fs/quota/dquot.c

/*
 * Implementation of the diskquota system for the LINUX operating system. QUOTA
 * is implemented using the BSD system call interface as the means of
 * communication with the user level. 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 one of the several variants of the LINUX
 * inode-subsystem with added complexity of the diskquota system.
 * 
 * Author:	Marco van Wieringen <mvw@planets.elm.net>
 *
 * Fixes:   Dmitry Gorodchanin <pgmdsg@ibi.com>, 11 Feb 96
 *
 *		Revised list management to avoid races
 *		-- Bill Hawes, <whawes@star.net>, 9/98
 *
 *		Fixed races in dquot_transfer(), dqget() and dquot_alloc_...().
 *		As the consequence the locking was moved from dquot_decr_...(),
 *		dquot_incr_...() to calling functions.
 *		invalidate_dquots() now writes modified dquots.
 *		Serialized quota_off() and quota_on() for mount point.
 *		Fixed a few bugs in grow_dquots().
 *		Fixed deadlock in write_dquot() - we no longer account quotas on
 *		quota files
 *		remove_dquot_ref() moved to inode.c - it now traverses through inodes
 *		add_dquot_ref() restarts after blocking
 *		Added check for bogus uid and fixed check for group in quotactl.
 *		Jan Kara, <jack@suse.cz>, sponsored by SuSE CR, 10-11/99
 *
 *		Used struct list_head instead of own list struct
 *		Invalidation of referenced dquots is no longer possible
 *		Improved free_dquots list management
 *		Quota and i_blocks are now updated in one place to avoid races
 *		Warnings are now delayed so we won't block in critical section
 *		Write updated not to require dquot lock
 *		Jan Kara, <jack@suse.cz>, 9/2000
 *
 *		Added dynamic quota structure allocation
 *		Jan Kara <jack@suse.cz> 12/2000
 *
 *		Rewritten quota interface. Implemented new quota format and
 *		formats registering.
 *		Jan Kara, <jack@suse.cz>, 2001,2002
 *
 *		New SMP locking.
 *		Jan Kara, <jack@suse.cz>, 10/2002
 *
 *		Added journalled quota support, fix lock inversion problems
 *		Jan Kara, <jack@suse.cz>, 2003,2004
 *
 * (C) Copyright 1994 - 1997 Marco van Wieringen 
 */

#include <linux/errno.h>
#include <linux/kernel.h>
#include <linux/fs.h>
#include <linux/mount.h>
#include <linux/mm.h>
#include <linux/time.h>
#include <linux/types.h>
#include <linux/string.h>
#include <linux/fcntl.h>
#include <linux/stat.h>
#include <linux/tty.h>
#include <linux/file.h>
#include <linux/slab.h>
#include <linux/sysctl.h>
#include <linux/init.h>
#include <linux/module.h>
#include <linux/proc_fs.h>
#include <linux/security.h>
#include <linux/kmod.h>
#include <linux/namei.h>
#include <linux/buffer_head.h>
#include <linux/capability.h>
#include <linux/quotaops.h>
#include <linux/writeback.h> /* for inode_lock, oddly enough.. */
#ifdef CONFIG_QUOTA_NETLINK_INTERFACE
#include <net/netlink.h>
#include <net/genetlink.h>
#endif

#include <asm/uaccess.h>

#define __DQUOT_PARANOIA

/*
 * There are three quota SMP locks. dq_list_lock protects all lists with quotas
 * and quota formats, dqstats structure containing statistics about the lists
 * dq_data_lock protects data from dq_dqb and also mem_dqinfo structures and
 * also guards consistency of dquot->dq_dqb with inode->i_blocks, i_bytes.
 * i_blocks and i_bytes updates itself are guarded by i_lock acquired directly
 * in inode_add_bytes() and inode_sub_bytes(). dq_state_lock protects
 * modifications of quota state (on quotaon and quotaoff) and readers who care
 * about latest values take it as well.
 *
 * The spinlock ordering is hence: dq_data_lock > dq_list_lock > i_lock,
 *   dq_list_lock > dq_state_lock
 *
 * Note that some things (eg. sb pointer, type, id) doesn't change during
 * the life of the dquot structure and so needn't to be protected by a lock
 *
 * Any operation working on dquots via inode pointers must hold dqptr_sem.  If
 * operation is just reading pointers from inode (or not using them at all) the
 * read lock is enough. If pointers are altered function must hold write lock
 * (these locking rules also apply for S_NOQUOTA flag in the inode - note that
 * for altering the flag i_mutex is also needed).
 *
 * Each dquot has its dq_lock mutex. Locked dquots might not be referenced
 * from inodes (dquot_alloc_space() and such don't check the dq_lock).
 * Currently dquot is locked only when it is being read to memory (or space for
 * it is being allocated) on the first dqget() and when it is being released on
 * the last dqput(). The allocation and release oparations are serialized by
 * the dq_lock and by checking the use count in dquot_release().  Write
 * operations on dquots don't hold dq_lock as they copy data under dq_data_lock
 * spinlock to internal buffers before writing.
 *
 * Lock ordering (including related VFS locks) is the following:
 *   i_mutex > dqonoff_sem > journal_lock > dqptr_sem > dquot->dq_lock >
 *   dqio_mutex
 * The lock ordering of dqptr_sem imposed by quota code is only dqonoff_sem >
 * dqptr_sem. But filesystem has to count with the fact that functions such as
 * dquot_alloc_space() acquire dqptr_sem and they usually have to be called
 * from inside a transaction to keep filesystem consistency after a crash. Also
 * filesystems usually want to do some IO on dquot from ->mark_dirty which is
 * called with dqptr_sem held.
 * i_mutex on quota files is special (it's below dqio_mutex)
 */

static __cacheline_aligned_in_smp DEFINE_SPINLOCK(dq_list_lock);
static __cacheline_aligned_in_smp DEFINE_SPINLOCK(dq_state_lock);
__cacheline_aligned_in_smp DEFINE_SPINLOCK(dq_data_lock);
EXPORT_SYMBOL(dq_data_lock);

static char *quotatypes[] = INITQFNAMES;
static struct quota_format_type *quota_formats;	/* List of registered formats */
static struct quota_module_name module_names[] = INIT_QUOTA_MODULE_NAMES;

/* SLAB cache for dquot structures */
static struct kmem_cache *dquot_cachep;

int register_quota_format(struct quota_format_type *fmt)
{
	spin_lock(&dq_list_lock);
	fmt->qf_next = quota_formats;
	quota_formats = fmt;
	spin_unlock(&dq_list_lock);
	return 0;
}
EXPORT_SYMBOL(register_quota_format);

void unregister_quota_format(struct quota_format_type *fmt)
{
	struct quota_format_type **actqf;

	spin_lock(&dq_list_lock);
	for (actqf = &quota_formats; *actqf && *actqf != fmt;
	     actqf = &(*actqf)->qf_next)
		;
	if (*actqf)
		*actqf = (*actqf)->qf_next;
	spin_unlock(&dq_list_lock);
}
EXPORT_SYMBOL(unregister_quota_format);

static struct quota_format_type *find_quota_format(int id)
{
	struct quota_format_type *actqf;

	spin_lock(&dq_list_lock);
	for (actqf = quota_formats; actqf && actqf->qf_fmt_id != id;
	     actqf = actqf->qf_next)
		;
	if (!actqf || !try_module_get(actqf->qf_owner)) {
		int qm;

		spin_unlock(&dq_list_lock);
		
		for (qm = 0; module_names[qm].qm_fmt_id &&
			     module_names[qm].qm_fmt_id != id; qm++)
			;
		if (!module_names[qm].qm_fmt_id ||
		    request_module(module_names[qm].qm_mod_name))
			return NULL;

		spin_lock(&dq_list_lock);
		for (actqf = quota_formats; actqf && actqf->qf_fmt_id != id;
		     actqf = actqf->qf_next)
			;
		if (actqf && !try_module_get(actqf->qf_owner))
			actqf = NULL;
	}
	spin_unlock(&dq_list_lock);
	return actqf;
}

static void put_quota_format(struct quota_format_type *fmt)
{
	module_put(fmt->qf_owner);
}

/*
 * Dquot List Management:
 * The quota code uses three lists for dquot management: the inuse_list,
 * free_dquots, and dquot_hash[] array. A single dquot structure may be
 * on all three lists, depending on its current state.
 *
 * All dquots are placed to the end of inuse_list when first created, and this
 * list is used for invalidate operation, which must look at every dquot.
 *
 * Unused dquots (dq_count == 0) are added to the free_dquots list when freed,
 * and this list is searched whenever we need an available dquot.  Dquots are
 * removed from the list as soon as they are used again, and
 * dqstats.free_dquots gives the number of dquots on the list. When
 * dquot is invalidated it's completely released from memory.
 *
 * Dquots with a specific identity (device, type and id) are placed on
 * one of the dquot_hash[] hash chains. The provides an efficient search
 * mechanism to locate a specific dquot.
 */

static LIST_HEAD(inuse_list);
static LIST_HEAD(free_dquots);
static unsigned int dq_hash_bits, dq_hash_mask;
static struct hlist_head *dquot_hash;

struct dqstats dqstats;
EXPORT_SYMBOL(dqstats);

static inline unsigned int
hashfn(const struct super_block *sb, unsigned int id, int type)
{
	unsigned long tmp;

	tmp = (((unsigned long)sb>>L1_CACHE_SHIFT) ^ id) * (MAXQUOTAS - type);
	return (tmp + (tmp >> dq_hash_bits)) & dq_hash_mask;
}

/*
 * Following list functions expect dq_list_lock to be held
 */
static inline void insert_dquot_hash(struct dquot *dquot)
{
	struct hlist_head *head;
	head = dquot_hash + hashfn(dquot->dq_sb, dquot->dq_id, dquot->dq_type);
	hlist_add_head(&dquot->dq_hash, head);
}

static inline void remove_dquot_hash(struct dquot *dquot)
{
	hlist_del_init(&dquot->dq_hash);
}

static struct dquot *find_dquot(unsigned int hashent, struct super_block *sb,
				unsigned int id, int type)
{
	struct hlist_node *node;
	struct dquot *dquot;

	hlist_for_each (node, dquot_hash+hashent) {
		dquot = hlist_entry(node, struct dquot, dq_hash);
		if (dquot->dq_sb == sb && dquot->dq_id == id &&
		    dquot->dq_type == type)
			return dquot;
	}
	return NULL;
}

/* Add a dquot to the tail of the free list */
static inline void put_dquot_last(struct dquot *dquot)
{
	list_add_tail(&dquot->dq_free, &free_dquots);
	dqstats.free_dquots++;
}

static inline void remove_free_dquot(struct dquot *dquot)
{
	if (list_empty(&dquot->dq_free))
		return;
	list_del_init(&dquot->dq_free);
	dqstats.free_dquots--;
}

static inline void put_inuse(struct dquot *dquot)
{
	/* We add to the back of inuse list so we don't have to restart
	 * when traversing this list and we block */
	list_add_tail(&dquot->dq_inuse, &inuse_list);
	dqstats.allocated_dquots++;
}

static inline void remove_inuse(struct dquot *dquot)
{
	dqstats.allocated_dquots--;
	list_del(&dquot->dq_inuse);
}
/*
 * End of list functions needing dq_list_lock
 */

static void wait_on_dquot(struct dquot *dquot)
{
	mutex_lock(&dquot->dq_lock);
	mutex_unlock(&dquot->dq_lock);
}

static inline int dquot_dirty(struct dquot *dquot)
{
	return test_bit(DQ_MOD_B, &dquot->dq_flags);
}

static inline int mark_dquot_dirty(struct dquot *dquot)
{
	return dquot->dq_sb->dq_op->mark_dirty(dquot);
}

int dquot_mark_dquot_dirty(struct dquot *dquot)
{
	spin_lock(&dq_list_lock);
	if (!test_and_set_bit(DQ_MOD_B, &dquot->dq_flags))
		list_add(&dquot->dq_dirty, &sb_dqopt(dquot->dq_sb)->
				info[dquot->dq_type].dqi_dirty_list);
	spin_unlock(&dq_list_lock);
	return 0;
}
EXPORT_SYMBOL(dquot_mark_dquot_dirty);

