a/fs/ext4/ext4.h
+++ b/fs/ext4/ext4.h
@@ -1311,7 +1311,9 @@ struct ext4_super_block {
 	__u8	s_first_error_time_hi;
 	__u8	s_last_error_time_hi;
 	__u8	s_pad[2];
-	__le32	s_reserved[96];		/* Padding to the end of the block */
+	__le16  s_encoding;		/* Filename charset encoding */
+	__le16  s_encoding_flags;	/* Filename charset encoding flags */
+	__le32	s_reserved[95];		/* Padding to the end of the block */
 	__le32	s_checksum;		/* crc32c(superblock) */
 };
 
@@ -1661,6 +1663,7 @@ static inline void ext4_clear_state_flags(struct ext4_inode_info *ei)
 #define EXT4_FEATURE_INCOMPAT_LARGEDIR		0x4000 /* >2GB or 3-lvl htree */
 #define EXT4_FEATURE_INCOMPAT_INLINE_DATA	0x8000 /* data in inode */
 #define EXT4_FEATURE_INCOMPAT_ENCRYPT		0x10000
+#define EXT4_FEATURE_INCOMPAT_FNAME_ENCODING	0x20000
 
 #define EXT4_FEATURE_COMPAT_FUNCS(name, flagname) \
 static inline bool ext4_has_feature_##name(struct super_block *sb) \
@@ -1749,6 +1752,7 @@ EXT4_FEATURE_INCOMPAT_FUNCS(csum_seed,		CSUM_SEED)
 EXT4_FEATURE_INCOMPAT_FUNCS(largedir,		LARGEDIR)
 EXT4_FEATURE_INCOMPAT_FUNCS(inline_data,	INLINE_DATA)
 EXT4_FEATURE_INCOMPAT_FUNCS(encrypt,		ENCRYPT)
+EXT4_FEATURE_INCOMPAT_FUNCS(fname_encoding,	FNAME_ENCODING)
 
 #define EXT2_FEATURE_COMPAT_SUPP	EXT4_FEATURE_COMPAT_EXT_ATTR
 #define EXT2_FEATURE_INCOMPAT_SUPP	(EXT4_FEATURE_INCOMPAT_FILETYPE| \
@@ -1776,6 +1780,7 @@ EXT4_FEATURE_INCOMPAT_FUNCS(encrypt,		ENCRYPT)
 					 EXT4_FEATURE_INCOMPAT_MMP | \
 					 EXT4_FEATURE_INCOMPAT_INLINE_DATA | \
 					 EXT4_FEATURE_INCOMPAT_ENCRYPT | \
+					 EXT4_FEATURE_INCOMPAT_FNAME_ENCODING | \
 					 EXT4_FEATURE_INCOMPAT_CSUM_SEED | \
 					 EXT4_FEATURE_INCOMPAT_LARGEDIR)
 #define EXT4_FEATURE_RO_COMPAT_SUPP	(EXT4_FEATURE_RO_COMPAT_SPARSE_SUPER| \
-- 
2.20.0.rc2