dquot.c

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/*
 * Implementation of the diskquota system for the LINUX operating
 * system. QUOTA is implemented using the BSD systemcall interface as
 * the means of communication with the user level. Currently only the
 * ext2-filesystem has support for diskquotas. Other filesystems may
 * be added in future time. This file contains the generic routines
 * called by the different filesystems on allocation of an inode or
 * block. These routines take care of the administration needed to
 * have a consistent diskquota tracking system. The ideas of both
 * user and group quotas are based on the Melbourne quota system as
 * used on BSD derived systems. The internal implementation is 
 * based on the LINUX inode-subsystem with added complexity of the
 * diskquota system. This implementation is not based on any BSD
 * kernel sourcecode.
 * 
 * Version: $Id: dquot.c,v 1.2 1999/07/16 23:52:00 bjornw Exp $
 * 
 * Author:  Marco van Wieringen <[e-mail]> <[e-mail]>
 * 
 * Fixes:   Dmitry Gorodchanin <[e-mail]>, 11 Feb 96
 *	    removed race conditions in dqput(), dqget() and iput(). 
 *          Nick Kralevich <[e-mail]>, 21 Jul 97
 *          Fixed a condition where user and group quotas could get mixed up.
 *
 * (C) Copyright 1994, 1995 Marco van Wieringen 
 *
 */

#include <linux/errno.h>
#include <linux/kernel.h>
#include <linux/sched.h>
#include <linux/types.h>
#include <linux/string.h>
#include <linux/fcntl.h>
#include <linux/stat.h>
#include <linux/tty.h>
#include <linux/malloc.h>
#include <linux/mount.h>

#include <asm/segment.h>

#define __DQUOT_VERSION__	"dquot_5.6.0"

static char quotamessage[MAX_QUOTA_MESSAGE];
static char *quotatypes[] = INITQFNAMES;

static int nr_dquots = 0, nr_free_dquots = 0;
static struct dquot *hash_table[NR_DQHASH];
static struct dquot *first_dquot;
static struct dqstats dqstats;

static struct wait_queue *dquot_wait = (struct wait_queue *)NULL;

extern void add_dquot_ref(kdev_t dev, short type);
extern void reset_dquot_ptrs(kdev_t dev, short type);

#ifndef min
#define min(a,b) ((a) < (b)) ? (a) : (b)
#endif

/*
 * Functions for management of the hashlist.
 */
static inline int const hashfn(kdev_t dev, unsigned int id, short type)
{
	return((HASHDEV(dev) ^ id) * (MAXQUOTAS - type)) % NR_DQHASH;
}

static inline struct dquot **const hash(kdev_t dev, unsigned int id, short type)
{
	return(hash_table + hashfn(dev, id, type));
}

static inline int has_quota_enabled(kdev_t dev, short type)
{
	struct vfsmount *vfsmnt;

	return((vfsmnt = lookup_vfsmnt(dev)) != (struct vfsmount *)NULL &&
	       (vfsmnt->mnt_quotas[type] != (struct file *)NULL));
}

static void insert_dquot_free(struct dquot *dquot)
{
	dquot->dq_next = first_dquot;
	dquot->dq_prev = first_dquot->dq_prev;
	dquot->dq_next->dq_prev = dquot;
	dquot->dq_prev->dq_next = dquot;
	first_dquot = dquot;
}

static void remove_dquot_free(struct dquot *dquot)
{
	if (first_dquot == dquot)
		first_dquot = first_dquot->dq_next;
	if (dquot->dq_next)
		dquot->dq_next->dq_prev = dquot->dq_prev;
	if (dquot->dq_prev)
		dquot->dq_prev->dq_next = dquot->dq_next;
	dquot->dq_next = dquot->dq_prev = NODQUOT;
}

static void insert_dquot_hash(struct dquot *dquot)
{
	struct dquot **hash_ent;

	hash_ent = hash(dquot->dq_dev, dquot->dq_id, dquot->dq_type);
	dquot->dq_hash_next = *hash_ent;
	dquot->dq_hash_prev = NODQUOT;
	if (dquot->dq_hash_next)
		dquot->dq_hash_next->dq_hash_prev = dquot;
	*hash_ent = dquot;
}