/* This function needs dq_list_lock */
static inline int clear_dquot_dirty(struct dquot *dquot)
{
	if (!test_and_clear_bit(DQ_MOD_B, &dquot->dq_flags))
		return 0;
	list_del_init(&dquot->dq_dirty);
	return 1;
}

void mark_info_dirty(struct super_block *sb, int type)
{
	set_bit(DQF_INFO_DIRTY_B, &sb_dqopt(sb)->info[type].dqi_flags);
}
EXPORT_SYMBOL(mark_info_dirty);

/*
 *	Read dquot from disk and alloc space for it
 */

int dquot_acquire(struct dquot *dquot)
{
	int ret = 0, ret2 = 0;
	struct quota_info *dqopt = sb_dqopt(dquot->dq_sb);

	mutex_lock(&dquot->dq_lock);
	mutex_lock(&dqopt->dqio_mutex);
	if (!test_bit(DQ_READ_B, &dquot->dq_flags))
		ret = dqopt->ops[dquot->dq_type]->read_dqblk(dquot);
	if (ret < 0)
		goto out_iolock;
	set_bit(DQ_READ_B, &dquot->dq_flags);
	/* Instantiate dquot if needed */
	if (!test_bit(DQ_ACTIVE_B, &dquot->dq_flags) && !dquot->dq_off) {
		ret = dqopt->ops[dquot->dq_type]->commit_dqblk(dquot);
		/* Write the info if needed */
		if (info_dirty(&dqopt->info[dquot->dq_type])) {
			ret2 = dqopt->ops[dquot->dq_type]->write_file_info(
						dquot->dq_sb, dquot->dq_type);
		}
		if (ret < 0)
			goto out_iolock;
		if (ret2 < 0) {
			ret = ret2;
			goto out_iolock;
		}
	}
	set_bit(DQ_ACTIVE_B, &dquot->dq_flags);
out_iolock:
	mutex_unlock(&dqopt->dqio_mutex);
	mutex_unlock(&dquot->dq_lock);
	return ret;
}
EXPORT_SYMBOL(dquot_acquire);

/*
 *	Write dquot to disk
 */
int dquot_commit(struct dquot *dquot)
{
	int ret = 0, ret2 = 0;
	struct quota_info *dqopt = sb_dqopt(dquot->dq_sb);

	mutex_lock(&dqopt->dqio_mutex);
	spin_lock(&dq_list_lock);
	if (!clear_dquot_dirty(dquot)) {
		spin_unlock(&dq_list_lock);
		goto out_sem;
	}
	spin_unlock(&dq_list_lock);
	/* Inactive dquot can be only if there was error during read/init
	 * => we have better not writing it */
	if (test_bit(DQ_ACTIVE_B, &dquot->dq_flags)) {
		ret = dqopt->ops[dquot->dq_type]->commit_dqblk(dquot);
		if (info_dirty(&dqopt->info[dquot->dq_type])) {
			ret2 = dqopt->ops[dquot->dq_type]->write_file_info(
						dquot->dq_sb, dquot->dq_type);
		}
		if (ret >= 0)
			ret = ret2;
	}
out_sem:
	mutex_unlock(&dqopt->dqio_mutex);
	return ret;
}
EXPORT_SYMBOL(dquot_commit);

/*
 *	Release dquot
 */
int dquot_release(struct dquot *dquot)
{
	int ret = 0, ret2 = 0;
	struct quota_info *dqopt = sb_dqopt(dquot->dq_sb);

	mutex_lock(&dquot->dq_lock);
	/* Check whether we are not racing with some other dqget() */
	if (atomic_read(&dquot->dq_count) > 1)
		goto out_dqlock;
	mutex_lock(&dqopt->dqio_mutex);
	if (dqopt->ops[dquot->dq_type]->release_dqblk) {
		ret = dqopt->ops[dquot->dq_type]->release_dqblk(dquot);
		/* Write the info */
		if (info_dirty(&dqopt->info[dquot->dq_type])) {
			ret2 = dqopt->ops[dquot->dq_type]->write_file_info(
						dquot->dq_sb, dquot->dq_type);
		}
		if (ret >= 0)
			ret = ret2;
	}
	clear_bit(DQ_ACTIVE_B, &dquot->dq_flags);
	mutex_unlock(&dqopt->dqio_mutex);
out_dqlock:
	mutex_unlock(&dquot->dq_lock);
	return ret;
}
EXPORT_SYMBOL(dquot_release);

void dquot_destroy(struct dquot *dquot)
{
	kmem_cache_free(dquot_cachep, dquot);
}
EXPORT_SYMBOL(dquot_destroy);

static inline void do_destroy_dquot(struct dquot *dquot)
{
	dquot->dq_sb->dq_op->destroy_dquot(dquot);
}

/* Invalidate all dquots on the list. Note that this function is called after
 * quota is disabled and pointers from inodes removed so there cannot be new
 * quota users. There can still be some users of quotas due to inodes being
 * just deleted or pruned by prune_icache() (those are not attached to any
 * list) or parallel quotactl call. We have to wait for such users.
 */
static void invalidate_dquots(struct super_block *sb, int type)
{
	struct dquot *dquot, *tmp;

restart:
	spin_lock(&dq_list_lock);
	list_for_each_entry_safe(dquot, tmp, &inuse_list, dq_inuse) {
		if (dquot->dq_sb != sb)
			continue;
		if (dquot->dq_type != type)
			continue;
		/* Wait for dquot users */
		if (atomic_read(&dquot->dq_count)) {
			DEFINE_WAIT(wait);

			atomic_inc(&dquot->dq_count);
			prepare_to_wait(&dquot->dq_wait_unused, &wait,
					TASK_UNINTERRUPTIBLE);
			spin_unlock(&dq_list_lock);
			/* Once dqput() wakes us up, we know it's time to free
			 * the dquot.
			 * IMPORTANT: we rely on the fact that there is always
			 * at most one process waiting for dquot to free.
			 * Otherwise dq_count would be > 1 and we would never
			 * wake up.
			 */
			if (atomic_read(&dquot->dq_count) > 1)
				schedule();
			finish_wait(&dquot->dq_wait_unused, &wait);
			dqput(dquot);
			/* At this moment dquot() need not exist (it could be
			 * reclaimed by prune_dqcache(). Hence we must
			 * restart. */
			goto restart;
		}
		/*
		 * Quota now has no users and it has been written on last
		 * dqput()
		 */
		remove_dquot_hash(dquot);
		remove_free_dquot(dquot);
		remove_inuse(dquot);
		do_destroy_dquot(dquot);
	}
	spin_unlock(&dq_list_lock);
}

/* Call callback for every active dquot on given filesystem */
int dquot_scan_active(struct super_block *sb,
		      int (*fn)(struct dquot *dquot, unsigned long priv),
		      unsigned long priv)
{
	struct dquot *dquot, *old_dquot = NULL;
	int ret = 0;

	mutex_lock(&sb_dqopt(sb)->dqonoff_mutex);
	spin_lock(&dq_list_lock);
	list_for_each_entry(dquot, &inuse_list, dq_inuse) {
		if (!test_bit(DQ_ACTIVE_B, &dquot->dq_flags))
			continue;
		if (dquot->dq_sb != sb)
			continue;
		/* Now we have active dquot so we can just increase use count */
		atomic_inc(&dquot->dq_count);
		dqstats.lookups++;
		spin_unlock(&dq_list_lock);
		dqput(old_dquot);
		old_dquot = dquot;
		ret = fn(dquot, priv);
		if (ret < 0)
			goto out;
		spin_lock(&dq_list_lock);
		/* We are safe to continue now because our dquot could not
		 * be moved out of the inuse list while we hold the reference */
	}
	spin_unlock(&dq_list_lock);
out:
	dqput(old_dquot);
	mutex_unlock(&sb_dqopt(sb)->dqonoff_mutex);
	return ret;
}
EXPORT_SYMBOL(dquot_scan_active);

int vfs_quota_sync(struct super_block *sb, int type)
{
	struct list_head *dirty;
	struct dquot *dquot;
	struct quota_info *dqopt = sb_dqopt(sb);
	int cnt;

	mutex_lock(&dqopt->dqonoff_mutex);
	for (cnt = 0; cnt < MAXQUOTAS; cnt++) {
		if (type != -1 && cnt != type)
			continue;
		if (!sb_has_quota_active(sb, cnt))
			continue;
		spin_lock(&dq_list_lock);
		dirty = &dqopt->info[cnt].dqi_dirty_list;
		while (!list_empty(dirty)) {
			dquot = list_first_entry(dirty, struct dquot,
						 dq_dirty);
			/* Dirty and inactive can be only bad dquot... */
			if (!test_bit(DQ_ACTIVE_B, &dquot->dq_flags)) {
				clear_dquot_dirty(dquot);
				continue;
			}
			/* Now we have active dquot from which someone is
 			 * holding reference so we can safely just increase
			 * use count */
			atomic_inc(&dquot->dq_count);
			dqstats.lookups++;
			spin_unlock(&dq_list_lock);
			sb->dq_op->write_dquot(dquot);
			dqput(dquot);
			spin_lock(&dq_list_lock);
		}
		spin_unlock(&dq_list_lock);
	}

	for (cnt = 0; cnt < MAXQUOTAS; cnt++)
		if ((cnt == type || type == -1) && sb_has_quota_active(sb, cnt)
		    && info_dirty(&dqopt->info[cnt]))
			sb->dq_op->write_info(sb, cnt);
	spin_lock(&dq_list_lock);
	dqstats.syncs++;
	spin_unlock(&dq_list_lock);
	mutex_unlock(&dqopt->dqonoff_mutex);

	return 0;
}
EXPORT_SYMBOL(vfs_quota_sync);

/* Free unused dquots from cache */
static void prune_dqcache(int count)
{
	struct list_head *head;
	struct dquot *dquot;

	head = free_dquots.prev;
	while (head != &free_dquots && count) {
		dquot = list_entry(head, struct dquot, dq_free);
		remove_dquot_hash(dquot);
		remove_free_dquot(dquot);
		remove_inuse(dquot);
		do_destroy_dquot(dquot);
		count--;
		head = free_dquots.prev;
	}
}

/*
 * This is called from kswapd when we think we need some
 * more memory
 */

static int shrink_dqcache_memory(int nr, gfp_t gfp_mask)
{
	if (nr) {
		spin_lock(&dq_list_lock);
		prune_dqcache(nr);
		spin_unlock(&dq_list_lock);
	}
	return (dqstats.free_dquots / 100) * sysctl_vfs_cache_pressure;
}

static struct shrinker dqcache_shrinker = {
	.shrink = shrink_dqcache_memory,
	.seeks = DEFAULT_SEEKS,
};

