Re: [PATCH 02/16 v2] f2fs: add on-disk layout

From: Vyacheslav Dubeyko
Date: Wed Oct 24 2012 - 07:25:51 EST

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Hi,

On Tue, 2012-10-23 at 11:26 +0900, Jaegeuk Kim wrote:
> This adds a header file describing the on-disk layout of f2fs.
>
> Signed-off-by: Changman Lee <cm224.lee@xxxxxxxxxxx>
> Signed-off-by: Chul Lee <chur.lee@xxxxxxxxxxx>
> Signed-off-by: Jaegeuk Kim <jaegeuk.kim@xxxxxxxxxxx>
> ---
> include/linux/f2fs_fs.h | 362 +++++++++++++++++++++++++++++++++++++++++++++++
> 1 file changed, 362 insertions(+)
> create mode 100644 include/linux/f2fs_fs.h
>
> diff --git a/include/linux/f2fs_fs.h b/include/linux/f2fs_fs.h
> new file mode 100644
> index 0000000..bd9c217
> --- /dev/null
> +++ b/include/linux/f2fs_fs.h
> @@ -0,0 +1,362 @@
> +/**
> + * include/linux/f2fs_fs.h
> + *
> + * Copyright (c) 2012 Samsung Electronics Co., Ltd.
> + * http://www.samsung.com/
> + *
> + * This program is free software; you can redistribute it and/or modify
> + * it under the terms of the GNU General Public License version 2 as
> + * published by the Free Software Foundation.
> + */
> +#ifndef _LINUX_F2FS_FS_H
> +#define _LINUX_F2FS_FS_H
> +
> +#include <linux/pagemap.h>
> +#include <linux/types.h>
> +
> +#define F2FS_SUPER_MAGIC 0xF2F52010
> +#define F2FS_SUPER_OFFSET 0 /* start sector # for sb */

Does f2fs superblock really haven't any offset from the volume begin?

> +#define F2FS_BLKSIZE 4096
> +#define F2FS_MAX_EXTENSION 64
> +
> +#define NULL_ADDR 0x0U
> +#define NEW_ADDR -1U

Does NULL_ADDR and NEW_ADDR declarations really need? Does kernel
haven't any analogous?

> +
> +#define F2FS_ROOT_INO(sbi) (sbi->root_ino_num)
> +#define F2FS_NODE_INO(sbi) (sbi->node_ino_num)
> +#define F2FS_META_INO(sbi) (sbi->meta_ino_num)
> +
> +#define GFP_F2FS_MOVABLE (__GFP_WAIT | __GFP_IO | __GFP_ZERO)
> +
> +#define MAX_ACTIVE_LOGS 16
> +#define MAX_ACTIVE_NODE_LOGS 8
> +#define MAX_ACTIVE_DATA_LOGS 8

I think that it makes sense to comment the reasons of such limitations
in MAX_ACTIVE_LOGS, MAX_ACTIVE_NODE_LOGS, MAX_ACTIVE_DATA_LOGS.

> +
> +/*
> + * For superblock
> + */
> +struct f2fs_super_block {
> + __le32 magic; /* Magic Number */
> + __le16 major_ver; /* Major Version */
> + __le16 minor_ver; /* Minor Version */
> + __le32 log_sectorsize; /* log2 (Sector size in bytes) */
> + __le32 log_sectors_per_block; /* log2 (Number of sectors per block */
> + __le32 log_blocksize; /* log2 (Block size in bytes) */
> + __le32 log_blocks_per_seg; /* log2 (Number of blocks per segment) */

>From my point of view, __le32 is big data type for log2 (<value>). What
do you think?

> + __le32 segs_per_sec; /* Number of segments per section */
> + __le32 secs_per_zone; /* Number of sections per zone */
> + __le32 checksum_offset; /* Checksum position in this super block */
> + __le64 block_count; /* Total number of blocks */
> + __le32 section_count; /* Total number of sections */
> + __le32 segment_count; /* Total number of segments */
> + __le32 segment_count_ckpt; /* Total number of segments
> + in Checkpoint area */
> + __le32 segment_count_sit; /* Total number of segments
> + in Segment information table */
> + __le32 segment_count_nat; /* Total number of segments
> + in Node address table */
> + /*Total number of segments in Segment summary area */
> + __le32 segment_count_ssa;
> + /* Total number of segments in Main area */
> + __le32 segment_count_main;
> + __le32 failure_safe_block_distance;
> + __le32 segment0_blkaddr; /* Start block address of Segment 0 */
> + __le32 start_segment_checkpoint; /* Start block address of ckpt */
> + __le32 sit_blkaddr; /* Start block address of SIT */
> + __le32 nat_blkaddr; /* Start block address of NAT */
> + __le32 ssa_blkaddr; /* Start block address of SSA */
> + __le32 main_blkaddr; /* Start block address of Main area */
> + __le32 root_ino; /* Root directory inode number */
> + __le32 node_ino; /* node inode number */
> + __le32 meta_ino; /* meta inode number */
> + __le32 volume_serial_number; /* VSN is optional field */

