erofs: tidy up EROFS on-disk naming

 - Get rid of all "vle" (variable-length extents) expressions
   since they only expand overall name lengths unnecessarily;
 - Rename COMPRESSION_LEGACY to COMPRESSED_FULL;
 - Move on-disk directory definitions ahead of compression;
 - Drop unused extended attribute definitions;
 - Move inode ondisk union `i_u` out as `union erofs_inode_i_u`.

No actual logical change.
Signed-off-by: Gao Xiang <hsiangkao@linux.alibaba.com>
Reviewed-by: Yue Hu <huyue2@coolpad.com>
Reviewed-by: Chao Yu <chao@kernel.org>
Link: https://lore.kernel.org/r/20230331063149.25611-1-hsiangkao@linux.alibaba.com

fs/erofs/erofs_fs.h

@@ -82,32 +82,27 @@ struct erofs_super_block {
 };
 
 /*
- * erofs inode datalayout (i_format in on-disk inode):
+ * EROFS inode datalayout (i_format in on-disk inode):
  * 0 - uncompressed flat inode without tail-packing inline data:
- * inode, [xattrs], ... | ... | no-holed data
  * 1 - compressed inode with non-compact indexes:
- * inode, [xattrs], [map_header], extents ... | ...
  * 2 - uncompressed flat inode with tail-packing inline data:
- * inode, [xattrs], tailpacking data, ... | ... | no-holed data
  * 3 - compressed inode with compact indexes:
- * inode, [xattrs], map_header, extents ... | ...
  * 4 - chunk-based inode with (optional) multi-device support:
- * inode, [xattrs], chunk indexes ... | ...
  * 5~7 - reserved
  */
 enum {
 	EROFS_INODE_FLAT_PLAIN			= 0,
-	EROFS_INODE_FLAT_COMPRESSION_LEGACY	= 1,
+	EROFS_INODE_COMPRESSED_FULL		= 1,
 	EROFS_INODE_FLAT_INLINE			= 2,
-	EROFS_INODE_FLAT_COMPRESSION		= 3,
+	EROFS_INODE_COMPRESSED_COMPACT		= 3,
 	EROFS_INODE_CHUNK_BASED			= 4,
 	EROFS_INODE_DATALAYOUT_MAX
 };
 
 static inline bool erofs_inode_is_data_compressed(unsigned int datamode)
 {
-	return datamode == EROFS_INODE_FLAT_COMPRESSION ||
-		datamode == EROFS_INODE_FLAT_COMPRESSION_LEGACY;
+	return datamode == EROFS_INODE_COMPRESSED_COMPACT ||
+		datamode == EROFS_INODE_COMPRESSED_FULL;
 }
 
 /* bit definitions of inode i_format */
@@ -128,11 +123,30 @@ static inline bool erofs_inode_is_data_compressed(unsigned int datamode)
 #define EROFS_CHUNK_FORMAT_ALL	\
 	(EROFS_CHUNK_FORMAT_BLKBITS_MASK | EROFS_CHUNK_FORMAT_INDEXES)
 
+/* 32-byte on-disk inode */
+#define EROFS_INODE_LAYOUT_COMPACT	0
+/* 64-byte on-disk inode */
+#define EROFS_INODE_LAYOUT_EXTENDED	1
+
 struct erofs_inode_chunk_info {
 	__le16 format;		/* chunk blkbits, etc. */
 	__le16 reserved;
 };
 
+union erofs_inode_i_u {
+	/* total compressed blocks for compressed inodes */
+	__le32 compressed_blocks;
+
+	/* block address for uncompressed flat inodes */
+	__le32 raw_blkaddr;
+
+	/* for device files, used to indicate old/new device # */
+	__le32 rdev;
+
+	/* for chunk-based files, it contains the summary info */
+	struct erofs_inode_chunk_info c;
+};
+
 /* 32-byte reduced form of an ondisk inode */
 struct erofs_inode_compact {
 	__le16 i_format;	/* inode format hints */
@@ -143,29 +157,14 @@ struct erofs_inode_compact {
 	__le16 i_nlink;
 	__le32 i_size;
 	__le32 i_reserved;
-	union {
-		/* total compressed blocks for compressed inodes */
-		__le32 compressed_blocks;
-		/* block address for uncompressed flat inodes */
-		__le32 raw_blkaddr;
-
-		/* for device files, used to indicate old/new device # */
-		__le32 rdev;
-
-		/* for chunk-based files, it contains the summary info */
-		struct erofs_inode_chunk_info c;
-	} i_u;
-	__le32 i_ino;           /* only used for 32-bit stat compatibility */
+	union erofs_inode_i_u i_u;
+
+	__le32 i_ino;		/* only used for 32-bit stat compatibility */
 	__le16 i_uid;
 	__le16 i_gid;
 	__le32 i_reserved2;
 };
 