/*
 * Put reference to dquot
 * NOTE: If you change this function please check whether dqput_blocks() works right...
 */
void dqput(struct dquot *dquot)
{
	int ret;

	if (!dquot)
		return;
#ifdef __DQUOT_PARANOIA
	if (!atomic_read(&dquot->dq_count)) {
		printk("VFS: dqput: trying to free free dquot\n");
		printk("VFS: device %s, dquot of %s %d\n",
			dquot->dq_sb->s_id,
			quotatypes[dquot->dq_type],
			dquot->dq_id);
		BUG();
	}
#endif
	
	spin_lock(&dq_list_lock);
	dqstats.drops++;
	spin_unlock(&dq_list_lock);
we_slept:
	spin_lock(&dq_list_lock);
	if (atomic_read(&dquot->dq_count) > 1) {
		/* We have more than one user... nothing to do */
		atomic_dec(&dquot->dq_count);
		/* Releasing dquot during quotaoff phase? */
		if (!sb_has_quota_active(dquot->dq_sb, dquot->dq_type) &&
		    atomic_read(&dquot->dq_count) == 1)
			wake_up(&dquot->dq_wait_unused);
		spin_unlock(&dq_list_lock);
		return;
	}
	/* Need to release dquot? */
	if (test_bit(DQ_ACTIVE_B, &dquot->dq_flags) && dquot_dirty(dquot)) {
		spin_unlock(&dq_list_lock);
		/* Commit dquot before releasing */
		ret = dquot->dq_sb->dq_op->write_dquot(dquot);
		if (ret < 0) {
			printk(KERN_ERR "VFS: cannot write quota structure on "
				"device %s (error %d). Quota may get out of "
				"sync!\n", dquot->dq_sb->s_id, ret);
			/*
			 * We clear dirty bit anyway, so that we avoid
			 * infinite loop here
			 */
			spin_lock(&dq_list_lock);
			clear_dquot_dirty(dquot);
			spin_unlock(&dq_list_lock);
		}
		goto we_slept;
	}
	/* Clear flag in case dquot was inactive (something bad happened) */
	clear_dquot_dirty(dquot);
	if (test_bit(DQ_ACTIVE_B, &dquot->dq_flags)) {
		spin_unlock(&dq_list_lock);
		dquot->dq_sb->dq_op->release_dquot(dquot);
		goto we_slept;
	}
	atomic_dec(&dquot->dq_count);
#ifdef __DQUOT_PARANOIA
	/* sanity check */
	BUG_ON(!list_empty(&dquot->dq_free));
#endif
	put_dquot_last(dquot);
	spin_unlock(&dq_list_lock);
}
EXPORT_SYMBOL(dqput);

struct dquot *dquot_alloc(struct super_block *sb, int type)
{
	return kmem_cache_zalloc(dquot_cachep, GFP_NOFS);
}
EXPORT_SYMBOL(dquot_alloc);

static struct dquot *get_empty_dquot(struct super_block *sb, int type)
{
	struct dquot *dquot;

	dquot = sb->dq_op->alloc_dquot(sb, type);
	if(!dquot)
		return NULL;

	mutex_init(&dquot->dq_lock);
	INIT_LIST_HEAD(&dquot->dq_free);
	INIT_LIST_HEAD(&dquot->dq_inuse);
	INIT_HLIST_NODE(&dquot->dq_hash);
	INIT_LIST_HEAD(&dquot->dq_dirty);
	init_waitqueue_head(&dquot->dq_wait_unused);
	dquot->dq_sb = sb;
	dquot->dq_type = type;
	atomic_set(&dquot->dq_count, 1);

	return dquot;
}

/*
 * Get reference to dquot
 *
 * Locking is slightly tricky here. We are guarded from parallel quotaoff()
 * destroying our dquot by:
 *   a) checking for quota flags under dq_list_lock and
 *   b) getting a reference to dquot before we release dq_list_lock
 */
struct dquot *dqget(struct super_block *sb, unsigned int id, int type)
{
	unsigned int hashent = hashfn(sb, id, type);
	struct dquot *dquot = NULL, *empty = NULL;

        if (!sb_has_quota_active(sb, type))
		return NULL;
we_slept:
	spin_lock(&dq_list_lock);
	spin_lock(&dq_state_lock);
	if (!sb_has_quota_active(sb, type)) {
		spin_unlock(&dq_state_lock);
		spin_unlock(&dq_list_lock);
		goto out;
	}
	spin_unlock(&dq_state_lock);

	dquot = find_dquot(hashent, sb, id, type);
	if (!dquot) {
		if (!empty) {
			spin_unlock(&dq_list_lock);
			empty = get_empty_dquot(sb, type);
			if (!empty)
				schedule();	/* Try to wait for a moment... */
			goto we_slept;
		}
		dquot = empty;
		empty = NULL;
		dquot->dq_id = id;
		/* all dquots go on the inuse_list */
		put_inuse(dquot);
		/* hash it first so it can be found */
		insert_dquot_hash(dquot);
		dqstats.lookups++;
		spin_unlock(&dq_list_lock);
	} else {
		if (!atomic_read(&dquot->dq_count))
			remove_free_dquot(dquot);
		atomic_inc(&dquot->dq_count);
		dqstats.cache_hits++;
		dqstats.lookups++;
		spin_unlock(&dq_list_lock);
	}
	/* Wait for dq_lock - after this we know that either dquot_release() is
	 * already finished or it will be canceled due to dq_count > 1 test */
	wait_on_dquot(dquot);
	/* Read the dquot / allocate space in quota file */
	if (!test_bit(DQ_ACTIVE_B, &dquot->dq_flags) &&
	    sb->dq_op->acquire_dquot(dquot) < 0) {
		dqput(dquot);
		dquot = NULL;
		goto out;
	}
#ifdef __DQUOT_PARANOIA
	BUG_ON(!dquot->dq_sb);	/* Has somebody invalidated entry under us? */
#endif
out:
	if (empty)
		do_destroy_dquot(empty);

	return dquot;
}
EXPORT_SYMBOL(dqget);

static int dqinit_needed(struct inode *inode, int type)
{
	int cnt;

	if (IS_NOQUOTA(inode))
		return 0;
	if (type != -1)
		return !inode->i_dquot[type];
	for (cnt = 0; cnt < MAXQUOTAS; cnt++)
		if (!inode->i_dquot[cnt])
			return 1;
	return 0;
}

/* This routine is guarded by dqonoff_mutex mutex */
static void add_dquot_ref(struct super_block *sb, int type)
{
	struct inode *inode, *old_inode = NULL;

	spin_lock(&inode_lock);
	list_for_each_entry(inode, &sb->s_inodes, i_sb_list) {
		if (!atomic_read(&inode->i_writecount))
			continue;
		if (!dqinit_needed(inode, type))
			continue;
		if (inode->i_state & (I_FREEING|I_WILL_FREE))
			continue;

		__iget(inode);
		spin_unlock(&inode_lock);

		iput(old_inode);
		sb->dq_op->initialize(inode, type);
		/* We hold a reference to 'inode' so it couldn't have been
		 * removed from s_inodes list while we dropped the inode_lock.
		 * We cannot iput the inode now as we can be holding the last
		 * reference and we cannot iput it under inode_lock. So we
		 * keep the reference and iput it later. */
		old_inode = inode;
		spin_lock(&inode_lock);
	}
	spin_unlock(&inode_lock);
	iput(old_inode);
}

/*
 * Return 0 if dqput() won't block.
 * (note that 1 doesn't necessarily mean blocking)
 */
static inline int dqput_blocks(struct dquot *dquot)
{
	if (atomic_read(&dquot->dq_count) <= 1)
		return 1;
	return 0;
}

/*
 * Remove references to dquots from inode and add dquot to list for freeing
 * if we have the last referece to dquot
 * We can't race with anybody because we hold dqptr_sem for writing...
 */
static int remove_inode_dquot_ref(struct inode *inode, int type,
				  struct list_head *tofree_head)
{
	struct dquot *dquot = inode->i_dquot[type];

	inode->i_dquot[type] = NULL;
	if (dquot) {
		if (dqput_blocks(dquot)) {
#ifdef __DQUOT_PARANOIA
			if (atomic_read(&dquot->dq_count) != 1)
				printk(KERN_WARNING "VFS: Adding dquot with dq_count %d to dispose list.\n", atomic_read(&dquot->dq_count));
#endif
			spin_lock(&dq_list_lock);
			/* As dquot must have currently users it can't be on
			 * the free list... */
			list_add(&dquot->dq_free, tofree_head);
			spin_unlock(&dq_list_lock);
			return 1;
		}
		else
			dqput(dquot);   /* We have guaranteed we won't block */
	}
	return 0;
}

/*
 * Free list of dquots
 * Dquots are removed from inodes and no new references can be got so we are
 * the only ones holding reference
 */
static void put_dquot_list(struct list_head *tofree_head)
{
	struct list_head *act_head;
	struct dquot *dquot;

	act_head = tofree_head->next;
	while (act_head != tofree_head) {
		dquot = list_entry(act_head, struct dquot, dq_free);
		act_head = act_head->next;
		/* Remove dquot from the list so we won't have problems... */
		list_del_init(&dquot->dq_free);
		dqput(dquot);
	}
}

static void remove_dquot_ref(struct super_block *sb, int type,
		struct list_head *tofree_head)
{
	struct inode *inode;

	spin_lock(&inode_lock);
	list_for_each_entry(inode, &sb->s_inodes, i_sb_list) {
		if (!IS_NOQUOTA(inode))
			remove_inode_dquot_ref(inode, type, tofree_head);
	}
	spin_unlock(&inode_lock);
}

/* Gather all references from inodes and drop them */
static void drop_dquot_ref(struct super_block *sb, int type)
{
	LIST_HEAD(tofree_head);

	if (sb->dq_op) {
		down_write(&sb_dqopt(sb)->dqptr_sem);
		remove_dquot_ref(sb, type, &tofree_head);
		up_write(&sb_dqopt(sb)->dqptr_sem);
		put_dquot_list(&tofree_head);
	}
}

static inline void dquot_incr_inodes(struct dquot *dquot, qsize_t number)
{
	dquot->dq_dqb.dqb_curinodes += number;
}

static inline void dquot_incr_space(struct dquot *dquot, qsize_t number)
{
	dquot->dq_dqb.dqb_curspace += number;
}

static inline void dquot_resv_space(struct dquot *dquot, qsize_t number)
{
	dquot->dq_dqb.dqb_rsvspace += number;
}

/*
 * Claim reserved quota space
 */
static void dquot_claim_reserved_space(struct dquot *dquot,
						qsize_t number)
{
	WARN_ON(dquot->dq_dqb.dqb_rsvspace < number);
	dquot->dq_dqb.dqb_curspace += number;
	dquot->dq_dqb.dqb_rsvspace -= number;
}

static inline
void dquot_free_reserved_space(struct dquot *dquot, qsize_t number)
{
	dquot->dq_dqb.dqb_rsvspace -= number;
}

static void dquot_decr_inodes(struct dquot *dquot, qsize_t number)
{
	if (sb_dqopt(dquot->dq_sb)->flags & DQUOT_NEGATIVE_USAGE ||
	    dquot->dq_dqb.dqb_curinodes >= number)
		dquot->dq_dqb.dqb_curinodes -= number;
	else
		dquot->dq_dqb.dqb_curinodes = 0;
	if (dquot->dq_dqb.dqb_curinodes <= dquot->dq_dqb.dqb_isoftlimit)
		dquot->dq_dqb.dqb_itime = (time_t) 0;
	clear_bit(DQ_INODES_B, &dquot->dq_flags);
}

static void dquot_decr_space(struct dquot *dquot, qsize_t number)
{
	if (sb_dqopt(dquot->dq_sb)->flags & DQUOT_NEGATIVE_USAGE ||
	    dquot->dq_dqb.dqb_curspace >= number)
		dquot->dq_dqb.dqb_curspace -= number;
	else
		dquot->dq_dqb.dqb_curspace = 0;
	if (dquot->dq_dqb.dqb_curspace <= dquot->dq_dqb.dqb_bsoftlimit)
		dquot->dq_dqb.dqb_btime = (time_t) 0;
	clear_bit(DQ_BLKS_B, &dquot->dq_flags);
}

static int warning_issued(struct dquot *dquot, const int warntype)
{
	int flag = (warntype == QUOTA_NL_BHARDWARN ||
		warntype == QUOTA_NL_BSOFTLONGWARN) ? DQ_BLKS_B :
		((warntype == QUOTA_NL_IHARDWARN ||
		warntype == QUOTA_NL_ISOFTLONGWARN) ? DQ_INODES_B : 0);

	if (!flag)
		return 0;
	return test_and_set_bit(flag, &dquot->dq_flags);
}

#ifdef CONFIG_PRINT_QUOTA_WARNING
static int flag_print_warnings = 1;

static int need_print_warning(struct dquot *dquot)
{
	if (!flag_print_warnings)
		return 0;

	switch (dquot->dq_type) {
		case USRQUOTA:
			return current_fsuid() == dquot->dq_id;
		case GRPQUOTA:
			return in_group_p(dquot->dq_id);
	}
	return 0;
}

