Merge with Linux 2.4.0-test5-pre1. This works again on Origin UP.

[linux-2.6/linux-mips.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. Currently only the
 * ext2 filesystem has support for disk quotas. Other filesystems may
 * be added in the future. 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
 *
 * (C) Copyright 1994 - 1997 Marco van Wieringen 
 */

#include <linux/errno.h>
#include <linux/kernel.h>
#include <linux/sched.h>

#include <linux/types.h>
#include <linux/string.h>
#include <linux/fcntl.h>
#include <linux/stat.h>
#include <linux/tty.h>
#include <linux/file.h>
#include <linux/malloc.h>
#include <linux/mount.h>
#include <linux/smp.h>
#include <linux/smp_lock.h>
#include <linux/init.h>
#include <linux/slab.h>

#include <asm/uaccess.h>

#define __DQUOT_VERSION__       "dquot_6.4.0"

int nr_dquots, nr_free_dquots;
int max_dquots = NR_DQUOTS;

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

static kmem_cache_t *dquot_cachep;

static inline struct quota_mount_options *sb_dqopt(struct super_block *sb)
{
        return &sb->s_dquot;
}

/*
 * 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 on the inuse_list when first created, and this
 * list is used for the sync and invalidate operations, 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
 * nr_free_dquots gives the number of dquots on the list.
 *
 * 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 lcoate a specific dquot.
 */

static struct dquot *inuse_list;
static LIST_HEAD(free_dquots);
static struct dquot *dquot_hash[NR_DQHASH];
static int dquot_updating[NR_DQHASH];

static struct dqstats dqstats;
static DECLARE_WAIT_QUEUE_HEAD(dquot_wait);
static DECLARE_WAIT_QUEUE_HEAD(update_wait);

static void dqput(struct dquot *);
static struct dquot *dqduplicate(struct dquot *);

static inline char is_enabled(struct quota_mount_options *dqopt, short type)
{
        switch (type) {
                case USRQUOTA:
                        return((dqopt->flags & DQUOT_USR_ENABLED) != 0);
                case GRPQUOTA:
                        return((dqopt->flags & DQUOT_GRP_ENABLED) != 0);
        }
        return(0);
}

static inline char sb_has_quota_enabled(struct super_block *sb, short type)
{
        return is_enabled(sb_dqopt(sb), type);
}

static inline int const hashfn(kdev_t dev, unsigned int id, short type)
{
        return((HASHDEV(dev) ^ id) * (MAXQUOTAS - type)) % NR_DQHASH;
}

static inline void insert_dquot_hash(struct dquot *dquot)
{
        struct dquot **htable;

        htable = &dquot_hash[hashfn(dquot->dq_dev, dquot->dq_id, dquot->dq_type)];
        if ((dquot->dq_hash_next = *htable) != NULL)
                (*htable)->dq_hash_pprev = &dquot->dq_hash_next;
        *htable = dquot;
        dquot->dq_hash_pprev = htable;
}

static inline void hash_dquot(struct dquot *dquot)
{
        insert_dquot_hash(dquot);
}

static inline void unhash_dquot(struct dquot *dquot)
{
        if (dquot->dq_hash_pprev) {
                if (dquot->dq_hash_next)
                        dquot->dq_hash_next->dq_hash_pprev = dquot->dq_hash_pprev;
                *(dquot->dq_hash_pprev) = dquot->dq_hash_next;
                dquot->dq_hash_pprev = NULL;
        }
}

static inline struct dquot *find_dquot(unsigned int hashent, kdev_t dev, unsigned int id, short type)
{
        struct dquot *dquot;

        for (dquot = dquot_hash[hashent]; dquot; dquot = dquot->dq_hash_next)
                if (dquot->dq_dev == dev && dquot->dq_id == id && dquot->dq_type == type)
                        break;
        return dquot;
}

/* Add a dquot to the head of the free list */
static inline void put_dquot_head(struct dquot *dquot)
{
        list_add(&dquot->dq_free, &free_dquots);
        nr_free_dquots++;
}

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

static inline void remove_free_dquot(struct dquot *dquot)
{
        /* sanity check */
        if (list_empty(&dquot->dq_free)) {
                printk("remove_free_dquot: dquot not on the free list??\n");
                return;         /* J.K. Just don't do anything */
        }
        list_del(&dquot->dq_free);
        INIT_LIST_HEAD(&dquot->dq_free);
        nr_free_dquots--;
}

static inline void put_inuse(struct dquot *dquot)
{
        if ((dquot->dq_next = inuse_list) != NULL)
                inuse_list->dq_pprev = &dquot->dq_next;
        inuse_list = dquot;
        dquot->dq_pprev = &inuse_list;
}

#if 0   /* currently not needed */
static inline void remove_inuse(struct dquot *dquot)
{
        if (dquot->dq_pprev) {
                if (dquot->dq_next)
                        dquot->dq_next->dq_pprev = dquot->dq_pprev;
                *dquot->dq_pprev = dquot->dq_next;
                dquot->dq_pprev = NULL;
        }
}
#endif

static void __wait_on_dquot(struct dquot *dquot)
{
        DECLARE_WAITQUEUE(wait, current);

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

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

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

static inline void unlock_dquot(struct dquot *dquot)
{
        dquot->dq_flags &= ~DQ_LOCKED;
        wake_up(&dquot->dq_wait);
}

/*
 *      We don't have to be afraid of deadlocks as we never have quotas on quota files...
 */
static void write_dquot(struct dquot *dquot)
{
        short type = dquot->dq_type;
        struct file *filp;
        mm_segment_t fs;
        loff_t offset;
        ssize_t ret;
        struct semaphore *sem = &dquot->dq_sb->s_dquot.dqio_sem;

        lock_dquot(dquot);
        if (!dquot->dq_sb) {    /* Invalidated quota? */
                unlock_dquot(dquot);
                return;
        }
        down(sem);
        filp = dquot->dq_sb->s_dquot.files[type];
        offset = dqoff(dquot->dq_id);
        fs = get_fs();
        set_fs(KERNEL_DS);

