/*
 * linux/fs/inode.c
 *
 * (C) 1997 Linus Torvalds
 */

#include <linux/config.h>
#include <linux/fs.h>
#include <linux/string.h>
#include <linux/mm.h>
#include <linux/dcache.h>
#include <linux/init.h>
#include <linux/quotaops.h>
#include <linux/slab.h>
#include <linux/cache.h>
#include <linux/swap.h>
#include <linux/swapctl.h>
#include <linux/prefetch.h>
#include <linux/locks.h>

/*
 * New inode.c implementation.
 *
 * This implementation has the basic premise of trying
 * to be extremely low-overhead and SMP-safe, yet be
 * simple enough to be "obviously correct".
 *
 * Famous last words.
 */

/* inode dynamic allocation 1999, Andrea Arcangeli <andrea@suse.de> */

/* #define INODE_PARANOIA 1 */
/* #define INODE_DEBUG 1 */

/*
 * Inode lookup is no longer as critical as it used to be:
 * most of the lookups are going to be through the dcache.
 */
#define I_HASHBITS      i_hash_shift
#define I_HASHMASK      i_hash_mask

static unsigned int i_hash_mask;
static unsigned int i_hash_shift;

/*
 * Each inode can be on two separate lists. One is
 * the hash list of the inode, used for lookups. The
 * other linked list is the "type" list:
 *  "in_use" - valid inode, i_count > 0, i_nlink > 0
 *  "dirty"  - as "in_use" but also dirty
 *  "unused" - valid inode, i_count = 0
 *
 * A "dirty" list is maintained for each super block,
 * allowing for low-overhead inode sync() operations.
 */

static LIST_HEAD(inode_in_use);
static LIST_HEAD(inode_unused);
static struct list_head *inode_hashtable;
static LIST_HEAD(anon_hash_chain); /* for inodes with NULL i_sb */

/*
 * A simple spinlock to protect the list manipulations.
 *
 * NOTE! You also have to own the lock if you change
 * the i_state of an inode while it is in use..
 */
static spinlock_t inode_lock = SPIN_LOCK_UNLOCKED;

/*
 * Statistics gathering..
 */
struct inodes_stat_t inodes_stat;

static kmem_cache_t * inode_cachep;

#define alloc_inode() \
         ((struct inode *) kmem_cache_alloc(inode_cachep, SLAB_KERNEL))
static void destroy_inode(struct inode *inode) 
{
        if (inode_has_buffers(inode))
                BUG();
        kmem_cache_free(inode_cachep, (inode));
}


/*
 * These are initializations that only need to be done
 * once, because the fields are idempotent across use
 * of the inode, so let the slab aware of that.
 */
static void init_once(void * foo, kmem_cache_t * cachep, unsigned long flags)
{
        struct inode * inode = (struct inode *) foo;

        if ((flags & (SLAB_CTOR_VERIFY|SLAB_CTOR_CONSTRUCTOR)) ==
            SLAB_CTOR_CONSTRUCTOR)
        {
                memset(inode, 0, sizeof(*inode));
                init_waitqueue_head(&inode->i_wait);
                INIT_LIST_HEAD(&inode->i_hash);
                INIT_LIST_HEAD(&inode->i_data.clean_pages);
                INIT_LIST_HEAD(&inode->i_data.dirty_pages);
                INIT_LIST_HEAD(&inode->i_data.locked_pages);
                INIT_LIST_HEAD(&inode->i_dentry);
                INIT_LIST_HEAD(&inode->i_dirty_buffers);
                INIT_LIST_HEAD(&inode->i_dirty_data_buffers);
                INIT_LIST_HEAD(&inode->i_devices);
                sema_init(&inode->i_sem, 1);
                sema_init(&inode->i_zombie, 1);
                spin_lock_init(&inode->i_data.i_shared_lock);
        }
}

/*
 * Put the inode on the super block's dirty list.
 *
 * CAREFUL! We mark it dirty unconditionally, but
 * move it onto the dirty list only if it is hashed.
 * If it was not hashed, it will never be added to
 * the dirty list even if it is later hashed, as it
 * will have been marked dirty already.
 *
 * In short, make sure you hash any inodes _before_
 * you start marking them dirty..
 */
 
/**
 *      __mark_inode_dirty -    internal function
 *      @inode: inode to mark
 *      @flags: what kind of dirty (i.e. I_DIRTY_SYNC)
 *      Mark an inode as dirty. Callers should use mark_inode_dirty or
 *      mark_inode_dirty_sync.
 */
 
void __mark_inode_dirty(struct inode *inode, int flags)
{
        struct super_block * sb = inode->i_sb;

        if (!sb)
                return;

