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

#include <linux/config.h>
#include <linux/fs.h>
#include <linux/mm.h>
#include <linux/dcache.h>
#include <linux/init.h>
#include <linux/quotaops.h>
#include <linux/slab.h>
#include <linux/writeback.h>
#include <linux/module.h>
#include <linux/backing-dev.h>
#include <linux/wait.h>
#include <linux/hash.h>
#include <linux/security.h>

/*
 * This is needed for the following functions:
 *  - inode_has_buffers
 *  - invalidate_inode_buffers
 *  - fsync_bdev
 *  - invalidate_bdev
 *
 * FIXME: remove all knowledge of the buffer layer from this file
 */
#include <linux/buffer_head.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.
 */

LIST_HEAD(inode_in_use);
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..
 */
spinlock_t inode_lock = SPIN_LOCK_UNLOCKED;

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

static kmem_cache_t * inode_cachep;

static struct inode *alloc_inode(struct super_block *sb)
{
	static struct address_space_operations empty_aops;
	static struct inode_operations empty_iops;
	static struct file_operations empty_fops;
	struct inode *inode;

	if (sb->s_op->alloc_inode)
		inode = sb->s_op->alloc_inode(sb);
	else
		inode = (struct inode *) kmem_cache_alloc(inode_cachep, SLAB_KERNEL);

	if (inode) {
		struct address_space * const mapping = &inode->i_data;

		inode->i_security = NULL;
		if (security_ops->inode_alloc_security(inode)) {
			if (inode->i_sb->s_op->destroy_inode)
				inode->i_sb->s_op->destroy_inode(inode);
			else
				kmem_cache_free(inode_cachep, (inode));
			return NULL;
		}
		inode->i_sb = sb;
		inode->i_dev = sb->s_dev;
		inode->i_blkbits = sb->s_blocksize_bits;
		inode->i_flags = 0;
		atomic_set(&inode->i_count, 1);
		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_bytes = 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;

		mapping->a_ops = &empty_aops;
 		mapping->host = inode;
		mapping->gfp_mask = GFP_HIGHUSER;
		mapping->dirtied_when = 0;
		mapping->assoc_mapping = NULL;
		mapping->backing_dev_info = &default_backing_dev_info;
		if (sb->s_bdev)
			inode->i_data.backing_dev_info = sb->s_bdev->bd_inode->i_mapping->backing_dev_info;
		memset(&inode->u, 0, sizeof(inode->u));
		inode->i_mapping = mapping;
	}
	return inode;
}

static void destroy_inode(struct inode *inode) 
{
	if (inode_has_buffers(inode))
		BUG();
	security_ops->inode_free_security(inode);
	if (inode->i_sb->s_op->destroy_inode)
		inode->i_sb->s_op->destroy_inode(inode);
	else
		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.
 */
void inode_init_once(struct inode *inode)
{
	memset(inode, 0, sizeof(*inode));
	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_data.io_pages);
	INIT_LIST_HEAD(&inode->i_dentry);
	INIT_LIST_HEAD(&inode->i_devices);
	sema_init(&inode->i_sem, 1);
	INIT_RADIX_TREE(&inode->i_data.page_tree, GFP_ATOMIC);
	rwlock_init(&inode->i_data.page_lock);
	spin_lock_init(&inode->i_data.i_shared_lock);
	INIT_LIST_HEAD(&inode->i_data.private_list);
	spin_lock_init(&inode->i_data.private_lock);
	INIT_LIST_HEAD(&inode->i_data.i_mmap);
	INIT_LIST_HEAD(&inode->i_data.i_mmap_shared);
}

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)
		inode_init_once(inode);
}

/*
 * inode_lock must be held
 */
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--;
}

/**
 * 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_io, 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;
	struct block_device *bdev = bdget(kdev_t_to_nr(dev));
	int res;

	if (!bdev)
		return 0;

	if (do_sync)
		fsync_bdev(bdev);

	res = 0;
	sb = get_super(bdev);
	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_bdev(bdev, 0);
	bdput(bdev);
	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_init(&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);
}