-/* 32-byte on-disk inode */
-#define EROFS_INODE_LAYOUT_COMPACT	0
-/* 64-byte on-disk inode */
-#define EROFS_INODE_LAYOUT_EXTENDED	1
-
 /* 64-byte complete form of an ondisk inode */
 struct erofs_inode_extended {
 	__le16 i_format;	/* inode format hints */
@@ -175,22 +174,9 @@ struct erofs_inode_extended {
 	__le16 i_mode;
 	__le16 i_reserved;
 	__le64 i_size;
-	union {
-		/* total compressed blocks for compressed inodes */
-		__le32 compressed_blocks;
-		/* block address for uncompressed flat inodes */
-		__le32 raw_blkaddr;
-
-		/* for device files, used to indicate old/new device # */
-		__le32 rdev;
-
-		/* for chunk-based files, it contains the summary info */
-		struct erofs_inode_chunk_info c;
-	} i_u;
-
-	/* only used for 32-bit stat compatibility */
-	__le32 i_ino;
+	union erofs_inode_i_u i_u;
 
+	__le32 i_ino;		/* only used for 32-bit stat compatibility */
 	__le32 i_uid;
 	__le32 i_gid;
 	__le64 i_mtime;
@@ -199,10 +185,6 @@ struct erofs_inode_extended {
 	__u8   i_reserved2[16];
 };
 
-#define EROFS_MAX_SHARED_XATTRS         (128)
-/* h_shared_count between 129 ... 255 are special # */
-#define EROFS_SHARED_XATTR_EXTENT       (255)
-
 /*
  * inline xattrs (n == i_xattr_icount):
  * erofs_xattr_ibody_header(1) + (n - 1) * 4 bytes
@@ -268,6 +250,22 @@ struct erofs_inode_chunk_index {
 	__le32 blkaddr;		/* start block address of this inode chunk */
 };
 
+/* dirent sorts in alphabet order, thus we can do binary search */
+struct erofs_dirent {
+	__le64 nid;     /* node number */
+	__le16 nameoff; /* start offset of file name */
+	__u8 file_type; /* file type */
+	__u8 reserved;  /* reserved */
+} __packed;
+
+/*
+ * EROFS file types should match generic FT_* types and
+ * it seems no need to add BUILD_BUG_ONs since potential
+ * unmatchness will break other fses as well...
+ */
+
+#define EROFS_NAME_LEN      255
+
 /* maximum supported size of a physical compression cluster */
 #define Z_EROFS_PCLUSTER_MAX_SIZE	(1024 * 1024)
 
@@ -337,10 +335,8 @@ struct z_erofs_map_header {
 	__u8	h_clusterbits;
 };
 
-#define Z_EROFS_VLE_LEGACY_HEADER_PADDING       8
-
 /*
- * Fixed-sized output compression on-disk logical cluster type:
+ * On-disk logical cluster type:
  *    0   - literal (uncompressed) lcluster
  *    1,3 - compressed lcluster (for HEAD lclusters)
  *    2   - compressed lcluster (for NONHEAD lclusters)
@@ -364,27 +360,27 @@ struct z_erofs_map_header {
  *        di_u.delta[1] = distance to the next HEAD lcluster
  */
 enum {
-	Z_EROFS_VLE_CLUSTER_TYPE_PLAIN		= 0,
-	Z_EROFS_VLE_CLUSTER_TYPE_HEAD1		= 1,
-	Z_EROFS_VLE_CLUSTER_TYPE_NONHEAD	= 2,
-	Z_EROFS_VLE_CLUSTER_TYPE_HEAD2		= 3,
-	Z_EROFS_VLE_CLUSTER_TYPE_MAX
+	Z_EROFS_LCLUSTER_TYPE_PLAIN	= 0,
+	Z_EROFS_LCLUSTER_TYPE_HEAD1	= 1,
+	Z_EROFS_LCLUSTER_TYPE_NONHEAD	= 2,
+	Z_EROFS_LCLUSTER_TYPE_HEAD2	= 3,
+	Z_EROFS_LCLUSTER_TYPE_MAX
 };
 
