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

#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/random.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.
 */

#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 HASH_BITS       8
#define HASH_SIZE       (1UL << HASH_BITS)
#define HASH_MASK       (HASH_SIZE-1)

/*
 * 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, hashed if i_nlink > 0
 *  "dirty"  - valid inode, hashed if i_nlink > 0, dirty.
 *  "unused" - ready to be re-used. Not hashed.
 *
 * A "dirty" list is maintained for each super block,
 * allowing for low-overhead inode sync() operations.
 */

LIST_HEAD(inode_in_use);
static LIST_HEAD(inode_unused);
static struct list_head inode_hashtable[HASH_SIZE];

__u32 inode_generation_count = 0;

/*
 * 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..
 */
spinlock_t inode_lock = SPIN_LOCK_UNLOCKED;

/*
 * Statistics gathering..
 */
struct {
        int nr_inodes;
        int nr_free_inodes;
        int dummy[5];
} inodes_stat = {0, 0,};

int max_inodes;

/*
 * 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..
 */
void __mark_inode_dirty(struct inode *inode)
{
        struct super_block * sb = inode->i_sb;

        if (sb) {
                spin_lock(&inode_lock);
                if (!(inode->i_state & I_DIRTY)) {
                        inode->i_state |= I_DIRTY;
                        /* Only add valid (ie hashed) inodes to the dirty list */
                        if (!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)
{
        struct wait_queue wait = { current, NULL };

        add_wait_queue(&inode->i_wait, &wait);
repeat:
        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);
}

/*
 * These are initializations that only need to be done
 * once, because the fields are idempotent across use
 * of the inode..
 */
static inline void init_once(struct inode * inode)
{
        memset(inode, 0, sizeof(*inode));
        init_waitqueue(&inode->i_wait);
        INIT_LIST_HEAD(&inode->i_hash);
        INIT_LIST_HEAD(&inode->i_dentry);
        sema_init(&inode->i_sem, 1);
        sema_init(&inode->i_atomic_write, 1);
}

static inline void write_inode(struct inode *inode)
{
        if (inode->i_sb && inode->i_sb->s_op && inode->i_sb->s_op->write_inode)
                inode->i_sb->s_op->write_inode(inode);
}

static inline void sync_one(struct inode *inode)
{
        if (inode->i_state & I_LOCK) {
                spin_unlock(&inode_lock);
                __wait_on_inode(inode);
                spin_lock(&inode_lock);
        } else {
                list_del(&inode->i_list);
                list_add(&inode->i_list, &inode_in_use);
                /* Set I_LOCK, reset I_DIRTY */
                inode->i_state ^= I_DIRTY | I_LOCK;
                spin_unlock(&inode_lock);

                write_inode(inode);

                spin_lock(&inode_lock);
                inode->i_state &= ~I_LOCK;
                wake_up(&inode->i_wait);
        }
}

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));
}

/*
 * "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 * sb = sb_entry(super_blocks.next);

        /*
         * Search the super_blocks array for the device(s) to sync.
         */
        spin_lock(&inode_lock);
        for (; sb != sb_entry(&super_blocks); sb = sb_entry(sb->s_list.next)) {
                if (!sb->s_dev)
                        continue;
                if (dev && sb->s_dev != dev)
                        continue;

                sync_list(&sb->s_dirty);

                if (dev)
                        break;
        }
        spin_unlock(&inode_lock);
}

/*
 * Called with the spinlock already held..
 */
static void sync_all_inodes(void)
{
        struct super_block * sb = sb_entry(super_blocks.next);
        for (; sb != sb_entry(&super_blocks); sb = sb_entry(sb->s_list.next)) {
                if (!sb->s_dev)
                        continue;
                sync_list(&sb->s_dirty);
        }
}

/*
 * Needed by knfsd
 */
void write_inode_now(struct inode *inode)
{
        struct super_block * sb = inode->i_sb;