Usually, it is used 128-bits UUID for serial number. Why do you use
__le32 as volume_serial_number?

> + __le16 volume_name[512]; /* Volume Name */
> + __le32 extension_count;
> + __u8 extension_list[F2FS_MAX_EXTENSION][8]; /* extension array */
> +} __packed;
> +
> +/*
> + * For checkpoint
> + */
> +struct f2fs_checkpoint {
> + __le64 checkpoint_ver; /* Checkpoint block version number */
> + __le64 user_block_count; /* # of user blocks */
> + __le64 valid_block_count; /* # of valid blocks in Main area */
> + __le32 rsvd_segment_count; /* # of reserved segments for gc */
> + __le32 overprov_segment_count; /* # of overprovision segments */
> + __le32 free_segment_count; /* # of free segments in Main area */
> +
> + /* information of current node segments */
> + __le32 cur_node_segno[MAX_ACTIVE_NODE_LOGS];
> + __le16 cur_node_blkoff[MAX_ACTIVE_NODE_LOGS];
> + __le16 nat_upd_blkoff[MAX_ACTIVE_NODE_LOGS];
> + /* information of current data segments */
> + __le32 cur_data_segno[MAX_ACTIVE_DATA_LOGS];
> + __le16 cur_data_blkoff[MAX_ACTIVE_DATA_LOGS];
> + __le32 ckpt_flags; /* Flags : umount and journal_present */
> + __le32 cp_pack_total_block_count;
> + __le32 cp_pack_start_sum; /* start block number of data summary */
> + __le32 valid_node_count; /* Total number of valid nodes */
> + __le32 valid_inode_count; /* Total number of valid inodes */
> + __le32 next_free_nid; /* Next free node number */
> + __le32 sit_ver_bitmap_bytesize; /* Default value 64 */
> + __le32 nat_ver_bitmap_bytesize; /* Default value 256 */
> + __le32 checksum_offset; /* Checksum position
> + in this checkpoint block */
> + __le64 elapsed_time; /* elapsed time while partition
> + is mounted */
> + /* allocation type of current segment */
> + unsigned char alloc_type[MAX_ACTIVE_LOGS];
> +
> + /* SIT and NAT version bitmap */
> + unsigned char sit_nat_version_bitmap[1];
> +} __packed;
> +
> +/*
> + * For orphan inode management
> + */
> +#define F2FS_ORPHANS_PER_BLOCK 1020
> +
> +struct f2fs_orphan_block {
> + __le32 ino[F2FS_ORPHANS_PER_BLOCK]; /* inode numbers */
> + __le32 reserved;
> + __le16 blk_addr; /* block index in current CP */
> + __le16 blk_count; /* Number of orphan inode blocks in CP */
> + __le32 entry_count; /* Total number of orphan nodes in current CP */
> + __le32 check_sum; /* CRC32 for orphan inode block */
> +} __packed;
> +
> +/*
> + * For NODE structure
> + */
> +struct f2fs_extent {
> + __le32 fofs;
> + __le32 blk_addr;
> + __le32 len;
> +} __packed;
> +
> +#define F2FS_MAX_NAME_LEN 256
> +#define ADDRS_PER_INODE 927 /* Address Pointers in an Inode */
> +#define ADDRS_PER_BLOCK 1018 /* Address Pointers in a Direct Block */
> +#define NIDS_PER_BLOCK 1018 /* Node IDs in an Indirect Block */
> +
> +struct f2fs_inode {
> + __le16 i_mode; /* File mode */
> + __u8 i_advise; /* File hints */
> + __u8 i_reserved; /* Reserved */
> + __le32 i_uid; /* User ID */
> + __le32 i_gid; /* Group ID */
> + __le32 i_links; /* Links count */
> + __le64 i_size; /* File size in bytes */
> + __le64 i_blocks; /* File size in blocks */
> + __le64 i_ctime; /* Inode change time */
> + __le64 i_mtime; /* Modification time */
> + __le32 i_ctime_nsec;
> + __le32 i_mtime_nsec;
> + __le32 current_depth;
> + __le32 i_xattr_nid; /* nid to save xattr */
> + __le32 i_flags; /* file attributes */
> + __le32 i_pino; /* parent inode number */
> + __le32 i_namelen; /* file name length */
> + __u8 i_name[F2FS_MAX_NAME_LEN]; /* file name for SPOR */
> +
> + struct f2fs_extent i_ext; /* caching a largest extent */
> +
> + __le32 i_addr[ADDRS_PER_INODE]; /* Pointers to data blocks */
> +
> + __le32 i_nid[5]; /* direct(2), indirect(2),
> + double_indirect(1) node id */
> +} __packed;
> +
> +struct direct_node {
> + __le32 addr[ADDRS_PER_BLOCK]; /* array of data block address */
> +} __packed;
> +