/* Print warning to user which exceeded quota */
static void print_warning(struct dquot *dquot, const int warntype)
{
	char *msg = NULL;
	struct tty_struct *tty;

	if (warntype == QUOTA_NL_IHARDBELOW ||
	    warntype == QUOTA_NL_ISOFTBELOW ||
	    warntype == QUOTA_NL_BHARDBELOW ||
	    warntype == QUOTA_NL_BSOFTBELOW || !need_print_warning(dquot))
		return;

	tty = get_current_tty();
	if (!tty)
		return;
	tty_write_message(tty, dquot->dq_sb->s_id);
	if (warntype == QUOTA_NL_ISOFTWARN || warntype == QUOTA_NL_BSOFTWARN)
		tty_write_message(tty, ": warning, ");
	else
		tty_write_message(tty, ": write failed, ");
	tty_write_message(tty, quotatypes[dquot->dq_type]);
	switch (warntype) {
		case QUOTA_NL_IHARDWARN:
			msg = " file limit reached.\r\n";
			break;
		case QUOTA_NL_ISOFTLONGWARN:
			msg = " file quota exceeded too long.\r\n";
			break;
		case QUOTA_NL_ISOFTWARN:
			msg = " file quota exceeded.\r\n";
			break;
		case QUOTA_NL_BHARDWARN:
			msg = " block limit reached.\r\n";
			break;
		case QUOTA_NL_BSOFTLONGWARN:
			msg = " block quota exceeded too long.\r\n";
			break;
		case QUOTA_NL_BSOFTWARN:
			msg = " block quota exceeded.\r\n";
			break;
	}
	tty_write_message(tty, msg);
	tty_kref_put(tty);
}
#endif

#ifdef CONFIG_QUOTA_NETLINK_INTERFACE

/* Netlink family structure for quota */
static struct genl_family quota_genl_family = {
	.id = GENL_ID_GENERATE,
	.hdrsize = 0,
	.name = "VFS_DQUOT",
	.version = 1,
	.maxattr = QUOTA_NL_A_MAX,
};

/* Send warning to userspace about user which exceeded quota */
static void send_warning(const struct dquot *dquot, const char warntype)
{
	static atomic_t seq;
	struct sk_buff *skb;
	void *msg_head;
	int ret;
	int msg_size = 4 * nla_total_size(sizeof(u32)) +
		       2 * nla_total_size(sizeof(u64));

	/* We have to allocate using GFP_NOFS as we are called from a
	 * filesystem performing write and thus further recursion into
	 * the fs to free some data could cause deadlocks. */
	skb = genlmsg_new(msg_size, GFP_NOFS);
	if (!skb) {
		printk(KERN_ERR
		  "VFS: Not enough memory to send quota warning.\n");
		return;
	}
	msg_head = genlmsg_put(skb, 0, atomic_add_return(1, &seq),
			&quota_genl_family, 0, QUOTA_NL_C_WARNING);
	if (!msg_head) {
		printk(KERN_ERR
		  "VFS: Cannot store netlink header in quota warning.\n");
		goto err_out;
	}
	ret = nla_put_u32(skb, QUOTA_NL_A_QTYPE, dquot->dq_type);
	if (ret)
		goto attr_err_out;
	ret = nla_put_u64(skb, QUOTA_NL_A_EXCESS_ID, dquot->dq_id);
	if (ret)
		goto attr_err_out;
	ret = nla_put_u32(skb, QUOTA_NL_A_WARNING, warntype);
	if (ret)
		goto attr_err_out;
	ret = nla_put_u32(skb, QUOTA_NL_A_DEV_MAJOR,
		MAJOR(dquot->dq_sb->s_dev));
	if (ret)
		goto attr_err_out;
	ret = nla_put_u32(skb, QUOTA_NL_A_DEV_MINOR,
		MINOR(dquot->dq_sb->s_dev));
	if (ret)
		goto attr_err_out;
	ret = nla_put_u64(skb, QUOTA_NL_A_CAUSED_ID, current_uid());
	if (ret)
		goto attr_err_out;
	genlmsg_end(skb, msg_head);

	ret = genlmsg_multicast(skb, 0, quota_genl_family.id, GFP_NOFS);
	if (ret < 0 && ret != -ESRCH)
		printk(KERN_ERR
			"VFS: Failed to send notification message: %d\n", ret);
	return;
attr_err_out:
	printk(KERN_ERR "VFS: Not enough space to compose quota message!\n");
err_out:
	kfree_skb(skb);
}
#endif
/*
 * Write warnings to the console and send warning messages over netlink.
 *
 * Note that this function can sleep.
 */
static void flush_warnings(struct dquot *const *dquots, char *warntype)
{
	int i;

	for (i = 0; i < MAXQUOTAS; i++)
		if (dquots[i] && warntype[i] != QUOTA_NL_NOWARN &&
		    !warning_issued(dquots[i], warntype[i])) {
#ifdef CONFIG_PRINT_QUOTA_WARNING
			print_warning(dquots[i], warntype[i]);
#endif
#ifdef CONFIG_QUOTA_NETLINK_INTERFACE
			send_warning(dquots[i], warntype[i]);
#endif
		}
}

static int ignore_hardlimit(struct dquot *dquot)
{
	struct mem_dqinfo *info = &sb_dqopt(dquot->dq_sb)->info[dquot->dq_type];

	return capable(CAP_SYS_RESOURCE) &&
	       (info->dqi_format->qf_fmt_id != QFMT_VFS_OLD ||
		!(info->dqi_flags & V1_DQF_RSQUASH));
}

/* needs dq_data_lock */
static int check_idq(struct dquot *dquot, qsize_t inodes, char *warntype)
{
	qsize_t newinodes = dquot->dq_dqb.dqb_curinodes + inodes;

	*warntype = QUOTA_NL_NOWARN;
	if (!sb_has_quota_limits_enabled(dquot->dq_sb, dquot->dq_type) ||
	    test_bit(DQ_FAKE_B, &dquot->dq_flags))
		return QUOTA_OK;

	if (dquot->dq_dqb.dqb_ihardlimit &&
	    newinodes > dquot->dq_dqb.dqb_ihardlimit &&
            !ignore_hardlimit(dquot)) {
		*warntype = QUOTA_NL_IHARDWARN;
		return NO_QUOTA;
	}

	if (dquot->dq_dqb.dqb_isoftlimit &&
	    newinodes > dquot->dq_dqb.dqb_isoftlimit &&
	    dquot->dq_dqb.dqb_itime &&
	    get_seconds() >= dquot->dq_dqb.dqb_itime &&
            !ignore_hardlimit(dquot)) {
		*warntype = QUOTA_NL_ISOFTLONGWARN;
		return NO_QUOTA;
	}

	if (dquot->dq_dqb.dqb_isoftlimit &&
	    newinodes > dquot->dq_dqb.dqb_isoftlimit &&
	    dquot->dq_dqb.dqb_itime == 0) {
		*warntype = QUOTA_NL_ISOFTWARN;
		dquot->dq_dqb.dqb_itime = get_seconds() +
		    sb_dqopt(dquot->dq_sb)->info[dquot->dq_type].dqi_igrace;
	}

	return QUOTA_OK;
}

/* needs dq_data_lock */
static int check_bdq(struct dquot *dquot, qsize_t space, int prealloc, char *warntype)
{
	qsize_t tspace;
	struct super_block *sb = dquot->dq_sb;

	*warntype = QUOTA_NL_NOWARN;
	if (!sb_has_quota_limits_enabled(sb, dquot->dq_type) ||
	    test_bit(DQ_FAKE_B, &dquot->dq_flags))
		return QUOTA_OK;

	tspace = dquot->dq_dqb.dqb_curspace + dquot->dq_dqb.dqb_rsvspace
		+ space;

	if (dquot->dq_dqb.dqb_bhardlimit &&
	    tspace > dquot->dq_dqb.dqb_bhardlimit &&
            !ignore_hardlimit(dquot)) {
		if (!prealloc)
			*warntype = QUOTA_NL_BHARDWARN;
		return NO_QUOTA;
	}

	if (dquot->dq_dqb.dqb_bsoftlimit &&
	    tspace > dquot->dq_dqb.dqb_bsoftlimit &&
	    dquot->dq_dqb.dqb_btime &&
	    get_seconds() >= dquot->dq_dqb.dqb_btime &&
            !ignore_hardlimit(dquot)) {
		if (!prealloc)
			*warntype = QUOTA_NL_BSOFTLONGWARN;
		return NO_QUOTA;
	}

	if (dquot->dq_dqb.dqb_bsoftlimit &&
	    tspace > dquot->dq_dqb.dqb_bsoftlimit &&
	    dquot->dq_dqb.dqb_btime == 0) {
		if (!prealloc) {
			*warntype = QUOTA_NL_BSOFTWARN;
			dquot->dq_dqb.dqb_btime = get_seconds() +
			    sb_dqopt(sb)->info[dquot->dq_type].dqi_bgrace;
		}
		else
			/*
			 * We don't allow preallocation to exceed softlimit so exceeding will
			 * be always printed
			 */
			return NO_QUOTA;
	}

	return QUOTA_OK;
}

static int info_idq_free(struct dquot *dquot, qsize_t inodes)
{
	qsize_t newinodes;

	if (test_bit(DQ_FAKE_B, &dquot->dq_flags) ||
	    dquot->dq_dqb.dqb_curinodes <= dquot->dq_dqb.dqb_isoftlimit ||
	    !sb_has_quota_limits_enabled(dquot->dq_sb, dquot->dq_type))
		return QUOTA_NL_NOWARN;

	newinodes = dquot->dq_dqb.dqb_curinodes - inodes;
	if (newinodes <= dquot->dq_dqb.dqb_isoftlimit)
		return QUOTA_NL_ISOFTBELOW;
	if (dquot->dq_dqb.dqb_curinodes >= dquot->dq_dqb.dqb_ihardlimit &&
	    newinodes < dquot->dq_dqb.dqb_ihardlimit)
		return QUOTA_NL_IHARDBELOW;
	return QUOTA_NL_NOWARN;
}

static int info_bdq_free(struct dquot *dquot, qsize_t space)
{
	if (test_bit(DQ_FAKE_B, &dquot->dq_flags) ||
	    dquot->dq_dqb.dqb_curspace <= dquot->dq_dqb.dqb_bsoftlimit)
		return QUOTA_NL_NOWARN;

	if (dquot->dq_dqb.dqb_curspace - space <= dquot->dq_dqb.dqb_bsoftlimit)
		return QUOTA_NL_BSOFTBELOW;
	if (dquot->dq_dqb.dqb_curspace >= dquot->dq_dqb.dqb_bhardlimit &&
	    dquot->dq_dqb.dqb_curspace - space < dquot->dq_dqb.dqb_bhardlimit)
		return QUOTA_NL_BHARDBELOW;
	return QUOTA_NL_NOWARN;
}
/*
 *	Initialize quota pointers in inode
 *	We do things in a bit complicated way but by that we avoid calling
 *	dqget() and thus filesystem callbacks under dqptr_sem.
 */
int dquot_initialize(struct inode *inode, int type)
{
	unsigned int id = 0;
	int cnt, ret = 0;
	struct dquot *got[MAXQUOTAS] = { NULL, NULL };
	struct super_block *sb = inode->i_sb;

	/* First test before acquiring mutex - solves deadlocks when we
         * re-enter the quota code and are already holding the mutex */
	if (IS_NOQUOTA(inode))
		return 0;

	/* First get references to structures we might need. */
	for (cnt = 0; cnt < MAXQUOTAS; cnt++) {
		if (type != -1 && cnt != type)
			continue;
		switch (cnt) {
		case USRQUOTA:
			id = inode->i_uid;
			break;
		case GRPQUOTA:
			id = inode->i_gid;
			break;
		}
		got[cnt] = dqget(sb, id, cnt);
	}

	down_write(&sb_dqopt(sb)->dqptr_sem);
	/* Having dqptr_sem we know NOQUOTA flags can't be altered... */
	if (IS_NOQUOTA(inode))
		goto out_err;
	for (cnt = 0; cnt < MAXQUOTAS; cnt++) {
		if (type != -1 && cnt != type)
			continue;
		/* Avoid races with quotaoff() */
		if (!sb_has_quota_active(sb, cnt))
			continue;
		if (!inode->i_dquot[cnt]) {
			inode->i_dquot[cnt] = got[cnt];
			got[cnt] = NULL;
		}
	}
out_err:
	up_write(&sb_dqopt(sb)->dqptr_sem);
	/* Drop unused references */
	for (cnt = 0; cnt < MAXQUOTAS; cnt++)
		dqput(got[cnt]);
	return ret;
}
EXPORT_SYMBOL(dquot_initialize);