        /* Don't do this for I_DIRTY_PAGES - that doesn't actually dirty the inode itself */
        if (flags & (I_DIRTY_SYNC | I_DIRTY_DATASYNC)) {
                if (sb->s_op && sb->s_op->dirty_inode)
                        sb->s_op->dirty_inode(inode);
        }

        /* avoid the locking if we can */
        if ((inode->i_state & flags) == flags)
                return;

        spin_lock(&inode_lock);
        if ((inode->i_state & flags) != flags) {
                inode->i_state |= flags;
                /* Only add valid (ie hashed) inodes to the dirty list */
                if (!(inode->i_state & I_LOCK) && !list_empty(&inode->i_hash)) {
                        list_del(&inode->i_list);
                        list_add(&inode->i_list, &sb->s_dirty);
                }
        }
        spin_unlock(&inode_lock);
}

static void __wait_on_inode(struct inode * inode)
{
        DECLARE_WAITQUEUE(wait, current);

        add_wait_queue(&inode->i_wait, &wait);
repeat:
        set_current_state(TASK_UNINTERRUPTIBLE);
        if (inode->i_state & I_LOCK) {
                schedule();
                goto repeat;
        }
        remove_wait_queue(&inode->i_wait, &wait);
        current->state = TASK_RUNNING;
}

static inline void wait_on_inode(struct inode *inode)
{
        if (inode->i_state & I_LOCK)
                __wait_on_inode(inode);
}


static inline void write_inode(struct inode *inode, int sync)
{
        if (inode->i_sb && inode->i_sb->s_op && inode->i_sb->s_op->write_inode && !is_bad_inode(inode))
                inode->i_sb->s_op->write_inode(inode, sync);
}

static inline void __iget(struct inode * inode)
{
        if (atomic_read(&inode->i_count)) {
                atomic_inc(&inode->i_count);
                return;
        }
        atomic_inc(&inode->i_count);
        if (!(inode->i_state & (I_DIRTY|I_LOCK))) {
                list_del(&inode->i_list);
                list_add(&inode->i_list, &inode_in_use);
        }
        inodes_stat.nr_unused--;
}

static inline void __sync_one(struct inode *inode, int sync)
{
        unsigned dirty;

        list_del(&inode->i_list);
        list_add(&inode->i_list, &inode->i_sb->s_locked_inodes);

        if (inode->i_state & I_LOCK)
                BUG();

        /* Set I_LOCK, reset I_DIRTY */
        dirty = inode->i_state & I_DIRTY;
        inode->i_state |= I_LOCK;
        inode->i_state &= ~I_DIRTY;
        spin_unlock(&inode_lock);

        filemap_fdatasync(inode->i_mapping);

        /* Don't write the inode if only I_DIRTY_PAGES was set */
        if (dirty & (I_DIRTY_SYNC | I_DIRTY_DATASYNC))
                write_inode(inode, sync);

        filemap_fdatawait(inode->i_mapping);

        spin_lock(&inode_lock);
        inode->i_state &= ~I_LOCK;
        if (!(inode->i_state & I_FREEING)) {
                struct list_head *to;
                if (inode->i_state & I_DIRTY)
                        to = &inode->i_sb->s_dirty;
                else if (atomic_read(&inode->i_count))
                        to = &inode_in_use;
                else
                        to = &inode_unused;
                list_del(&inode->i_list);
                list_add(&inode->i_list, to);
        }
        wake_up(&inode->i_wait);
}

static inline void sync_one(struct inode *inode, int sync)
{
        while (inode->i_state & I_LOCK) {
                __iget(inode);
                spin_unlock(&inode_lock);
                __wait_on_inode(inode);
                iput(inode);
                spin_lock(&inode_lock);
        }

        __sync_one(inode, sync);
}

static inline void sync_list(struct list_head *head)
{
        struct list_head * tmp;

        while ((tmp = head->prev) != head) 
                __sync_one(list_entry(tmp, struct inode, i_list), 0);
}

static inline void wait_on_locked(struct list_head *head)
{
        struct list_head * tmp;
        while ((tmp = head->prev) != head) {
                struct inode *inode = list_entry(tmp, struct inode, i_list);
                __iget(inode);
                spin_unlock(&inode_lock);
                __wait_on_inode(inode);
                iput(inode);
                spin_lock(&inode_lock);
        }
}

static inline int try_to_sync_unused_list(struct list_head *head, int nr_inodes)
{
        struct list_head *tmp = head;
        struct inode *inode;

        while (nr_inodes && (tmp = tmp->prev) != head) {
                inode = list_entry(tmp, struct inode, i_list);

                if (!atomic_read(&inode->i_count)) {
                        __sync_one(inode, 0);
                        nr_inodes--;

