text: /*
   * (C) 1997 Linus Torvalds
   * (C) 1999 Andrea Arcangeli <andrea@suse.de> (dynamic inode allocation)
   */
  #include <linux/export.h>
  #include <linux/fs.h>
  #include <linux/mm.h>
  #include <linux/backing-dev.h>
  #include <linux/hash.h>
  #include <linux/swap.h>
  #include <linux/security.h>
  #include <linux/cdev.h>
  #include <linux/bootmem.h>
  #include <linux/fsnotify.h>
  #include <linux/mount.h>
  #include <linux/posix_acl.h>
  #include <linux/prefetch.h>
  #include <linux/buffer_head.h> /* for inode_has_buffers */
  #include <linux/ratelimit.h>
  #include "internal.h"
  
  /*
   * Inode locking rules:
   *
   * inode->i_lock protects:
   *   inode->i_state, inode->i_hash, __iget()
   * inode->i_sb->s_inode_lru_lock protects:
   *   inode->i_sb->s_inode_lru, inode->i_lru
   * inode_sb_list_lock protects:
   *   sb->s_inodes, inode->i_sb_list
   * bdi->wb.list_lock protects:
   *   bdi->wb.b_{dirty,io,more_io}, inode->i_wb_list
   * inode_hash_lock protects:
   *   inode_hashtable, inode->i_hash
   *
   * Lock ordering:
   *
   * inode_sb_list_lock
   *   inode->i_lock
   *     inode->i_sb->s_inode_lru_lock
   *
   * bdi->wb.list_lock
   *   inode->i_lock
   *
   * inode_hash_lock
   *   inode_sb_list_lock
   *   inode->i_lock
   *
   * iunique_lock
   *   inode_hash_lock
   */
  
  static unsigned int i_hash_mask __read_mostly;
  static unsigned int i_hash_shift __read_mostly;
  static struct hlist_head *inode_hashtable __read_mostly;
  static __cacheline_aligned_in_smp DEFINE_SPINLOCK(inode_hash_lock);
  
  __cacheline_aligned_in_smp DEFINE_SPINLOCK(inode_sb_list_lock);
  
  /*
   * Empty aops. Can be used for the cases where the user does not
   * define any of the address_space operations.
   */
  const struct address_space_operations empty_aops = {
  };
  EXPORT_SYMBOL(empty_aops);
  
  /*
   * Statistics gathering..
   */
  struct inodes_stat_t inodes_stat;
  
  static DEFINE_PER_CPU(unsigned int, nr_inodes);
  static DEFINE_PER_CPU(unsigned int, nr_unused);
  
  static struct kmem_cache *inode_cachep __read_mostly;
  
  static int get_nr_inodes(void)
  {
  	int i;
  	int sum = 0;
  	for_each_possible_cpu(i)
  		sum += per_cpu(nr_inodes, i);
  	return sum < 0 ? 0 : sum;
  }
  
  static inline int get_nr_inodes_unused(void)
  {
  	int i;
  	int sum = 0;
  	for_each_possible_cpu(i)
  		sum += per_cpu(nr_unused, i);
  	return sum < 0 ? 0 : sum;
  }
  
  int get_nr_dirty_inodes(void)
  {
  	/* not actually dirty inodes, but a wild approximation */
  	int nr_dirty = get_nr_inodes() - get_nr_inodes_unused();
  	return nr_dirty > 0 ? nr_dirty : 0;
  }
  
  /*
   * Handle nr_inode sysctl
   */
  #ifdef CONFIG_SYSCTL
  int proc_nr_inodes(ctl_table *table, int write,
  		   void __user *buffer, size_t *lenp, loff_t *ppos)
  {
  	inodes_stat.nr_inodes = get_nr_inodes();
  	inodes_stat.nr_unused = get_nr_inodes_unused();
  	return proc_dointvec(table, write, buffer, lenp, ppos);
  }
  #endif
  
