[PATCH] per-task-delay-accounting: documentation

[usb.git] / fs / 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.
 * 
 * Version: $Id: dquot.c,v 6.3 1996/11/17 18:35:34 mvw Exp mvw $
 * 
 * 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/smp_lock.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 <asm/uaccess.h>

#define __DQUOT_PARANOIA

/*
 * There are two quota SMP locks. dq_list_lock protects all lists with quotas
 * and quota formats and also 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().
 *
 * The spinlock ordering is hence: dq_data_lock > dq_list_lock > i_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).  If operation is holding
 * reference to dquot in other way (e.g. quotactl ops) it must be guarded by
 * dqonoff_mutex.
 * This locking assures that:
 *   a) update/access to dquot pointers in inode is serialized
 *   b) everyone is guarded against invalidate_dquots()
 *
 * 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
 * i_mutex on quota files is special (it's below dqio_mutex)
 */

static DEFINE_SPINLOCK(dq_list_lock);
DEFINE_SPINLOCK(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 kmem_cache_t *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;
}

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);
}

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;

static void dqput(struct dquot *dquot);

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 = 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 inline 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 NODQUOT;
}

/* 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);
}

#define mark_dquot_dirty(dquot) ((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;
}

/* 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;
}

/*
 *      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;
}

/*
 *      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;
}

/* 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). 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);
                kmem_cache_free(dquot_cachep, dquot);
        }
        spin_unlock(&dq_list_lock);
}

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_enabled(sb, cnt))
                        continue;
                spin_lock(&dq_list_lock);
                dirty = &dqopt->info[cnt].dqi_dirty_list;
                while (!list_empty(dirty)) {
                        dquot = list_entry(dirty->next, 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_enabled(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;
}

/* 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);
                kmem_cache_free(dquot_cachep, 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;
}

/*
 * Put reference to dquot
 * NOTE: If you change this function please check whether dqput_blocks() works right...
 * MUST be called with either dqptr_sem or dqonoff_mutex held
 */
static void dqput(struct dquot *dquot)
{
        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_enabled(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 */
                dquot->dq_sb->dq_op->write_dquot(dquot);
                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);
}

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

        dquot = kmem_cache_alloc(dquot_cachep, SLAB_NOFS);
        if(!dquot)
                return NODQUOT;

        memset((caddr_t)dquot, 0, sizeof(struct dquot));
        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
 * MUST be called with either dqptr_sem or dqonoff_mutex held
 */
static struct dquot *dqget(struct super_block *sb, unsigned int id, int type)
{
        unsigned int hashent = hashfn(sb, id, type);
        struct dquot *dquot, *empty = NODQUOT;

        if (!sb_has_quota_enabled(sb, type))
                return NODQUOT;
we_slept:
        spin_lock(&dq_list_lock);
        if ((dquot = find_dquot(hashent, sb, id, type)) == NODQUOT) {
                if (empty == NODQUOT) {
                        spin_unlock(&dq_list_lock);
                        if ((empty = get_empty_dquot(sb, type)) == NODQUOT)
                                schedule();     /* Try to wait for a moment... */
                        goto we_slept;
                }
                dquot = empty;
                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);
                if (empty)
                        kmem_cache_free(dquot_cachep, empty);
        }
        /* 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 and instantiate it (everything done only if needed) */
        if (!test_bit(DQ_ACTIVE_B, &dquot->dq_flags) && sb->dq_op->acquire_dquot(dquot) < 0) {
                dqput(dquot);
                return NODQUOT;
        }
#ifdef __DQUOT_PARANOIA
        BUG_ON(!dquot->dq_sb);  /* Has somebody invalidated entry under us? */
#endif

        return dquot;
}

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

/* This routine is guarded by dqonoff_mutex mutex */
static void add_dquot_ref(struct super_block *sb, int type)
{
        struct list_head *p;

restart:
        file_list_lock();
        list_for_each(p, &sb->s_files) {
                struct file *filp = list_entry(p, struct file, f_u.fu_list);
                struct inode *inode = filp->f_dentry->d_inode;
                if (filp->f_mode & FMODE_WRITE && dqinit_needed(inode, type)) {
                        struct dentry *dentry = dget(filp->f_dentry);
                        file_list_unlock();
                        sb->dq_op->initialize(inode, type);
                        dput(dentry);
                        /* As we may have blocked we had better restart... */
                        goto restart;
                }
        }
        file_list_unlock();
}