                        /* 
                         * __sync_one moved the inode to another list,
                         * so we have to start looking from the list head.
                         */
                        tmp = head;
                }
        }

        return nr_inodes;
}

void sync_inodes_sb(struct super_block *sb)
{
        spin_lock(&inode_lock);
        while (!list_empty(&sb->s_dirty)||!list_empty(&sb->s_locked_inodes)) {
                sync_list(&sb->s_dirty);
                wait_on_locked(&sb->s_locked_inodes);
        }
        spin_unlock(&inode_lock);
}

/*
 * Note:
 * We don't need to grab a reference to superblock here. If it has non-empty
 * ->s_dirty it's hadn't been killed yet and kill_super() won't proceed
 * past sync_inodes_sb() until both ->s_dirty and ->s_locked_inodes are
 * empty. Since __sync_one() regains inode_lock before it finally moves
 * inode from superblock lists we are OK.
 */

void sync_unlocked_inodes(void)
{
        struct super_block * sb;
        spin_lock(&inode_lock);
        spin_lock(&sb_lock);
        sb = sb_entry(super_blocks.next);
        for (; sb != sb_entry(&super_blocks); sb = sb_entry(sb->s_list.next)) {
                if (!list_empty(&sb->s_dirty)) {
                        spin_unlock(&sb_lock);
                        sync_list(&sb->s_dirty);
                        spin_lock(&sb_lock);
                }
        }
        spin_unlock(&sb_lock);
        spin_unlock(&inode_lock);
}

/*
 * Find a superblock with inodes that need to be synced
 */

static struct super_block *get_super_to_sync(void)
{
        struct list_head *p;
restart:
        spin_lock(&inode_lock);
        spin_lock(&sb_lock);
        list_for_each(p, &super_blocks) {
                struct super_block *s = list_entry(p,struct super_block,s_list);
                if (list_empty(&s->s_dirty) && list_empty(&s->s_locked_inodes))
                        continue;
                s->s_count++;
                spin_unlock(&sb_lock);
                spin_unlock(&inode_lock);
                down_read(&s->s_umount);
                if (!s->s_root) {
                        drop_super(s);
                        goto restart;
                }
                return s;
        }
        spin_unlock(&sb_lock);
        spin_unlock(&inode_lock);
        return NULL;
}

/**
 *      sync_inodes
 *      @dev: device to sync the inodes from.
 *
 *      sync_inodes goes through the super block's dirty list, 
 *      writes them out, and puts them back on the normal list.
 */

void sync_inodes(kdev_t dev)
{
        struct super_block * s;

        /*
         * Search the super_blocks array for the device(s) to sync.
         */
        if (dev) {
                if ((s = get_super(dev)) != NULL) {
                        sync_inodes_sb(s);
                        drop_super(s);
                }
        } else {
                while ((s = get_super_to_sync()) != NULL) {
                        sync_inodes_sb(s);
                        drop_super(s);
                }
        }
}

static void try_to_sync_unused_inodes(void * arg)
{
        struct super_block * sb;
        int nr_inodes = inodes_stat.nr_unused;

        spin_lock(&inode_lock);
        spin_lock(&sb_lock);
        sb = sb_entry(super_blocks.next);
        for (; nr_inodes && sb != sb_entry(&super_blocks); sb = sb_entry(sb->s_list.next)) {
                if (list_empty(&sb->s_dirty))
                        continue;
                spin_unlock(&sb_lock);
                nr_inodes = try_to_sync_unused_list(&sb->s_dirty, nr_inodes);
                spin_lock(&sb_lock);
        }
        spin_unlock(&sb_lock);
        spin_unlock(&inode_lock);
}

static struct tq_struct unused_inodes_flush_task;

/**
 *      write_inode_now -       write an inode to disk
 *      @inode: inode to write to disk
 *      @sync: whether the write should be synchronous or not
 *
 *      This function commits an inode to disk immediately if it is
 *      dirty. This is primarily needed by knfsd.
 */
 
void write_inode_now(struct inode *inode, int sync)
{
        struct super_block * sb = inode->i_sb;

        if (sb) {
                spin_lock(&inode_lock);
                while (inode->i_state & I_DIRTY)
                        sync_one(inode, sync);
                spin_unlock(&inode_lock);
                if (sync)
                        wait_on_inode(inode);
        }
        else
                printk(KERN_ERR "write_inode_now: no super block\n");
}

/**
 * generic_osync_inode - flush all dirty data for a given inode to disk
 * @inode: inode to write
 * @datasync: if set, don't bother flushing timestamps
 *
 * This can be called by file_write functions for files which have the
 * O_SYNC flag set, to flush dirty writes to disk.  
 */

int generic_osync_inode(struct inode *inode, int what)
{
        int err = 0, err2 = 0, need_write_inode_now = 0;
        
