portdat.h

这是一个同样来自贝尔实验室的和UNIX有着渊源的操作系统, 其简洁的设计和实现易于我们学习和理解

/*
 * fundamental constants and types of the implementation
 * changing any of these changes the layout on disk
 */

#define SUPER_ADDR	2		/* block address of superblock */
#define ROOT_ADDR	3		/* block address of root directory */

#ifdef OLD
/*
 * compatible on disk with the old 32-bit file server.
 * this lets people run this kernel on their old file systems.
 */
#define	NAMELEN		28		/* max size of file name components */
#define	NDBLOCK		6		/* number of direct blocks in Dentry */
#define NIBLOCK		2		/* max depth of indirect blocks */

typedef long Off;	/* file offsets & sizes, in bytes & blocks */

#else			/* OLD */

/* the glorious new, incompatible (on disk) 64-bit world */

/* keeping NAMELEN ≤ 50 bytes permits 3 Dentrys per mag disk sector */
#define	NAMELEN		56		/* max size of file name components */
#define	NDBLOCK		6		/* number of direct blocks in Dentry */
#define NIBLOCK		4		/* max depth of indirect blocks */

/*
 * file offsets & sizes, in bytes & blocks.  typically long or vlong.
 * vlong is used in the code where would be needed if Off were just long.
 */
typedef vlong Off;

#endif			/* OLD */

/* constants that don't affect disk layout */
#define	MAXDAT		8192		/* max allowable data message */
#define	MAXMSG		128		/* max size protocol message sans data */
#define	OFFMSG		60		/* offset of msg in buffer */

#define	C0a		59		/* time constants for filters */
#define	C0b		60
#define	C1a		599
#define	C1b		600
#define	C2a		5999
#define	C2b		6000

/* more fundamental types */
typedef vlong Wideoff; /* type to widen Off to for printing; ≥ as wide as Off */
typedef short	Userid;		/* signed internal representation of user-id */
typedef long	Timet;		/* in seconds since epoch */
typedef vlong	Devsize;	/* in bytes */

/*
 * tunable parameters
 */
enum {
	Maxword = 200,			/* max bytes per command-line word */
};
#define NDRIVE		16		/* size of drive structure */
#define NTLOCK		200		/* number of active file Tlocks */
#define	LRES		3		/* profiling resolution */
#define NATTID		10		/* the last 10 ID's in attaches */

/*
 * derived constants
 */
#define	BUFSIZE		(RBUFSIZE-sizeof(Tag))
#define DIRPERBUF	(BUFSIZE/sizeof(Dentry))
#define INDPERBUF	(BUFSIZE/sizeof(Off))
#define FEPERBUF	((BUFSIZE-sizeof(Super1)-sizeof(Off))/sizeof(Off))
#define	SMALLBUF	(MAXMSG)
#define	LARGEBUF	(MAXMSG+MAXDAT+256)
#define	RAGAP		(300*1024)/BUFSIZE		/* readahead parameter */
#define CEPERBK		((BUFSIZE-BKPERBLK*sizeof(Off))/\
				(sizeof(Centry)*BKPERBLK))
#define	BKPERBLK	10

typedef struct	Alarm	Alarm;
typedef struct	Auth	Auth;
typedef	struct	Conf	Conf;
typedef	struct	Label	Label;
typedef	struct	Lock	Lock;
typedef	struct	Mach	Mach;
typedef	struct	QLock	QLock;
typedef	struct	Ureg	Ureg;
typedef	struct	User	User;
typedef	struct	Fbuf	Fbuf;
typedef	struct	Super1	Super1;
typedef	struct	Superb	Superb;
typedef	struct	Filsys	Filsys;
typedef	struct	Startsb	Startsb;
typedef	struct	Dentry	Dentry;
typedef	struct	Tag	Tag;
typedef struct  Talarm	Talarm;
typedef	struct	Uid	Uid;
typedef struct	Device	Device;
typedef struct	Qid9p1	Qid9p1;
typedef	struct	Iobuf	Iobuf;
typedef	struct	Wpath	Wpath;
typedef	struct	File	File;
typedef	struct	Chan	Chan;
typedef	struct	Cons	Cons;
typedef	struct	Time	Time;
typedef	struct	Tm	Tm;
typedef	struct	Rtc	Rtc;
typedef	struct	Hiob	Hiob;
typedef	struct	RWlock	RWlock;
typedef	struct	Msgbuf	Msgbuf;
typedef	struct	Queue	Queue;
typedef	struct	Command	Command;
typedef	struct	Flag	Flag;
typedef	struct	Bp	Bp;
typedef	struct	Rabuf	Rabuf;
typedef	struct	Rendez	Rendez;
typedef	struct	Filter	Filter;
typedef		ulong	Float;
typedef	struct	Tlock	Tlock;
typedef	struct	Cache	Cache;
typedef	struct	Centry	Centry;
typedef	struct	Bucket	Bucket;