        /*
         * Note: clear the DQ_MOD flag unconditionally,
         * so we don't loop forever on failure.
         */
        dquot->dq_flags &= ~DQ_MOD;
        ret = 0;
        if (filp)
                ret = filp->f_op->write(filp, (char *)&dquot->dq_dqb, 
                                        sizeof(struct dqblk), &offset);
        if (ret != sizeof(struct dqblk))
                printk(KERN_WARNING "VFS: dquota write failed on dev %s\n",
                        kdevname(dquot->dq_dev));

        set_fs(fs);
        up(sem);
        unlock_dquot(dquot);

        dqstats.writes++;
}

static void read_dquot(struct dquot *dquot)
{
        short type = dquot->dq_type;
        struct file *filp;
        mm_segment_t fs;
        loff_t offset;

        filp = dquot->dq_sb->s_dquot.files[type];
        if (filp == (struct file *)NULL)
                return;

        lock_dquot(dquot);
        if (!dquot->dq_sb)      /* Invalidated quota? */
                goto out_lock;
        /* Now we are sure filp is valid - the dquot isn't invalidated */
        down(&dquot->dq_sb->s_dquot.dqio_sem);
        offset = dqoff(dquot->dq_id);
        fs = get_fs();
        set_fs(KERNEL_DS);
        filp->f_op->read(filp, (char *)&dquot->dq_dqb, sizeof(struct dqblk), &offset);
        up(&dquot->dq_sb->s_dquot.dqio_sem);
        set_fs(fs);

        if (dquot->dq_bhardlimit == 0 && dquot->dq_bsoftlimit == 0 &&
            dquot->dq_ihardlimit == 0 && dquot->dq_isoftlimit == 0)
                dquot->dq_flags |= DQ_FAKE;
        dqstats.reads++;
out_lock:
        unlock_dquot(dquot);
}

/*
 * Unhash and selectively clear the dquot structure,
 * but preserve the use count, list pointers, and
 * wait queue.
 */
void clear_dquot(struct dquot *dquot)
{
        /* unhash it first */
        unhash_dquot(dquot);
        dquot->dq_sb = NULL;
        dquot->dq_flags = 0;
        dquot->dq_referenced = 0;
        memset(&dquot->dq_dqb, 0, sizeof(struct dqblk));
}

void invalidate_dquots(kdev_t dev, short type)
{
        struct dquot *dquot, *next;
        int need_restart;

restart:
        next = inuse_list;      /* Here it is better. Otherwise the restart doesn't have any sense ;-) */
        need_restart = 0;
        while ((dquot = next) != NULL) {
                next = dquot->dq_next;
                if (dquot->dq_dev != dev)
                        continue;
                if (dquot->dq_type != type)
                        continue;
                if (!dquot->dq_sb)      /* Already invalidated entry? */
                        continue;
                if (dquot->dq_flags & DQ_LOCKED) {
                        __wait_on_dquot(dquot);

                        /* Set the flag for another pass. */
                        need_restart = 1;
                        /*
                         * Make sure it's still the same dquot.
                         */
                        if (dquot->dq_dev != dev)
                                continue;
                        if (dquot->dq_type != type)
                                continue;
                        if (!dquot->dq_sb)
                                continue;
                }
                /*
                 *  Because inodes needn't to be the only holders of dquot
                 *  the quota needn't to be written to disk. So we write it
                 *  ourselves before discarding the data just for sure...
                 */
                if (dquot->dq_flags & DQ_MOD && dquot->dq_sb)
                {
                        write_dquot(dquot);
                        need_restart = 1;       /* We slept on IO */
                }
                clear_dquot(dquot);
        }
        /*
         * If anything blocked, restart the operation
         * to ensure we don't miss any dquots.
         */ 
        if (need_restart)
                goto restart;
}

int sync_dquots(kdev_t dev, short type)
{
        struct dquot *dquot, *next, *ddquot;
        int need_restart;

restart:
        next = inuse_list;
        need_restart = 0;
        while ((dquot = next) != NULL) {
                next = dquot->dq_next;
                if (dev && dquot->dq_dev != dev)
                        continue;
                if (type != -1 && dquot->dq_type != type)
                        continue;
                if (!dquot->dq_sb)      /* Invalidated? */
                        continue;
                if (!(dquot->dq_flags & (DQ_LOCKED | DQ_MOD)))
                        continue;

                if ((ddquot = dqduplicate(dquot)) == NODQUOT)
                        continue;
                if (ddquot->dq_flags & DQ_MOD)
                        write_dquot(ddquot);
                dqput(ddquot);
                /* Set the flag for another pass. */
                need_restart = 1;
        }
        /*
         * If anything blocked, restart the operation
         * to ensure we don't miss any dquots.
         */ 
        if (need_restart)
                goto restart;

        dqstats.syncs++;
        return(0);
}

/* NOTE: If you change this function please check whether dqput_blocks() works right... */
static void dqput(struct dquot *dquot)
{
        if (!dquot)
                return;
        if (!dquot->dq_count) {
                printk("VFS: dqput: trying to free free dquot\n");
                printk("VFS: device %s, dquot of %s %d\n",
                        kdevname(dquot->dq_dev), quotatypes[dquot->dq_type],
                        dquot->dq_id);
                return;
        }

        /*
         * If the dq_sb pointer isn't initialized this entry needs no
         * checking and doesn't need to be written. It's just an empty
         * dquot that is put back on to the freelist.
         */
        if (dquot->dq_sb)
                dqstats.drops++;
we_slept:
        if (dquot->dq_count > 1) {
                /* We have more than one user... We can simply decrement use count */
                dquot->dq_count--;
                return;
        }
        if (dquot->dq_flags & DQ_LOCKED) {
                printk(KERN_ERR "VFS: Locked quota to be put on the free list.\n");
                dquot->dq_flags &= ~DQ_LOCKED;
        }
        if (dquot->dq_sb && dquot->dq_flags & DQ_MOD) {
                write_dquot(dquot);
                goto we_slept;
        }