> +struct indirect_node {
> + __le32 nid[NIDS_PER_BLOCK]; /* array of data block address */
> +} __packed;
> +
> +enum {
> + COLD_BIT_SHIFT = 0,
> + FSYNC_BIT_SHIFT,
> + DENT_BIT_SHIFT,
> + OFFSET_BIT_SHIFT
> +};
> +
> +struct node_footer {
> + __le32 nid; /* node id */
> + __le32 ino; /* inode nunmber */
> + __le32 flag; /* include cold/fsync/dentry marks and offset */
> + __le64 cp_ver; /* checkpoint version */
> + __le32 next_blkaddr; /* next node page block address */
> +} __packed;
> +
> +struct f2fs_node {
> + union {
> + struct f2fs_inode i;
> + struct direct_node dn;
> + struct indirect_node in;
> + };
> + struct node_footer footer;
> +} __packed;
> +
> +/*
> + * For NAT entries
> + */
> +#define NAT_ENTRY_PER_BLOCK (PAGE_CACHE_SIZE / sizeof(struct f2fs_nat_entry))
> +
> +struct f2fs_nat_entry {
> + __u8 version;
> + __le32 ino;
> + __le32 block_addr;
> +} __packed;
> +
> +struct f2fs_nat_block {
> + struct f2fs_nat_entry entries[NAT_ENTRY_PER_BLOCK];
> +} __packed;
> +
> +/*
> + * For SIT entries
> + */
> +#define SIT_VBLOCK_MAP_SIZE 64
> +#define SIT_ENTRY_PER_BLOCK (PAGE_CACHE_SIZE / sizeof(struct f2fs_sit_entry))
> +
> +struct f2fs_sit_entry {
> + __le16 vblocks;
> + __u8 valid_map[SIT_VBLOCK_MAP_SIZE];
> + __le64 mtime;
> +} __packed;
> +
> +struct f2fs_sit_block {
> + struct f2fs_sit_entry entries[SIT_ENTRY_PER_BLOCK];
> +} __packed;
> +
> +/**
> + * For segment summary
> + *
> + * NOTE : For initializing fields, you must use set_summary
> + *
> + * - If data page, nid represents dnode's nid
> + * - If node page, nid represents the node page's nid.
> + *
> + * The ofs_in_node is used by only data page. It represents offset
> + * from node's page's beginning to get a data block address.
> + * ex) data_blkaddr = (block_t)(nodepage_start_address + ofs_in_node)
> + */
> +struct f2fs_summary {
> + __le32 nid;
> + union {
> + __u8 reserved[3];
> + struct {
> + __u8 version;
> + __le16 ofs_in_node;
> + } __packed;
> + };
> +} __packed;
> +
> +struct summary_footer {
> + unsigned char entry_type;
> + __u32 check_sum;
> +} __packed;
> +
> +#define SUMMARY_SIZE (sizeof(struct f2fs_summary))
> +#define SUM_FOOTER_SIZE (sizeof(struct summary_footer))
> +#define ENTRIES_IN_SUM 512
> +#define SUM_ENTRY_SIZE (SUMMARY_SIZE * ENTRIES_IN_SUM)
> +#define SUM_JOURNAL_SIZE (PAGE_CACHE_SIZE - SUM_FOOTER_SIZE -\
> + SUM_ENTRY_SIZE)
> +struct nat_journal_entry {
> + __le32 nid;
> + struct f2fs_nat_entry ne;
> +} __packed;
> +
> +struct sit_journal_entry {
> + __le32 segno;
> + struct f2fs_sit_entry se;
> +} __packed;
> +
> +#define NAT_JOURNAL_ENTRIES ((SUM_JOURNAL_SIZE - 2) /\
> + sizeof(struct nat_journal_entry))
> +#define NAT_JOURNAL_RESERVED ((SUM_JOURNAL_SIZE - 2) %\
> + sizeof(struct nat_journal_entry))
> +#define SIT_JOURNAL_ENTRIES ((SUM_JOURNAL_SIZE - 2) /\
> + sizeof(struct sit_journal_entry))
> +#define SIT_JOURNAL_RESERVED ((SUM_JOURNAL_SIZE - 2) %\
> + sizeof(struct sit_journal_entry))
> +enum {
> + NAT_JOURNAL = 0,
> + SIT_JOURNAL
> +};
> +
> +struct nat_journal {
> + struct nat_journal_entry entries[NAT_JOURNAL_ENTRIES];
> + __u8 reserved[NAT_JOURNAL_RESERVED];
> +} __packed;
> +
> +struct sit_journal {
> + struct sit_journal_entry entries[SIT_JOURNAL_ENTRIES];
> + __u8 reserved[SIT_JOURNAL_RESERVED];
> +} __packed;
> +
> +struct f2fs_summary_block {
> + struct f2fs_summary entries[ENTRIES_IN_SUM];
> + union {
> + __le16 n_nats;
> + __le16 n_sits;
> + };
> + union {
> + struct nat_journal nat_j;
> + struct sit_journal sit_j;
> + };
> + struct summary_footer footer;
> +} __packed;
> +
> +/*
> + * For directory operations
> + */
> +#define F2FS_DOT_HASH 0
> +#define F2FS_DDOT_HASH F2FS_DOT_HASH
> +#define F2FS_MAX_HASH (~((0x3ULL) << 62))
> +#define F2FS_HASH_COL_BIT ((0x1ULL) << 63)
> +
> +typedef __le32 f2fs_hash_t;
> +
> +#define F2FS_NAME_LEN 8