/*
 * 	Release all quotas referenced by inode
 */
int dquot_drop(struct inode *inode)
{
	int cnt;
	struct dquot *put[MAXQUOTAS];

	down_write(&sb_dqopt(inode->i_sb)->dqptr_sem);
	for (cnt = 0; cnt < MAXQUOTAS; cnt++) {
		put[cnt] = inode->i_dquot[cnt];
		inode->i_dquot[cnt] = NULL;
	}
	up_write(&sb_dqopt(inode->i_sb)->dqptr_sem);

	for (cnt = 0; cnt < MAXQUOTAS; cnt++)
		dqput(put[cnt]);
	return 0;
}
EXPORT_SYMBOL(dquot_drop);

/* Wrapper to remove references to quota structures from inode */
void vfs_dq_drop(struct inode *inode)
{
	/* Here we can get arbitrary inode from clear_inode() so we have
	 * to be careful. OTOH we don't need locking as quota operations
	 * are allowed to change only at mount time */
	if (!IS_NOQUOTA(inode) && inode->i_sb && inode->i_sb->dq_op
	    && inode->i_sb->dq_op->drop) {
		int cnt;
		/* Test before calling to rule out calls from proc and such
                 * where we are not allowed to block. Note that this is
		 * actually reliable test even without the lock - the caller
		 * must assure that nobody can come after the DQUOT_DROP and
		 * add quota pointers back anyway */
		for (cnt = 0; cnt < MAXQUOTAS; cnt++)
			if (inode->i_dquot[cnt])
				break;
		if (cnt < MAXQUOTAS)
			inode->i_sb->dq_op->drop(inode);
	}
}
EXPORT_SYMBOL(vfs_dq_drop);

/*
 * Following four functions update i_blocks+i_bytes fields and
 * quota information (together with appropriate checks)
 * NOTE: We absolutely rely on the fact that caller dirties
 * the inode (usually macros in quotaops.h care about this) and
 * holds a handle for the current transaction so that dquot write and
 * inode write go into the same transaction.
 */

/*
 * This operation can block, but only after everything is updated
 */
int __dquot_alloc_space(struct inode *inode, qsize_t number,
			int warn, int reserve)
{
	int cnt, ret = QUOTA_OK;
	char warntype[MAXQUOTAS];

	for (cnt = 0; cnt < MAXQUOTAS; cnt++)
		warntype[cnt] = QUOTA_NL_NOWARN;

	spin_lock(&dq_data_lock);
	for (cnt = 0; cnt < MAXQUOTAS; cnt++) {
		if (!inode->i_dquot[cnt])
			continue;
		if (check_bdq(inode->i_dquot[cnt], number, warn, warntype+cnt)
		    == NO_QUOTA) {
			ret = NO_QUOTA;
			goto out_unlock;
		}
	}
	for (cnt = 0; cnt < MAXQUOTAS; cnt++) {
		if (!inode->i_dquot[cnt])
			continue;
		if (reserve)
			dquot_resv_space(inode->i_dquot[cnt], number);
		else
			dquot_incr_space(inode->i_dquot[cnt], number);
	}
	if (!reserve)
		inode_add_bytes(inode, number);
out_unlock:
	spin_unlock(&dq_data_lock);
	flush_warnings(inode->i_dquot, warntype);
	return ret;
}

int dquot_alloc_space(struct inode *inode, qsize_t number, int warn)
{
	int cnt, ret = QUOTA_OK;

	/*
	 * First test before acquiring mutex - solves deadlocks when we
	 * re-enter the quota code and are already holding the mutex
	 */
	if (IS_NOQUOTA(inode)) {
		inode_add_bytes(inode, number);
		goto out;
	}

	down_read(&sb_dqopt(inode->i_sb)->dqptr_sem);
	if (IS_NOQUOTA(inode)) {
		inode_add_bytes(inode, number);
		goto out_unlock;
	}

	ret = __dquot_alloc_space(inode, number, warn, 0);
	if (ret == NO_QUOTA)
		goto out_unlock;

	/* Dirtify all the dquots - this can block when journalling */
	for (cnt = 0; cnt < MAXQUOTAS; cnt++)
		if (inode->i_dquot[cnt])
			mark_dquot_dirty(inode->i_dquot[cnt]);
out_unlock:
	up_read(&sb_dqopt(inode->i_sb)->dqptr_sem);
out:
	return ret;
}
EXPORT_SYMBOL(dquot_alloc_space);

int dquot_reserve_space(struct inode *inode, qsize_t number, int warn)
{
	int ret = QUOTA_OK;

	if (IS_NOQUOTA(inode))
		goto out;

	down_read(&sb_dqopt(inode->i_sb)->dqptr_sem);
	if (IS_NOQUOTA(inode))
		goto out_unlock;

	ret = __dquot_alloc_space(inode, number, warn, 1);
out_unlock:
	up_read(&sb_dqopt(inode->i_sb)->dqptr_sem);
out:
	return ret;
}
EXPORT_SYMBOL(dquot_reserve_space);

/*
 * This operation can block, but only after everything is updated
 */
int dquot_alloc_inode(const struct inode *inode, qsize_t number)
{
	int cnt, ret = NO_QUOTA;
	char warntype[MAXQUOTAS];

	/* First test before acquiring mutex - solves deadlocks when we
         * re-enter the quota code and are already holding the mutex */
	if (IS_NOQUOTA(inode))
		return QUOTA_OK;
	for (cnt = 0; cnt < MAXQUOTAS; cnt++)
		warntype[cnt] = QUOTA_NL_NOWARN;
	down_read(&sb_dqopt(inode->i_sb)->dqptr_sem);
	if (IS_NOQUOTA(inode)) {
		up_read(&sb_dqopt(inode->i_sb)->dqptr_sem);
		return QUOTA_OK;
	}
	spin_lock(&dq_data_lock);
	for (cnt = 0; cnt < MAXQUOTAS; cnt++) {
		if (!inode->i_dquot[cnt])
			continue;
		if (check_idq(inode->i_dquot[cnt], number, warntype+cnt)
		    == NO_QUOTA)
			goto warn_put_all;
	}

	for (cnt = 0; cnt < MAXQUOTAS; cnt++) {
		if (!inode->i_dquot[cnt])
			continue;
		dquot_incr_inodes(inode->i_dquot[cnt], number);
	}
	ret = QUOTA_OK;
warn_put_all:
	spin_unlock(&dq_data_lock);
	if (ret == QUOTA_OK)
		/* Dirtify all the dquots - this can block when journalling */
		for (cnt = 0; cnt < MAXQUOTAS; cnt++)
			if (inode->i_dquot[cnt])
				mark_dquot_dirty(inode->i_dquot[cnt]);
	flush_warnings(inode->i_dquot, warntype);
	up_read(&sb_dqopt(inode->i_sb)->dqptr_sem);
	return ret;
}
EXPORT_SYMBOL(dquot_alloc_inode);

int dquot_claim_space(struct inode *inode, qsize_t number)
{
	int cnt;
	int ret = QUOTA_OK;

	if (IS_NOQUOTA(inode)) {
		inode_add_bytes(inode, number);
		goto out;
	}

	down_read(&sb_dqopt(inode->i_sb)->dqptr_sem);
	if (IS_NOQUOTA(inode))	{
		up_read(&sb_dqopt(inode->i_sb)->dqptr_sem);
		inode_add_bytes(inode, number);
		goto out;
	}

	spin_lock(&dq_data_lock);
	/* Claim reserved quotas to allocated quotas */
	for (cnt = 0; cnt < MAXQUOTAS; cnt++) {
		if (inode->i_dquot[cnt])
			dquot_claim_reserved_space(inode->i_dquot[cnt],
							number);
	}
	/* Update inode bytes */
	inode_add_bytes(inode, number);
	spin_unlock(&dq_data_lock);
	/* Dirtify all the dquots - this can block when journalling */
	for (cnt = 0; cnt < MAXQUOTAS; cnt++)
		if (inode->i_dquot[cnt])
			mark_dquot_dirty(inode->i_dquot[cnt]);
	up_read(&sb_dqopt(inode->i_sb)->dqptr_sem);
out:
	return ret;
}
EXPORT_SYMBOL(dquot_claim_space);

/*
 * Release reserved quota space
 */
void dquot_release_reserved_space(struct inode *inode, qsize_t number)
{
	int cnt;

	if (IS_NOQUOTA(inode))
		goto out;

	down_read(&sb_dqopt(inode->i_sb)->dqptr_sem);
	if (IS_NOQUOTA(inode))
		goto out_unlock;

	spin_lock(&dq_data_lock);
	/* Release reserved dquots */
	for (cnt = 0; cnt < MAXQUOTAS; cnt++) {
		if (inode->i_dquot[cnt])
			dquot_free_reserved_space(inode->i_dquot[cnt], number);
	}
	spin_unlock(&dq_data_lock);

out_unlock:
	up_read(&sb_dqopt(inode->i_sb)->dqptr_sem);
out:
	return;
}
EXPORT_SYMBOL(dquot_release_reserved_space);

/*
 * This operation can block, but only after everything is updated
 */
int dquot_free_space(struct inode *inode, qsize_t number)
{
	unsigned int cnt;
	char warntype[MAXQUOTAS];

	/* First test before acquiring mutex - solves deadlocks when we
         * re-enter the quota code and are already holding the mutex */
	if (IS_NOQUOTA(inode)) {
out_sub:
		inode_sub_bytes(inode, number);
		return QUOTA_OK;
	}

	down_read(&sb_dqopt(inode->i_sb)->dqptr_sem);
	/* Now recheck reliably when holding dqptr_sem */
	if (IS_NOQUOTA(inode)) {
		up_read(&sb_dqopt(inode->i_sb)->dqptr_sem);
		goto out_sub;
	}
	spin_lock(&dq_data_lock);
	for (cnt = 0; cnt < MAXQUOTAS; cnt++) {
		if (!inode->i_dquot[cnt])
			continue;
		warntype[cnt] = info_bdq_free(inode->i_dquot[cnt], number);
		dquot_decr_space(inode->i_dquot[cnt], number);
	}
	inode_sub_bytes(inode, number);
	spin_unlock(&dq_data_lock);
	/* Dirtify all the dquots - this can block when journalling */
	for (cnt = 0; cnt < MAXQUOTAS; cnt++)
		if (inode->i_dquot[cnt])
			mark_dquot_dirty(inode->i_dquot[cnt]);
	flush_warnings(inode->i_dquot, warntype);
	up_read(&sb_dqopt(inode->i_sb)->dqptr_sem);
	return QUOTA_OK;
}
EXPORT_SYMBOL(dquot_free_space);

/*
 * This operation can block, but only after everything is updated
 */
int dquot_free_inode(const struct inode *inode, qsize_t number)
{
	unsigned int cnt;
	char warntype[MAXQUOTAS];