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

/*
 * 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)
{
        if (inode->i_nrpages)
                truncate_inode_pages(inode, 0);
        wait_on_inode(inode);
        if (IS_QUOTAINIT(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);

        inode->i_state = 0;
}

/*
 * Dispose-list gets a local list, so it doesn't need to
 * worry about list corruption. It releases the inode lock
 * while clearing the inodes.
 */
static void dispose_list(struct list_head * head)
{
        struct list_head *next;
        int count = 0;

        spin_unlock(&inode_lock);
        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);
                clear_inode(inode);
                count++;
        }

        /* Add them all to the unused list in one fell swoop */
        spin_lock(&inode_lock);
        list_splice(head, &inode_unused);
        inodes_stat.nr_free_inodes += count;
}

/*
 * 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;

        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;
                if (!inode->i_count) {
                        list_del(&inode->i_hash);
                        INIT_LIST_HEAD(&inode->i_hash);
                        list_del(&inode->i_list);
                        list_add(&inode->i_list, dispose);
                        inode->i_state |= I_FREEING;
                        continue;
                }
                busy = 1;
        }
        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..
 */
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(&sb->s_dirty, sb, &throw_away);
        dispose_list(&throw_away);
        spin_unlock(&inode_lock);

        return busy;
}

/*
 * 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_count | (inode)->i_state) == 0)
#define INODE(entry)    (list_entry(entry, struct inode, i_list))

static int __free_inodes(struct list_head * freeable)
{
        struct list_head *entry;
        int found = 0;

        entry = inode_in_use.next;
        while (entry != &inode_in_use) {
                struct list_head *tmp = entry;

                entry = entry->next;
                if (!CAN_UNUSE(INODE(tmp)))
                        continue;
                list_del(tmp);
                list_del(&INODE(tmp)->i_hash);
                INIT_LIST_HEAD(&INODE(tmp)->i_hash);
                list_add(tmp, freeable);
                list_entry(tmp, struct inode, i_list)->i_state = I_FREEING;
                found++;
        }

        return found;
}

static void free_inodes(void)
{
        LIST_HEAD(throw_away);
        if (__free_inodes(&throw_away))
                dispose_list(&throw_away);
}

/*
 * Searches the inodes list for freeable inodes,
 * shrinking the dcache before (and possible after,
 * if we're low)
 */
static void try_to_free_inodes(int goal)
{
        static int block;
        static struct wait_queue * wait_inode_freeing;
        LIST_HEAD(throw_away);
        
        /* We must make sure to not eat the inodes
           while the blocker task sleeps otherwise
           the blocker task may find none inode
           available. */
        if (block)
        {
                struct wait_queue __wait;

                __wait.task = current;
                add_wait_queue(&wait_inode_freeing, &__wait);
                for (;;)
                {
                        /* NOTE: we rely only on the inode_lock to be sure
                           to not miss the unblock event */
                        current->state = TASK_UNINTERRUPTIBLE;
                        spin_unlock(&inode_lock);
                        schedule();
                        spin_lock(&inode_lock);
                        if (!block)
                                break;
                }
                remove_wait_queue(&wait_inode_freeing, &__wait);
                current->state = TASK_RUNNING;
        }

        block = 1;
        /*
         * First stry to just get rid of unused inodes.
         *
         * If we can't reach our goal that way, we'll have
         * to try to shrink the dcache and sync existing
         * inodes..
         */
        goal -= __free_inodes(&throw_away);
        if (goal > 0) {
                spin_unlock(&inode_lock);
                prune_dcache(0, goal);
                spin_lock(&inode_lock);
                sync_all_inodes();
                __free_inodes(&throw_away);
        }
        if (!list_empty(&throw_away))
                dispose_list(&throw_away);
        block = 0;
        wake_up(&wait_inode_freeing);
}

/*
 * This is the externally visible routine for
 * inode memory management.
 */
void free_inode_memory(void)
{
        spin_lock(&inode_lock);
        free_inodes();
        spin_unlock(&inode_lock);
}