        /* sanity check */
        if (!list_empty(&dquot->dq_free)) {
                printk(KERN_ERR "dqput: dquot already on free list??\n");
                dquot->dq_count--;      /* J.K. Just decrementing use count seems safer... */
                return;
        }
        dquot->dq_count--;
        dquot->dq_flags &= ~DQ_MOD;     /* Modified flag has no sense on free list */
        /* Place at end of LRU free queue */
        put_dquot_last(dquot);
        wake_up(&dquot_wait);
}

static int grow_dquots(void)
{
        struct dquot *dquot;
        int cnt = 0;

        while (cnt < 32) {
                dquot = kmem_cache_alloc(dquot_cachep, SLAB_KERNEL);
                if(!dquot)
                        return cnt;

                nr_dquots++;
                memset((caddr_t)dquot, 0, sizeof(struct dquot));
                init_waitqueue_head(&dquot->dq_wait);
                /* all dquots go on the inuse_list */
                put_inuse(dquot);
                put_dquot_head(dquot);
                cnt++;
        }
        return cnt;
}

static struct dquot *find_best_candidate_weighted(void)
{
        struct list_head *tmp = &free_dquots;
        struct dquot *dquot, *best = NULL;
        unsigned long myscore, bestscore = ~0U;
        int limit = (nr_free_dquots > 128) ? nr_free_dquots >> 2 : 32;

        while ((tmp = tmp->next) != &free_dquots && --limit) {
                dquot = list_entry(tmp, struct dquot, dq_free);
                /* This should never happen... */
                if (dquot->dq_flags & (DQ_LOCKED | DQ_MOD))
                        continue;
                myscore = dquot->dq_referenced;
                if (myscore < bestscore) {
                        bestscore = myscore;
                        best = dquot;
                }
        }
        return best;
}

static inline struct dquot *find_best_free(void)
{
        struct list_head *tmp = &free_dquots;
        struct dquot *dquot;
        int limit = (nr_free_dquots > 1024) ? nr_free_dquots >> 5 : 32;

        while ((tmp = tmp->next) != &free_dquots && --limit) {
                dquot = list_entry(tmp, struct dquot, dq_free);
                if (dquot->dq_referenced == 0)
                        return dquot;
        }
        return NULL;
}

struct dquot *get_empty_dquot(void)
{
        struct dquot *dquot;
        int shrink = 1; /* Number of times we should try to shrink dcache and icache */

repeat:
        dquot = find_best_free();
        if (!dquot)
                goto pressure;
got_it:
        /* Sanity checks */
        if (dquot->dq_flags & DQ_LOCKED)
                printk(KERN_ERR "VFS: Locked dquot on the free list\n");
        if (dquot->dq_count != 0)
                printk(KERN_ERR "VFS: free dquot count=%d\n", dquot->dq_count);

        remove_free_dquot(dquot);
        dquot->dq_count = 1;
        /* unhash and selectively clear the structure */
        clear_dquot(dquot);
        return dquot;

pressure:
        if (nr_dquots < max_dquots)
                if (grow_dquots())
                        goto repeat;

        dquot = find_best_candidate_weighted();
        if (dquot)
                goto got_it;
        /*
         * Try pruning the dcache to free up some dquots ...
         */
        if (shrink) {
                printk(KERN_DEBUG "get_empty_dquot: pruning dcache and icache\n");
                prune_dcache(128);
                prune_icache(128);
                shrink--;
                goto repeat;
        }

        printk("VFS: No free dquots, contact mvw@planets.elm.net\n");
        sleep_on(&dquot_wait);
        goto repeat;
}

static struct dquot *dqget(struct super_block *sb, unsigned int id, short type)
{
        unsigned int hashent = hashfn(sb->s_dev, id, type);
        struct dquot *dquot, *empty = NULL;
        struct quota_mount_options *dqopt = sb_dqopt(sb);

        if (!is_enabled(dqopt, type))
                return(NODQUOT);

we_slept:
        if ((dquot = find_dquot(hashent, sb->s_dev, id, type)) == NULL) {
                if (empty == NULL) {
                        dquot_updating[hashent]++;
                        empty = get_empty_dquot();
                        if (!--dquot_updating[hashent])
                                wake_up(&update_wait);
                        goto we_slept;
                }
                dquot = empty;
                dquot->dq_id = id;
                dquot->dq_type = type;
                dquot->dq_dev = sb->s_dev;
                dquot->dq_sb = sb;
                /* hash it first so it can be found */
                hash_dquot(dquot);
                read_dquot(dquot);
        } else {
                if (!dquot->dq_count++) {
                        remove_free_dquot(dquot);
                } else
                        dqstats.cache_hits++;
                wait_on_dquot(dquot);
                if (empty)
                        dqput(empty);
        }

        while (dquot_updating[hashent])
                sleep_on(&update_wait);

        if (!dquot->dq_sb) {    /* Has somebody invalidated entry under us? */
                /*
                 *  Do it as if the quota was invalidated before we started
                 */
                dqput(dquot);
                return NODQUOT;
        }
        dquot->dq_referenced++;
        dqstats.lookups++;

        return dquot;
}

static struct dquot *dqduplicate(struct dquot *dquot)
{
        if (dquot == NODQUOT || !dquot->dq_sb)
                return NODQUOT;
        dquot->dq_count++;
        wait_on_dquot(dquot);
        if (!dquot->dq_sb) {
                dquot->dq_count--;
                return NODQUOT;
        }
        dquot->dq_referenced++;
        dqstats.lookups++;
        return dquot;
}

/* Check whether this inode is quota file */
static inline int is_quotafile(struct inode *inode)
{
        int cnt;
        struct quota_mount_options *dqopt = sb_dqopt(inode->i_sb);
        struct file **files;

        if (!dqopt)
                return 0;
        files = dqopt->files;
        for (cnt = 0; cnt < MAXQUOTAS; cnt++)
                if (files[cnt] && files[cnt]->f_dentry->d_inode == inode)
                        return 1;
        return 0;
}