	/* First test before acquiring mutex - solves deadlocks when we
         * re-enter the quota code and are already holding the mutex */
	if (IS_NOQUOTA(inode))
		return QUOTA_OK;

	down_read(&sb_dqopt(inode->i_sb)->dqptr_sem);
	/* Now recheck reliably when holding dqptr_sem */
	if (IS_NOQUOTA(inode)) {
		up_read(&sb_dqopt(inode->i_sb)->dqptr_sem);
		return QUOTA_OK;
	}
	spin_lock(&dq_data_lock);
	for (cnt = 0; cnt < MAXQUOTAS; cnt++) {
		if (!inode->i_dquot[cnt])
			continue;
		warntype[cnt] = info_idq_free(inode->i_dquot[cnt], number);
		dquot_decr_inodes(inode->i_dquot[cnt], number);
	}
	spin_unlock(&dq_data_lock);
	/* Dirtify all the dquots - this can block when journalling */
	for (cnt = 0; cnt < MAXQUOTAS; cnt++)
		if (inode->i_dquot[cnt])
			mark_dquot_dirty(inode->i_dquot[cnt]);
	flush_warnings(inode->i_dquot, warntype);
	up_read(&sb_dqopt(inode->i_sb)->dqptr_sem);
	return QUOTA_OK;
}
EXPORT_SYMBOL(dquot_free_inode);

/*
 * call back function, get reserved quota space from underlying fs
 */
qsize_t dquot_get_reserved_space(struct inode *inode)
{
	qsize_t reserved_space = 0;

	if (sb_any_quota_active(inode->i_sb) &&
	    inode->i_sb->dq_op->get_reserved_space)
		reserved_space = inode->i_sb->dq_op->get_reserved_space(inode);
	return reserved_space;
}

/*
 * Transfer the number of inode and blocks from one diskquota to an other.
 *
 * This operation can block, but only after everything is updated
 * A transaction must be started when entering this function.
 */
int dquot_transfer(struct inode *inode, struct iattr *iattr)
{
	qsize_t space, cur_space;
	qsize_t rsv_space = 0;
	struct dquot *transfer_from[MAXQUOTAS];
	struct dquot *transfer_to[MAXQUOTAS];
	int cnt, ret = QUOTA_OK;
	int chuid = iattr->ia_valid & ATTR_UID && inode->i_uid != iattr->ia_uid,
	    chgid = iattr->ia_valid & ATTR_GID && inode->i_gid != iattr->ia_gid;
	char warntype_to[MAXQUOTAS];
	char warntype_from_inodes[MAXQUOTAS], warntype_from_space[MAXQUOTAS];

	/* First test before acquiring mutex - solves deadlocks when we
         * re-enter the quota code and are already holding the mutex */
	if (IS_NOQUOTA(inode))
		return QUOTA_OK;
	/* Initialize the arrays */
	for (cnt = 0; cnt < MAXQUOTAS; cnt++) {
		transfer_from[cnt] = NULL;
		transfer_to[cnt] = NULL;
		warntype_to[cnt] = QUOTA_NL_NOWARN;
	}
	if (chuid)
		transfer_to[USRQUOTA] = dqget(inode->i_sb, iattr->ia_uid,
					      USRQUOTA);
	if (chgid)
		transfer_to[GRPQUOTA] = dqget(inode->i_sb, iattr->ia_gid,
					      GRPQUOTA);

	down_write(&sb_dqopt(inode->i_sb)->dqptr_sem);
	/* Now recheck reliably when holding dqptr_sem */
	if (IS_NOQUOTA(inode)) {	/* File without quota accounting? */
		up_write(&sb_dqopt(inode->i_sb)->dqptr_sem);
		goto put_all;
	}
	spin_lock(&dq_data_lock);
	cur_space = inode_get_bytes(inode);
	rsv_space = dquot_get_reserved_space(inode);
	space = cur_space + rsv_space;
	/* Build the transfer_from list and check the limits */
	for (cnt = 0; cnt < MAXQUOTAS; cnt++) {
		if (!transfer_to[cnt])
			continue;
		transfer_from[cnt] = inode->i_dquot[cnt];
		if (check_idq(transfer_to[cnt], 1, warntype_to + cnt) ==
		    NO_QUOTA || check_bdq(transfer_to[cnt], space, 0,
		    warntype_to + cnt) == NO_QUOTA)
			goto over_quota;
	}

	/*
	 * Finally perform the needed transfer from transfer_from to transfer_to
	 */
	for (cnt = 0; cnt < MAXQUOTAS; cnt++) {
		/*
		 * Skip changes for same uid or gid or for turned off quota-type.
		 */
		if (!transfer_to[cnt])
			continue;

		/* Due to IO error we might not have transfer_from[] structure */
		if (transfer_from[cnt]) {
			warntype_from_inodes[cnt] =
				info_idq_free(transfer_from[cnt], 1);
			warntype_from_space[cnt] =
				info_bdq_free(transfer_from[cnt], space);
			dquot_decr_inodes(transfer_from[cnt], 1);
			dquot_decr_space(transfer_from[cnt], cur_space);
			dquot_free_reserved_space(transfer_from[cnt],
						  rsv_space);
		}

		dquot_incr_inodes(transfer_to[cnt], 1);
		dquot_incr_space(transfer_to[cnt], cur_space);
		dquot_resv_space(transfer_to[cnt], rsv_space);

		inode->i_dquot[cnt] = transfer_to[cnt];
	}
	spin_unlock(&dq_data_lock);
	up_write(&sb_dqopt(inode->i_sb)->dqptr_sem);

	/* Dirtify all the dquots - this can block when journalling */
	for (cnt = 0; cnt < MAXQUOTAS; cnt++) {
		if (transfer_from[cnt])
			mark_dquot_dirty(transfer_from[cnt]);
		if (transfer_to[cnt]) {
			mark_dquot_dirty(transfer_to[cnt]);
			/* The reference we got is transferred to the inode */
			transfer_to[cnt] = NULL;
		}
	}
warn_put_all:
	flush_warnings(transfer_to, warntype_to);
	flush_warnings(transfer_from, warntype_from_inodes);
	flush_warnings(transfer_from, warntype_from_space);
put_all:
	for (cnt = 0; cnt < MAXQUOTAS; cnt++) {
		dqput(transfer_from[cnt]);
		dqput(transfer_to[cnt]);
	}
	return ret;
over_quota:
	spin_unlock(&dq_data_lock);
	up_write(&sb_dqopt(inode->i_sb)->dqptr_sem);
	/* Clear dquot pointers we don't want to dqput() */
	for (cnt = 0; cnt < MAXQUOTAS; cnt++)
		transfer_from[cnt] = NULL;
	ret = NO_QUOTA;
	goto warn_put_all;
}
EXPORT_SYMBOL(dquot_transfer);

/* Wrapper for transferring ownership of an inode */
int vfs_dq_transfer(struct inode *inode, struct iattr *iattr)
{
	if (sb_any_quota_active(inode->i_sb) && !IS_NOQUOTA(inode)) {
		vfs_dq_init(inode);
		if (inode->i_sb->dq_op->transfer(inode, iattr) == NO_QUOTA)
			return 1;
	}
	return 0;
}
EXPORT_SYMBOL(vfs_dq_transfer);

/*
 * Write info of quota file to disk
 */
int dquot_commit_info(struct super_block *sb, int type)
{
	int ret;
	struct quota_info *dqopt = sb_dqopt(sb);

	mutex_lock(&dqopt->dqio_mutex);
	ret = dqopt->ops[type]->write_file_info(sb, type);
	mutex_unlock(&dqopt->dqio_mutex);
	return ret;
}
EXPORT_SYMBOL(dquot_commit_info);

/*
 * Definitions of diskquota operations.
 */
struct dquot_operations dquot_operations = {
	.initialize	= dquot_initialize,
	.drop		= dquot_drop,
	.alloc_space	= dquot_alloc_space,
	.alloc_inode	= dquot_alloc_inode,
	.free_space	= dquot_free_space,
	.free_inode	= dquot_free_inode,
	.transfer	= dquot_transfer,
	.write_dquot	= dquot_commit,
	.acquire_dquot	= dquot_acquire,
	.release_dquot	= dquot_release,
	.mark_dirty	= dquot_mark_dquot_dirty,
	.write_info	= dquot_commit_info,
	.alloc_dquot	= dquot_alloc,
	.destroy_dquot	= dquot_destroy,
};

/*
 * Turn quota off on a device. type == -1 ==> quotaoff for all types (umount)
 */
int vfs_quota_disable(struct super_block *sb, int type, unsigned int flags)
{
	int cnt, ret = 0;
	struct quota_info *dqopt = sb_dqopt(sb);
	struct inode *toputinode[MAXQUOTAS];

	/* Cannot turn off usage accounting without turning off limits, or
	 * suspend quotas and simultaneously turn quotas off. */
	if ((flags & DQUOT_USAGE_ENABLED && !(flags & DQUOT_LIMITS_ENABLED))
	    || (flags & DQUOT_SUSPENDED && flags & (DQUOT_LIMITS_ENABLED |
	    DQUOT_USAGE_ENABLED)))
		return -EINVAL;

	/* We need to serialize quota_off() for device */
	mutex_lock(&dqopt->dqonoff_mutex);

	/*
	 * Skip everything if there's nothing to do. We have to do this because
	 * sometimes we are called when fill_super() failed and calling
	 * sync_fs() in such cases does no good.
	 */
	if (!sb_any_quota_loaded(sb)) {
		mutex_unlock(&dqopt->dqonoff_mutex);
		return 0;
	}
	for (cnt = 0; cnt < MAXQUOTAS; cnt++) {
		toputinode[cnt] = NULL;
		if (type != -1 && cnt != type)
			continue;
		if (!sb_has_quota_loaded(sb, cnt))
			continue;

		if (flags & DQUOT_SUSPENDED) {
			spin_lock(&dq_state_lock);
			dqopt->flags |=
				dquot_state_flag(DQUOT_SUSPENDED, cnt);
			spin_unlock(&dq_state_lock);
		} else {
			spin_lock(&dq_state_lock);
			dqopt->flags &= ~dquot_state_flag(flags, cnt);
			/* Turning off suspended quotas? */
			if (!sb_has_quota_loaded(sb, cnt) &&
			    sb_has_quota_suspended(sb, cnt)) {
				dqopt->flags &=	~dquot_state_flag(
							DQUOT_SUSPENDED, cnt);
				spin_unlock(&dq_state_lock);
				iput(dqopt->files[cnt]);
				dqopt->files[cnt] = NULL;
				continue;
			}
			spin_unlock(&dq_state_lock);
		}

		/* We still have to keep quota loaded? */
		if (sb_has_quota_loaded(sb, cnt) && !(flags & DQUOT_SUSPENDED))
			continue;

		/* Note: these are blocking operations */
		drop_dquot_ref(sb, cnt);
		invalidate_dquots(sb, cnt);
		/*
		 * Now all dquots should be invalidated, all writes done so we
		 * should be only users of the info. No locks needed.
		 */
		if (info_dirty(&dqopt->info[cnt]))
			sb->dq_op->write_info(sb, cnt);
		if (dqopt->ops[cnt]->free_file_info)
			dqopt->ops[cnt]->free_file_info(sb, cnt);
		put_quota_format(dqopt->info[cnt].dqi_format);

		toputinode[cnt] = dqopt->files[cnt];
		if (!sb_has_quota_loaded(sb, cnt))
			dqopt->files[cnt] = NULL;
		dqopt->info[cnt].dqi_flags = 0;
		dqopt->info[cnt].dqi_igrace = 0;
		dqopt->info[cnt].dqi_bgrace = 0;
		dqopt->ops[cnt] = NULL;
	}
	mutex_unlock(&dqopt->dqonoff_mutex);

	/* Skip syncing and setting flags if quota files are hidden */
	if (dqopt->flags & DQUOT_QUOTA_SYS_FILE)
		goto put_inodes;