/*
 * This is called with the spinlock held, but releases
 * the lock when freeing or allocating inodes.
 * Look out! This returns with the inode lock held if
 * it got an inode..
 *
 * We do inode allocations two pages at a time to reduce
 * fragmentation.
 */
#define INODE_PAGE_ORDER        1
#define INODE_ALLOCATION_SIZE   (PAGE_SIZE << INODE_PAGE_ORDER)
#define INODES_PER_ALLOCATION   (INODE_ALLOCATION_SIZE/sizeof(struct inode))

static struct inode * grow_inodes(void)
{
        struct inode * inode;

        /*
         * Check whether to restock the unused list.
         */
        if (inodes_stat.nr_inodes > max_inodes) {
                struct list_head *tmp;
                try_to_free_inodes(inodes_stat.nr_inodes >> 2);
                tmp = inode_unused.next;
                if (tmp != &inode_unused) {
                        inodes_stat.nr_free_inodes--;
                        list_del(tmp);
                        inode = list_entry(tmp, struct inode, i_list);
                        return inode;
                }
                spin_unlock(&inode_lock);
                printk(KERN_WARNING
                       "grow_inodes: inode-max limit reached\n");
                return NULL;
        }
                
        spin_unlock(&inode_lock);
        inode = (struct inode *)__get_free_pages(GFP_KERNEL,INODE_PAGE_ORDER);
        if (inode) {
                int size;
                struct inode * tmp;

                size = INODE_ALLOCATION_SIZE - 2*sizeof(struct inode);
                tmp = inode;
                spin_lock(&inode_lock);
                do {
                        tmp++;
                        init_once(tmp);
                        list_add(&tmp->i_list, &inode_unused);
                        size -= sizeof(struct inode);
                } while (size >= 0);
                init_once(inode);
                /*
                 * Update the inode statistics
                 */
                inodes_stat.nr_inodes += INODES_PER_ALLOCATION;
                inodes_stat.nr_free_inodes += INODES_PER_ALLOCATION - 1;
                return inode;
        }

        /*
         * If the allocation failed, do an extensive pruning of 
         * the dcache and then try again to free some inodes.
         */
        prune_dcache(0, inodes_stat.nr_inodes >> 2);

        spin_lock(&inode_lock);
        free_inodes();
        {
                struct list_head *tmp = inode_unused.next;
                if (tmp != &inode_unused) {
                        inodes_stat.nr_free_inodes--;
                        list_del(tmp);
                        inode = list_entry(tmp, struct inode, i_list);
                        return inode;
                }
        }
        spin_unlock(&inode_lock);

        printk("grow_inodes: allocation failed\n");
        return NULL;
}

/*
 * Called with the inode lock held.
 */
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_sb != sb)
                        continue;
                if (inode->i_ino != ino)
                        continue;
                if (find_actor && !find_actor(inode, ino, opaque))
                        continue;
                inode->i_count++;
                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..
 */
void clean_inode(struct inode *inode)
{
        memset(&inode->u, 0, sizeof(inode->u));
        inode->i_sock = 0;
        inode->i_op = NULL;
        inode->i_nlink = 1;
        inode->i_writecount = 0;
        inode->i_size = 0;
        inode->i_generation = 0;
        memset(&inode->i_dquot, 0, sizeof(inode->i_dquot));
        sema_init(&inode->i_sem, 1);
}

/*
 * 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.
 */
struct inode * get_empty_inode(void)
{
        static unsigned long last_ino = 0;
        struct inode * inode;
        struct list_head * tmp;

        spin_lock(&inode_lock);
        tmp = inode_unused.next;
        if (tmp != &inode_unused) {
                list_del(tmp);
                inodes_stat.nr_free_inodes--;
                inode = list_entry(tmp, struct inode, i_list);
add_new_inode:
                list_add(&inode->i_list, &inode_in_use);
                inode->i_sb = NULL;
                inode->i_dev = 0;
                inode->i_ino = ++last_ino;
                inode->i_flags = 0;
                inode->i_count = 1;
                inode->i_state = 0;
                spin_unlock(&inode_lock);
                clean_inode(inode);
                return inode;
        }