static void remove_dquot_hash(struct dquot *dquot)
{
	struct dquot **hash_ent;

	hash_ent = hash(dquot->dq_dev, dquot->dq_id, dquot->dq_type);
	if (*hash_ent == dquot)
		*hash_ent = dquot->dq_hash_next;
	if (dquot->dq_hash_next)
		dquot->dq_hash_next->dq_hash_prev = dquot->dq_hash_prev;
	if (dquot->dq_hash_prev)
		dquot->dq_hash_prev->dq_hash_next = dquot->dq_hash_next;
	dquot->dq_hash_prev = dquot->dq_hash_next = NODQUOT;
}

static void put_last_free(struct dquot *dquot)
{
	remove_dquot_free(dquot);
	dquot->dq_prev = first_dquot->dq_prev;
	dquot->dq_prev->dq_next = dquot;
	dquot->dq_next = first_dquot;
	dquot->dq_next->dq_prev = dquot;
}

static void grow_dquots(void)
{
	struct dquot *dquot;
	int cnt;

	if (!(dquot = (struct dquot*) get_free_page(GFP_KERNEL)))
		return;
	dqstats.pages_allocated++;
	cnt = PAGE_SIZE / sizeof(struct dquot);
	nr_dquots += cnt;
	nr_free_dquots += cnt;
	if (!first_dquot) {
		dquot->dq_next = dquot->dq_prev = first_dquot = dquot++;
		cnt--;
	}
	for (; cnt; cnt--)
		insert_dquot_free(dquot++);
}

/*
 * Functions for locking and waiting on dquots.
 */
static void __wait_on_dquot(struct dquot *dquot)
{
	struct wait_queue wait = {current, NULL};

	add_wait_queue(&dquot->dq_wait, &wait);
repeat:
	current->state = TASK_UNINTERRUPTIBLE;
	if (dquot->dq_flags & DQ_LOCKED) {
		dquot->dq_flags |= DQ_WANT;
		schedule();
		goto repeat;
	}
	remove_wait_queue(&dquot->dq_wait, &wait);
	current->state = TASK_RUNNING;
}

static inline void wait_on_dquot(struct dquot *dquot)
{
	if (dquot->dq_flags & DQ_LOCKED)
		__wait_on_dquot(dquot);
}

static inline void lock_dquot(struct dquot *dquot)
{
	wait_on_dquot(dquot);
	dquot->dq_flags |= DQ_LOCKED;
}

static inline void unlock_dquot(struct dquot *dquot)
{
	dquot->dq_flags &= ~DQ_LOCKED;
	if (dquot->dq_flags & DQ_WANT) {
		dquot->dq_flags &= ~DQ_WANT;
		wake_up(&dquot->dq_wait);
	}
}
/*
 * Note that we don't want to disturb any wait-queues when we discard
 * an dquot.
 *
 * FIXME: As soon as we have a nice solution for the inode problem we
 *		  can also fix this one. I.e. the volatile part.
 */
static void clear_dquot(struct dquot * dquot)
{
	struct wait_queue *wait;

	wait_on_dquot(dquot);
	remove_dquot_hash(dquot);
	remove_dquot_free(dquot);
	wait = ((volatile struct dquot *) dquot)->dq_wait;
	if (dquot->dq_count)
		nr_free_dquots++;
	memset(dquot, 0, sizeof(*dquot));
	((volatile struct dquot *) dquot)->dq_wait = wait;
	insert_dquot_free(dquot);
}

static void write_dquot(struct dquot *dquot)
{
	short type = dquot->dq_type;
	struct file *filp = dquot->dq_mnt->mnt_quotas[type];
	unsigned short fs;