	/* Sync the superblock so that buffers with quota data are written to
	 * disk (and so userspace sees correct data afterwards). */
	if (sb->s_op->sync_fs)
		sb->s_op->sync_fs(sb, 1);
	sync_blockdev(sb->s_bdev);
	/* Now the quota files are just ordinary files and we can set the
	 * inode flags back. Moreover we discard the pagecache so that
	 * userspace sees the writes we did bypassing the pagecache. We
	 * must also discard the blockdev buffers so that we see the
	 * changes done by userspace on the next quotaon() */
	for (cnt = 0; cnt < MAXQUOTAS; cnt++)
		if (toputinode[cnt]) {
			mutex_lock(&dqopt->dqonoff_mutex);
			/* If quota was reenabled in the meantime, we have
			 * nothing to do */
			if (!sb_has_quota_loaded(sb, cnt)) {
				mutex_lock_nested(&toputinode[cnt]->i_mutex,
						  I_MUTEX_QUOTA);
				toputinode[cnt]->i_flags &= ~(S_IMMUTABLE |
				  S_NOATIME | S_NOQUOTA);
				truncate_inode_pages(&toputinode[cnt]->i_data,
						     0);
				mutex_unlock(&toputinode[cnt]->i_mutex);
				mark_inode_dirty(toputinode[cnt]);
			}
			mutex_unlock(&dqopt->dqonoff_mutex);
		}
	if (sb->s_bdev)
		invalidate_bdev(sb->s_bdev);
put_inodes:
	for (cnt = 0; cnt < MAXQUOTAS; cnt++)
		if (toputinode[cnt]) {
			/* On remount RO, we keep the inode pointer so that we
			 * can reenable quota on the subsequent remount RW. We
			 * have to check 'flags' variable and not use sb_has_
			 * function because another quotaon / quotaoff could
			 * change global state before we got here. We refuse
			 * to suspend quotas when there is pending delete on
			 * the quota file... */
			if (!(flags & DQUOT_SUSPENDED))
				iput(toputinode[cnt]);
			else if (!toputinode[cnt]->i_nlink)
				ret = -EBUSY;
		}
	return ret;
}
EXPORT_SYMBOL(vfs_quota_disable);

int vfs_quota_off(struct super_block *sb, int type, int remount)
{
	return vfs_quota_disable(sb, type, remount ? DQUOT_SUSPENDED :
				 (DQUOT_USAGE_ENABLED | DQUOT_LIMITS_ENABLED));
}
EXPORT_SYMBOL(vfs_quota_off);
/*
 *	Turn quotas on on a device
 */

/*
 * Helper function to turn quotas on when we already have the inode of
 * quota file and no quota information is loaded.
 */
static int vfs_load_quota_inode(struct inode *inode, int type, int format_id,
	unsigned int flags)
{
	struct quota_format_type *fmt = find_quota_format(format_id);
	struct super_block *sb = inode->i_sb;
	struct quota_info *dqopt = sb_dqopt(sb);
	int error;
	int oldflags = -1;

	if (!fmt)
		return -ESRCH;
	if (!S_ISREG(inode->i_mode)) {
		error = -EACCES;
		goto out_fmt;
	}
	if (IS_RDONLY(inode)) {
		error = -EROFS;
		goto out_fmt;
	}
	if (!sb->s_op->quota_write || !sb->s_op->quota_read) {
		error = -EINVAL;
		goto out_fmt;
	}
	/* Usage always has to be set... */
	if (!(flags & DQUOT_USAGE_ENABLED)) {
		error = -EINVAL;
		goto out_fmt;
	}

	if (!(dqopt->flags & DQUOT_QUOTA_SYS_FILE)) {
		/* As we bypass the pagecache we must now flush the inode so
		 * that we see all the changes from userspace... */
		write_inode_now(inode, 1);
		/* And now flush the block cache so that kernel sees the
		 * changes */
		invalidate_bdev(sb->s_bdev);
	}
	mutex_lock(&inode->i_mutex);
	mutex_lock(&dqopt->dqonoff_mutex);
	if (sb_has_quota_loaded(sb, type)) {
		error = -EBUSY;
		goto out_lock;
	}

	if (!(dqopt->flags & DQUOT_QUOTA_SYS_FILE)) {
		/* We don't want quota and atime on quota files (deadlocks
		 * possible) Also nobody should write to the file - we use
		 * special IO operations which ignore the immutable bit. */
		down_write(&dqopt->dqptr_sem);
		oldflags = inode->i_flags & (S_NOATIME | S_IMMUTABLE |
					     S_NOQUOTA);
		inode->i_flags |= S_NOQUOTA | S_NOATIME | S_IMMUTABLE;
		up_write(&dqopt->dqptr_sem);
		sb->dq_op->drop(inode);
	}

	error = -EIO;
	dqopt->files[type] = igrab(inode);
	if (!dqopt->files[type])
		goto out_lock;
	error = -EINVAL;
	if (!fmt->qf_ops->check_quota_file(sb, type))
		goto out_file_init;

	dqopt->ops[type] = fmt->qf_ops;
	dqopt->info[type].dqi_format = fmt;
	dqopt->info[type].dqi_fmt_id = format_id;
	INIT_LIST_HEAD(&dqopt->info[type].dqi_dirty_list);
	mutex_lock(&dqopt->dqio_mutex);
	error = dqopt->ops[type]->read_file_info(sb, type);
	if (error < 0) {
		mutex_unlock(&dqopt->dqio_mutex);
		goto out_file_init;
	}
	mutex_unlock(&dqopt->dqio_mutex);
	mutex_unlock(&inode->i_mutex);
	spin_lock(&dq_state_lock);
	dqopt->flags |= dquot_state_flag(flags, type);
	spin_unlock(&dq_state_lock);

	add_dquot_ref(sb, type);
	mutex_unlock(&dqopt->dqonoff_mutex);

	return 0;

out_file_init:
	dqopt->files[type] = NULL;
	iput(inode);
out_lock:
	mutex_unlock(&dqopt->dqonoff_mutex);
	if (oldflags != -1) {
		down_write(&dqopt->dqptr_sem);
		/* Set the flags back (in the case of accidental quotaon()
		 * on a wrong file we don't want to mess up the flags) */
		inode->i_flags &= ~(S_NOATIME | S_NOQUOTA | S_IMMUTABLE);
		inode->i_flags |= oldflags;
		up_write(&dqopt->dqptr_sem);
	}
	mutex_unlock(&inode->i_mutex);
out_fmt:
	put_quota_format(fmt);

	return error; 
}

/* Reenable quotas on remount RW */
static int vfs_quota_on_remount(struct super_block *sb, int type)
{
	struct quota_info *dqopt = sb_dqopt(sb);
	struct inode *inode;
	int ret;
	unsigned int flags;

	mutex_lock(&dqopt->dqonoff_mutex);
	if (!sb_has_quota_suspended(sb, type)) {
		mutex_unlock(&dqopt->dqonoff_mutex);
		return 0;
	}
	inode = dqopt->files[type];
	dqopt->files[type] = NULL;
	spin_lock(&dq_state_lock);
	flags = dqopt->flags & dquot_state_flag(DQUOT_USAGE_ENABLED |
						DQUOT_LIMITS_ENABLED, type);
	dqopt->flags &= ~dquot_state_flag(DQUOT_STATE_FLAGS, type);
	spin_unlock(&dq_state_lock);
	mutex_unlock(&dqopt->dqonoff_mutex);

	flags = dquot_generic_flag(flags, type);
	ret = vfs_load_quota_inode(inode, type, dqopt->info[type].dqi_fmt_id,
				   flags);
	iput(inode);

	return ret;
}

int vfs_quota_on_path(struct super_block *sb, int type, int format_id,
		      struct path *path)
{
	int error = security_quota_on(path->dentry);
	if (error)
		return error;
	/* Quota file not on the same filesystem? */
	if (path->mnt->mnt_sb != sb)
		error = -EXDEV;
	else
		error = vfs_load_quota_inode(path->dentry->d_inode, type,
					     format_id, DQUOT_USAGE_ENABLED |
					     DQUOT_LIMITS_ENABLED);
	return error;
}
EXPORT_SYMBOL(vfs_quota_on_path);

int vfs_quota_on(struct super_block *sb, int type, int format_id, char *name,
		 int remount)
{
	struct path path;
	int error;

	if (remount)
		return vfs_quota_on_remount(sb, type);

	error = kern_path(name, LOOKUP_FOLLOW, &path);
	if (!error) {
		error = vfs_quota_on_path(sb, type, format_id, &path);
		path_put(&path);
	}
	return error;
}
EXPORT_SYMBOL(vfs_quota_on);

/*
 * More powerful function for turning on quotas allowing setting
 * of individual quota flags
 */
int vfs_quota_enable(struct inode *inode, int type, int format_id,
		unsigned int flags)
{
	int ret = 0;
	struct super_block *sb = inode->i_sb;
	struct quota_info *dqopt = sb_dqopt(sb);

	/* Just unsuspend quotas? */
	if (flags & DQUOT_SUSPENDED)
		return vfs_quota_on_remount(sb, type);
	if (!flags)
		return 0;
	/* Just updating flags needed? */
	if (sb_has_quota_loaded(sb, type)) {
		mutex_lock(&dqopt->dqonoff_mutex);
		/* Now do a reliable test... */
		if (!sb_has_quota_loaded(sb, type)) {
			mutex_unlock(&dqopt->dqonoff_mutex);
			goto load_quota;
		}
		if (flags & DQUOT_USAGE_ENABLED &&
		    sb_has_quota_usage_enabled(sb, type)) {
			ret = -EBUSY;
			goto out_lock;
		}
		if (flags & DQUOT_LIMITS_ENABLED &&
		    sb_has_quota_limits_enabled(sb, type)) {
			ret = -EBUSY;
			goto out_lock;
		}
		spin_lock(&dq_state_lock);
		sb_dqopt(sb)->flags |= dquot_state_flag(flags, type);
		spin_unlock(&dq_state_lock);
out_lock:
		mutex_unlock(&dqopt->dqonoff_mutex);
		return ret;
	}

load_quota:
	return vfs_load_quota_inode(inode, type, format_id, flags);
}
EXPORT_SYMBOL(vfs_quota_enable);

/*
 * This function is used when filesystem needs to initialize quotas
 * during mount time.
 */
int vfs_quota_on_mount(struct super_block *sb, char *qf_name,
		int format_id, int type)
{
	struct dentry *dentry;
	int error;

	dentry = lookup_one_len(qf_name, sb->s_root, strlen(qf_name));
	if (IS_ERR(dentry))
		return PTR_ERR(dentry);

	if (!dentry->d_inode) {
		error = -ENOENT;
		goto out;
	}

	error = security_quota_on(dentry);
	if (!error)
		error = vfs_load_quota_inode(dentry->d_inode, type, format_id,
				DQUOT_USAGE_ENABLED | DQUOT_LIMITS_ENABLED);

out:
	dput(dentry);
	return error;
}
EXPORT_SYMBOL(vfs_quota_on_mount);

/* Wrapper to turn on quotas when remounting rw */
int vfs_dq_quota_on_remount(struct super_block *sb)
{
	int cnt;
	int ret = 0, err;

	if (!sb->s_qcop || !sb->s_qcop->quota_on)
		return -ENOSYS;
	for (cnt = 0; cnt < MAXQUOTAS; cnt++) {
		err = sb->s_qcop->quota_on(sb, cnt, 0, NULL, 1);
		if (err < 0 && !ret)
			ret = err;
	}
	return ret;
}
EXPORT_SYMBOL(vfs_dq_quota_on_remount);

static inline qsize_t qbtos(qsize_t blocks)
{
	return blocks << QIF_DQBLKSIZE_BITS;
}

static inline qsize_t stoqb(qsize_t space)
{
	return (space + QIF_DQBLKSIZE - 1) >> QIF_DQBLKSIZE_BITS;
}

/* Generic routine for getting common part of quota structure */
static void do_get_dqblk(struct dquot *dquot, struct if_dqblk *di)
{
	struct mem_dqblk *dm = &dquot->dq_dqb;

	spin_lock(&dq_data_lock);
	di->dqb_bhardlimit = stoqb(dm->dqb_bhardlimit);
	di->dqb_bsoftlimit = stoqb(dm->dqb_bsoftlimit);
	di->dqb_curspace = dm->dqb_curspace + dm->dqb_rsvspace;
	di->dqb_ihardlimit = dm->dqb_ihardlimit;
	di->dqb_isoftlimit = dm->dqb_isoftlimit;
	di->dqb_curinodes = dm->dqb_curinodes;
	di->dqb_btime = dm->dqb_btime;
	di->dqb_itime = dm->dqb_itime;
	di->dqb_valid = QIF_ALL;
	spin_unlock(&dq_data_lock);
}

int vfs_get_dqblk(struct super_block *sb, int type, qid_t id,
		  struct if_dqblk *di)
{
	struct dquot *dquot;

	dquot = dqget(sb, id, type);
	if (!dquot)
		return -ESRCH;
	do_get_dqblk(dquot, di);
	dqput(dquot);

	return 0;
}
EXPORT_SYMBOL(vfs_get_dqblk);