        /* 
         * WARNING
         *
         * Currently, the filesystem write path does not pass the
         * filp down to the low-level write functions.  Therefore it
         * is impossible for (say) __block_commit_write to know if
         * the operation is O_SYNC or not.
         *
         * Ideally, O_SYNC writes would have the filesystem call
         * ll_rw_block as it went to kick-start the writes, and we
         * could call osync_inode_buffers() here to wait only for
         * those IOs which have already been submitted to the device
         * driver layer.  As it stands, if we did this we'd not write
         * anything to disk since our writes have not been queued by
         * this point: they are still on the dirty LRU.
         * 
         * So, currently we will call fsync_inode_buffers() instead,
         * to flush _all_ dirty buffers for this inode to disk on 
         * every O_SYNC write, not just the synchronous I/Os.  --sct
         */

        if (what & OSYNC_METADATA)
                err = fsync_inode_buffers(inode);
        if (what & OSYNC_DATA)
                err2 = fsync_inode_data_buffers(inode);
        if (!err)
                err = err2;

        spin_lock(&inode_lock);
        if ((inode->i_state & I_DIRTY) &&
            ((what & OSYNC_INODE) || (inode->i_state & I_DIRTY_DATASYNC)))
                need_write_inode_now = 1;
        spin_unlock(&inode_lock);

        if (need_write_inode_now)
                write_inode_now(inode, 1);
        else
                wait_on_inode(inode);

        return err;
}

/**
 * clear_inode - clear an inode
 * @inode: inode to clear
 *
 * This is called by the filesystem to tell us
 * that the inode is no longer useful. We just
 * terminate it with extreme prejudice.
 */
 
void clear_inode(struct inode *inode)
{
        invalidate_inode_buffers(inode);
       
        if (inode->i_data.nrpages)
                BUG();
        if (!(inode->i_state & I_FREEING))
                BUG();
        if (inode->i_state & I_CLEAR)
                BUG();
        wait_on_inode(inode);
        DQUOT_DROP(inode);
        if (inode->i_sb && inode->i_sb->s_op && inode->i_sb->s_op->clear_inode)
                inode->i_sb->s_op->clear_inode(inode);
        if (inode->i_bdev)
                bd_forget(inode);
        else if (inode->i_cdev) {
                cdput(inode->i_cdev);
                inode->i_cdev = NULL;
        }
        inode->i_state = I_CLEAR;
}

/*
 * Dispose-list gets a local list with local inodes in it, so it doesn't
 * need to worry about list corruption and SMP locks.
 */
static void dispose_list(struct list_head * head)
{
        struct list_head * inode_entry;
        struct inode * inode;

        while ((inode_entry = head->next) != head)
        {
                list_del(inode_entry);

                inode = list_entry(inode_entry, struct inode, i_list);
                if (inode->i_data.nrpages)
                        truncate_inode_pages(&inode->i_data, 0);
                clear_inode(inode);
                destroy_inode(inode);
                inodes_stat.nr_inodes--;
        }
}

/*
 * Invalidate all inodes for a device.
 */
static int invalidate_list(struct list_head *head, struct super_block * sb, struct list_head * dispose)
{
        struct list_head *next;
        int busy = 0, count = 0;

        next = head->next;
        for (;;) {
                struct list_head * tmp = next;
                struct inode * inode;

                next = next->next;
                if (tmp == head)
                        break;
                inode = list_entry(tmp, struct inode, i_list);
                if (inode->i_sb != sb)
                        continue;
                invalidate_inode_buffers(inode);
                if (!atomic_read(&inode->i_count)) {
                        list_del_init(&inode->i_hash);
                        list_del(&inode->i_list);
                        list_add(&inode->i_list, dispose);
                        inode->i_state |= I_FREEING;
                        count++;
                        continue;
                }
                busy = 1;
        }
        /* only unused inodes may be cached with i_count zero */
        inodes_stat.nr_unused -= count;
        return busy;
}

/*
 * This is a two-stage process. First we collect all
 * offending inodes onto the throw-away list, and in
 * the second stage we actually dispose of them. This
 * is because we don't want to sleep while messing
 * with the global lists..
 */
 