	if (!(dquot->dq_flags & DQ_MOD) || (filp == (struct file *)NULL))
		return;
	lock_dquot(dquot);
	down(&dquot->dq_mnt->mnt_sem);
	if (filp->f_op->lseek) {
		if (filp->f_op->lseek(filp->f_inode, filp,
		    dqoff(dquot->dq_id), 0) != dqoff(dquot->dq_id)) {
			up(&dquot->dq_mnt->mnt_sem);
			unlock_dquot(dquot);
			return;
		}
	}
	else
	{
		int p = dqoff(dquot->dq_id);
		if(p>=0)
			filp->f_pos = p;
	}
	fs = get_fs();
	set_fs(KERNEL_DS);
	if (filp->f_op->write(filp->f_inode, filp,
	   (char *)&dquot->dq_dqb, sizeof(struct dqblk)) == sizeof(struct dqblk))
		dquot->dq_flags &= ~DQ_MOD;
	up(&dquot->dq_mnt->mnt_sem);
	set_fs(fs);
	unlock_dquot(dquot);
	dqstats.writes++;
}

static void read_dquot(struct dquot *dquot)
{
	short type = dquot->dq_type;
	struct file *filp = dquot->dq_mnt->mnt_quotas[type];
	unsigned short fs;

	if (filp == (struct file *)NULL)
		return;
	lock_dquot(dquot);
	down(&dquot->dq_mnt->mnt_sem);
	if (filp->f_op->lseek) {
		if (filp->f_op->lseek(filp->f_inode, filp,
		    dqoff(dquot->dq_id), 0) != dqoff(dquot->dq_id)) {
			up(&dquot->dq_mnt->mnt_sem);
			unlock_dquot(dquot);
			return;
		}
	} else
		filp->f_pos = dqoff(dquot->dq_id);
	fs = get_fs();
	set_fs(KERNEL_DS);
	filp->f_op->read(filp->f_inode, filp, (char *)&dquot->dq_dqb, sizeof(struct dqblk));
	up(&dquot->dq_mnt->mnt_sem);
	set_fs(fs);
	if (dquot->dq_bhardlimit == 0 && dquot->dq_bsoftlimit == 0 &&
	    dquot->dq_ihardlimit == 0 && dquot->dq_isoftlimit == 0)
		dquot->dq_flags |= DQ_FAKE;
	unlock_dquot(dquot);
	dqstats.reads++;
}

int sync_dquots(kdev_t dev, short type)
{
	struct dquot *dquot = first_dquot;
	int i;

	dqstats.syncs++;
	for (i = 0; i < nr_dquots * 2; i++, dquot = dquot->dq_next) {
		if (dev == NODEV || dquot->dq_count == 0 || dquot->dq_dev != dev)
			continue;
		if (type != -1 && dquot->dq_type != type)
			continue;
		wait_on_dquot(dquot);
		if (dquot->dq_flags & DQ_MOD)
			write_dquot(dquot);
	}
	return(0);
}

/*
 * Trash the cache for a certain type on a device.
 */
void invalidate_dquots(kdev_t dev, short type)
{
	struct dquot *dquot, *next;
	int cnt;

	next = first_dquot;
	for (cnt = nr_dquots ; cnt > 0 ; cnt--) {
		dquot = next;
		next = dquot->dq_next;
		if (dquot->dq_dev != dev || dquot->dq_type != type)
			continue;
		if (dquot->dq_flags & DQ_LOCKED) {
			printk("VFS: dquot busy on removed device %s\n", kdevname(dev));
			continue;
		}
		if (dquot->dq_flags & DQ_MOD)
			write_dquot(dquot);
		dqstats.drops++;
		clear_dquot(dquot);
	}
}

static inline void dquot_incr_inodes(struct dquot *dquot, unsigned long number)
{
	lock_dquot(dquot);
	dquot->dq_curinodes += number;
	dquot->dq_flags |= DQ_MOD;
	unlock_dquot(dquot);
}

static inline void dquot_incr_blocks(struct dquot *dquot, unsigned long number)
{
	lock_dquot(dquot);
	dquot->dq_curblocks += number;
	dquot->dq_flags |= DQ_MOD;
	unlock_dquot(dquot);
}