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

        if (!(S_ISREG(inode->i_mode) || S_ISDIR(inode->i_mode) || S_ISLNK(inode->i_mode)))
                return 0;
        if (is_quotafile(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;
}

static void add_dquot_ref(struct super_block *sb, short type)
{
        struct list_head *p;
        struct inode *inode;

        if (!sb->dq_op)
                return; /* nothing to do */

restart:
        file_list_lock();
        for (p = sb->s_files.next; p != &sb->s_files; p = p->next) {
                struct file *filp = list_entry(p, struct file, f_list);
                if (!filp->f_dentry)
                        continue;
                inode = filp->f_dentry->d_inode;
                if (!inode)
                        continue;
                if (filp->f_mode & FMODE_WRITE && dqinit_needed(inode, type)) {
                        file_list_unlock();
                        sb->dq_op->initialize(inode, type);
                        inode->i_flags |= S_QUOTA;
                        /* 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 (dquot->dq_count == 1)
                return 1;
        return 0;
}

/* Remove references to dquots from inode - add dquot to list for freeing if needed */
int remove_inode_dquot_ref(struct inode *inode, short type, struct list_head *tofree_head)
{
        struct dquot *dquot = inode->i_dquot[type];
        int cnt;

        inode->i_dquot[type] = NODQUOT;
        /* any other quota in use? */
        for (cnt = 0; cnt < MAXQUOTAS; cnt++) {
                if (inode->i_dquot[cnt] != NODQUOT)
                        goto put_it;
        }
        inode->i_flags &= ~S_QUOTA;
put_it:
        if (dquot != NODQUOT) {
                if (dqput_blocks(dquot)) {
                        if (dquot->dq_count != 1)
                                printk(KERN_WARNING "VFS: Adding dquot with dq_count %d to dispose list.\n", dquot->dq_count);
                        list_add(&dquot->dq_free, tofree_head); /* As dquot must have currently users it can't be on the free list... */
                        return 1;
                } else {
                        dqput(dquot);   /* We have guaranteed we won't block */
                }
        }
        return 0;
}

/* Free list of dquots - called from inode.c */
void put_dquot_list(struct list_head *tofree_head)
{
        struct list_head *act_head = tofree_head;
        struct dquot *dquot;

        /* 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(&dquot->dq_free);      /* Remove dquot from the list so we won't have problems... */
                INIT_LIST_HEAD(&dquot->dq_free);
                dqput(dquot);
        }
}

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

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

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

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

static inline int need_print_warning(struct dquot *dquot, int flag)
{
        switch (dquot->dq_type) {
                case USRQUOTA:
                        return current->fsuid == dquot->dq_id && !(dquot->dq_flags & flag);
                case GRPQUOTA:
                        return in_group_p(dquot->dq_id) && !(dquot->dq_flags & flag);
        }
        return 0;
}

static void print_warning(struct dquot *dquot, int flag, const char *fmtstr)
{
        if (!need_print_warning(dquot, flag))
                return;
        sprintf(quotamessage, fmtstr,
                bdevname(dquot->dq_sb->s_dev), quotatypes[dquot->dq_type]);
        tty_write_message(current->tty, quotamessage);
        dquot->dq_flags |= flag;
}

static inline char ignore_hardlimit(struct dquot *dquot)
{
        return capable(CAP_SYS_RESOURCE) && !dquot->dq_sb->s_dquot.rsquash[dquot->dq_type];
}

static int check_idq(struct dquot *dquot, u_long inodes)
{
        if (inodes <= 0 || dquot->dq_flags & DQ_FAKE)
                return QUOTA_OK;

        if (dquot->dq_ihardlimit &&
           (dquot->dq_curinodes + inodes) > dquot->dq_ihardlimit &&
            !ignore_hardlimit(dquot)) {
                print_warning(dquot, DQ_INODES, "%s: write failed, %s file limit reached\n");
                return NO_QUOTA;
        }

        if (dquot->dq_isoftlimit &&
           (dquot->dq_curinodes + inodes) > dquot->dq_isoftlimit &&
            dquot->dq_itime && CURRENT_TIME >= dquot->dq_itime &&
            !ignore_hardlimit(dquot)) {
                print_warning(dquot, DQ_INODES, "%s: warning, %s file quota exceeded too long.\n");
                return NO_QUOTA;
        }

        if (dquot->dq_isoftlimit &&
           (dquot->dq_curinodes + inodes) > dquot->dq_isoftlimit &&
            dquot->dq_itime == 0) {
                print_warning(dquot, 0, "%s: warning, %s file quota exceeded\n");
                dquot->dq_itime = CURRENT_TIME + dquot->dq_sb->s_dquot.inode_expire[dquot->dq_type];
        }

        return QUOTA_OK;
}

static int check_bdq(struct dquot *dquot, u_long blocks, char prealloc)
{
        if (blocks <= 0 || dquot->dq_flags & DQ_FAKE)
                return QUOTA_OK;

        if (dquot->dq_bhardlimit &&
           (dquot->dq_curblocks + blocks) > dquot->dq_bhardlimit &&
            !ignore_hardlimit(dquot)) {
                if (!prealloc)
                        print_warning(dquot, DQ_BLKS, "%s: write failed, %s disk limit reached.\n");
                return NO_QUOTA;
        }

        if (dquot->dq_bsoftlimit &&
           (dquot->dq_curblocks + blocks) > dquot->dq_bsoftlimit &&
            dquot->dq_btime && CURRENT_TIME >= dquot->dq_btime &&
            !ignore_hardlimit(dquot)) {
                if (!prealloc)
                        print_warning(dquot, DQ_BLKS, "%s: write failed, %s disk quota exceeded too long.\n");
                return NO_QUOTA;
        }

        if (dquot->dq_bsoftlimit &&
           (dquot->dq_curblocks + blocks) > dquot->dq_bsoftlimit &&
            dquot->dq_btime == 0) {
                if (!prealloc) {
                        print_warning(dquot, 0, "%s: warning, %s disk quota exceeded\n");
                        dquot->dq_btime = CURRENT_TIME + dquot->dq_sb->s_dquot.block_expire[dquot->dq_type];
                }
                else
                        /*
                         * We don't allow preallocation to exceed softlimit so exceeding will
                         * be always printed
                         */
                        return NO_QUOTA;
        }