/* Generic routine for setting common part of quota structure */
static int do_set_dqblk(struct dquot *dquot, struct if_dqblk *di)
{
	struct mem_dqblk *dm = &dquot->dq_dqb;
	int check_blim = 0, check_ilim = 0;
	struct mem_dqinfo *dqi = &sb_dqopt(dquot->dq_sb)->info[dquot->dq_type];

	if ((di->dqb_valid & QIF_BLIMITS &&
	     (di->dqb_bhardlimit > dqi->dqi_maxblimit ||
	      di->dqb_bsoftlimit > dqi->dqi_maxblimit)) ||
	    (di->dqb_valid & QIF_ILIMITS &&
	     (di->dqb_ihardlimit > dqi->dqi_maxilimit ||
	      di->dqb_isoftlimit > dqi->dqi_maxilimit)))
		return -ERANGE;

	spin_lock(&dq_data_lock);
	if (di->dqb_valid & QIF_SPACE) {
		dm->dqb_curspace = di->dqb_curspace - dm->dqb_rsvspace;
		check_blim = 1;
		__set_bit(DQ_LASTSET_B + QIF_SPACE_B, &dquot->dq_flags);
	}
	if (di->dqb_valid & QIF_BLIMITS) {
		dm->dqb_bsoftlimit = qbtos(di->dqb_bsoftlimit);
		dm->dqb_bhardlimit = qbtos(di->dqb_bhardlimit);
		check_blim = 1;
		__set_bit(DQ_LASTSET_B + QIF_BLIMITS_B, &dquot->dq_flags);
	}
	if (di->dqb_valid & QIF_INODES) {
		dm->dqb_curinodes = di->dqb_curinodes;
		check_ilim = 1;
		__set_bit(DQ_LASTSET_B + QIF_INODES_B, &dquot->dq_flags);
	}
	if (di->dqb_valid & QIF_ILIMITS) {
		dm->dqb_isoftlimit = di->dqb_isoftlimit;
		dm->dqb_ihardlimit = di->dqb_ihardlimit;
		check_ilim = 1;
		__set_bit(DQ_LASTSET_B + QIF_ILIMITS_B, &dquot->dq_flags);
	}
	if (di->dqb_valid & QIF_BTIME) {
		dm->dqb_btime = di->dqb_btime;
		check_blim = 1;
		__set_bit(DQ_LASTSET_B + QIF_BTIME_B, &dquot->dq_flags);
	}
	if (di->dqb_valid & QIF_ITIME) {
		dm->dqb_itime = di->dqb_itime;
		check_ilim = 1;
		__set_bit(DQ_LASTSET_B + QIF_ITIME_B, &dquot->dq_flags);
	}

	if (check_blim) {
		if (!dm->dqb_bsoftlimit ||
		    dm->dqb_curspace < dm->dqb_bsoftlimit) {
			dm->dqb_btime = 0;
			clear_bit(DQ_BLKS_B, &dquot->dq_flags);
		} else if (!(di->dqb_valid & QIF_BTIME))
			/* Set grace only if user hasn't provided his own... */
			dm->dqb_btime = get_seconds() + dqi->dqi_bgrace;
	}
	if (check_ilim) {
		if (!dm->dqb_isoftlimit ||
		    dm->dqb_curinodes < dm->dqb_isoftlimit) {
			dm->dqb_itime = 0;
			clear_bit(DQ_INODES_B, &dquot->dq_flags);
		} else if (!(di->dqb_valid & QIF_ITIME))
			/* Set grace only if user hasn't provided his own... */
			dm->dqb_itime = get_seconds() + dqi->dqi_igrace;
	}
	if (dm->dqb_bhardlimit || dm->dqb_bsoftlimit || dm->dqb_ihardlimit ||
	    dm->dqb_isoftlimit)
		clear_bit(DQ_FAKE_B, &dquot->dq_flags);
	else
		set_bit(DQ_FAKE_B, &dquot->dq_flags);
	spin_unlock(&dq_data_lock);
	mark_dquot_dirty(dquot);

	return 0;
}

int vfs_set_dqblk(struct super_block *sb, int type, qid_t id,
		  struct if_dqblk *di)
{
	struct dquot *dquot;
	int rc;

	dquot = dqget(sb, id, type);
	if (!dquot) {
		rc = -ESRCH;
		goto out;
	}
	rc = do_set_dqblk(dquot, di);
	dqput(dquot);
out:
	return rc;
}
EXPORT_SYMBOL(vfs_set_dqblk);

/* Generic routine for getting common part of quota file information */
int vfs_get_dqinfo(struct super_block *sb, int type, struct if_dqinfo *ii)
{
	struct mem_dqinfo *mi;
  
	mutex_lock(&sb_dqopt(sb)->dqonoff_mutex);
	if (!sb_has_quota_active(sb, type)) {
		mutex_unlock(&sb_dqopt(sb)->dqonoff_mutex);
		return -ESRCH;
	}
	mi = sb_dqopt(sb)->info + type;
	spin_lock(&dq_data_lock);
	ii->dqi_bgrace = mi->dqi_bgrace;
	ii->dqi_igrace = mi->dqi_igrace;
	ii->dqi_flags = mi->dqi_flags & DQF_MASK;
	ii->dqi_valid = IIF_ALL;
	spin_unlock(&dq_data_lock);
	mutex_unlock(&sb_dqopt(sb)->dqonoff_mutex);
	return 0;
}
EXPORT_SYMBOL(vfs_get_dqinfo);

/* Generic routine for setting common part of quota file information */
int vfs_set_dqinfo(struct super_block *sb, int type, struct if_dqinfo *ii)
{
	struct mem_dqinfo *mi;
	int err = 0;

	mutex_lock(&sb_dqopt(sb)->dqonoff_mutex);
	if (!sb_has_quota_active(sb, type)) {
		err = -ESRCH;
		goto out;
	}
	mi = sb_dqopt(sb)->info + type;
	spin_lock(&dq_data_lock);
	if (ii->dqi_valid & IIF_BGRACE)
		mi->dqi_bgrace = ii->dqi_bgrace;
	if (ii->dqi_valid & IIF_IGRACE)
		mi->dqi_igrace = ii->dqi_igrace;
	if (ii->dqi_valid & IIF_FLAGS)
		mi->dqi_flags = (mi->dqi_flags & ~DQF_MASK) |
				(ii->dqi_flags & DQF_MASK);
	spin_unlock(&dq_data_lock);
	mark_info_dirty(sb, type);
	/* Force write to disk */
	sb->dq_op->write_info(sb, type);
out:
	mutex_unlock(&sb_dqopt(sb)->dqonoff_mutex);
	return err;
}
EXPORT_SYMBOL(vfs_set_dqinfo);

struct quotactl_ops vfs_quotactl_ops = {
	.quota_on	= vfs_quota_on,
	.quota_off	= vfs_quota_off,
	.quota_sync	= vfs_quota_sync,
	.get_info	= vfs_get_dqinfo,
	.set_info	= vfs_set_dqinfo,
	.get_dqblk	= vfs_get_dqblk,
	.set_dqblk	= vfs_set_dqblk
};

static ctl_table fs_dqstats_table[] = {
	{
		.ctl_name	= FS_DQ_LOOKUPS,
		.procname	= "lookups",
		.data		= &dqstats.lookups,
		.maxlen		= sizeof(int),
		.mode		= 0444,
		.proc_handler	= &proc_dointvec,
	},
	{
		.ctl_name	= FS_DQ_DROPS,
		.procname	= "drops",
		.data		= &dqstats.drops,
		.maxlen		= sizeof(int),
		.mode		= 0444,
		.proc_handler	= &proc_dointvec,
	},
	{
		.ctl_name	= FS_DQ_READS,
		.procname	= "reads",
		.data		= &dqstats.reads,
		.maxlen		= sizeof(int),
		.mode		= 0444,
		.proc_handler	= &proc_dointvec,
	},
	{
		.ctl_name	= FS_DQ_WRITES,
		.procname	= "writes",
		.data		= &dqstats.writes,
		.maxlen		= sizeof(int),
		.mode		= 0444,
		.proc_handler	= &proc_dointvec,
	},
	{
		.ctl_name	= FS_DQ_CACHE_HITS,
		.procname	= "cache_hits",
		.data		= &dqstats.cache_hits,
		.maxlen		= sizeof(int),
		.mode		= 0444,
		.proc_handler	= &proc_dointvec,
	},
	{
		.ctl_name	= FS_DQ_ALLOCATED,
		.procname	= "allocated_dquots",
		.data		= &dqstats.allocated_dquots,
		.maxlen		= sizeof(int),
		.mode		= 0444,
		.proc_handler	= &proc_dointvec,
	},
	{
		.ctl_name	= FS_DQ_FREE,
		.procname	= "free_dquots",
		.data		= &dqstats.free_dquots,
		.maxlen		= sizeof(int),
		.mode		= 0444,
		.proc_handler	= &proc_dointvec,
	},
	{
		.ctl_name	= FS_DQ_SYNCS,
		.procname	= "syncs",
		.data		= &dqstats.syncs,
		.maxlen		= sizeof(int),
		.mode		= 0444,
		.proc_handler	= &proc_dointvec,
	},
#ifdef CONFIG_PRINT_QUOTA_WARNING
	{
		.ctl_name	= FS_DQ_WARNINGS,
		.procname	= "warnings",
		.data		= &flag_print_warnings,
		.maxlen		= sizeof(int),
		.mode		= 0644,
		.proc_handler	= &proc_dointvec,
	},
#endif
	{ .ctl_name = 0 },
};

static ctl_table fs_table[] = {
	{
		.ctl_name	= FS_DQSTATS,
		.procname	= "quota",
		.mode		= 0555,
		.child		= fs_dqstats_table,
	},
	{ .ctl_name = 0 },
};

static ctl_table sys_table[] = {
	{
		.ctl_name	= CTL_FS,
		.procname	= "fs",
		.mode		= 0555,
		.child		= fs_table,
	},
	{ .ctl_name = 0 },
};

static int __init dquot_init(void)
{
	int i;
	unsigned long nr_hash, order;

	printk(KERN_NOTICE "VFS: Disk quotas %s\n", __DQUOT_VERSION__);

	register_sysctl_table(sys_table);

	dquot_cachep = kmem_cache_create("dquot",
			sizeof(struct dquot), sizeof(unsigned long) * 4,
			(SLAB_HWCACHE_ALIGN|SLAB_RECLAIM_ACCOUNT|
				SLAB_MEM_SPREAD|SLAB_PANIC),
			NULL);

	order = 0;
	dquot_hash = (struct hlist_head *)__get_free_pages(GFP_ATOMIC, order);
	if (!dquot_hash)
		panic("Cannot create dquot hash table");

	/* Find power-of-two hlist_heads which can fit into allocation */
	nr_hash = (1UL << order) * PAGE_SIZE / sizeof(struct hlist_head);
	dq_hash_bits = 0;
	do {
		dq_hash_bits++;
	} while (nr_hash >> dq_hash_bits);
	dq_hash_bits--;

	nr_hash = 1UL << dq_hash_bits;
	dq_hash_mask = nr_hash - 1;
	for (i = 0; i < nr_hash; i++)
		INIT_HLIST_HEAD(dquot_hash + i);

	printk("Dquot-cache hash table entries: %ld (order %ld, %ld bytes)\n",
			nr_hash, order, (PAGE_SIZE << order));

	register_shrinker(&dqcache_shrinker);

#ifdef CONFIG_QUOTA_NETLINK_INTERFACE
	if (genl_register_family(&quota_genl_family) != 0)
		printk(KERN_ERR
		       "VFS: Failed to create quota netlink interface.\n");
#endif

	return 0;
}
module_init(dquot_init);