static inline void dquot_decr_inodes(struct dquot *dquot, unsigned long number)
{
	lock_dquot(dquot);
	if (dquot->dq_curinodes > number)
		dquot->dq_curinodes -= number;
	else
		dquot->dq_curinodes = 0;
	if (dquot->dq_curinodes < dquot->dq_isoftlimit)
		dquot->dq_itime = (time_t) 0;
	dquot->dq_flags &= ~DQ_INODES;
	dquot->dq_flags |= DQ_MOD;
	unlock_dquot(dquot);
}

static inline void dquot_decr_blocks(struct dquot *dquot, unsigned long number)
{
	lock_dquot(dquot);
	if (dquot->dq_curblocks > number)
		dquot->dq_curblocks -= number;
	else
		dquot->dq_curblocks = 0;
	if (dquot->dq_curblocks < dquot->dq_bsoftlimit)
		dquot->dq_btime = (time_t) 0;
	dquot->dq_flags &= ~DQ_BLKS;
	dquot->dq_flags |= DQ_MOD;
	unlock_dquot(dquot);
}

static inline int need_print_warning(short type, struct dquot *dquot)
{
	switch (type) {
		case USRQUOTA:
			return(current->fsuid == dquot->dq_id);
		case GRPQUOTA:
			return(current->fsgid == dquot->dq_id);
	}
	return(0);
}

static int check_idq(struct dquot *dquot, short type, u_long short inodes)
{
	if (inodes <= 0 || dquot->dq_flags & DQ_FAKE)
		return(QUOTA_OK);
	if (dquot->dq_ihardlimit &&
	   (dquot->dq_curinodes + inodes) > dquot->dq_ihardlimit && !fsuser()) {
		if ((dquot->dq_flags & DQ_INODES) == 0 &&
                     need_print_warning(type, dquot)) {
			sprintf(quotamessage, "%s: write failed, %s file limit reached\r\n",
			        dquot->dq_mnt->mnt_dirname, quotatypes[type]);
			tty_write_message(current->tty, quotamessage);
			dquot->dq_flags |= DQ_INODES;
		}
		return(NO_QUOTA);
	}
	if (dquot->dq_isoftlimit &&
	   (dquot->dq_curinodes + inodes) > dquot->dq_isoftlimit &&
	    dquot->dq_itime && CURRENT_TIME >= dquot->dq_itime && !fsuser()) {
                if (need_print_warning(type, dquot)) {
			sprintf(quotamessage, "%s: warning, %s file quota exceeded too long.\r\n",
		        	dquot->dq_mnt->mnt_dirname, quotatypes[type]);
			tty_write_message(current->tty, quotamessage);
		}
		return(NO_QUOTA);
	}
	if (dquot->dq_isoftlimit &&
	   (dquot->dq_curinodes + inodes) > dquot->dq_isoftlimit &&
	    dquot->dq_itime == 0 && !fsuser()) {
                if (need_print_warning(type, dquot)) {
			sprintf(quotamessage, "%s: warning, %s file quota exceeded\r\n",
		        	dquot->dq_mnt->mnt_dirname, quotatypes[type]);
			tty_write_message(current->tty, quotamessage);
		}
		dquot->dq_itime = CURRENT_TIME + dquot->dq_mnt->mnt_iexp[type];
	}
	return(QUOTA_OK);
}

