quota.h

linux的文件系统的部分代码的详细注释

/*
 * Copyright (c) 1982, 1986 Regents of the University of California.
 * All rights reserved.
 *
 * This code is derived from software contributed to Berkeley by
 * Robert Elz at The University of Melbourne.
 *
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions
 * are met:
 * 1. Redistributions of source code must retain the above copyright
 *    notice, this list of conditions and the following disclaimer.
 * 2. Redistributions in binary form must reproduce the above copyright
 *    notice, this list of conditions and the following disclaimer in the
 *    documentation and/or other materials provided with the distribution.
 * 3. All advertising materials mentioning features or use of this software
 *    must display the following acknowledgement:
 *   This product includes software developed by the University of
 *   California, Berkeley and its contributors.
 * 4. Neither the name of the University nor the names of its contributors
 *    may be used to endorse or promote products derived from this software
 *    without specific prior written permission.
 *
 * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
 * ARE DISCLAIMED.  IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
 * SUCH DAMAGE.
 *
 * Version: $Id: quota.h,v 2.0 1996/11/17 16:48:14 mvw Exp mvw $
 */

#ifndef _LINUX_QUOTA_
#define _LINUX_QUOTA_

#include <linux/errno.h>

/*
 * Convert diskblocks to blocks and the other way around.
 */
#define dbtob(num) (num << BLOCK_SIZE_BITS)
#define btodb(num) (num >> BLOCK_SIZE_BITS)

/*
 * Convert count of filesystem blocks to diskquota blocks, meant
 * for filesystems where i_blksize != BLOCK_SIZE
 */
#define fs_to_dq_blocks(num, blksize) (((num) * (blksize)) / BLOCK_SIZE)

/*
 * Definitions for disk quotas imposed on the average user
 * (big brother finally hits Linux).
 *
 * The following constants define the amount of time given a user
 * before the soft limits are treated as hard limits (usually resulting
 * in an allocation failure). The timer is started when the user crosses
 * their soft limit, it is reset when they go below their soft limit.
 */
#define MAX_IQ_TIME  604800	/* (7*24*60*60) 1 week */
#define MAX_DQ_TIME  604800	/* (7*24*60*60) 1 week */

#define MAXQUOTAS 2
#define USRQUOTA  0		/* element used for user quotas */
#define GRPQUOTA  1		/* element used for group quotas */

/*
 * Definitions for the default names of the quotas files.
 */
#define INITQFNAMES { \
	"user",    /* USRQUOTA */ \
	"group",   /* GRPQUOTA */ \
	"undefined", \
};

#define QUOTAFILENAME "quota"
#define QUOTAGROUP "staff"

/*
 * Command definitions for the 'quotactl' system call.
 * The commands are broken into a main command defined below
 * and a subcommand that is used to convey the type of
 * quota that is being manipulated (see above).
 */
#define SUBCMDMASK  0x00ff
#define SUBCMDSHIFT 8
#define QCMD(cmd, type)  (((cmd) << SUBCMDSHIFT) | ((type) & SUBCMDMASK))

#define Q_QUOTAON  0x0100	/* enable quotas */
#define Q_QUOTAOFF 0x0200	/* disable quotas */
#define Q_GETQUOTA 0x0300	/* get limits and usage */
#define Q_SETQUOTA 0x0400	/* set limits and usage */
#define Q_SETUSE   0x0500	/* set usage */
#define Q_SYNC     0x0600	/* sync disk copy of a filesystems quotas */
#define Q_SETQLIM  0x0700	/* set limits */
#define Q_GETSTATS 0x0800	/* get collected stats */
#define Q_RSQUASH  0x1000	/* set root_squash option */

