[NOMERGE,RFC,01/12] erofs: add on-disk layout
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Message ID 1527764790-22311-1-git-send-email-gaoxiang25@huawei.com
State New
Headers show

Commit Message

Gao Xiang May 31, 2018, 11:06 a.m. UTC
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@huawei.com>
Thanks-to: Sun Qiuyang <sunqiuyang@huawei.com>
Signed-off-by: Miao Xie <miaoxie@huawei.com>
Signed-off-by: Chao Yu <yuchao0@huawei.com>
Signed-off-by: Gao Xiang <gaoxiang25@huawei.com>
---
 fs/erofs/erofs_fs.h | 258 ++++++++++++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 258 insertions(+)
 create mode 100644 fs/erofs/erofs_fs.h

Patch
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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@huawei.com>
+ *
+ * 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
+