  /**
   * inode_init_always - perform inode structure intialisation
   * @sb: superblock inode belongs to
   * @inode: inode to initialise
   *
   * These are initializations that need to be done on every inode
   * allocation as the fields are not initialised by slab allocation.
   */
  int inode_init_always(struct super_block *sb, struct inode *inode)
  {
  	static const struct inode_operations empty_iops;
  	static const struct file_operations empty_fops;
  	struct address_space *const mapping = &inode->i_data;
  
  	inode->i_sb = sb;
  	inode->i_blkbits = sb->s_blocksize_bits;
  	inode->i_flags = 0;
  	atomic_set(&inode->i_count, 1);
  	inode->i_op = &empty_iops;
  	inode->i_fop = &empty_fops;
  	inode->__i_nlink = 1;
  	inode->i_opflags = 0;
  	i_uid_write(inode, 0);
  	i_gid_write(inode, 0);
  	atomic_set(&inode->i_writecount, 0);
  	inode->i_size = 0;
  	inode->i_blocks = 0;
  	inode->i_bytes = 0;
  	inode->i_generation = 0;
  #ifdef CONFIG_QUOTA
  	memset(&inode->i_dquot, 0, sizeof(inode->i_dquot));
  #endif
  	inode->i_pipe = NULL;
  	inode->i_bdev = NULL;
  	inode->i_cdev = NULL;
  	inode->i_rdev = 0;
  	inode->dirtied_when = 0;
  
  	if (security_inode_alloc(inode))
  		goto out;
  	spin_lock_init(&inode->i_lock);
  	lockdep_set_class(&inode->i_lock, &sb->s_type->i_lock_key);
  
  	mutex_init(&inode->i_mutex);
  	lockdep_set_class(&inode->i_mutex, &sb->s_type->i_mutex_key);
  
  	atomic_set(&inode->i_dio_count, 0);
  
  	mapping->a_ops = &empty_aops;
  	mapping->host = inode;
  	mapping->flags = 0;
  
          //mapping_set_gfp_mask(mapping, (GFP_HIGHUSER_MOVABLE & ~__GFP_HIGHMEM) | __GFP_SLOWHIGHMEM);
          mapping_set_gfp_mask(mapping, GFP_HIGHUSER_MOVABLE);
  
  	mapping->private_data = NULL;
  	mapping->backing_dev_info = &default_backing_dev_info;
  	mapping->writeback_index = 0;
  
  	/*
  	 * If the block_device provides a backing_dev_info for client
  	 * inodes then use that.  Otherwise the inode share the bdev's
  	 * backing_dev_info.
  	 */
  	if (sb->s_bdev) {
  		struct backing_dev_info *bdi;
  
  		bdi = sb->s_bdev->bd_inode->i_mapping->backing_dev_info;
  		mapping->backing_dev_info = bdi;
  	}
  	inode->i_private = NULL;
  	inode->i_mapping = mapping;
  	INIT_HLIST_HEAD(&inode->i_dentry);	/* buggered by rcu freeing */
  #ifdef CONFIG_FS_POSIX_ACL
  	inode->i_acl = inode->i_default_acl = ACL_NOT_CACHED;
  #endif
  
  #ifdef CONFIG_FSNOTIFY
  	inode->i_fsnotify_mask = 0;
  #endif
  
  	this_cpu_inc(nr_inodes);
  
  	return 0;
  out:
  	return -ENOMEM;
  }
  EXPORT_SYMBOL(inode_init_always);
  
  static struct inode *alloc_inode(struct super_block *sb)
  {
  	struct inode *inode;
  
  	if (sb->s_op->alloc_inode)
  		inode = sb->s_op->alloc_inode(sb);
  	else
  		inode = kmem_cache_alloc(inode_cachep, GFP_KERNEL);
  
  	if (!inode)
  		return NULL;
  
  	if (unlikely(inode_init_always(sb, 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;
  	}
  
  	return inode;
  }
  
  void free_inode_nonrcu(struct inode *inode)
  {
  	kmem_cache_free(inode_cachep, inode);
  }
  EXPORT_SYMBOL(free_inode_nonrcu);
  
  void __destroy_inode(struct inode *inode)
  {
  	BUG_ON(inode_has_buffers(inode));
  	security_inode_free(inode);
  	fsnotify_inode_delete(inode);
  	if (!inode->i_nlink) {
  		WARN_ON(atomic_long_read(&inode->i_sb->s_remove_count) == 0);
  		atomic_long_dec(&inode->i_sb->s_remove_count);
  	}
  