/* 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 - add dquot to list for freeing if needed */
/* We can't race with anybody because we hold dqptr_sem for writing... */
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] = NODQUOT;
        if (dquot != NODQUOT) {
                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);
                        list_add(&dquot->dq_free, tofree_head); /* As dquot must have currently users it can't be on the free list... */
                        spin_unlock(&dq_list_lock);
                        return 1;
                }
                else
                        dqput(dquot);   /* We have guaranteed we won't block */
        }
        return 0;
}

/* Free list of dquots - called from inode.c */
/* dquots are removed from inodes, 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;
        /* So now we have dquots on the list... Just free them */
        while (act_head != tofree_head) {
                dquot = list_entry(act_head, struct dquot, dq_free);
                act_head = act_head->next;
                list_del_init(&dquot->dq_free); /* Remove dquot from the list so we won't have problems... */
                dqput(dquot);
        }
}

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

        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, unsigned long 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_decr_inodes(struct dquot *dquot, unsigned long number)
{
        if (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 inline void dquot_decr_space(struct dquot *dquot, qsize_t number)
{
        if (dquot->dq_dqb.dqb_curspace > number)
                dquot->dq_dqb.dqb_curspace -= number;
        else
                dquot->dq_dqb.dqb_curspace = 0;
        if (toqb(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 flag_print_warnings = 1;

static inline 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;
}

/* Values of warnings */
#define NOWARN 0
#define IHARDWARN 1
#define ISOFTLONGWARN 2
#define ISOFTWARN 3
#define BHARDWARN 4
#define BSOFTLONGWARN 5
#define BSOFTWARN 6

/* Print warning to user which exceeded quota */
static void print_warning(struct dquot *dquot, const char warntype)
{
        char *msg = NULL;
        int flag = (warntype == BHARDWARN || warntype == BSOFTLONGWARN) ? DQ_BLKS_B :
          ((warntype == IHARDWARN || warntype == ISOFTLONGWARN) ? DQ_INODES_B : 0);

        if (!need_print_warning(dquot) || (flag && test_and_set_bit(flag, &dquot->dq_flags)))
                return;

        tty_write_message(current->signal->tty, dquot->dq_sb->s_id);
        if (warntype == ISOFTWARN || warntype == BSOFTWARN)
                tty_write_message(current->signal->tty, ": warning, ");
        else
                tty_write_message(current->signal->tty, ": write failed, ");
        tty_write_message(current->signal->tty, quotatypes[dquot->dq_type]);
        switch (warntype) {
                case IHARDWARN:
                        msg = " file limit reached.\r\n";
                        break;
                case ISOFTLONGWARN:
                        msg = " file quota exceeded too long.\r\n";
                        break;
                case ISOFTWARN:
                        msg = " file quota exceeded.\r\n";
                        break;
                case BHARDWARN:
                        msg = " block limit reached.\r\n";
                        break;
                case BSOFTLONGWARN:
                        msg = " block quota exceeded too long.\r\n";
                        break;
                case BSOFTWARN:
                        msg = " block quota exceeded.\r\n";
                        break;
        }
        tty_write_message(current->signal->tty, msg);
}

static inline void flush_warnings(struct dquot **dquots, char *warntype)
{
        int i;

        for (i = 0; i < MAXQUOTAS; i++)
                if (dquots[i] != NODQUOT && warntype[i] != NOWARN)
                        print_warning(dquots[i], warntype[i]);
}

static inline char 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, ulong inodes, char *warntype)
{
        *warntype = NOWARN;
        if (inodes <= 0 || test_bit(DQ_FAKE_B, &dquot->dq_flags))
                return QUOTA_OK;

        if (dquot->dq_dqb.dqb_ihardlimit &&
           (dquot->dq_dqb.dqb_curinodes + inodes) > dquot->dq_dqb.dqb_ihardlimit &&
            !ignore_hardlimit(dquot)) {
                *warntype = IHARDWARN;
                return NO_QUOTA;
        }