        return QUOTA_OK;
}

/*
 * Initialize a dquot-struct with new quota info. This is used by the
 * system call interface functions.
 */ 
static int set_dqblk(struct super_block *sb, int id, short type, int flags, struct dqblk *dqblk)
{
        struct dquot *dquot;
        int error = -EFAULT;
        struct dqblk dq_dqblk;

        if (dqblk == (struct dqblk *)NULL)
                return error;

        if (flags & QUOTA_SYSCALL) {
                if (copy_from_user(&dq_dqblk, dqblk, sizeof(struct dqblk)))
                        return(error);
        } else
                memcpy((caddr_t)&dq_dqblk, (caddr_t)dqblk, sizeof(struct dqblk));

        if (sb && (dquot = dqget(sb, id, type)) != NODQUOT) {
                lock_dquot(dquot);

                if (id > 0 && ((flags & SET_QUOTA) || (flags & SET_QLIMIT))) {
                        dquot->dq_bhardlimit = dq_dqblk.dqb_bhardlimit;
                        dquot->dq_bsoftlimit = dq_dqblk.dqb_bsoftlimit;
                        dquot->dq_ihardlimit = dq_dqblk.dqb_ihardlimit;
                        dquot->dq_isoftlimit = dq_dqblk.dqb_isoftlimit;
                }

                if ((flags & SET_QUOTA) || (flags & SET_USE)) {
                        if (dquot->dq_isoftlimit &&
                            dquot->dq_curinodes < dquot->dq_isoftlimit &&
                            dq_dqblk.dqb_curinodes >= dquot->dq_isoftlimit)
                                dquot->dq_itime = CURRENT_TIME + dquot->dq_sb->s_dquot.inode_expire[type];
                        dquot->dq_curinodes = dq_dqblk.dqb_curinodes;
                        if (dquot->dq_curinodes < dquot->dq_isoftlimit)
                                dquot->dq_flags &= ~DQ_INODES;
                        if (dquot->dq_bsoftlimit &&
                            dquot->dq_curblocks < dquot->dq_bsoftlimit &&
                            dq_dqblk.dqb_curblocks >= dquot->dq_bsoftlimit)
                                dquot->dq_btime = CURRENT_TIME + dquot->dq_sb->s_dquot.block_expire[type];
                        dquot->dq_curblocks = dq_dqblk.dqb_curblocks;
                        if (dquot->dq_curblocks < dquot->dq_bsoftlimit)
                                dquot->dq_flags &= ~DQ_BLKS;
                }

                if (id == 0) {
                        dquot->dq_sb->s_dquot.block_expire[type] = dquot->dq_btime = dq_dqblk.dqb_btime;
                        dquot->dq_sb->s_dquot.inode_expire[type] = dquot->dq_itime = dq_dqblk.dqb_itime;
                }

                if (dq_dqblk.dqb_bhardlimit == 0 && dq_dqblk.dqb_bsoftlimit == 0 &&
                    dq_dqblk.dqb_ihardlimit == 0 && dq_dqblk.dqb_isoftlimit == 0)
                        dquot->dq_flags |= DQ_FAKE;
                else
                        dquot->dq_flags &= ~DQ_FAKE;

                dquot->dq_flags |= DQ_MOD;
                unlock_dquot(dquot);
                dqput(dquot);
        }
        return(0);
}

static int get_quota(struct super_block *sb, int id, short type, struct dqblk *dqblk)
{
        struct dquot *dquot;
        int error = -ESRCH;

        if (!sb || !sb_has_quota_enabled(sb, type))
                goto out;
        dquot = dqget(sb, id, type);
        if (dquot == NODQUOT)
                goto out;

        lock_dquot(dquot);      /* We must protect against invalidating the quota */
        error = -EFAULT;
        if (dqblk && !copy_to_user(dqblk, &dquot->dq_dqb, sizeof(struct dqblk)))
                error = 0;
        unlock_dquot(dquot);
        dqput(dquot);
out:
        return error;
}

static int get_stats(caddr_t addr)
{
        int error = -EFAULT;
        struct dqstats stats;

        dqstats.allocated_dquots = nr_dquots;
        dqstats.free_dquots = nr_free_dquots;

        /* make a copy, in case we page-fault in user space */
        memcpy(&stats, &dqstats, sizeof(struct dqstats));
        if (!copy_to_user(addr, &stats, sizeof(struct dqstats)))
                error = 0;
        return error;
}

static int quota_root_squash(struct super_block *sb, short type, int *addr)
{
        int new_value, error;

        if (!sb)
                return(-ENODEV);

        error = -EFAULT;
        if (!copy_from_user(&new_value, addr, sizeof(int))) {
                sb_dqopt(sb)->rsquash[type] = new_value;
                error = 0;
        }
        return error;
}

/*
 * This is a simple algorithm that calculates the size of a file in blocks.
 * This is only used on filesystems that do not have an i_blocks count.
 */
static u_long isize_to_blocks(loff_t isize, size_t blksize_bits)
{
        u_long blocks;
        u_long indirect;

        if (!blksize_bits)
                blksize_bits = BLOCK_SIZE_BITS;
        blocks = (isize >> blksize_bits) + ((isize & ~((1 << blksize_bits)-1)) ? 1 : 0);
        if (blocks > 10) {
                indirect = ((blocks - 11) >> 8) + 1; /* single indirect blocks */
                if (blocks > (10 + 256)) {
                        indirect += ((blocks - 267) >> 16) + 1; /* double indirect blocks */
                        if (blocks > (10 + 256 + (256 << 8)))
                                indirect++; /* triple indirect blocks */
                }
                blocks += indirect;
        }
        return blocks;
}