static int check_bdq(struct dquot *dquot, short type, u_long blocks)
{
	if (blocks <= 0 || dquot->dq_flags & DQ_FAKE)
		return(QUOTA_OK);
	if (dquot->dq_bhardlimit &&
	   (dquot->dq_curblocks + blocks) > dquot->dq_bhardlimit && !fsuser()) {
		if ((dquot->dq_flags & DQ_BLKS) == 0 &&
                     need_print_warning(type, dquot)) {
			sprintf(quotamessage, "%s: write failed, %s disk limit reached.\r\n",
			        dquot->dq_mnt->mnt_dirname, quotatypes[type]);
			tty_write_message(current->tty, quotamessage);
			dquot->dq_flags |= DQ_BLKS;
		}
		return(NO_QUOTA);
	}
	if (dquot->dq_bsoftlimit &&
	   (dquot->dq_curblocks + blocks) > dquot->dq_bsoftlimit &&
	    dquot->dq_btime && CURRENT_TIME >= dquot->dq_btime && !fsuser()) {
                if (need_print_warning(type, dquot)) {
			sprintf(quotamessage, "%s: write failed, %s disk quota exceeded too long.\r\n",
		        	dquot->dq_mnt->mnt_dirname, quotatypes[type]);
			tty_write_message(current->tty, quotamessage);
		}
		return(NO_QUOTA);
	}
	if (dquot->dq_bsoftlimit &&
	   (dquot->dq_curblocks + blocks) > dquot->dq_bsoftlimit &&
	    dquot->dq_btime == 0 && !fsuser()) {
                if (need_print_warning(type, dquot)) {
			sprintf(quotamessage, "%s: warning, %s disk quota exceeded\r\n",
		        	dquot->dq_mnt->mnt_dirname, quotatypes[type]);
			tty_write_message(current->tty, quotamessage);
		}
		dquot->dq_btime = CURRENT_TIME + dquot->dq_mnt->mnt_bexp[type];
	}
	return(QUOTA_OK);
}

static void dqput(struct dquot *dquot)
{
	if (!dquot)
		return;
	/*
	 * If the dq_mnt pointer isn't initialized this entry needs no
	 * checking and doesn't need to be written. It just an empty
	 * dquot that is put back into the freelist.
	 */
	if (dquot->dq_mnt != (struct vfsmount *)NULL) {
		dqstats.drops++;
		wait_on_dquot(dquot);
		if (!dquot->dq_count) {
			printk("VFS: dqput: trying to free free dquot\n");
			printk("VFS: device %s, dquot of %s %d\n", kdevname(dquot->dq_dev),
			       quotatypes[dquot->dq_type], dquot->dq_id);
			return;
		}
repeat:
		if (dquot->dq_count > 1) {
			dquot->dq_count--;
			return;
		}
		wake_up(&dquot_wait);
		if (dquot->dq_flags & DQ_MOD) {
			write_dquot(dquot);	/* we can sleep - so do again */
			wait_on_dquot(dquot);
			goto repeat;
		}
	}
	if (dquot->dq_count) {
		dquot->dq_count--;
		nr_free_dquots++;
	}
	return;
}

static struct dquot *get_empty_dquot(void)
{
	struct dquot *dquot, *best;
	int cnt;

	if (nr_dquots < NR_DQUOTS && nr_free_dquots < (nr_dquots >> 2))
		grow_dquots();

repeat:
	dquot = first_dquot;
	best = NODQUOT;
	for (cnt = 0; cnt < nr_dquots; dquot = dquot->dq_next, cnt++) {
		if (!dquot->dq_count) {
			if (!best)
				best = dquot;
			if (!(dquot->dq_flags & DQ_MOD) && !(dquot->dq_flags & DQ_LOCKED)) {
				best = dquot;
				break;
			}
		}
	}
	if (!best || best->dq_flags & DQ_MOD || best->dq_flags & DQ_LOCKED)
		if (nr_dquots < NR_DQUOTS) {
			grow_dquots();
			goto repeat;
		}
	dquot = best;
	if (!dquot) {
		printk("VFS: No free dquots - contact [e-mail]\n");
		sleep_on(&dquot_wait);
		goto repeat;
	}
	if (dquot->dq_flags & DQ_LOCKED) {
		wait_on_dquot(dquot);
		goto repeat;
	}
	if (dquot->dq_flags & DQ_MOD) {
		write_dquot(dquot);
		goto repeat;
	}
	if (dquot->dq_count)
		goto repeat;
	clear_dquot(dquot);
	dquot->dq_count = 1;
	nr_free_dquots--;
	if (nr_free_dquots < 0) {
		printk ("VFS: get_empty_dquot: bad free dquot count.\n");
		nr_free_dquots = 0;
	}
	return(dquot);
}

static struct dquot *dqget(kdev_t dev, unsigned int id, short type)