  #ifdef CONFIG_FS_POSIX_ACL
  	if (inode->i_acl && inode->i_acl != ACL_NOT_CACHED)
  		posix_acl_release(inode->i_acl);
  	if (inode->i_default_acl && inode->i_default_acl != ACL_NOT_CACHED)
  		posix_acl_release(inode->i_default_acl);
  #endif
  	this_cpu_dec(nr_inodes);
  }
  EXPORT_SYMBOL(__destroy_inode);
  
  static void i_callback(struct rcu_head *head)
  {
  	struct inode *inode = container_of(head, struct inode, i_rcu);
  	kmem_cache_free(inode_cachep, inode);
  }
  
  static void destroy_inode(struct inode *inode)
  {
  	BUG_ON(!list_empty(&inode->i_lru));
  	__destroy_inode(inode);
  	if (inode->i_sb->s_op->destroy_inode)
  		inode->i_sb->s_op->destroy_inode(inode);
  	else
  		call_rcu(&inode->i_rcu, i_callback);
  }
  
  /**
   * drop_nlink - directly drop an inode's link count
   * @inode: inode
   *
   * This is a low-level filesystem helper to replace any
   * direct filesystem manipulation of i_nlink.  In cases
   * where we are attempting to track writes to the
   * filesystem, a decrement to zero means an imminent
   * write when the file is truncated and actually unlinked
   * on the filesystem.
   */
  void drop_nlink(struct inode *inode)
  {
  	WARN_ON(inode->i_nlink == 0);
  	inode->__i_nlink--;
  	if (!inode->i_nlink)
  		atomic_long_inc(&inode->i_sb->s_remove_count);
  }
  EXPORT_SYMBOL(drop_nlink);
  
  /**
   * clear_nlink - directly zero an inode's link count
   * @inode: inode
   *
   * This is a low-level filesystem helper to replace any
   * direct filesystem manipulation of i_nlink.  See
   * drop_nlink() for why we care about i_nlink hitting zero.
   */
  void clear_nlink(struct inode *inode)
  {
  	if (inode->i_nlink) {
  		inode->__i_nlink = 0;
  		atomic_long_inc(&inode->i_sb->s_remove_count);
  	}
  }
  EXPORT_SYMBOL(clear_nlink);
  
  /**
   * set_nlink - directly set an inode's link count
   * @inode: inode
   * @nlink: new nlink (should be non-zero)
   *
   * This is a low-level filesystem helper to replace any
   * direct filesystem manipulation of i_nlink.
   */
  void set_nlink(struct inode *inode, unsigned int nlink)
  {
  	if (!nlink) {
  		clear_nlink(inode);
  	} else {
  		/* Yes, some filesystems do change nlink from zero to one */
  		if (inode->i_nlink == 0)
  			atomic_long_dec(&inode->i_sb->s_remove_count);
  
  		inode->__i_nlink = nlink;
  	}
  }
  EXPORT_SYMBOL(set_nlink);
  
  /**
   * inc_nlink - directly increment an inode's link count
   * @inode: inode
   *
   * This is a low-level filesystem helper to replace any
   * direct filesystem manipulation of i_nlink.  Currently,
   * it is only here for parity with dec_nlink().
   */
  void inc_nlink(struct inode *inode)
  {
  	if (WARN_ON(inode->i_nlink == 0))
  		atomic_long_dec(&inode->i_sb->s_remove_count);
  
  	inode->__i_nlink++;
  }
  EXPORT_SYMBOL(inc_nlink);
  
  void address_space_init_once(struct address_space *mapping)
  {
  	memset(mapping, 0, sizeof(*mapping));
  	INIT_RADIX_TREE(&mapping->page_tree, GFP_ATOMIC);
  	spin_lock_init(&mapping->tree_lock);
  	mutex_init(&mapping->i_mmap_mutex);
  	INIT_LIST_HEAD(&mapping->private_list);
  	spin_lock_init(&mapping->private_lock);
  	mapping->i_mmap = RB_ROOT;
  	INIT_LIST_HEAD(&mapping->i_mmap_nonlinear);
  }
  EXPORT_SYMBOL(address_space_init_once);
  