        if (dquot->dq_dqb.dqb_isoftlimit &&
           (dquot->dq_dqb.dqb_curinodes + inodes) > dquot->dq_dqb.dqb_isoftlimit &&
            dquot->dq_dqb.dqb_itime && get_seconds() >= dquot->dq_dqb.dqb_itime &&
            !ignore_hardlimit(dquot)) {
                *warntype = ISOFTLONGWARN;
                return NO_QUOTA;
        }

        if (dquot->dq_dqb.dqb_isoftlimit &&
           (dquot->dq_dqb.dqb_curinodes + inodes) > dquot->dq_dqb.dqb_isoftlimit &&
            dquot->dq_dqb.dqb_itime == 0) {
                *warntype = 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)
{
        *warntype = 0;
        if (space <= 0 || test_bit(DQ_FAKE_B, &dquot->dq_flags))
                return QUOTA_OK;

        if (dquot->dq_dqb.dqb_bhardlimit &&
           toqb(dquot->dq_dqb.dqb_curspace + space) > dquot->dq_dqb.dqb_bhardlimit &&
            !ignore_hardlimit(dquot)) {
                if (!prealloc)
                        *warntype = BHARDWARN;
                return NO_QUOTA;
        }

        if (dquot->dq_dqb.dqb_bsoftlimit &&
           toqb(dquot->dq_dqb.dqb_curspace + space) > dquot->dq_dqb.dqb_bsoftlimit &&
            dquot->dq_dqb.dqb_btime && get_seconds() >= dquot->dq_dqb.dqb_btime &&
            !ignore_hardlimit(dquot)) {
                if (!prealloc)
                        *warntype = BSOFTLONGWARN;
                return NO_QUOTA;
        }

        if (dquot->dq_dqb.dqb_bsoftlimit &&
           toqb(dquot->dq_dqb.dqb_curspace + space) > dquot->dq_dqb.dqb_bsoftlimit &&
            dquot->dq_dqb.dqb_btime == 0) {
                if (!prealloc) {
                        *warntype = BSOFTWARN;
                        dquot->dq_dqb.dqb_btime = get_seconds() + sb_dqopt(dquot->dq_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;
}

/*
 *      Initialize quota pointers in inode
 *      Transaction must be started at entry
 */
int dquot_initialize(struct inode *inode, int type)
{
        unsigned int id = 0;
        int cnt, ret = 0;

        /* 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;
        down_write(&sb_dqopt(inode->i_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;
                if (inode->i_dquot[cnt] == NODQUOT) {
                        switch (cnt) {
                                case USRQUOTA:
                                        id = inode->i_uid;
                                        break;
                                case GRPQUOTA:
                                        id = inode->i_gid;
                                        break;
                        }
                        inode->i_dquot[cnt] = dqget(inode->i_sb, id, cnt);
                }
        }
out_err:
        up_write(&sb_dqopt(inode->i_sb)->dqptr_sem);
        return ret;
}

/*
 *      Release all quotas referenced by inode
 *      Transaction must be started at an entry
 */
int dquot_drop(struct inode *inode)
{
        int cnt;

        down_write(&sb_dqopt(inode->i_sb)->dqptr_sem);
        for (cnt = 0; cnt < MAXQUOTAS; cnt++) {
                if (inode->i_dquot[cnt] != NODQUOT) {
                        dqput(inode->i_dquot[cnt]);
                        inode->i_dquot[cnt] = NODQUOT;
                }
        }
        up_write(&sb_dqopt(inode->i_sb)->dqptr_sem);
        return 0;
}

/*
 * 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 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)) {
out_add:
                inode_add_bytes(inode, number);
                return QUOTA_OK;
        }
        for (cnt = 0; cnt < MAXQUOTAS; cnt++)
                warntype[cnt] = NOWARN;

        down_read(&sb_dqopt(inode->i_sb)->dqptr_sem);
        if (IS_NOQUOTA(inode)) {        /* Now we can do reliable test... */
                up_read(&sb_dqopt(inode->i_sb)->dqptr_sem);
                goto out_add;
        }
        spin_lock(&dq_data_lock);
        for (cnt = 0; cnt < MAXQUOTAS; cnt++) {
                if (inode->i_dquot[cnt] == NODQUOT)
                        continue;
                if (check_bdq(inode->i_dquot[cnt], number, warn, warntype+cnt) == NO_QUOTA)
                        goto warn_put_all;
        }
        for (cnt = 0; cnt < MAXQUOTAS; cnt++) {
                if (inode->i_dquot[cnt] == NODQUOT)
                        continue;
                dquot_incr_space(inode->i_dquot[cnt], number);
        }
        inode_add_bytes(inode, 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;
}