/**
 *      invalidate_inodes       - discard the inodes on a device
 *      @sb: superblock
 *
 *      Discard all of the inodes for a given superblock. If the discard
 *      fails because there are busy inodes then a non zero value is returned.
 *      If the discard is successful all the inodes have been discarded.
 */
 
int invalidate_inodes(struct super_block * sb)
{
        int busy;
        LIST_HEAD(throw_away);

        spin_lock(&inode_lock);
        busy = invalidate_list(&inode_in_use, sb, &throw_away);
        busy |= invalidate_list(&inode_unused, sb, &throw_away);
        busy |= invalidate_list(&sb->s_dirty, sb, &throw_away);
        busy |= invalidate_list(&sb->s_locked_inodes, sb, &throw_away);
        spin_unlock(&inode_lock);

        dispose_list(&throw_away);

        return busy;
}
 
int invalidate_device(kdev_t dev, int do_sync)
{
        struct super_block *sb;
        int res;

        if (do_sync)
                fsync_dev(dev);

        res = 0;
        sb = get_super(dev);
        if (sb) {
                /*
                 * no need to lock the super, get_super holds the
                 * read semaphore so the filesystem cannot go away
                 * under us (->put_super runs with the write lock
                 * hold).
                 */
                shrink_dcache_sb(sb);
                res = invalidate_inodes(sb);
                drop_super(sb);
        }
        invalidate_buffers(dev);
        return res;
}


/*
 * This is called with the inode lock held. It searches
 * the in-use for freeable inodes, which are moved to a
 * temporary list and then placed on the unused list by
 * dispose_list. 
 *
 * We don't expect to have to call this very often.
 *
 * N.B. The spinlock is released during the call to
 *      dispose_list.
 */
#define CAN_UNUSE(inode) \
        ((((inode)->i_state | (inode)->i_data.nrpages) == 0)  && \
         !inode_has_buffers(inode))
#define INODE(entry)    (list_entry(entry, struct inode, i_list))

void prune_icache(int goal)
{
        LIST_HEAD(list);
        struct list_head *entry, *freeable = &list;
        int count;
        struct inode * inode;

        spin_lock(&inode_lock);

        count = 0;
        entry = inode_unused.prev;
        while (entry != &inode_unused)
        {
                struct list_head *tmp = entry;

                entry = entry->prev;
                inode = INODE(tmp);
                if (inode->i_state & (I_FREEING|I_CLEAR|I_LOCK))
                        continue;
                if (!CAN_UNUSE(inode))
                        continue;
                if (atomic_read(&inode->i_count))
                        continue;
                list_del(tmp);
                list_del(&inode->i_hash);
                INIT_LIST_HEAD(&inode->i_hash);
                list_add(tmp, freeable);
                inode->i_state |= I_FREEING;
                count++;
                if (!--goal)
                        break;
        }
        inodes_stat.nr_unused -= count;
        spin_unlock(&inode_lock);

        dispose_list(freeable);

        /* 
         * If we didn't freed enough clean inodes schedule
         * a sync of the dirty inodes, we cannot do it
         * from here or we're either synchronously dogslow
         * or we deadlock with oom.
         */
        if (goal)
                schedule_task(&unused_inodes_flush_task);
}

int shrink_icache_memory(int priority, int gfp_mask)
{
        int count = 0;

        /*
         * Nasty deadlock avoidance..
         *
         * We may hold various FS locks, and we don't
         * want to recurse into the FS that called us
         * in clear_inode() and friends..
         */
        if (!(gfp_mask & __GFP_FS))
                return 0;

        count = inodes_stat.nr_unused / priority;

        prune_icache(count);
        return kmem_cache_shrink(inode_cachep);
}

/*
 * Called with the inode lock held.
 * NOTE: we are not increasing the inode-refcount, you must call __iget()
 * by hand after calling find_inode now! This simplifies iunique and won't
 * add any additional branch in the common code.
 */
static struct inode * find_inode(struct super_block * sb, unsigned long ino, struct list_head *head, find_inode_t find_actor, void *opaque)
{
        struct list_head *tmp;
        struct inode * inode;

        tmp = head;
        for (;;) {
                tmp = tmp->next;
                inode = NULL;
                if (tmp == head)
                        break;
                inode = list_entry(tmp, struct inode, i_hash);
                if (inode->i_ino != ino)
                        continue;
                if (inode->i_sb != sb)
                        continue;
                if (find_actor && !find_actor(inode, ino, opaque))
                        continue;
                break;
        }
        return inode;
}

/*
 * This just initializes the inode fields
 * to known values before returning the inode..
 *
 * i_sb, i_ino, i_count, i_state and the lists have
 * been initialized elsewhere..
 */
static void clean_inode(struct inode *inode)
{
        static struct address_space_operations empty_aops;
        static struct inode_operations empty_iops;
        static struct file_operations empty_fops;
        memset(&inode->u, 0, sizeof(inode->u));
        inode->i_sock = 0;
        inode->i_op = &empty_iops;
        inode->i_fop = &empty_fops;
        inode->i_nlink = 1;
        atomic_set(&inode->i_writecount, 0);
        inode->i_size = 0;
        inode->i_blocks = 0;
        inode->i_generation = 0;
        memset(&inode->i_dquot, 0, sizeof(inode->i_dquot));
        inode->i_pipe = NULL;
        inode->i_bdev = NULL;
        inode->i_cdev = NULL;
        inode->i_data.a_ops = &empty_aops;
        inode->i_data.host = inode;
        inode->i_data.gfp_mask = GFP_HIGHUSER;
        inode->i_mapping = &inode->i_data;
}