        /*
         * Warning: if this succeeded, we will now
         * return with the inode lock.
         */
        inode = grow_inodes();
        if (inode)
                goto add_new_inode;

        return inode;
}

/*
 * This is called with 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;
        struct list_head * tmp = inode_unused.next;

        if (tmp != &inode_unused) {
                list_del(tmp);
                inodes_stat.nr_free_inodes--;
                inode = list_entry(tmp, struct inode, i_list);
add_new_inode:
                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_ino = ino;
                inode->i_flags = 0;
                inode->i_count = 1;
                inode->i_state = I_LOCK;
                spin_unlock(&inode_lock);

                clean_inode(inode);
                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;
        }

        /*
         * We need to expand. Note that "grow_inodes()" will
         * release the spinlock, but will return with the lock 
         * held again if the allocation succeeded.
         */
        inode = grow_inodes();
        if (inode) {
                /* We released the lock, so.. */
                struct inode * old = find_inode(sb, ino, head, find_actor, opaque);
                if (!old)
                        goto add_new_inode;
                list_add(&inode->i_list, &inode_unused);
                inodes_stat.nr_free_inodes++;
                spin_unlock(&inode_lock);
                wait_on_inode(old);
                return old;
        }
        return inode;
}

static inline unsigned long hash(struct super_block *sb, unsigned long i_ino)
{
        unsigned long tmp = i_ino | (unsigned long) sb;
        tmp = tmp + (tmp >> HASH_BITS);
        return tmp & HASH_MASK;
}

/* Yeah, I know about quadratic hash. Maybe, later. */
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;
                }
                inode->i_count--; /* compensate find_inode() */
        } else {
                counter = max_reserved + 1;
        }
        goto retry;
        
}

struct inode *igrab(struct inode *inode)
{
        spin_lock(&inode_lock);
        if (inode->i_state & I_FREEING)
                inode = NULL;
        else
                inode->i_count++;
        spin_unlock(&inode_lock);
        if (inode)
                wait_on_inode(inode);
        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) {
                spin_unlock(&inode_lock);
                wait_on_inode(inode);
                return inode;
        }
        /*
         * get_new_inode() will do the right thing, releasing
         * the inode lock and re-trying the search in case it
         * had to block at any point.
         */
        return get_new_inode(sb, ino, head, find_actor, opaque);
}

struct inode *iget(struct super_block *sb, unsigned long ino)
{
        return iget4(sb, ino, NULL, NULL);
}

void insert_inode_hash(struct inode *inode)
{
        struct list_head *head = inode_hashtable + hash(inode->i_sb, inode->i_ino);
        spin_lock(&inode_lock);
        list_add(&inode->i_hash, head);
        spin_unlock(&inode_lock);
}

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);
}

void iput(struct inode *inode)
{
        if (inode) {
                struct super_operations *op = NULL;

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

                spin_lock(&inode_lock);
                if (!--inode->i_count) {
                        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;
                                if (op && op->delete_inode) {
                                        void (*delete)(struct inode *) = op->delete_inode;
                                        spin_unlock(&inode_lock);
                                        delete(inode);
                                        spin_lock(&inode_lock);
                                }
                        }
                        if (list_empty(&inode->i_hash)) {
                                list_del(&inode->i_list);
                                INIT_LIST_HEAD(&inode->i_list);
                                inode->i_state|=I_FREEING;
                                spin_unlock(&inode_lock);
                                clear_inode(inode);
                                spin_lock(&inode_lock);
                                list_add(&inode->i_list, &inode_unused);
                                inodes_stat.nr_free_inodes++;
                        }
                        else if (!(inode->i_state & I_DIRTY)) {
                                list_del(&inode->i_list);
                                list_add(&inode->i_list, &inode_in_use);
                        }
#ifdef INODE_PARANOIA
if (inode->i_flock)
printk(KERN_ERR "iput: inode %s/%ld still has locks!\n",
kdevname(inode->i_dev), inode->i_ino);
if (!list_empty(&inode->i_dentry))
printk(KERN_ERR "iput: device %s inode %ld still has aliases!\n",
kdevname(inode->i_dev), inode->i_ino);
if (inode->i_count)
printk(KERN_ERR "iput: device %s inode %ld count changed, count=%d\n",
kdevname(inode->i_dev), inode->i_ino, inode->i_count);
if (atomic_read(&inode->i_sem.count) != 1)
printk(KERN_ERR "iput: Aieee, semaphore in use inode %s/%ld, count=%d\n",
kdevname(inode->i_dev), inode->i_ino, atomic_read(&inode->i_sem.count));
if (atomic_read(&inode->i_atomic_write.count) != 1)
printk(KERN_ERR "iput: Aieee, atomic write semaphore in use inode %s/%ld, count=%d\n",
kdevname(inode->i_dev), inode->i_ino, atomic_read(&inode->i_sem.count));
#endif
                }
                if (inode->i_count > (1<<31)) {
                        printk(KERN_ERR "iput: inode %s/%ld count wrapped\n",
                                kdevname(inode->i_dev), inode->i_ino);
                }
                spin_unlock(&inode_lock);
        }
}

