ext2_fs.h

linux的文件系统的部分代码的详细注释

#define clear_opt(o, opt)		o &= ~EXT2_MOUNT_##opt
#define set_opt(o, opt)			o |= EXT2_MOUNT_##opt
#define test_opt(sb, opt)		((sb)->u.ext2_sb.s_mount_opt & \
					 EXT2_MOUNT_##opt)
/*
 * Maximal mount counts between two filesystem checks
 */
#define EXT2_DFL_MAX_MNT_COUNT		20	/* Allow 20 mounts */
#define EXT2_DFL_CHECKINTERVAL		0	/* Don't use interval check */

/*
 * Behaviour when detecting errors
 */
#define EXT2_ERRORS_CONTINUE		1	/* Continue execution */
#define EXT2_ERRORS_RO			2	/* Remount fs read-only */
#define EXT2_ERRORS_PANIC		3	/* Panic */
#define EXT2_ERRORS_DEFAULT		EXT2_ERRORS_CONTINUE

/*
 * Structure of the super block
 */
struct ext2_super_block {
	__u32	s_inodes_count;		/* Inodes count */
	__u32	s_blocks_count;		/* Blocks count */
	__u32	s_r_blocks_count;	/* Reserved blocks count */
	__u32	s_free_blocks_count;	/* Free blocks count */
	__u32	s_free_inodes_count;	/* Free inodes count */
	__u32	s_first_data_block;	/* First Data Block */
	__u32	s_log_block_size;	/* Block size */
	__s32	s_log_frag_size;	/* Fragment size */
	__u32	s_blocks_per_group;	/* # Blocks per group */
	__u32	s_frags_per_group;	/* # Fragments per group */
	__u32	s_inodes_per_group;	/* # Inodes per group */
	__u32	s_mtime;		/* Mount time */
	__u32	s_wtime;		/* Write time */
	__u16	s_mnt_count;		/* Mount count */
	__s16	s_max_mnt_count;	/* Maximal mount count */
	__u16	s_magic;		/* Magic signature */
	__u16	s_state;		/* File system state */
	__u16	s_errors;		/* Behaviour when detecting errors */
	__u16	s_minor_rev_level; 	/* minor revision level */
	__u32	s_lastcheck;		/* time of last check */
	__u32	s_checkinterval;	/* max. time between checks */
	__u32	s_creator_os;		/* OS */
	__u32	s_rev_level;		/* Revision level */
	__u16	s_def_resuid;		/* Default uid for reserved blocks */
	__u16	s_def_resgid;		/* Default gid for reserved blocks */
	/*
	 * These fields are for EXT2_DYNAMIC_REV superblocks only.
	 *
	 * Note: the difference between the compatible feature set and
	 * the incompatible feature set is that if there is a bit set
	 * in the incompatible feature set that the kernel doesn't
	 * know about, it should refuse to mount the filesystem.
	 * 
	 * e2fsck's requirements are more strict; if it doesn't know
	 * about a feature in either the compatible or incompatible
	 * feature set, it must abort and not try to meddle with
	 * things it doesn't understand...
	 */
	__u32	s_first_ino; 		/* First non-reserved inode */
	__u16   s_inode_size; 		/* size of inode structure */
	__u16	s_block_group_nr; 	/* block group # of this superblock */
	__u32	s_feature_compat; 	/* compatible feature set */
	__u32	s_feature_incompat; 	/* incompatible feature set */
	__u32	s_feature_ro_compat; 	/* readonly-compatible feature set */
	__u8	s_uuid[16];		/* 128-bit uuid for volume */
	char	s_volume_name[16]; 	/* volume name */
	char	s_last_mounted[64]; 	/* directory where last mounted */
	__u32	s_algorithm_usage_bitmap; /* For compression */
	/*
	 * Performance hints.  Directory preallocation should only
	 * happen if the EXT2_COMPAT_PREALLOC flag is on.
	 */
	__u8	s_prealloc_blocks;	/* Nr of blocks to try to preallocate*/
	__u8	s_prealloc_dir_blocks;	/* Nr to preallocate for dirs */
	__u16	s_padding1;
	__u32	s_reserved[204];	/* Padding to the end of the block */
};

#ifdef __KERNEL__
#define EXT2_SB(sb)	(&((sb)->u.ext2_sb))
#else
/* Assume that user mode programs are passing in an ext2fs superblock, not
 * a kernel struct super_block.  This will allow us to call the feature-test
 * macros from user land. */
#define EXT2_SB(sb)	(sb)
#endif

/*
 * Codes for operating systems
 */
#define EXT2_OS_LINUX		0
#define EXT2_OS_HURD		1
#define EXT2_OS_MASIX		2
#define EXT2_OS_FREEBSD		3
#define EXT2_OS_LITES		4

/*
 * Revision levels
 */
#define EXT2_GOOD_OLD_REV	0	/* The good old (original) format */
#define EXT2_DYNAMIC_REV	1 	/* V2 format w/ dynamic inode sizes */