/**
 * get_empty_inode      - obtain an inode
 *
 * This is called by things like the networking layer
 * etc that want to get an inode without any inode
 * number, or filesystems that allocate new inodes with
 * no pre-existing information.
 *
 * On a successful return the inode pointer is returned. On a failure
 * a %NULL pointer is returned. The returned inode is not on any superblock
 * lists.
 */
 
struct inode * get_empty_inode(void)
{
        static unsigned long last_ino;
        struct inode * inode;

        spin_lock_prefetch(&inode_lock);
        
        inode = alloc_inode();
        if (inode)
        {
                spin_lock(&inode_lock);
                inodes_stat.nr_inodes++;
                list_add(&inode->i_list, &inode_in_use);
                inode->i_sb = NULL;
                inode->i_dev = 0;
                inode->i_blkbits = 0;
                inode->i_ino = ++last_ino;
                inode->i_flags = 0;
                atomic_set(&inode->i_count, 1);
                inode->i_state = 0;
                spin_unlock(&inode_lock);
                clean_inode(inode);
        }
        return inode;
}

/*
 * This is called without the inode lock held.. Be careful.
 *
 * We no longer cache the sb_flags in i_flags - see fs.h
 *      -- rmk@arm.uk.linux.org
 */
static struct inode * get_new_inode(struct super_block *sb, unsigned long ino, struct list_head *head, find_inode_t find_actor, void *opaque)
{
        struct inode * inode;

        inode = alloc_inode();
        if (inode) {
                struct inode * old;

                spin_lock(&inode_lock);
                /* We released the lock, so.. */
                old = find_inode(sb, ino, head, find_actor, opaque);
                if (!old) {
                        inodes_stat.nr_inodes++;
                        list_add(&inode->i_list, &inode_in_use);
                        list_add(&inode->i_hash, head);
                        inode->i_sb = sb;
                        inode->i_dev = sb->s_dev;
                        inode->i_blkbits = sb->s_blocksize_bits;
                        inode->i_ino = ino;
                        inode->i_flags = 0;
                        atomic_set(&inode->i_count, 1);
                        inode->i_state = I_LOCK;
                        spin_unlock(&inode_lock);

                        clean_inode(inode);

                        /* reiserfs specific hack right here.  We don't
                        ** want this to last, and are looking for VFS changes
                        ** that will allow us to get rid of it.
                        ** -- mason@suse.com 
                        */
                        if (sb->s_op->read_inode2) {
                                sb->s_op->read_inode2(inode, opaque) ;
                        } else {
                                sb->s_op->read_inode(inode);
                        }

                        /*
                         * This is special!  We do not need the spinlock
                         * when clearing I_LOCK, because we're guaranteed
                         * that nobody else tries to do anything about the
                         * state of the inode when it is locked, as we
                         * just created it (so there can be no old holders
                         * that haven't tested I_LOCK).
                         */
                        inode->i_state &= ~I_LOCK;
                        wake_up(&inode->i_wait);

                        return inode;
                }

                /*
                 * Uhhuh, somebody else created the same inode under
                 * us. Use the old inode instead of the one we just
                 * allocated.
                 */
                __iget(old);
                spin_unlock(&inode_lock);
                destroy_inode(inode);
                inode = old;
                wait_on_inode(inode);
        }
        return inode;
}

static inline unsigned long hash(struct super_block *sb, unsigned long i_ino)
{
        unsigned long tmp = i_ino + ((unsigned long) sb / L1_CACHE_BYTES);
        tmp = tmp + (tmp >> I_HASHBITS);
        return tmp & I_HASHMASK;
}

/* Yeah, I know about quadratic hash. Maybe, later. */

/**
 *      iunique - get a unique inode number
 *      @sb: superblock
 *      @max_reserved: highest reserved inode number
 *
 *      Obtain an inode number that is unique on the system for a given
 *      superblock. This is used by file systems that have no natural
 *      permanent inode numbering system. An inode number is returned that
 *      is higher than the reserved limit but unique.
 *
 *      BUGS:
 *      With a large number of inodes live on the file system this function
 *      currently becomes quite slow.
 */
 
ino_t iunique(struct super_block *sb, ino_t max_reserved)
{
        static ino_t counter = 0;
        struct inode *inode;
        struct list_head * head;
        ino_t res;
        spin_lock(&inode_lock);
retry:
        if (counter > max_reserved) {
                head = inode_hashtable + hash(sb,counter);
                inode = find_inode(sb, res = counter++, head, NULL, NULL);
                if (!inode) {
                        spin_unlock(&inode_lock);
                        return res;
                }
        } else {
                counter = max_reserved + 1;
        }
        goto retry;
        