/*
 * Externally referenced functions through dquot_operations in inode.
 *
 * Note: this is a blocking operation.
 */
void dquot_initialize(struct inode *inode, short type)
{
        struct dquot *dquot;
        unsigned int id = 0;
        short cnt;

        if (!S_ISREG(inode->i_mode) && !S_ISDIR(inode->i_mode) &&
            !S_ISLNK(inode->i_mode))
                return;
        lock_kernel();
        /* We don't want to have quotas on quota files - nasty deadlocks possible */
        if (is_quotafile(inode)) {
                unlock_kernel();
                return;
        }
        for (cnt = 0; cnt < MAXQUOTAS; cnt++) {
                if (type != -1 && cnt != type)
                        continue;

                if (!sb_has_quota_enabled(inode->i_sb, cnt))
                        continue;

                if (inode->i_dquot[cnt] == NODQUOT) {
                        switch (cnt) {
                                case USRQUOTA:
                                        id = inode->i_uid;
                                        break;
                                case GRPQUOTA:
                                        id = inode->i_gid;
                                        break;
                        }
                        dquot = dqget(inode->i_sb, id, cnt);
                        if (dquot == NODQUOT)
                                continue;
                        if (inode->i_dquot[cnt] != NODQUOT) {
                                dqput(dquot);
                                continue;
                        } 
                        inode->i_dquot[cnt] = dquot;
                        inode->i_flags |= S_QUOTA;
                }
        }
        unlock_kernel();
}

/*
 * Release all quota for the specified inode.
 *
 * Note: this is a blocking operation.
 */
void dquot_drop(struct inode *inode)
{
        struct dquot *dquot;
        short cnt;

        lock_kernel();
        inode->i_flags &= ~S_QUOTA;
        for (cnt = 0; cnt < MAXQUOTAS; cnt++) {
                if (inode->i_dquot[cnt] == NODQUOT)
                        continue;
                dquot = inode->i_dquot[cnt];
                inode->i_dquot[cnt] = NODQUOT;
                dqput(dquot);
        }
        unlock_kernel();
}

/*
 * Note: this is a blocking operation.
 */
int dquot_alloc_block(const struct inode *inode, unsigned long number, char warn)
{
        int cnt;
        struct dquot *dquot[MAXQUOTAS];

        for (cnt = 0; cnt < MAXQUOTAS; cnt++) {
                dquot[cnt] = dqduplicate(inode->i_dquot[cnt]);
                if (dquot[cnt] == NODQUOT)
                        continue;
                lock_dquot(dquot[cnt]);
                if (check_bdq(dquot[cnt], number, warn))
                        goto put_all;
        }

        for (cnt = 0; cnt < MAXQUOTAS; cnt++) {
                if (dquot[cnt] == NODQUOT)
                        continue;
                dquot_incr_blocks(dquot[cnt], number);
                unlock_dquot(dquot[cnt]);
                dqput(dquot[cnt]);
        }

        return QUOTA_OK;
put_all:
        for (; cnt >= 0; cnt--) {
                if (dquot[cnt] == NODQUOT)
                        continue;
                unlock_dquot(dquot[cnt]);
                dqput(dquot[cnt]);
        }
        return NO_QUOTA;
}

/*
 * Note: this is a blocking operation.
 */
int dquot_alloc_inode(const struct inode *inode, unsigned long number)
{
        int cnt;
        struct dquot *dquot[MAXQUOTAS];

        for (cnt = 0; cnt < MAXQUOTAS; cnt++) {
                dquot[cnt] = dqduplicate(inode -> i_dquot[cnt]);
                if (dquot[cnt] == NODQUOT)
                        continue;
                lock_dquot(dquot[cnt]);
                if (check_idq(dquot[cnt], number))
                        goto put_all;
        }

        for (cnt = 0; cnt < MAXQUOTAS; cnt++) {
                if (dquot[cnt] == NODQUOT)
                        continue;
                dquot_incr_inodes(dquot[cnt], number);
                unlock_dquot(dquot[cnt]);
                dqput(dquot[cnt]);
        }

        return QUOTA_OK;
put_all:
        for (; cnt >= 0; cnt--) {
                if (dquot[cnt] == NODQUOT)
                        continue;
                unlock_dquot(dquot[cnt]);
                dqput(dquot[cnt]);
        }
        return NO_QUOTA;
}

/*
 * Note: this is a blocking operation.
 */
void dquot_free_block(const struct inode *inode, unsigned long number)
{
        unsigned short cnt;
        struct dquot *dquot;

        for (cnt = 0; cnt < MAXQUOTAS; cnt++) {
                dquot = inode->i_dquot[cnt];
                if (dquot == NODQUOT)
                        continue;
                wait_on_dquot(dquot);
                dquot_decr_blocks(dquot, number);
        }
}

/*
 * Note: this is a blocking operation.
 */
void dquot_free_inode(const struct inode *inode, unsigned long number)
{
        unsigned short cnt;
        struct dquot *dquot;

        for (cnt = 0; cnt < MAXQUOTAS; cnt++) {
                dquot = inode->i_dquot[cnt];
                if (dquot == NODQUOT)
                        continue;
                wait_on_dquot(dquot);
                dquot_decr_inodes(dquot, number);
        }
}

/*
 * Transfer the number of inode and blocks from one diskquota to an other.
 *
 * Note: this is a blocking operation.
 */
int dquot_transfer(struct dentry *dentry, struct iattr *iattr)
{
        struct inode *inode = dentry -> d_inode;
        unsigned long blocks;
        struct dquot *transfer_from[MAXQUOTAS];
        struct dquot *transfer_to[MAXQUOTAS];
        short cnt, disc;
        int error = -EDQUOT;

        if (!inode)
                return -ENOENT;
        /* Arguably we could consider that as error, but... no fs - no quota */
        if (!inode->i_sb)
                return 0;

        lock_kernel();
        /*
         * Find out if this filesystem uses i_blocks.
         */
        if (!inode->i_sb->s_blocksize)
                blocks = isize_to_blocks(inode->i_size, BLOCK_SIZE_BITS);
        else
                blocks = (inode->i_blocks >> 1);

