[PATCH v3 01/24] erofs: add on-disk layout

Gao Xiang
2019-07-22T02:51:12Z

This commit adds the on-disk layout header file of erofs.
On-disk format is compatible with erofs-staging added in 4.19.

In addition, add EROFS_SUPER_MAGIC_V1 to magic.h.

Signed-off-by: Gao Xiang <gaoxiang25@huawei.com>
---
fs/erofs/erofs_fs.h | 316 +++++++++++++++++++++++++++++++++++++
include/uapi/linux/magic.h | 1 +
2 files changed, 317 insertions(+)
create mode 100644 fs/erofs/erofs_fs.h

diff --git a/fs/erofs/erofs_fs.h b/fs/erofs/erofs_fs.h
new file mode 100644
index 000000000000..e418725abfd6
--- /dev/null
+++ b/fs/erofs/erofs_fs.h
@@ -0,0 +1,316 @@
+/* SPDX-License-Identifier: GPL-2.0 OR Apache-2.0 */
+/*
+ * linux/fs/erofs/erofs_fs.h
+ *
+ * Copyright (C) 2017-2018 HUAWEI, Inc.
+ * http://www.huawei.com/
+ * Created by Gao Xiang <gaoxiang25@huawei.com>
+ */
+#ifndef __EROFS_FS_H
+#define __EROFS_FS_H
+
+/* Enhanced(Extended) ROM File System */
+#define EROFS_SUPER_OFFSET 1024
+
+/*
+ * Any bits that aren't in EROFS_ALL_REQUIREMENTS should be
+ * incompatible with this kernel version.
+ */
+#define EROFS_REQUIREMENT_LZ4_0PADDING 0x00000001
+#define EROFS_ALL_REQUIREMENTS 0
+
+struct erofs_super_block {
+/* 0 */__le32 magic; /* in the little endian */
+/* 4 */__le32 checksum; /* crc32c(super_block) */
+/* 8 */__le32 features; /* (aka. feature_compat) */
+/* 12 */__u8 blkszbits; /* support block_size == PAGE_SIZE only */
+/* 13 */__u8 reserved;
+
+/* 14 */__le16 root_nid;
+/* 16 */__le64 inos; /* total valid ino # (== f_files - f_favail) */
+
+/* 24 */__le64 build_time; /* inode v1 time derivation */
+/* 32 */__le32 build_time_nsec;
+/* 36 */__le32 blocks; /* used for statfs */
+/* 40 */__le32 meta_blkaddr;
+/* 44 */__le32 xattr_blkaddr;
+/* 48 */__u8 uuid[16]; /* 128-bit uuid for volume */
+/* 64 */__u8 volume_name[16]; /* volume name */
+/* 80 */__le32 requirements; /* (aka. feature_incompat) */
+
+/* 84 */__u8 reserved2[44];
+} __packed; /* 128 bytes */
+
+/*
+ * erofs inode data mapping:
+ * 0 - inode plain without inline data A:
+ * inode, [xattrs], ... | ... | no-holed data
+ * 1 - inode VLE compression B (legacy):
+ * inode, [xattrs], extents ... | ...
+ * 2 - inode plain with inline data C:
+ * inode, [xattrs], last_inline_data, ... | ... | no-holed data
+ * 3 - inode compression D:
+ * inode, [xattrs], map_header, extents ... | ...
+ * 4~7 - reserved
+ */
+enum {
+ EROFS_INODE_FLAT_PLAIN,
+ EROFS_INODE_FLAT_COMPRESSION_LEGACY,
+ EROFS_INODE_FLAT_INLINE,
+ EROFS_INODE_FLAT_COMPRESSION,
+ EROFS_INODE_LAYOUT_MAX
+};
+
+static bool erofs_inode_is_data_compressed(unsigned int datamode)
+{
+ if (datamode == EROFS_INODE_FLAT_COMPRESSION)
+ return true;
+ return datamode == EROFS_INODE_FLAT_COMPRESSION_LEGACY;
+}
+
+/* bit definitions of inode i_advise */
+#define EROFS_I_VERSION_BITS 1
+#define EROFS_I_DATA_MAPPING_BITS 3
+
+#define EROFS_I_VERSION_BIT 0
+#define EROFS_I_DATA_MAPPING_BIT 1
+
+struct erofs_inode_v1 {
+/* 0 */__le16 i_advise;
+
+/* 1 header + n-1 * 4 bytes inline xattr to keep continuity */
+/* 2 */__le16 i_xattr_icount;
+/* 4 */__le16 i_mode;
+/* 6 */__le16 i_nlink;
+/* 8 */__le32 i_size;
+/* 12 */__le32 i_reserved;
+/* 16 */union {
+ /* file total compressed blocks for data mapping 1 */
+ __le32 compressed_blocks;
+ __le32 raw_blkaddr;
+