-#define Z_EROFS_VLE_DI_CLUSTER_TYPE_BITS        2
-#define Z_EROFS_VLE_DI_CLUSTER_TYPE_BIT         0
+#define Z_EROFS_LI_LCLUSTER_TYPE_BITS        2
+#define Z_EROFS_LI_LCLUSTER_TYPE_BIT         0
 
 /* (noncompact only, HEAD) This pcluster refers to partial decompressed data */
-#define Z_EROFS_VLE_DI_PARTIAL_REF		(1 << 15)
+#define Z_EROFS_LI_PARTIAL_REF		(1 << 15)
 
 /*
  * D0_CBLKCNT will be marked _only_ at the 1st non-head lcluster to store the
  * compressed block count of a compressed extent (in logical clusters, aka.
  * block count of a pcluster).
  */
-#define Z_EROFS_VLE_DI_D0_CBLKCNT		(1 << 11)
+#define Z_EROFS_LI_D0_CBLKCNT		(1 << 11)
 
-struct z_erofs_vle_decompressed_index {
+struct z_erofs_lcluster_index {
 	__le16 di_advise;
 	/* where to decompress in the head lcluster */
 	__le16 di_clusterofs;
@@ -401,25 +397,8 @@ struct z_erofs_vle_decompressed_index {
 	} di_u;
 };
 
-#define Z_EROFS_VLE_LEGACY_INDEX_ALIGN(size) \
-	(round_up(size, sizeof(struct z_erofs_vle_decompressed_index)) + \
-	 sizeof(struct z_erofs_map_header) + Z_EROFS_VLE_LEGACY_HEADER_PADDING)
-
-/* dirent sorts in alphabet order, thus we can do binary search */
-struct erofs_dirent {
-	__le64 nid;     /* node number */
-	__le16 nameoff; /* start offset of file name */
-	__u8 file_type; /* file type */
-	__u8 reserved;  /* reserved */
-} __packed;
-
-/*
- * EROFS file types should match generic FT_* types and
- * it seems no need to add BUILD_BUG_ONs since potential
- * unmatchness will break other fses as well...
- */
-
-#define EROFS_NAME_LEN      255
+#define Z_EROFS_FULL_INDEX_ALIGN(end)	\
+	(ALIGN(end, 8) + sizeof(struct z_erofs_map_header) + 8)
 
 /* check the EROFS on-disk layout strictly at compile time */
 static inline void erofs_check_ondisk_layout_definitions(void)
@@ -436,15 +415,15 @@ static inline void erofs_check_ondisk_layout_definitions(void)
 	BUILD_BUG_ON(sizeof(struct erofs_inode_chunk_info) != 4);
 	BUILD_BUG_ON(sizeof(struct erofs_inode_chunk_index) != 8);
 	BUILD_BUG_ON(sizeof(struct z_erofs_map_header) != 8);
-	BUILD_BUG_ON(sizeof(struct z_erofs_vle_decompressed_index) != 8);
+	BUILD_BUG_ON(sizeof(struct z_erofs_lcluster_index) != 8);
 	BUILD_BUG_ON(sizeof(struct erofs_dirent) != 12);
 	/* keep in sync between 2 index structures for better extendibility */
 	BUILD_BUG_ON(sizeof(struct erofs_inode_chunk_index) !=
-		     sizeof(struct z_erofs_vle_decompressed_index));
+		     sizeof(struct z_erofs_lcluster_index));
 	BUILD_BUG_ON(sizeof(struct erofs_deviceslot) != 128);
 
-	BUILD_BUG_ON(BIT(Z_EROFS_VLE_DI_CLUSTER_TYPE_BITS) <
-		     Z_EROFS_VLE_CLUSTER_TYPE_MAX - 1);
+	BUILD_BUG_ON(BIT(Z_EROFS_LI_LCLUSTER_TYPE_BITS) <
+		     Z_EROFS_LCLUSTER_TYPE_MAX - 1);
 	/* exclude old compiler versions like gcc 7.5.0 */
 	BUILD_BUG_ON(__builtin_constant_p(fmh) ?
 		     fmh != cpu_to_le64(1ULL << 63) : 0);