int bmap(struct inode * inode, int block)
{
        if (inode->i_op && inode->i_op->bmap)
                return inode->i_op->bmap(inode, block);
        return 0;
}

/*
 * Initialize the hash tables and default
 * value for max inodes
 */
#define MAX_INODE (16384)

void __init inode_init(void)
{
        int i, max;
        struct list_head *head = inode_hashtable;

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

        /* Initial guess at reasonable inode number */
        max = num_physpages >> 1;
        if (max > MAX_INODE)
                max = MAX_INODE;
        max_inodes = max;

        /* Get a random number. */
        get_random_bytes (&inode_generation_count,
                          sizeof (inode_generation_count));
}

/* This belongs in file_table.c, not here... */
int fs_may_remount_ro(struct super_block *sb)
{
        struct file *file;

        /* Check that no files are currently opened for writing. */
        for (file = inuse_filps; file; file = file->f_next) {
                struct inode *inode;
                if (!file->f_dentry)
                        continue;
                inode = file->f_dentry->d_inode;
                if (!inode || inode->i_sb != sb)
                        continue;

                /* File with pending delete? */
                if (inode->i_nlink == 0)
                        return 0;

                /* Writable file? */
                if (S_ISREG(inode->i_mode) && (file->f_mode & FMODE_WRITE))
                        return 0;
        }
        return 1; /* Tis' cool bro. */
}

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 (inode);
}   /*  End Function update_atime  */

/* This function is called by nfsd. */
struct inode *iget_in_use(struct super_block *sb, unsigned long ino)
{
        struct list_head * head = inode_hashtable + hash(sb,ino);
        struct inode * inode;

        spin_lock(&inode_lock);
        inode = find_inode(sb, ino, head, NULL, NULL);
        if (inode) {
                spin_unlock(&inode_lock);
                wait_on_inode(inode);
        }
        else
                inode = get_new_inode (sb, ino, head, NULL, NULL);

        /* When we get the inode, we have to check if it is in use. We
           have to release it if it is not. */
        if (inode) {
                spin_lock(&inode_lock);
                if (inode->i_nlink == 0 && inode->i_count == 1) {
                        --inode->i_count;
                        list_del(&inode->i_hash);
                        INIT_LIST_HEAD(&inode->i_hash);
                        list_del(&inode->i_list);
                        INIT_LIST_HEAD(&inode->i_list);
                        if (list_empty(&inode->i_hash)) {
                                list_del(&inode->i_list);
                                INIT_LIST_HEAD(&inode->i_list);
                                spin_unlock(&inode_lock);
                                clear_inode(inode);
                                spin_lock(&inode_lock);
                                list_add(&inode->i_list, &inode_unused);
                                inodes_stat.nr_free_inodes++;
                        }
                        else if (!(inode->i_state & I_DIRTY)) {
                                list_del(&inode->i_list);
                                list_add(&inode->i_list, &inode_in_use);
                        }
                        inode = NULL;
                }
                spin_unlock(&inode_lock);
        }
        return inode;
}