/*
 * This is called from kswapd when we think we need some
 * more memory, but aren't really sure how much. So we
 * carefully try to free a _bit_ of our icache, but not
 * too much.
 *
 * Priority:
 *   1 - very urgent: shrink everything
 *  ...
 *   6 - base-level: try to shrink a bit.
 */
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);
	kmem_cache_shrink(inode_cachep);
	return 0;
}

/*
 * 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, struct list_head *head, int (*test)(struct inode *, void *), void *data)
{
	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 (!test(inode, data))
			continue;
		break;
	}
	return inode;
}

/*
 * find_inode_fast is the fast path version of find_inode, see the comment at
 * iget_locked for details.
 */
static struct inode * find_inode_fast(struct super_block * sb, struct list_head *head, unsigned long ino)
{
	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;
		break;
	}
	return inode;
}

/**
 *	new_inode 	- obtain an inode
 *	@sb: superblock
 *
 *	Allocates a new inode for given superblock.
 */
 
struct inode *new_inode(struct super_block *sb)
{
	static unsigned long last_ino;
	struct inode * inode;

	spin_lock_prefetch(&inode_lock);
	
	inode = alloc_inode(sb);
	if (inode) {
		spin_lock(&inode_lock);
		inodes_stat.nr_inodes++;
		list_add(&inode->i_list, &inode_in_use);
		inode->i_ino = ++last_ino;
		inode->i_state = 0;
		spin_unlock(&inode_lock);
	}
	return inode;
}

void unlock_new_inode(struct 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|I_NEW);
	wake_up_inode(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, struct list_head *head, int (*test)(struct inode *, void *), int (*set)(struct inode *, void *), void *data)
{
	struct inode * inode;

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

		spin_lock(&inode_lock);
		/* We released the lock, so.. */
		old = find_inode(sb, head, test, data);
		if (!old) {
			if (set(inode, data))
				goto set_failed;

			inodes_stat.nr_inodes++;
			list_add(&inode->i_list, &inode_in_use);
			list_add(&inode->i_hash, head);
			inode->i_state = I_LOCK|I_NEW;
			spin_unlock(&inode_lock);

			/* Return the locked inode with I_NEW set, the
			 * caller is responsible for filling in the contents
			 */
			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;

set_failed:
	spin_unlock(&inode_lock);
	destroy_inode(inode);
	return NULL;
}

/*
 * get_new_inode_fast is the fast path version of get_new_inode, see the
 * comment at iget_locked for details.
 */
static struct inode * get_new_inode_fast(struct super_block *sb, struct list_head *head, unsigned long ino)
{
	struct inode * inode;

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

		spin_lock(&inode_lock);
		/* We released the lock, so.. */
		old = find_inode_fast(sb, head, ino);
		if (!old) {
			inode->i_ino = ino;
			inodes_stat.nr_inodes++;
			list_add(&inode->i_list, &inode_in_use);
			list_add(&inode->i_hash, head);
			inode->i_state = I_LOCK|I_NEW;
			spin_unlock(&inode_lock);

			/* Return the locked inode with I_NEW set, the
			 * caller is responsible for filling in the contents
			 */
			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 hashval)
{
	unsigned long tmp = hashval + ((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);
		res = counter++;
		inode = find_inode_fast(sb, head, res);
		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;
}

/*
 * This is iget without the read_inode portion of get_new_inode
 * the filesystem gets back a new locked and hashed inode and gets
 * to fill it in before unlocking it via unlock_new_inode().
 */
struct inode *iget5_locked(struct super_block *sb, unsigned long hashval, int (*test)(struct inode *, void *), int (*set)(struct inode *, void *), void *data)
{
	struct list_head * head = inode_hashtable + hash(sb, hashval);
	struct inode * inode;

	spin_lock(&inode_lock);
	inode = find_inode(sb, head, test, data);
	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, head, test, set, data);
}

/*
 * Because most filesystems are based on 32-bit unique inode numbers some
 * functions are duplicated to keep iget_locked as a fast path. We can avoid
 * unnecessary pointer dereferences and function calls for this specific
 * case. The duplicated functions (find_inode_fast and get_new_inode_fast)
 * have the same pre- and post-conditions as their original counterparts.
 */
struct inode *iget_locked(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_fast(sb, head, ino);
	if (inode) {
		__iget(inode);
		spin_unlock(&inode_lock);
		wait_on_inode(inode);
		return inode;
	}
	spin_unlock(&inode_lock);