        /*
         * Build the transfer_from and transfer_to lists and check quotas to see
         * if operation is permitted.
         */
        for (cnt = 0; cnt < MAXQUOTAS; cnt++) {
                transfer_from[cnt] = NODQUOT;
                transfer_to[cnt] = NODQUOT;

                if (!sb_has_quota_enabled(inode->i_sb, cnt))
                        continue;

                switch (cnt) {
                        case USRQUOTA:
                                if (inode->i_uid == iattr->ia_uid)
                                        continue;
                                /* We can get transfer_from from inode, can't we? */
                                transfer_from[cnt] = dqget(inode->i_sb, inode->i_uid, cnt);
                                transfer_to[cnt] = dqget(inode->i_sb, iattr->ia_uid, cnt);
                                break;
                        case GRPQUOTA:
                                if (inode->i_gid == iattr->ia_gid)
                                        continue;
                                transfer_from[cnt] = dqget(inode->i_sb, inode->i_gid, cnt);
                                transfer_to[cnt] = dqget(inode->i_sb, iattr->ia_gid, cnt);
                                break;
                }

                /* Something bad (eg. quotaoff) happened while we were sleeping? */
                if (transfer_from[cnt] == NODQUOT || transfer_to[cnt] == NODQUOT)
                {
                        if (transfer_from[cnt] != NODQUOT) {
                                dqput(transfer_from[cnt]);
                                transfer_from[cnt] = NODQUOT;
                        }
                        if (transfer_to[cnt] != NODQUOT) {
                                dqput(transfer_to[cnt]);
                                transfer_to[cnt] = NODQUOT;
                        }
                        continue;
                }
                /*
                 *  We have to lock the quotas to prevent races...
                 */
                if (transfer_from[cnt] < transfer_to[cnt])
                {
                        lock_dquot(transfer_from[cnt]);
                        lock_dquot(transfer_to[cnt]);
                }
                else
                {
                        lock_dquot(transfer_to[cnt]);
                        lock_dquot(transfer_from[cnt]);
                }

                /*
                 * The entries might got invalidated while locking. The second
                 * dqget() could block and so the first structure might got
                 * invalidated or locked...
                 */
                if (!transfer_to[cnt]->dq_sb || !transfer_from[cnt]->dq_sb ||
                    check_idq(transfer_to[cnt], 1) == NO_QUOTA ||
                    check_bdq(transfer_to[cnt], blocks, 0) == NO_QUOTA) {
                        cnt++;
                        goto put_all;
                }
        }

        if ((error = notify_change(dentry, iattr)))
                goto put_all; 
        /*
         * Finally perform the needed transfer from transfer_from to transfer_to,
         * and release any pointers to dquots not needed anymore.
         */
        for (cnt = 0; cnt < MAXQUOTAS; cnt++) {
                /*
                 * Skip changes for same uid or gid or for non-existing quota-type.
                 */
                if (transfer_from[cnt] == NODQUOT && transfer_to[cnt] == NODQUOT)
                        continue;

                dquot_decr_inodes(transfer_from[cnt], 1);
                dquot_decr_blocks(transfer_from[cnt], blocks);

                dquot_incr_inodes(transfer_to[cnt], 1);
                dquot_incr_blocks(transfer_to[cnt], blocks);

                unlock_dquot(transfer_from[cnt]);
                dqput(transfer_from[cnt]);
                if (inode->i_dquot[cnt] != NODQUOT) {
                        struct dquot *temp = inode->i_dquot[cnt];
                        inode->i_dquot[cnt] = transfer_to[cnt];
                        unlock_dquot(transfer_to[cnt]);
                        dqput(temp);
                } else {
                        unlock_dquot(transfer_to[cnt]);
                        dqput(transfer_to[cnt]);
                }
        }

        unlock_kernel();
        return 0;
put_all:
        for (disc = 0; disc < cnt; disc++) {
                /* There should be none or both pointers set but... */
                if (transfer_to[disc] != NODQUOT) {
                        unlock_dquot(transfer_to[disc]);
                        dqput(transfer_to[disc]);
                }
                if (transfer_from[disc] != NODQUOT) {
                        unlock_dquot(transfer_from[disc]);
                        dqput(transfer_from[disc]);
                }
        }
        unlock_kernel();
        return error;
}


void __init dquot_init_hash(void)
{
        printk(KERN_NOTICE "VFS: Diskquotas version %s initialized\n", __DQUOT_VERSION__);

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

        if (!dquot_cachep)
                panic("Cannot create dquot SLAB cache\n");

        memset(dquot_hash, 0, sizeof(dquot_hash));
        memset((caddr_t)&dqstats, 0, sizeof(dqstats));
}

/*
 * Definitions of diskquota operations.
 */
struct dquot_operations dquot_operations = {
        dquot_initialize,               /* mandatory */
        dquot_drop,                     /* mandatory */
        dquot_alloc_block,
        dquot_alloc_inode,
        dquot_free_block,
        dquot_free_inode,
        dquot_transfer
};

static inline void set_enable_flags(struct quota_mount_options *dqopt, short 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_mount_options *dqopt, short type)
{
        switch (type) {
                case USRQUOTA:
                        dqopt->flags &= ~DQUOT_USR_ENABLED;
                        break;
                case GRPQUOTA:
                        dqopt->flags &= ~DQUOT_GRP_ENABLED;
                        break;
        }
}

/* Function in inode.c - remove pointers to dquots in icache */
extern void remove_dquot_ref(kdev_t, short);

/*
 * Turn quota off on a device. type == -1 ==> quotaoff for all types (umount)
 */
int quota_off(struct super_block *sb, short type)
{
        struct file *filp;
        short cnt;
        int enabled = 0;
        struct quota_mount_options *dqopt = sb_dqopt(sb);

        if (!sb)
                goto out;

        /* We need to serialize quota_off() for device */
        down(&dqopt->dqoff_sem);
        for (cnt = 0; cnt < MAXQUOTAS; cnt++) {
                if (type != -1 && cnt != type)
                        continue;
                if (!is_enabled(dqopt, cnt))
                        continue;
                reset_enable_flags(dqopt, cnt);

