[NOMERGE] [RFC PATCH 01/12] erofs: add on-disk layout
From: Gao Xiang
Date: Thu May 31 2018 - 07:06:52 EST
This commit adds the on-disk layout header file of erofs.
Note that the on-disk layout is still WIP, and some fields are
reserved for the future use by design.
Any comments are welcome.
Thanks-to: Li Guifu <liguifu2@xxxxxxxxxx>
Thanks-to: Sun Qiuyang <sunqiuyang@xxxxxxxxxx>
Signed-off-by: Miao Xie <miaoxie@xxxxxxxxxx>
Signed-off-by: Chao Yu <yuchao0@xxxxxxxxxx>
Signed-off-by: Gao Xiang <gaoxiang25@xxxxxxxxxx>
---
fs/erofs/erofs_fs.h | 258 ++++++++++++++++++++++++++++++++++++++++++++++++++++
1 file changed, 258 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 0000000..c08d982
--- /dev/null
+++ b/fs/erofs/erofs_fs.h
@@ -0,0 +1,258 @@
+/* SPDX-License-Identifier: GPL-2.0
+ *
+ * linux/fs/erofs/erofs_fs.h
+ *
+ * Copyright (C) 2017-2018 HUAWEI, Inc.
+ * http://www.huawei.com/
+ * Created by Gao Xiang <gaoxiang25@xxxxxxxxxx>
+ *
+ * This file is subject to the terms and conditions of the GNU General Public
+ * License. See the file COPYING in the main directory of the Linux
+ * distribution for more details.
+ */
+#ifndef __EROFS_FS_H
+#define __EROFS_FS_H
+
+/* Enhanced(Extended) ROM File System */
+#define EROFS_SUPER_MAGIC_V1 0xE0F5E1E2
+#define EROFS_SUPER_OFFSET 1024
+
+struct erofs_super_block {
+/* 0 */__le32 magic; /* in the little endian */
+/* 4 */__le32 checksum; /* crc32c(super_block) */
+/* 8 */__le32 features;
+/* 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 */__u8 reserved2[48]; /* 128 bytes */
+} __packed;
+
+#define __EROFS_BIT(_prefix, _cur, _pre) enum { \
+ _prefix ## _cur ## _BIT = _prefix ## _pre ## _BIT + \
+ _prefix ## _pre ## _BITS }
+
+/*
+ * erofs inode data mapping:
+ * 0 - inode plain without inline data A:
+ * inode, [xattrs], ... | ... | no-holed data
+ * 1 - inode VLE compression B:
+ * inode, [xattrs], extents ... | ...
+ * 2 - inode plain with inline data C:
+ * inode, [xattrs], last_inline_data, ... | ... | no-holed data
+ * 3~7 - reserved
+ */
+enum {
+ EROFS_INODE_LAYOUT_PLAIN,
+ EROFS_INODE_LAYOUT_COMPRESSION,
+ EROFS_INODE_LAYOUT_INLINE,
+ EROFS_INODE_LAYOUT_MAX
+};
+#define EROFS_I_VERSION_BITS 1
+#define EROFS_I_DATA_MAPPING_BITS 3
+
+#define EROFS_I_VERSION_BIT 0
+__EROFS_BIT(EROFS_I_, DATA_MAPPING, VERSION);
+
+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_checksum;
+} __packed;
+
+/* 32 bytes inode */
+#define EROFS_INODE_V1 0
+/* 64 bytes inode */
+#define EROFS_INODE_V2 1
+
+struct erofs_inode_v2 {
+ __le16 i_advise;
+
+ /* 1 header + n-1 * 4 bytes inline xattr to keep continuity */
+ __le16 i_xattr_icount;
+ __le16 i_mode;
+ __le16 i_reserved; /* 8 bytes */
+ __le64 i_size; /* 16 bytes */
+ 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 */
+ __le32 i_ino; /* 24 bytes */
+
+ __le32 i_uid;
+ __le32 i_gid;
+ __le64 i_ctime; /* 32 bytes */
+ __le32 i_ctime_nsec;
+ __le32 i_nlink;
+ __u8 i_reserved2[12];
+ __le32 i_checksum; /* 64 bytes */
+} __packed;
+
+#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_checksum;
+ __u8 h_shared_count;
+ __u8 h_reserved[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
+#define EROFS_XATTR_INDEX_ADVISE 7
+
+/* 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))
+
+/* have to be aligned with 8 bytes on disk */
+struct erofs_extent_header {
+ __le32 eh_checksum;
+ __le32 eh_reserved[3];
+} __packed;
+
+/*
+ * EROFS Variable-sized Logical Extent cluster type:
+ * 0 - uncompressed logical cluster
+ * 1 - compressed logical cluster (for the head logical cluster)
+ * 2 - compressed logical cluster (for the rest logical clusters)
+ * For details:
+ * for the uncompressed logical cluster,
+ * di_advise = 0
+ * di_clusterofs =
+ * the uncompressed data offset of the cluster
+ * di_blkaddr = the blkaddr of the uncompressed cluster
+ * for the compressed head logical cluster,
+ * di_advise = 1
+ * di_clusterofs =
+ * the decompressed data offset of the cluster
+ * di_blkaddr = the blkaddr of the compressed cluster
+ * for the rest logical clusters,
+ * di_advise = 2
+ * di_clusterofs =
+ * the decompressed data offset in the head cluster
+ * di_u.delta[0] = pointing to the head cluster
+ * di_u.delta[1] = pointing to the tail cluster
+ * (di_advise could be 0, 1 or 2)
+ */
+#define EROFS_VLE_DI_CLUSTER_TYPE_BITS 2
+#define EROFS_VLE_DI_CLUSTER_TYPE_BIT 0
+
+struct erofs_decompressed_index_vle {
+ __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 EROFS_VLE_EXTENT_ALIGN(size) round_up(size, \
+ sizeof(struct erofs_decompressed_index_vle))
+
+#define ondisk_extent_size(data_mapping_mode, count) \
+ ((data_mapping_mode) == EROFS_INODE_LAYOUT_COMPRESSION ? \
+ (sizeof(struct erofs_extent_header) + \
+ sizeof(__u32) * le32_to_cpu(count)) : 0)
+
+/* 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
+
+#endif
+
--
1.9.1