/*
 * This operation can block, but only after everything is updated
 */
int dquot_alloc_inode(const struct inode *inode, unsigned long 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] = 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] == NODQUOT)
                        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] == NODQUOT)
                        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((struct dquot **)inode->i_dquot, warntype);
        up_read(&sb_dqopt(inode->i_sb)->dqptr_sem);
        return ret;
}

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

        /* 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] == NODQUOT)
                        continue;
                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]);
        up_read(&sb_dqopt(inode->i_sb)->dqptr_sem);
        return QUOTA_OK;
}

/*
 * This operation can block, but only after everything is updated
 */
int dquot_free_inode(const struct inode *inode, unsigned long number)
{
        unsigned int cnt;

        /* 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] == NODQUOT)
                        continue;
                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]);
        up_read(&sb_dqopt(inode->i_sb)->dqptr_sem);
        return QUOTA_OK;
}

/*
 * 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;
        struct dquot *transfer_from[MAXQUOTAS];
        struct dquot *transfer_to[MAXQUOTAS];
        int cnt, ret = NO_QUOTA, 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[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;
        /* Clear the arrays */
        for (cnt = 0; cnt < MAXQUOTAS; cnt++) {
                transfer_to[cnt] = transfer_from[cnt] = NODQUOT;
                warntype[cnt] = NOWARN;
        }
        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);
                return QUOTA_OK;
        }
        /* First build the transfer_to list - here we can block on
         * reading/instantiating of dquots.  We know that the transaction for
         * us was already started so we don't violate lock ranking here */
        for (cnt = 0; cnt < MAXQUOTAS; cnt++) {
                switch (cnt) {
                        case USRQUOTA:
                                if (!chuid)
                                        continue;
                                transfer_to[cnt] = dqget(inode->i_sb, iattr->ia_uid, cnt);
                                break;
                        case GRPQUOTA:
                                if (!chgid)
                                        continue;
                                transfer_to[cnt] = dqget(inode->i_sb, iattr->ia_gid, cnt);
                                break;
                }
        }
        spin_lock(&dq_data_lock);
        space = inode_get_bytes(inode);
        /* Build the transfer_from list and check the limits */
        for (cnt = 0; cnt < MAXQUOTAS; cnt++) {
                if (transfer_to[cnt] == NODQUOT)
                        continue;
                transfer_from[cnt] = inode->i_dquot[cnt];
                if (check_idq(transfer_to[cnt], 1, warntype+cnt) == NO_QUOTA ||
                    check_bdq(transfer_to[cnt], space, 0, warntype+cnt) == NO_QUOTA)
                        goto warn_put_all;
        }

        /*
         * 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] == NODQUOT)
                        continue;

                /* Due to IO error we might not have transfer_from[] structure */
                if (transfer_from[cnt]) {
                        dquot_decr_inodes(transfer_from[cnt], 1);
                        dquot_decr_space(transfer_from[cnt], space);
                }

                dquot_incr_inodes(transfer_to[cnt], 1);
                dquot_incr_space(transfer_to[cnt], space);

                inode->i_dquot[cnt] = transfer_to[cnt];
        }
        ret = QUOTA_OK;
warn_put_all:
        spin_unlock(&dq_data_lock);
        /* 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]);
        }
        flush_warnings(transfer_to, warntype);
        
        for (cnt = 0; cnt < MAXQUOTAS; cnt++) {
                if (ret == QUOTA_OK && transfer_from[cnt] != NODQUOT)
                        dqput(transfer_from[cnt]);
                if (ret == NO_QUOTA && transfer_to[cnt] != NODQUOT)
                        dqput(transfer_to[cnt]);
        }
        up_write(&sb_dqopt(inode->i_sb)->dqptr_sem);
        return ret;
}