}

struct inode *igrab(struct inode *inode)
{
        spin_lock(&inode_lock);
        if (!(inode->i_state & I_FREEING))
                __iget(inode);
        else
                /*
                 * Handle the case where s_op->clear_inode is not been
                 * called yet, and somebody is calling igrab
                 * while the inode is getting freed.
                 */
                inode = NULL;
        spin_unlock(&inode_lock);
        return inode;
}


struct inode *iget4(struct super_block *sb, unsigned long ino, find_inode_t find_actor, void *opaque)
{
        struct list_head * head = inode_hashtable + hash(sb,ino);
        struct inode * inode;

        spin_lock(&inode_lock);
        inode = find_inode(sb, ino, head, find_actor, opaque);
        if (inode) {
                __iget(inode);
                spin_unlock(&inode_lock);
                wait_on_inode(inode);
                return inode;
        }
        spin_unlock(&inode_lock);

        /*
         * get_new_inode() will do the right thing, re-trying the search
         * in case it had to block at any point.
         */
        return get_new_inode(sb, ino, head, find_actor, opaque);
}

/**
 *      insert_inode_hash - hash an inode
 *      @inode: unhashed inode
 *
 *      Add an inode to the inode hash for this superblock. If the inode
 *      has no superblock it is added to a separate anonymous chain.
 */
 
void insert_inode_hash(struct inode *inode)
{
        struct list_head *head = &anon_hash_chain;
        if (inode->i_sb)
                head = inode_hashtable + hash(inode->i_sb, inode->i_ino);
        spin_lock(&inode_lock);
        list_add(&inode->i_hash, head);

        spin_unlock(&inode_lock);
}

/**
 *      remove_inode_hash - remove an inode from the hash
 *      @inode: inode to unhash
 *
 *      Remove an inode from the superblock or anonymous hash.
 */
 
void remove_inode_hash(struct inode *inode)
{
        spin_lock(&inode_lock);
        list_del(&inode->i_hash);
        INIT_LIST_HEAD(&inode->i_hash);
        spin_unlock(&inode_lock);
}

/**
 *      iput    - put an inode 
 *      @inode: inode to put
 *
 *      Puts an inode, dropping its usage count. If the inode use count hits
 *      zero the inode is also then freed and may be destroyed.
 */
 
void iput(struct inode *inode)
{
        if (inode) {
                struct super_block *sb = inode->i_sb;
                struct super_operations *op = NULL;

                if (inode->i_state == I_CLEAR)
                        BUG();

                if (sb && sb->s_op)
                        op = sb->s_op;
                if (op && op->put_inode)
                        op->put_inode(inode);

                if (!atomic_dec_and_lock(&inode->i_count, &inode_lock))
                        return;

                if (!inode->i_nlink) {
                        list_del(&inode->i_hash);
                        INIT_LIST_HEAD(&inode->i_hash);
                        list_del(&inode->i_list);
                        INIT_LIST_HEAD(&inode->i_list);
                        inode->i_state|=I_FREEING;
                        inodes_stat.nr_inodes--;
                        spin_unlock(&inode_lock);

                        if (inode->i_data.nrpages)
                                truncate_inode_pages(&inode->i_data, 0);

                        if (op && op->delete_inode) {
                                void (*delete)(struct inode *) = op->delete_inode;
                                if (!is_bad_inode(inode))
                                        DQUOT_INIT(inode);
                                /* s_op->delete_inode internally recalls clear_inode() */
                                delete(inode);
                        } else
                                clear_inode(inode);
                        if (inode->i_state != I_CLEAR)
                                BUG();
                } else {
                        if (!list_empty(&inode->i_hash)) {
                                if (!(inode->i_state & (I_DIRTY|I_LOCK))) {
                                        list_del(&inode->i_list);
                                        list_add(&inode->i_list, &inode_unused);
                                }
                                inodes_stat.nr_unused++;
                                spin_unlock(&inode_lock);
                                if (!sb || (sb->s_flags & MS_ACTIVE))
                                        return;
                                write_inode_now(inode, 1);
                                spin_lock(&inode_lock);
                                inodes_stat.nr_unused--;
                                list_del_init(&inode->i_hash);
                        }
                        list_del_init(&inode->i_list);
                        inode->i_state|=I_FREEING;
                        inodes_stat.nr_inodes--;
                        spin_unlock(&inode_lock);
                        if (inode->i_data.nrpages)
                                truncate_inode_pages(&inode->i_data, 0);
                        clear_inode(inode);
                }
                destroy_inode(inode);
        }
}

void force_delete(struct inode *inode)
{
        /*
         * Kill off unused inodes ... iput() will unhash and
         * delete the inode if we set i_nlink to zero.
         */
        if (atomic_read(&inode->i_count) == 1)
                inode->i_nlink = 0;
}