It exists F2FS_MAX_NAME_LEN. I think that it makes sense to comment here
purpose of F2FS_NAME_LEN declaration.

> +#define NR_DENTRY_IN_BLOCK 214 /* the number of dentry in a block */
> +#define MAX_DIR_HASH_DEPTH 63 /* MAX level for dir lookup */
> +
> +#define SIZE_OF_DIR_ENTRY 11 /* by byte */
> +#define SIZE_OF_DENTRY_BITMAP ((NR_DENTRY_IN_BLOCK + BITS_PER_BYTE - 1) / \
> + BITS_PER_BYTE)
> +#define SIZE_OF_RESERVED (PAGE_SIZE - ((SIZE_OF_DIR_ENTRY + \
> + F2FS_NAME_LEN) * \
> + NR_DENTRY_IN_BLOCK + SIZE_OF_DENTRY_BITMAP))
> +
> +struct f2fs_dir_entry {
> + __le32 hash_code; /* hash code of file name */
> + __le32 ino; /* node number of inode */
> + __le16 name_len; /* the size of file name
> + length in unicode characters */
> + __u8 file_type;
> +} __packed;
> +
> +struct f2fs_dentry_block {
> + __u8 dentry_bitmap[SIZE_OF_DENTRY_BITMAP];
> + __u8 reserved[SIZE_OF_RESERVED];
> + struct f2fs_dir_entry dentry[NR_DENTRY_IN_BLOCK];
> + __u8 filename[NR_DENTRY_IN_BLOCK][F2FS_NAME_LEN];
> +} __packed;
> +
> +enum {
> + F2FS_FT_UNKNOWN,
> + F2FS_FT_REG_FILE,
> + F2FS_FT_DIR,
> + F2FS_FT_CHRDEV,
> + F2FS_FT_BLKDEV,
> + F2FS_FT_FIFO,
> + F2FS_FT_SOCK,
> + F2FS_FT_SYMLINK,
> + F2FS_FT_MAX
> +};
> +
> +#endif /* _LINUX_F2FS_FS_H */

With the best regards,
Vyacheslav Dubeyko.

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