  /*
   * 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_HLIST_NODE(&inode->i_hash);
  	INIT_LIST_HEAD(&inode->i_devices);
  	INIT_LIST_HEAD(&inode->i_wb_list);
  	INIT_LIST_HEAD(&inode->i_lru);
  	address_space_init_once(&inode->i_data);
  	i_size_ordered_init(inode);
  #ifdef CONFIG_FSNOTIFY
  	INIT_HLIST_HEAD(&inode->i_fsnotify_marks);
  #endif
  }
  EXPORT_SYMBOL(inode_init_once);
  
  static void init_once(void *foo)
  {
  	struct inode *inode = (struct inode *) foo;
  
  	inode_init_once(inode);
  }
  
  /*
   * inode->i_lock must be held
   */
  void __iget(struct inode *inode)
  {
  	atomic_inc(&inode->i_count);
  }
  
  /*
   * get additional reference to inode; caller must already hold one.
   */
  void ihold(struct inode *inode)
  {
  	WARN_ON(atomic_inc_return(&inode->i_count) < 2);
  }
  EXPORT_SYMBOL(ihold);
  
  static void inode_lru_list_add(struct inode *inode)
  {
  	spin_lock(&inode->i_sb->s_inode_lru_lock);
  	if (list_empty(&inode->i_lru)) {
  		list_add(&inode->i_lru, &inode->i_sb->s_inode_lru);
  		inode->i_sb->s_nr_inodes_unused++;
  		this_cpu_inc(nr_unused);
  	}
  	spin_unlock(&inode->i_sb->s_inode_lru_lock);
  }
  
  /*
   * Add inode to LRU if needed (inode is unused and clean).
   *
   * Needs inode->i_lock held.
   */
  void inode_add_lru(struct inode *inode)
  {
  	if (!(inode->i_state & (I_DIRTY | I_SYNC | I_FREEING | I_WILL_FREE)) &&
  	    !atomic_read(&inode->i_count) && inode->i_sb->s_flags & MS_ACTIVE)
  		inode_lru_list_add(inode);
  }
  
  
  static void inode_lru_list_del(struct inode *inode)
  {
  	spin_lock(&inode->i_sb->s_inode_lru_lock);
  	if (!list_empty(&inode->i_lru)) {
  		list_del_init(&inode->i_lru);
  		inode->i_sb->s_nr_inodes_unused--;
  		this_cpu_dec(nr_unused);
  	}
  	spin_unlock(&inode->i_sb->s_inode_lru_lock);
  }
  
  /**
   * inode_sb_list_add - add inode to the superblock list of inodes
   * @inode: inode to add
   */
  void inode_sb_list_add(struct inode *inode)
  {
  	spin_lock(&inode_sb_list_lock);
  	list_add(&inode->i_sb_list, &inode->i_sb->s_inodes);
  	spin_unlock(&inode_sb_list_lock);
  }
  EXPORT_SYMBOL_GPL(inode_sb_list_add);
  
  static inline void inode_sb_list_del(struct inode *inode)
  {
  	if (!list_empty(&inode->i_sb_list)) {
  		spin_lock(&inode_sb_list_lock);
  		list_del_init(&inode->i_sb_list);
  		spin_unlock(&inode_sb_list_lock);
  	}
  }
  
  static unsigned long hash(struct super_block *sb, unsigned long hashval)
  {
  	unsigned long tmp;
  
  	tmp = (hashval * (unsigned long)sb) ^ (GOLDEN_RATIO_PRIME + hashval) /
  			L1_CACHE_BYTES;
  	tmp = tmp ^ ((tmp ^ GOLDEN_RATIO_PRIME) >> i_hash_shift);
  	return tmp & i_hash_mask;
  }
  