+ /* for device files, used to indicate old/new device # */
+ __le32 rdev;
+ } i_u __packed;
+/* 20 */__le32 i_ino; /* only used for 32-bit stat compatibility */
+/* 24 */__le16 i_uid;
+/* 26 */__le16 i_gid;
+/* 28 */__le32 i_reserved2;
+} __packed;
+
+/* 32 bytes on-disk inode */
+#define EROFS_INODE_LAYOUT_V1 0
+/* 64 bytes on-disk inode */
+#define EROFS_INODE_LAYOUT_V2 1
+
+struct erofs_inode_v2 {
+/* 0 */__le16 i_advise;
+
+/* 1 header + n-1 * 4 bytes inline xattr to keep continuity */
+/* 2 */__le16 i_xattr_icount;
+/* 4 */__le16 i_mode;
+/* 6 */__le16 i_reserved;
+/* 8 */__le64 i_size;
+/* 16 */union {
+ /* file total compressed blocks for data mapping 1 */
+ __le32 compressed_blocks;
+ __le32 raw_blkaddr;
+
+ /* for device files, used to indicate old/new device # */
+ __le32 rdev;
+ } i_u __packed;
+
+ /* only used for 32-bit stat compatibility */
+/* 20 */__le32 i_ino;
+
+/* 24 */__le32 i_uid;
+/* 28 */__le32 i_gid;
+/* 32 */__le64 i_ctime;
+/* 40 */__le32 i_ctime_nsec;
+/* 44 */__le32 i_nlink;
+/* 48 */__u8 i_reserved2[16];
+} __packed; /* 64 bytes */
+
+#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
+ * 12 bytes / \
+ * / \
+ * /-----------------------\
+ * | erofs_xattr_entries+ |
+ * +-----------------------+
+ * inline xattrs must starts in erofs_xattr_ibody_header,
+ * for read-only fs, no need to introduce h_refcount
+ */
+struct erofs_xattr_ibody_header {
+ __le32 h_reserved;
+ __u8 h_shared_count;
+ __u8 h_reserved2[7];
+ __le32 h_shared_xattrs[0]; /* shared xattr id array */
+} __packed;
+
+/* Name indexes */
+#define EROFS_XATTR_INDEX_USER 1
+#define EROFS_XATTR_INDEX_POSIX_ACL_ACCESS 2
+#define EROFS_XATTR_INDEX_POSIX_ACL_DEFAULT 3
+#define EROFS_XATTR_INDEX_TRUSTED 4
+#define EROFS_XATTR_INDEX_LUSTRE 5
+#define EROFS_XATTR_INDEX_SECURITY 6
+
+/* xattr entry (for both inline & shared xattrs) */
+struct erofs_xattr_entry {
+ __u8 e_name_len; /* length of name */
+ __u8 e_name_index; /* attribute name index */
+ __le16 e_value_size; /* size of attribute value */
+ /* followed by e_name and e_value */
+ char e_name[0]; /* attribute name */
+} __packed;
+
+#define ondisk_xattr_ibody_size(count) ({\
+ u32 __count = le16_to_cpu(count); \
+ ((__count) == 0) ? 0 : \
+ sizeof(struct erofs_xattr_ibody_header) + \
+ sizeof(__u32) * ((__count) - 1); })
+
+#define EROFS_XATTR_ALIGN(size) round_up(size, sizeof(struct erofs_xattr_entry))
+#define EROFS_XATTR_ENTRY_SIZE(entry) EROFS_XATTR_ALIGN( \
+ sizeof(struct erofs_xattr_entry) + \
+ (entry)->e_name_len + le16_to_cpu((entry)->e_value_size))
+
+/* available compression algorithm types */
+enum {
+ Z_EROFS_COMPRESSION_LZ4,
+ Z_EROFS_COMPRESSION_MAX
+};
+
+/*
+ * bit 0 : COMPACTED_2B indexes (0 - off; 1 - on)
+ * e.g. for 4k logical cluster size, 4B if compacted 2B is off;
+ * (4B) + 2B + (4B) if compacted 2B is on.
+ */
+#define Z_EROFS_ADVISE_COMPACTED_2B_BIT 0
+
+#define Z_EROFS_ADVISE_COMPACTED_2B (1 << Z_EROFS_ADVISE_COMPACTED_2B_BIT)
+
+struct z_erofs_map_header {
+ __le32 h_reserved1;
+ __le16 h_advise;
+ /*
+ * bit 0-3 : algorithm type of head 1 (logical cluster type 01);
+ * bit 4-7 : algorithm type of head 2 (logical cluster type 11).
+ */
+ __u8 h_algorithmtype;
+ /*
+ * bit 0-2 : logical cluster bits - 12, e.g. 0 for 4096;
+ * bit 3-4 : (physical - logical) cluster bits of head 1:
+ * For example, if logical clustersize = 4096, 1 for 8192.
+ * bit 5-7 : (physical - logical) cluster bits of head 2.
+ */
+ __u8 h_clusterbits;
+};
+
+#define Z_EROFS_VLE_LEGACY_HEADER_PADDING 8
+
+/*
+ * Z_EROFS Variable-sized Logical Extent cluster type:
+ * 0 - literal (uncompressed) cluster
+ * 1 - compressed cluster (for the head logical cluster)
+ * 2 - compressed cluster (for the other logical clusters)
+ *
+ * In detail,
+ * 0 - literal (uncompressed) cluster,
+ * di_advise = 0
+ * di_clusterofs = the literal data offset of the cluster
+ * di_blkaddr = the blkaddr of the literal cluster
+ *
+ * 1 - compressed cluster (for the head logical cluster)
+ * di_advise = 1
+ * di_clusterofs = the decompressed data offset of the cluster
+ * di_blkaddr = the blkaddr of the compressed cluster
+ *
+ * 2 - compressed cluster (for the other logical clusters)
+ * di_advise = 2
+ * di_clusterofs =
+ * the decompressed data offset in its own head cluster
+ * di_u.delta[0] = distance to its corresponding head cluster
+ * di_u.delta[1] = distance to its corresponding tail cluster
+ * (di_advise could be 0, 1 or 2)
+ */
+enum {
+ Z_EROFS_VLE_CLUSTER_TYPE_PLAIN,
+ Z_EROFS_VLE_CLUSTER_TYPE_HEAD,
+ Z_EROFS_VLE_CLUSTER_TYPE_NONHEAD,
+ Z_EROFS_VLE_CLUSTER_TYPE_RESERVED,
+ Z_EROFS_VLE_CLUSTER_TYPE_MAX
+};
+
+#define Z_EROFS_VLE_DI_CLUSTER_TYPE_BITS 2
+#define Z_EROFS_VLE_DI_CLUSTER_TYPE_BIT 0
+
+struct z_erofs_vle_decompressed_index {
+ __le16 di_advise;
+ /* where to decompress in the head cluster */
+ __le16 di_clusterofs;
+
+ union {
+ /* for the head cluster */
+ __le32 blkaddr;
+ /*
+ * for the rest clusters
+ * eg. for 4k page-sized cluster, maximum 4K*64k = 256M)
+ * [0] - pointing to the head cluster
+ * [1] - pointing to the tail cluster
+ */
+ __le16 delta[2];
+ } di_u __packed; /* 8 bytes */
+} __packed;
+
+#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; /* 0, node number */
+ __le16 nameoff; /* 8, start offset of file name */
+ __u8 file_type; /* 10, file type */
+ __u8 reserved; /* 11, reserved */
+} __packed;
+
+/* file types used in inode_info->flags */
+enum {
+ EROFS_FT_UNKNOWN,
+ EROFS_FT_REG_FILE,
+ EROFS_FT_DIR,
+ EROFS_FT_CHRDEV,
+ EROFS_FT_BLKDEV,
+ EROFS_FT_FIFO,
+ EROFS_FT_SOCK,
+ EROFS_FT_SYMLINK,
+ EROFS_FT_MAX
+};
+
+#define EROFS_NAME_LEN 255
+
+/* check the EROFS on-disk layout strictly at compile time */
+static inline void erofs_check_ondisk_layout_definitions(void)
+{
+ BUILD_BUG_ON(sizeof(struct erofs_super_block) != 128);
+ BUILD_BUG_ON(sizeof(struct erofs_inode_v1) != 32);
+ BUILD_BUG_ON(sizeof(struct erofs_inode_v2) != 64);
+ BUILD_BUG_ON(sizeof(struct erofs_xattr_ibody_header) != 12);
+ BUILD_BUG_ON(sizeof(struct erofs_xattr_entry) != 4);
+ 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 erofs_dirent) != 12);
+
+ BUILD_BUG_ON(BIT(Z_EROFS_VLE_DI_CLUSTER_TYPE_BITS) <
+ Z_EROFS_VLE_CLUSTER_TYPE_MAX - 1);
+}
+
+#endif
+
diff --git a/include/uapi/linux/magic.h b/include/uapi/linux/magic.h
index f8c00045d537..2e236666a03e 100644
--- a/include/uapi/linux/magic.h
+++ b/include/uapi/linux/magic.h
@@ -19,6 +19,7 @@
#define SQUASHFS_MAGIC 0x73717368
#define ECRYPTFS_SUPER_MAGIC 0xf15f
#define EFS_SUPER_MAGIC 0x414A53
+#define EROFS_SUPER_MAGIC_V1 0xE0F5E1E2
#define EXT2_SUPER_MAGIC 0xEF53
#define EXT3_SUPER_MAGIC 0xEF53
#define XENFS_SUPER_MAGIC 0xabba1974
--
2.17.1