#define EXT2_CURRENT_REV	EXT2_GOOD_OLD_REV
#define EXT2_MAX_SUPP_REV	EXT2_DYNAMIC_REV

#define EXT2_GOOD_OLD_INODE_SIZE 128

/*
 * Feature set definitions
 */

#define EXT2_HAS_COMPAT_FEATURE(sb,mask)			\
	( EXT2_SB(sb)->s_es->s_feature_compat & cpu_to_le32(mask) )
#define EXT2_HAS_RO_COMPAT_FEATURE(sb,mask)			\
	( EXT2_SB(sb)->s_es->s_feature_ro_compat & cpu_to_le32(mask) )
#define EXT2_HAS_INCOMPAT_FEATURE(sb,mask)			\
	( EXT2_SB(sb)->s_es->s_feature_incompat & cpu_to_le32(mask) )
#define EXT2_SET_COMPAT_FEATURE(sb,mask)			\
	EXT2_SB(sb)->s_es->s_feature_compat |= cpu_to_le32(mask)
#define EXT2_SET_RO_COMPAT_FEATURE(sb,mask)			\
	EXT2_SB(sb)->s_es->s_feature_ro_compat |= cpu_to_le32(mask)
#define EXT2_SET_INCOMPAT_FEATURE(sb,mask)			\
	EXT2_SB(sb)->s_es->s_feature_incompat |= cpu_to_le32(mask)
#define EXT2_CLEAR_COMPAT_FEATURE(sb,mask)			\
	EXT2_SB(sb)->s_es->s_feature_compat &= ~cpu_to_le32(mask)
#define EXT2_CLEAR_RO_COMPAT_FEATURE(sb,mask)			\
	EXT2_SB(sb)->s_es->s_feature_ro_compat &= ~cpu_to_le32(mask)
#define EXT2_CLEAR_INCOMPAT_FEATURE(sb,mask)			\
	EXT2_SB(sb)->s_es->s_feature_incompat &= ~cpu_to_le32(mask)

#define EXT2_FEATURE_COMPAT_DIR_PREALLOC	0x0001
#define EXT2_FEATURE_COMPAT_IMAGIC_INODES	0x0002
#define EXT3_FEATURE_COMPAT_HAS_JOURNAL		0x0004
#define EXT2_FEATURE_COMPAT_EXT_ATTR		0x0008
#define EXT2_FEATURE_COMPAT_RESIZE_INO		0x0010
#define EXT2_FEATURE_COMPAT_DIR_INDEX		0x0020
#define EXT2_FEATURE_COMPAT_ANY			0xffffffff

#define EXT2_FEATURE_RO_COMPAT_SPARSE_SUPER	0x0001
#define EXT2_FEATURE_RO_COMPAT_LARGE_FILE	0x0002
#define EXT2_FEATURE_RO_COMPAT_BTREE_DIR	0x0004
#define EXT2_FEATURE_RO_COMPAT_ANY		0xffffffff

#define EXT2_FEATURE_INCOMPAT_COMPRESSION	0x0001
#define EXT2_FEATURE_INCOMPAT_FILETYPE		0x0002
#define EXT3_FEATURE_INCOMPAT_RECOVER		0x0004
#define EXT3_FEATURE_INCOMPAT_JOURNAL_DEV	0x0008
#define EXT2_FEATURE_INCOMPAT_ANY		0xffffffff

#define EXT2_FEATURE_COMPAT_SUPP	0
#define EXT2_FEATURE_INCOMPAT_SUPP	EXT2_FEATURE_INCOMPAT_FILETYPE
#define EXT2_FEATURE_RO_COMPAT_SUPP	(EXT2_FEATURE_RO_COMPAT_SPARSE_SUPER| \
					 EXT2_FEATURE_RO_COMPAT_LARGE_FILE| \
					 EXT2_FEATURE_RO_COMPAT_BTREE_DIR)
#define EXT2_FEATURE_RO_COMPAT_UNSUPPORTED	~EXT2_FEATURE_RO_COMPAT_SUPP
#define EXT2_FEATURE_INCOMPAT_UNSUPPORTED	~EXT2_FEATURE_INCOMPAT_SUPP

/*
 * Default values for user and/or group using reserved blocks
 */
#define	EXT2_DEF_RESUID		0
#define	EXT2_DEF_RESGID		0

/*
 * Structure of a directory entry
 */
#define EXT2_NAME_LEN 255

struct ext2_dir_entry {
	__u32	inode;			/* Inode number */
	__u16	rec_len;		/* Directory entry length */
	__u16	name_len;		/* Name length */
	char	name[EXT2_NAME_LEN];	/* File name */
};

/*
 * The new version of the directory entry.  Since EXT2 structures are
 * stored in intel byte order, and the name_len field could never be
 * bigger than 255 chars, it's safe to reclaim the extra byte for the
 * file_type field.
 */
struct ext2_dir_entry_2 {
	__u32	inode;			/* Inode number */
	__u16	rec_len;		/* Directory entry length */
	__u8	name_len;		/* Name length */
	__u8	file_type;
	char	name[EXT2_NAME_LEN];	/* File name */
};