/**
 *      bmap    - find a block number in a file
 *      @inode: inode of file
 *      @block: block to find
 *
 *      Returns the block number on the device holding the inode that
 *      is the disk block number for the block of the file requested.
 *      That is, asked for block 4 of inode 1 the function will return the
 *      disk block relative to the disk start that holds that block of the 
 *      file.
 */
 
int bmap(struct inode * inode, int block)
{
        int res = 0;
        if (inode->i_mapping->a_ops->bmap)
                res = inode->i_mapping->a_ops->bmap(inode->i_mapping, block);
        return res;
}

/*
 * Initialize the hash tables.
 */
void __init inode_init(unsigned long mempages)
{
        struct list_head *head;
        unsigned long order;
        unsigned int nr_hash;
        int i;

        mempages >>= (14 - PAGE_SHIFT);
        mempages *= sizeof(struct list_head);
        for (order = 0; ((1UL << order) << PAGE_SHIFT) < mempages; order++)
                ;

        do {
                unsigned long tmp;

                nr_hash = (1UL << order) * PAGE_SIZE /
                        sizeof(struct list_head);
                i_hash_mask = (nr_hash - 1);

                tmp = nr_hash;
                i_hash_shift = 0;
                while ((tmp >>= 1UL) != 0UL)
                        i_hash_shift++;

                inode_hashtable = (struct list_head *)
                        __get_free_pages(GFP_ATOMIC, order);
        } while (inode_hashtable == NULL && --order >= 0);

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

        if (!inode_hashtable)
                panic("Failed to allocate inode hash table\n");

        head = inode_hashtable;
        i = nr_hash;
        do {
                INIT_LIST_HEAD(head);
                head++;
                i--;
        } while (i);

        /* inode slab cache */
        inode_cachep = kmem_cache_create("inode_cache", sizeof(struct inode),
                                         0, SLAB_HWCACHE_ALIGN, init_once,
                                         NULL);
        if (!inode_cachep)
                panic("cannot create inode slab cache");

        unused_inodes_flush_task.routine = try_to_sync_unused_inodes;
}

/**
 *      update_atime    -       update the access time
 *      @inode: inode accessed
 *
 *      Update the accessed time on an inode and mark it for writeback.
 *      This function automatically handles read only file systems and media,
 *      as well as the "noatime" flag and inode specific "noatime" markers.
 */
 
void update_atime (struct inode *inode)
{
        if (inode->i_atime == CURRENT_TIME)
                return;
        if ( IS_NOATIME (inode) ) return;
        if ( IS_NODIRATIME (inode) && S_ISDIR (inode->i_mode) ) return;
        if ( IS_RDONLY (inode) ) return;
        inode->i_atime = CURRENT_TIME;
        mark_inode_dirty_sync (inode);
}   /*  End Function update_atime  */


/*
 *      Quota functions that want to walk the inode lists..
 */
#ifdef CONFIG_QUOTA

/* Functions back in dquot.c */
void put_dquot_list(struct list_head *);
int remove_inode_dquot_ref(struct inode *, short, struct list_head *);

void remove_dquot_ref(struct super_block *sb, short type)
{
        struct inode *inode;
        struct list_head *act_head;
        LIST_HEAD(tofree_head);

        if (!sb->dq_op)
                return; /* nothing to do */
        /* We have to be protected against other CPUs */
        lock_kernel();          /* This lock is for quota code */
        spin_lock(&inode_lock); /* This lock is for inodes code */
 
        list_for_each(act_head, &inode_in_use) {
                inode = list_entry(act_head, struct inode, i_list);
                if (inode->i_sb == sb && IS_QUOTAINIT(inode))
                        remove_inode_dquot_ref(inode, type, &tofree_head);
        }
        list_for_each(act_head, &inode_unused) {
                inode = list_entry(act_head, struct inode, i_list);
                if (inode->i_sb == sb && IS_QUOTAINIT(inode))
                        remove_inode_dquot_ref(inode, type, &tofree_head);
        }
        list_for_each(act_head, &sb->s_dirty) {
                inode = list_entry(act_head, struct inode, i_list);
                if (IS_QUOTAINIT(inode))
                        remove_inode_dquot_ref(inode, type, &tofree_head);
        }
        list_for_each(act_head, &sb->s_locked_inodes) {
                inode = list_entry(act_head, struct inode, i_list);
                if (IS_QUOTAINIT(inode))
                        remove_inode_dquot_ref(inode, type, &tofree_head);
        }
        spin_unlock(&inode_lock);
        unlock_kernel();

        put_dquot_list(&tofree_head);
}

#endif