#pragma incomplete Auth
#pragma incomplete Ureg

struct	Lock
{
	ulong*	sbsem;		/* addr of sync bus semaphore */
	ulong	pc;
	ulong	sr;
};

struct	Rendez
{
	Lock;
	User*	p;
};

struct	Filter
{
	ulong	count;			/* count and old count kept separate */
	ulong	oldcount;		/*	so interrput can read them */
	int	c1;			/* time const multiplier */
	int	c2;			/* time const divider */
	int	c3;			/* scale for printing */
	Float	filter;			/* filter */
};

struct	QLock
{
	Lock;			/* to use object */
	User*	head;		/* next process waiting for object */
	User*	tail;		/* last process waiting for object */
	char*	name;		/* for diagnostics */
	int	locked;		/* flag, is locked */
};

struct	RWlock
{
	int	nread;
	QLock	wr;
	QLock	rd;
};

/*
 * send/recv queue structure
 */
struct	Queue
{
	Lock;			/* to manipulate values */
	int	size;		/* size of queue */
	int	loc;		/* circular pointer */
	int	count;		/* how many in queue */
	User*	rhead;		/* process's waiting for send */
	User*	rtail;
	User*	whead;		/* process's waiting for recv */
	User*	wtail;
	void*	args[1];	/* list of saved pointers, [->size] */
};

struct	Tag
{
	short	pad;		/* make tag end at a long boundary */
	short	tag;
	Off	path;
};

struct	Device
{
	uchar	type;
	uchar	init;
	Device*	link;			/* link for mcat/mlev/mirror */
	Device*	dlink;			/* link all devices */
	void*	private;
	Devsize	size;
	union
	{
		struct			/* wren, ide, (l)worm in targ */
		{
			int	ctrl;	/* disks only */
			int	targ;
			int	lun;	/* wren only */
		} wren;
		struct			/* mcat mlev mirror */
		{
			Device*	first;
			Device*	last;
			int	ndev;
		} cat;
		struct			/* cw */
		{
			Device*	c;	/* cache device */
			Device*	w;	/* worm device */
			Device*	ro;	/* dump - readonly */
		} cw;
		struct			/* juke */
		{
			Device*	j;	/* (robotics, worm drives) - wrens */
			Device*	m;	/* (sides) - r or l devices */
		} j;
		struct			/* ro */
		{
			Device*	parent;
		} ro;
		struct			/* fworm */
		{
			Device*	fw;
		} fw;
		struct			/* part */
		{
			Device*	d;
			long	base;	/* percentages */
			long	size;
		} part;
		struct			/* byte-swapped */
		{
			Device*	d;
		} swab;
	};
};

typedef struct Sidestarts {
	Devsize	sstart;			/* blocks before start of side */
	Devsize	s1start;		/* blocks before start of next side */
} Sidestarts;

struct	Rabuf
{
	union
	{
		struct
		{
			Device*	dev;
			Off	addr;
		};
		Rabuf*	link;
	};
};

/* user-visible Qid, from <libc.h> */
typedef
struct Qid
{
	uvlong	path;			/* Off */
	ulong	vers;			/* should be Off */
	uchar	type;
} Qid;

/* bits in Qid.type */
#define QTDIR		0x80		/* type bit for directories */
#define QTAPPEND	0x40		/* type bit for append only files */
#define QTEXCL		0x20		/* type bit for exclusive use files */
#define QTMOUNT		0x10		/* type bit for mounted channel */
#define QTAUTH		0x08		/* type bit for authentication file */
#define QTFILE		0x00		/* plain file */

/* DONT TOUCH, this is the disk structure */
struct	Qid9p1
{
	Off	path;			/* was long */
	ulong	version;		/* should be Off */
};

struct	Hiob
{
	Iobuf*	link;
	Lock;
};

struct	Chan
{
	char	type;			/* major driver type i.e. Dev* */
	int	(*protocol)(Msgbuf*);	/* version */
	int	msize;			/* version */
	char	whochan[50];
	char	whoname[NAMELEN];
	void	(*whoprint)(Chan*);
	ulong	flags;
	int	chan;			/* overall channel number, mostly for printing */
	int	nmsgs;			/* outstanding messages, set under flock -- for flush */
	Timet	whotime;
	Filter	work;
	Filter	rate;
	int	nfile;			/* used by cmd_files */
	RWlock	reflock;
	Chan*	next;			/* link list of chans */
	Queue*	send;
	Queue*	reply;

	uchar	authinfo[64];

	void*	ifc;
	void*	pdata;
};

struct	Filsys
{
	char*	name;			/* name of filsys */
	char*	conf;			/* symbolic configuration */
	Device*	dev;			/* device that filsys is on */
	int	flags;
		#define	FREAM		(1<<0)	/* mkfs */
		#define	FRECOVER	(1<<1)	/* install last dump */
		#define	FEDIT		(1<<2)	/* modified */
};

struct	Startsb
{
	char*	name;
	Off	startsb;
};

struct	Time
{
	Timet	lasttoy;
	Timet	bias;
	Timet	offset;
};