/*
 * 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;
}

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

static inline void set_enable_flags(struct quota_info *dqopt, int type)
{
        switch (type) {
                case USRQUOTA:
                        dqopt->flags |= DQUOT_USR_ENABLED;
                        break;
                case GRPQUOTA:
                        dqopt->flags |= DQUOT_GRP_ENABLED;
                        break;
        }
}

static inline void reset_enable_flags(struct quota_info *dqopt, int type)
{
        switch (type) {
                case USRQUOTA:
                        dqopt->flags &= ~DQUOT_USR_ENABLED;
                        break;
                case GRPQUOTA:
                        dqopt->flags &= ~DQUOT_GRP_ENABLED;
                        break;
        }
}

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

        /* We need to serialize quota_off() for device */
        mutex_lock(&dqopt->dqonoff_mutex);
        for (cnt = 0; cnt < MAXQUOTAS; cnt++) {
                toputinode[cnt] = NULL;
                if (type != -1 && cnt != type)
                        continue;
                if (!sb_has_quota_enabled(sb, cnt))
                        continue;
                reset_enable_flags(dqopt, cnt);

                /* 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];
                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);
        /* 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_enabled(sb, cnt)) {
                                mutex_lock(&toputinode[cnt]->i_mutex);
                                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]);
                                iput(toputinode[cnt]);
                        }
                        mutex_unlock(&dqopt->dqonoff_mutex);
                }
        if (sb->s_bdev)
                invalidate_bdev(sb->s_bdev, 0);
        return 0;
}

/*
 *      Turn quotas on on a device
 */

/* Helper function when we already have the inode */
static int vfs_quota_on_inode(struct inode *inode, int type, int format_id)
{
        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;
        }

        /* 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, 0);
        mutex_lock(&inode->i_mutex);
        mutex_lock(&dqopt->dqonoff_mutex);
        if (sb_has_quota_enabled(sb, type)) {
                error = -EBUSY;
                goto out_lock;
        }
        /* We don't want quota and atime on quota files (deadlocks possible)
         * Also nobody should write to the file - we use special IO operations
         * which ignore the immutable bit. */
        down_write(&dqopt->dqptr_sem);
        oldflags = inode->i_flags & (S_NOATIME | S_IMMUTABLE | S_NOQUOTA);
        inode->i_flags |= S_NOQUOTA | S_NOATIME | S_IMMUTABLE;
        up_write(&dqopt->dqptr_sem);
        sb->dq_op->drop(inode);

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

        dqopt->ops[type] = fmt->qf_ops;
        dqopt->info[type].dqi_format = fmt;
        INIT_LIST_HEAD(&dqopt->info[type].dqi_dirty_list);
        mutex_lock(&dqopt->dqio_mutex);
        if ((error = dqopt->ops[type]->read_file_info(sb, type)) < 0) {
                mutex_unlock(&dqopt->dqio_mutex);
                goto out_file_init;
        }
        mutex_unlock(&dqopt->dqio_mutex);
        mutex_unlock(&inode->i_mutex);
        set_enable_flags(dqopt, type);

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

        return 0;

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

        return error; 
}

/* Actual function called from quotactl() */
int vfs_quota_on(struct super_block *sb, int type, int format_id, char *path)
{
        struct nameidata nd;
        int error;

        error = path_lookup(path, LOOKUP_FOLLOW, &nd);
        if (error < 0)
                return error;
        error = security_quota_on(nd.dentry);
        if (error)
                goto out_path;
        /* Quota file not on the same filesystem? */
        if (nd.mnt->mnt_sb != sb)
                error = -EXDEV;
        else
                error = vfs_quota_on_inode(nd.dentry->d_inode, type, format_id);
out_path:
        path_release(&nd);
        return error;
}

/*
 * 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_quota_on_inode(dentry->d_inode, type, format_id);

out:
        dput(dentry);
        return error;
}

/* 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 = dm->dqb_bhardlimit;
        di->dqb_bsoftlimit = dm->dqb_bsoftlimit;
        di->dqb_curspace = dm->dqb_curspace;
        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;

        mutex_lock(&sb_dqopt(sb)->dqonoff_mutex);
        if (!(dquot = dqget(sb, id, type))) {
                mutex_unlock(&sb_dqopt(sb)->dqonoff_mutex);
                return -ESRCH;
        }
        do_get_dqblk(dquot, di);
        dqput(dquot);
        mutex_unlock(&sb_dqopt(sb)->dqonoff_mutex);
        return 0;
}