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

EXPORT_SYMBOL(iget5_locked);
EXPORT_SYMBOL(iget_locked);
EXPORT_SYMBOL(unlock_new_inode);

/**
 *	__insert_inode_hash - hash an inode
 *	@inode: unhashed inode
 *	@hashval: unsigned long value used to locate this object in the
 *		inode_hashtable.
 *
 *	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, unsigned long hashval)
{
	struct list_head *head = &anon_hash_chain;
	if (inode->i_sb)
		head = inode_hashtable + hash(inode->i_sb, hashval);
	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_init(&inode->i_hash);
	spin_unlock(&inode_lock);
}

void generic_delete_inode(struct inode *inode)
{
	struct super_operations *op = inode->i_sb->s_op;

	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);

	security_ops->inode_delete(inode);

	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();
	destroy_inode(inode);
}
EXPORT_SYMBOL(generic_delete_inode);

static void generic_forget_inode(struct inode *inode)
{
	struct super_block *sb = inode->i_sb;

	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);
}

/*
 * Normal UNIX filesystem behaviour: delete the
 * inode when the usage count drops to zero, and
 * i_nlink is zero.
 */
static void generic_drop_inode(struct inode *inode)
{
	if (!inode->i_nlink)
		generic_delete_inode(inode);
	else
		generic_forget_inode(inode);
}

/*
 * Called when we're dropping the last reference
 * to an inode. 
 *
 * Call the FS "drop()" function, defaulting to
 * the legacy UNIX filesystem behaviour..
 *
 * NOTE! NOTE! NOTE! We're called with the inode lock
 * held, and the drop function is supposed to release
 * the lock!
 */
static inline void iput_final(struct inode *inode)
{
	struct super_operations *op = inode->i_sb->s_op;
	void (*drop)(struct inode *) = generic_drop_inode;

	if (op && op->drop_inode)
		drop = op->drop_inode;
	drop(inode);
}

/**
 *	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_operations *op = inode->i_sb->s_op;

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

		if (op && op->put_inode)
			op->put_inode(inode);

		if (atomic_dec_and_lock(&inode->i_count, &inode_lock))
			iput_final(inode);
	}
}

/**
 *	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;
}

/**
 *	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);
}

int inode_needs_sync(struct inode *inode)
{
	if (IS_SYNC(inode))
		return 1;
	if (S_ISDIR(inode->i_mode) && IS_DIRSYNC(inode))
		return 1;
	return 0;
}
EXPORT_SYMBOL(inode_needs_sync);

/*
 *	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 *, int, struct list_head *);

void remove_dquot_ref(struct super_block *sb, int 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_io) {
		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

/*
 * Hashed waitqueues for wait_on_inode().  The table is pretty small - the
 * kernel doesn't lock many inodes at the same time.
 */
#define I_WAIT_TABLE_ORDER	3
static struct i_wait_queue_head {
	wait_queue_head_t wqh;
} ____cacheline_aligned_in_smp i_wait_queue_heads[1<<I_WAIT_TABLE_ORDER];

/*
 * Return the address of the waitqueue_head to be used for this inode
 */
static wait_queue_head_t *i_waitq_head(struct inode *inode)
{
	return &i_wait_queue_heads[hash_ptr(inode, I_WAIT_TABLE_ORDER)].wqh;
}

void __wait_on_inode(struct inode *inode)
{
	DECLARE_WAITQUEUE(wait, current);
	wait_queue_head_t *wq = i_waitq_head(inode);

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

void wake_up_inode(struct inode *inode)
{
	wait_queue_head_t *wq = i_waitq_head(inode);

	/*
	 * Prevent speculative execution through spin_unlock(&inode_lock);
	 */
	smp_mb();
	if (waitqueue_active(wq))
		wake_up_all(wq);
}

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

	for (i = 0; i < ARRAY_SIZE(i_wait_queue_heads); i++)
		init_waitqueue_head(&i_wait_queue_heads[i].wqh);

	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("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");
}