/*
 * array of qids that are locked
 */
struct	Tlock
{
	Device*	dev;
	Timet	time;
	Off	qpath;
	File*	file;
};

struct	Cons
{
	ulong	flags;		/* overall flags for all channels */
	QLock;			/* generic qlock for mutex */
	int	uid;		/* botch -- used to get uid on cons_create */
	int	gid;		/* botch -- used to get gid on cons_create */
	int	nuid;		/* number of uids */
	int	ngid;		/* number of gids */
	Off	offset;		/* used to read files, c.f. fchar */
	int	chano;		/* generator for channel numbers */
	Chan*	chan;		/* console channel */
	Filsys*	curfs;		/* current filesystem */

	int	profile;	/* are we profiling? */
	long*	profbuf;
	ulong	minpc;
	ulong	maxpc;
	ulong	nprofbuf;

	long	nlarge;		/* number of large message buffers */
	long	nsmall;		/* ... small ... */
	long	nwormre;	/* worm read errors */
	long	nwormwe;	/* worm write errors */
	long	nwormhit;	/* worm read cache hits */
	long	nwormmiss;	/* worm read cache non-hits */
	int	noage;		/* dont update cache age, dump and check */
	long	nwrenre;	/* disk read errors */
	long	nwrenwe;	/* disk write errors */
	long	nreseq;		/* cache bucket resequence */

	Filter	work[3];	/* thruput in messages */
	Filter	rate[3];	/* thruput in bytes */
	Filter	bhit[3];	/* getbufs that hit */
	Filter	bread[3];	/* getbufs that miss and read */
	Filter	brahead[3];	/* messages to readahead */
	Filter	binit[3];	/* getbufs that miss and dont read */
};

struct	File
{
	QLock;
	Qid	qid;
	Wpath*	wpath;
	Chan*	cp;		/* null means a free slot */
	Tlock*	tlock;		/* if file is locked */
	File*	next;		/* in cp->flist */
	Filsys*	fs;
	Off	addr;
	long	slot;		/* ordinal # of Dentry with a directory block */
	Off	lastra;		/* read ahead address */
	ulong	fid;
	Userid	uid;
	Auth	*auth;
	char	open;
		#define	FREAD	1
		#define	FWRITE	2
		#define	FREMOV	4

	Off	doffset;	/* directory reading */
	ulong	dvers;
	long	dslot;
};

struct	Wpath
{
	Wpath*	up;		/* pointer upwards in path */
	Off	addr;		/* directory entry addr */
	long	slot;		/* directory entry slot */
	short	refs;		/* number of files using this structure */
};

struct	Iobuf
{
	QLock;
	Device*	dev;
	Iobuf*	fore;		/* for lru */
	Iobuf*	back;		/* for lru */
	char*	iobuf;		/* only active while locked */
	char*	xiobuf;		/* "real" buffer pointer */
	Off	addr;
	int	flags;
};

struct	Uid
{
	Userid	uid;		/* user id */
	Userid	lead;		/* leader of group */
	Userid	*gtab;		/* group table */
	int	ngrp;		/* number of group entries */
	char	name[NAMELEN];	/* user name */
};

/* DONT TOUCH, this is the disk structure */
struct	Dentry
{
	char	name[NAMELEN];
	Userid	uid;
	Userid	gid;
	ushort	mode;
		#define	DALLOC	0x8000
		#define	DDIR	0x4000
		#define	DAPND	0x2000
		#define	DLOCK	0x1000
		#define	DREAD	0x4
		#define	DWRITE	0x2
		#define	DEXEC	0x1
	Userid	muid;
	Qid9p1	qid;
	Off	size;
	Off	dblock[NDBLOCK];
	Off	iblocks[NIBLOCK];
	long	atime;
	long	mtime;
};

/* DONT TOUCH, this is the disk structure */
struct	Super1
{
	Off	fstart;
	Off	fsize;
	Off	tfree;
	Off	qidgen;		/* generator for unique ids */
	/*
	 * Stuff for WWC device
	 */
	Off	cwraddr;	/* cfs root addr */
	Off	roraddr;	/* dump root addr */
	Off	last;		/* last super block addr */
	Off	next;		/* next super block addr */
#ifdef AUTOSWAB
	vlong	magic;		/* for byte-order detection */
	/* in memory only, not on disk (maybe) */
	int	flags;
#endif
};

/* DONT TOUCH, this is the disk structure */
struct	Fbuf
{
	Off	nfree;
	Off	free[FEPERBUF];
};

/* DONT TOUCH, this is the disk structure */
struct	Superb