/*
 * Ext2 directory file types.  Only the low 3 bits are used.  The
 * other bits are reserved for now.
 */
enum {
	EXT2_FT_UNKNOWN,
	EXT2_FT_REG_FILE,
	EXT2_FT_DIR,
	EXT2_FT_CHRDEV,
	EXT2_FT_BLKDEV,
	EXT2_FT_FIFO,
	EXT2_FT_SOCK,
	EXT2_FT_SYMLINK,
	EXT2_FT_MAX
};

/*
 * EXT2_DIR_PAD defines the directory entries boundaries
 *
 * NOTE: It must be a multiple of 4
 */
#define EXT2_DIR_PAD		 	4
#define EXT2_DIR_ROUND 			(EXT2_DIR_PAD - 1)
#define EXT2_DIR_REC_LEN(name_len)	(((name_len) + 8 + EXT2_DIR_ROUND) & \
					 ~EXT2_DIR_ROUND)

#ifdef __KERNEL__
/*
 * Function prototypes
 */

/*
 * Ok, these declarations are also in <linux/kernel.h> but none of the
 * ext2 source programs needs to include it so they are duplicated here.
 */
# define NORET_TYPE    /**/
# define ATTRIB_NORET  __attribute__((noreturn))
# define NORET_AND     noreturn,

/* balloc.c */
extern int ext2_bg_has_super(struct super_block *sb, int group);
extern unsigned long ext2_bg_num_gdb(struct super_block *sb, int group);
extern int ext2_new_block (struct inode *, unsigned long,
			   __u32 *, __u32 *, int *);
extern void ext2_free_blocks (struct inode *, unsigned long,
			      unsigned long);
extern unsigned long ext2_count_free_blocks (struct super_block *);
extern void ext2_check_blocks_bitmap (struct super_block *);
extern struct ext2_group_desc * ext2_get_group_desc(struct super_block * sb,
						    unsigned int block_group,
						    struct buffer_head ** bh);

/* dir.c */
extern int ext2_add_link (struct dentry *, struct inode *);
extern ino_t ext2_inode_by_name(struct inode *, struct dentry *);
extern int ext2_make_empty(struct inode *, struct inode *);
extern struct ext2_dir_entry_2 * ext2_find_entry (struct inode *,struct dentry *, struct page **);
extern int ext2_delete_entry (struct ext2_dir_entry_2 *, struct page *);
extern int ext2_empty_dir (struct inode *);
extern struct ext2_dir_entry_2 * ext2_dotdot (struct inode *, struct page **);
extern void ext2_set_link(struct inode *, struct ext2_dir_entry_2 *, struct page *, struct inode *);

/* fsync.c */
extern int ext2_sync_file (struct file *, struct dentry *, int);
extern int ext2_fsync_inode (struct inode *, int);

/* ialloc.c */
extern struct inode * ext2_new_inode (const struct inode *, int);
extern void ext2_free_inode (struct inode *);
extern unsigned long ext2_count_free_inodes (struct super_block *);
extern void ext2_check_inodes_bitmap (struct super_block *);
extern unsigned long ext2_count_free (struct buffer_head *, unsigned);

/* inode.c */
extern void ext2_read_inode (struct inode *);
extern void ext2_write_inode (struct inode *, int);
extern void ext2_put_inode (struct inode *);
extern void ext2_delete_inode (struct inode *);
extern int ext2_sync_inode (struct inode *);
extern void ext2_discard_prealloc (struct inode *);
extern void ext2_truncate (struct inode *);

/* ioctl.c */
extern int ext2_ioctl (struct inode *, struct file *, unsigned int,
		       unsigned long);

/* super.c */
extern void ext2_error (struct super_block *, const char *, const char *, ...)
	__attribute__ ((format (printf, 3, 4)));
extern NORET_TYPE void ext2_panic (struct super_block *, const char *,
				   const char *, ...)
	__attribute__ ((NORET_AND format (printf, 3, 4)));
extern void ext2_warning (struct super_block *, const char *, const char *, ...)
	__attribute__ ((format (printf, 3, 4)));
extern void ext2_update_dynamic_rev (struct super_block *sb);
extern void ext2_put_super (struct super_block *);
extern void ext2_write_super (struct super_block *);
extern int ext2_remount (struct super_block *, int *, char *);
extern struct super_block * ext2_read_super (struct super_block *,void *,int);
extern int ext2_statfs (struct super_block *, struct statfs *);

/*
 * Inodes and files operations
 */

/* dir.c */
extern struct file_operations ext2_dir_operations;

/* file.c */
extern struct inode_operations ext2_file_inode_operations;
extern struct file_operations ext2_file_operations;

/* inode.c */
extern struct address_space_operations ext2_aops;

/* namei.c */
extern struct inode_operations ext2_dir_inode_operations;

/* symlink.c */
extern struct inode_operations ext2_fast_symlink_inode_operations;

#endif	/* __KERNEL__ */

#endif	/* _LINUX_EXT2_FS_H */