Date:	Wed, 24 Oct 2012 15:25:45 +0400
From:	Vyacheslav Dubeyko <slava@...eyko.com>
To:	Jaegeuk Kim <jaegeuk.kim@...sung.com>
Cc:	linux-fsdevel@...r.kernel.org, linux-kernel@...r.kernel.org,
	gregkh@...uxfoundation.org, viro@...iv.linux.org.uk, arnd@...db.de,
	tytso@....edu, chur.lee@...sung.com, cm224.lee@...sung.com,
	jooyoung.hwang@...sung.com
Subject: Re: [PATCH 02/16 v2] f2fs: add on-disk layout

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@...sung.com>
> Signed-off-by: Chul Lee <chur.lee@...sung.com>
> Signed-off-by: Jaegeuk Kim <jaegeuk.kim@...sung.com>
> ---
>  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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