/*
 * The following structure defines the format of the disk quota file
 * (as it appears on disk) - the file is an array of these structures
 * indexed by user or group number.
 */
struct dqblk {
	__u32 dqb_bhardlimit;	/* absolute limit on disk blks alloc 块的硬限制*/
	__u32 dqb_bsoftlimit;	/* preferred limit on disk blks 块的软限制*/
	__u32 dqb_curblocks;	/* current block count 当前占有的块数*/
	__u32 dqb_ihardlimit;	/* absolute limit on allocated inodes 索引节点的硬限制*/
	__u32 dqb_isoftlimit;	/* preferred inode limit 索引节点的软限制*/
	__u32 dqb_curinodes;	/* current # allocated inodes 当前占用的索引节点数*/
	time_t dqb_btime;		/* time limit for excessive disk use 块的软限制变为硬限制前，剩余的警告次数*/
	time_t dqb_itime;		/* time limit for excessive inode use 索引节点的软限制变为硬限制前，剩余的警告次数*/
};

/*
 * Shorthand notation.
 */
#define	dq_bhardlimit	dq_dqb.dqb_bhardlimit
#define	dq_bsoftlimit	dq_dqb.dqb_bsoftlimit
#define	dq_curblocks	dq_dqb.dqb_curblocks
#define	dq_ihardlimit	dq_dqb.dqb_ihardlimit
#define	dq_isoftlimit	dq_dqb.dqb_isoftlimit
#define	dq_curinodes	dq_dqb.dqb_curinodes
#define	dq_btime	dq_dqb.dqb_btime
#define	dq_itime	dq_dqb.dqb_itime

#define dqoff(UID)      ((loff_t)((UID) * sizeof (struct dqblk)))

struct dqstats {
	__u32 lookups;
	__u32 drops;
	__u32 reads;
	__u32 writes;
	__u32 cache_hits;
	__u32 allocated_dquots;
	__u32 free_dquots;
	__u32 syncs;
};

#ifdef __KERNEL__

extern int nr_dquots, nr_free_dquots;
extern int dquot_root_squash;

#define NR_DQHASH 43            /* Just an arbitrary number */

#define DQ_LOCKED     0x01	/* dquot under IO */
#define DQ_MOD        0x02	/* dquot modified since read */
#define DQ_BLKS       0x10	/* uid/gid has been warned about blk limit */
#define DQ_INODES     0x20	/* uid/gid has been warned about inode limit */
#define DQ_FAKE       0x40	/* no limits only usage */
#define DQ_INVAL      0x80	/* dquot is going to be invalidated */

struct dquot {
	struct list_head dq_hash;	/* Hash list in memory 在内存中的哈希表*/
	struct list_head dq_inuse;	/* List of all quotas 正在使用的限额块组成的链表*/
	struct list_head dq_free;	/* Free list element 空闲限额块组成的链表*/
	wait_queue_head_t dq_wait_lock;	/* Pointer to waitqueue on dquot lock 指向加锁限额块的等待队列*/
	wait_queue_head_t dq_wait_free;	/* Pointer to waitqueue for quota to be unused 指向未用限额块的等待队列*/
	int dq_count;			/* Reference count 引用计数*/

	/* fields after this point are cleared when invalidating */
	struct super_block *dq_sb;	/* superblock this applies to */
	unsigned int dq_id;		/* ID this applies to (uid, gid) */
	kdev_t dq_dev;			/* Device this applies to */
	short dq_type;			/* Type of quota */
	short dq_flags;			/* See DQ_* */
	unsigned long dq_referenced;	/* Number of times this dquot was 
					   referenced during its lifetime */
	struct dqblk dq_dqb;		/* Diskquota usage */
};

#define NODQUOT (struct dquot *)NULL

/*
 * Flags used for set_dqblk.
 */
#define SET_QUOTA         0x02
#define SET_USE           0x04
#define SET_QLIMIT        0x08

#define QUOTA_OK          0
#define NO_QUOTA          1

#else

# /* nodep */ include <sys/cdefs.h>

__BEGIN_DECLS
long quotactl __P ((int, const char *, int, caddr_t));
__END_DECLS

#endif /* __KERNEL__ */
#endif /* _QUOTA_ */