                /* Note: these are blocking operations */
                remove_dquot_ref(sb->s_dev, cnt);
                invalidate_dquots(sb->s_dev, cnt);

                /* Wait for any pending IO - remove me as soon as invalidate is more polite */
                down(&dqopt->dqio_sem);
                filp = dqopt->files[cnt];
                dqopt->files[cnt] = (struct file *)NULL;
                dqopt->inode_expire[cnt] = 0;
                dqopt->block_expire[cnt] = 0;
                up(&dqopt->dqio_sem);
                fput(filp);
        }       

        /*
         * Check whether any quota is still enabled,
         * and if not clear the dq_op pointer.
         */
        for (cnt = 0; cnt < MAXQUOTAS; cnt++)
                enabled |= is_enabled(dqopt, cnt);
        if (!enabled)
                sb->dq_op = NULL;
        up(&dqopt->dqoff_sem);
out:
        return(0);
}

static inline int check_quotafile_size(loff_t size)
{
        ulong blocks = size >> BLOCK_SIZE_BITS;
        size_t off = size & (BLOCK_SIZE - 1);

        return !(((blocks % sizeof(struct dqblk)) * BLOCK_SIZE + off % sizeof(struct dqblk)) % sizeof(struct dqblk));
}

static int quota_on(struct super_block *sb, short type, char *path)
{
        struct file *f;
        struct inode *inode;
        struct dquot *dquot;
        struct quota_mount_options *dqopt = sb_dqopt(sb);
        char *tmp;
        int error;

        if (is_enabled(dqopt, type))
                return -EBUSY;

        down(&dqopt->dqoff_sem);
        tmp = getname(path);
        error = PTR_ERR(tmp);
        if (IS_ERR(tmp))
                goto out_lock;

        f = filp_open(tmp, O_RDWR, 0600);
        putname(tmp);

        error = PTR_ERR(f);
        if (IS_ERR(f))
                goto out_lock;
        error = -EIO;
        if (!f->f_op->read && !f->f_op->write)
                goto out_f;
        inode = f->f_dentry->d_inode;
        error = -EACCES;
        if (!S_ISREG(inode->i_mode))
                goto out_f;
        error = -EINVAL;
        if (inode->i_size == 0 || !check_quotafile_size(inode->i_size))
                goto out_f;
        dquot_drop(inode);      /* We don't want quota on quota files */

        set_enable_flags(dqopt, type);
        dqopt->files[type] = f;

        dquot = dqget(sb, 0, type);
        dqopt->inode_expire[type] = (dquot != NODQUOT) ? dquot->dq_itime : MAX_IQ_TIME;
        dqopt->block_expire[type] = (dquot != NODQUOT) ? dquot->dq_btime : MAX_DQ_TIME;
        dqput(dquot);

        sb->dq_op = &dquot_operations;
        add_dquot_ref(sb, type);

        up(&dqopt->dqoff_sem);
        return 0;

out_f:
        filp_close(f, NULL);
out_lock:
        up(&dqopt->dqoff_sem);

        return error; 
}

/*
 * This is the system call interface. This communicates with
 * the user-level programs. Currently this only supports diskquota
 * calls. Maybe we need to add the process quotas etc. in the future,
 * but we probably should use rlimits for that.
 */
asmlinkage long sys_quotactl(int cmd, const char *special, int id, caddr_t addr)
{
        int cmds = 0, type = 0, flags = 0;
        kdev_t dev;
        struct super_block *sb = NULL;
        int ret = -EINVAL;

        lock_kernel();
        cmds = cmd >> SUBCMDSHIFT;
        type = cmd & SUBCMDMASK;

        if ((u_int) type >= MAXQUOTAS)
                goto out;
        if (id & ~0xFFFF)
                goto out;

        ret = -EPERM;
        switch (cmds) {
                case Q_SYNC:
                case Q_GETSTATS:
                        break;
                case Q_GETQUOTA:
                        if (((type == USRQUOTA && current->euid != id) ||
                             (type == GRPQUOTA && in_egroup_p(id))) &&
                            !capable(CAP_SYS_RESOURCE))
                                goto out;
                        break;
                default:
                        if (!capable(CAP_SYS_RESOURCE))
                                goto out;
        }

        ret = -EINVAL;
        dev = NODEV;
        if (special != NULL || (cmds != Q_SYNC && cmds != Q_GETSTATS)) {
                mode_t mode;
                struct nameidata nd;

                ret = user_path_walk(special, &nd);
                if (ret)
                        goto out;

                dev = nd.dentry->d_inode->i_rdev;
                mode = nd.dentry->d_inode->i_mode;
                path_release(&nd);

                ret = -ENOTBLK;
                if (!S_ISBLK(mode))
                        goto out;
                sb = get_super(dev);
        }

        ret = -EINVAL;
        switch (cmds) {
                case Q_QUOTAON:
                        ret = sb ? quota_on(sb, type, (char *) addr) : -ENODEV;
                        goto out;
                case Q_QUOTAOFF:
                        ret = quota_off(sb, type);
                        goto out;
                case Q_GETQUOTA:
                        ret = get_quota(sb, id, type, (struct dqblk *) addr);
                        goto out;
                case Q_SETQUOTA:
                        flags |= SET_QUOTA;
                        break;
                case Q_SETUSE:
                        flags |= SET_USE;
                        break;
                case Q_SETQLIM:
                        flags |= SET_QLIMIT;
                        break;
                case Q_SYNC:
                        ret = sync_dquots(dev, type);
                        goto out;
                case Q_GETSTATS:
                        ret = get_stats(addr);
                        goto out;
                case Q_RSQUASH:
                        ret = quota_root_squash(sb, type, (int *) addr);
                        goto out;
                default:
                        goto out;
        }

        flags |= QUOTA_SYSCALL;

        ret = -ESRCH;
        if (sb && sb_has_quota_enabled(sb, type))
                ret = set_dqblk(sb, id, type, flags, (struct dqblk *) addr);
out:
        unlock_kernel();
        return ret;
}