/* Generic routine for setting common part of quota structure */
static void do_set_dqblk(struct dquot *dquot, struct if_dqblk *di)
{
        struct mem_dqblk *dm = &dquot->dq_dqb;
        int check_blim = 0, check_ilim = 0;

        spin_lock(&dq_data_lock);
        if (di->dqb_valid & QIF_SPACE) {
                dm->dqb_curspace = di->dqb_curspace;
                check_blim = 1;
        }
        if (di->dqb_valid & QIF_BLIMITS) {
                dm->dqb_bsoftlimit = di->dqb_bsoftlimit;
                dm->dqb_bhardlimit = di->dqb_bhardlimit;
                check_blim = 1;
        }
        if (di->dqb_valid & QIF_INODES) {
                dm->dqb_curinodes = di->dqb_curinodes;
                check_ilim = 1;
        }
        if (di->dqb_valid & QIF_ILIMITS) {
                dm->dqb_isoftlimit = di->dqb_isoftlimit;
                dm->dqb_ihardlimit = di->dqb_ihardlimit;
                check_ilim = 1;
        }
        if (di->dqb_valid & QIF_BTIME)
                dm->dqb_btime = di->dqb_btime;
        if (di->dqb_valid & QIF_ITIME)
                dm->dqb_itime = di->dqb_itime;

        if (check_blim) {
                if (!dm->dqb_bsoftlimit || toqb(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() + sb_dqopt(dquot->dq_sb)->info[dquot->dq_type].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() + sb_dqopt(dquot->dq_sb)->info[dquot->dq_type].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);
}

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

        mutex_lock(&sb_dqopt(sb)->dqonoff_mutex);
        if (!(dquot = dqget(sb, id, type))) {
                mutex_unlock(&sb_dqopt(sb)->dqonoff_mutex);
                return -ESRCH;
        }
        do_set_dqblk(dquot, di);
        dqput(dquot);
        mutex_unlock(&sb_dqopt(sb)->dqonoff_mutex);
        return 0;
}

/* 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_enabled(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;
}

/* 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;

        mutex_lock(&sb_dqopt(sb)->dqonoff_mutex);
        if (!sb_has_quota_enabled(sb, type)) {
                mutex_unlock(&sb_dqopt(sb)->dqonoff_mutex);
                return -ESRCH;
        }
        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);
        mutex_unlock(&sb_dqopt(sb)->dqonoff_mutex);
        return 0;
}

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,
        },
        {
                .ctl_name       = FS_DQ_WARNINGS,
                .procname       = "warnings",
                .data           = &flag_print_warnings,
                .maxlen         = sizeof(int),
                .mode           = 0644,
                .proc_handler   = &proc_dointvec,
        },
        { .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, 0);

        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, 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));

        set_shrinker(DEFAULT_SEEKS, shrink_dqcache_memory);

        return 0;
}
module_init(dquot_init);

EXPORT_SYMBOL(register_quota_format);
EXPORT_SYMBOL(unregister_quota_format);
EXPORT_SYMBOL(dqstats);
EXPORT_SYMBOL(dq_data_lock);
EXPORT_SYMBOL(vfs_quota_on);
EXPORT_SYMBOL(vfs_quota_on_mount);
EXPORT_SYMBOL(vfs_quota_off);
EXPORT_SYMBOL(vfs_quota_sync);
EXPORT_SYMBOL(vfs_get_dqinfo);
EXPORT_SYMBOL(vfs_set_dqinfo);
EXPORT_SYMBOL(vfs_get_dqblk);
EXPORT_SYMBOL(vfs_set_dqblk);
EXPORT_SYMBOL(dquot_commit);
EXPORT_SYMBOL(dquot_commit_info);
EXPORT_SYMBOL(dquot_acquire);
EXPORT_SYMBOL(dquot_release);
EXPORT_SYMBOL(dquot_mark_dquot_dirty);
EXPORT_SYMBOL(dquot_initialize);
EXPORT_SYMBOL(dquot_drop);
EXPORT_SYMBOL(dquot_alloc_space);
EXPORT_SYMBOL(dquot_alloc_inode);
EXPORT_SYMBOL(dquot_free_space);
EXPORT_SYMBOL(dquot_free_inode);
EXPORT_SYMBOL(dquot_transfer);