Merge branch 'for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/ryusuke...

[linux-2.6/mini2440.git] / 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 (inode->i_state & (I_FREEING|I_CLEAR|I_WILL_FREE|I_NEW))
                        continue;
                if (!atomic_read(&inode->i_writecount))
                        continue;
                if (!dqinit_needed(inode, type))
                        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) {
                /*
                 *  We have to scan also I_NEW inodes because they can already
                 *  have quota pointer initialized. Luckily, we need to touch
                 *  only quota pointers and these have separate locking
                 *  (dqptr_sem).
                 */
                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);

        genlmsg_multicast(skb, 0, quota_genl_family.id, GFP_NOFS);
        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.
 */
const 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(&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);
                mutex_lock_nested(&inode->i_mutex, I_MUTEX_QUOTA);
                oldflags = inode->i_flags & (S_NOATIME | S_IMMUTABLE |
                                             S_NOQUOTA);
                inode->i_flags |= S_NOQUOTA | S_NOATIME | S_IMMUTABLE;
                mutex_unlock(&inode->i_mutex);
                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);
        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:
        if (oldflags != -1) {
                down_write(&dqopt->dqptr_sem);
                mutex_lock_nested(&inode->i_mutex, I_MUTEX_QUOTA);
                /* 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;
                mutex_unlock(&inode->i_mutex);
                up_write(&dqopt->dqptr_sem);
        }
        mutex_unlock(&dqopt->dqonoff_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);

const 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);