  /**
   *	__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.
   */
  void __insert_inode_hash(struct inode *inode, unsigned long hashval)
  {
  	struct hlist_head *b = inode_hashtable + hash(inode->i_sb, hashval);
  
  	spin_lock(&inode_hash_lock);
  	spin_lock(&inode->i_lock);
  	hlist_add_head(&inode->i_hash, b);
  	spin_unlock(&inode->i_lock);
  	spin_unlock(&inode_hash_lock);
  }
  EXPORT_SYMBOL(__insert_inode_hash);
  
  /**
   *	__remove_inode_hash - remove an inode from the hash
   *	@inode: inode to unhash
   *
   *	Remove an inode from the superblock.
   */
  void __remove_inode_hash(struct inode *inode)
  {
  	spin_lock(&inode_hash_lock);
  	spin_lock(&inode->i_lock);
  	hlist_del_init(&inode->i_hash);
  	spin_unlock(&inode->i_lock);
  	spin_unlock(&inode_hash_lock);
  }
  EXPORT_SYMBOL(__remove_inode_hash);
  
  void clear_inode(struct inode *inode)
  {
  	might_sleep();
  	/*
  	 * We have to cycle tree_lock here because reclaim can be still in the
  	 * process of removing the last page (in __delete_from_page_cache())
  	 * and we must not free mapping under it.
  	 */
  	spin_lock_irq(&inode->i_data.tree_lock);
  	BUG_ON(inode->i_data.nrpages);
  	spin_unlock_irq(&inode->i_data.tree_lock);
  	BUG_ON(!list_empty(&inode->i_data.private_list));
  	BUG_ON(!(inode->i_state & I_FREEING));
  	BUG_ON(inode->i_state & I_CLEAR);
  	/* don't need i_lock here, no concurrent mods to i_state */
  	inode->i_state = I_FREEING | I_CLEAR;
  }
  EXPORT_SYMBOL(clear_inode);
  
  /*
   * Free the inode passed in, removing it from the lists it is still connected
   * to. We remove any pages still attached to the inode and wait for any IO that
   * is still in progress before finally destroying the inode.
   *
   * An inode must already be marked I_FREEING so that we avoid the inode being
   * moved back onto lists if we race with other code that manipulates the lists
   * (e.g. writeback_single_inode). The caller is responsible for setting this.
   *
   * An inode must already be removed from the LRU list before being evicted from
   * the cache. This should occur atomically with setting the I_FREEING state
   * flag, so no inodes here should ever be on the LRU when being evicted.
   */
  static void evict(struct inode *inode)
  {
  	const struct super_operations *op = inode->i_sb->s_op;
  
  	BUG_ON(!(inode->i_state & I_FREEING));
  	BUG_ON(!list_empty(&inode->i_lru));
  
  	if (!list_empty(&inode->i_wb_list))
  		inode_wb_list_del(inode);
  
  	inode_sb_list_del(inode);
  
  	/*
  	 * Wait for flusher thread to be done with the inode so that filesystem
  	 * does not start destroying it while writeback is still running. Since
  	 * the inode has I_FREEING set, flusher thread won't start new work on
  	 * the inode.  We just have to wait for running writeback to finish.
  	 */
  	inode_wait_for_writeback(inode);
  
  	if (op->evict_inode) {
  		op->evict_inode(inode);
  	} else {
  		if (inode->i_data.nrpages)
  			truncate_inode_pages(&inode->i_data, 0);
  		clear_inode(inode);
  	}
  	if (S_ISBLK(inode->i_mode) && inode->i_bdev)
  		bd_forget(inode);
  	if (S_ISCHR(inode->i_mode) && inode->i_cdev)
  		cd_forget(inode);
  
  	remove_inode_hash(inode);
  
  	spin_lock(&inode->i_lock);
  	wake_up_bit(&inode->i_state, __I_NEW);
  	BUG_ON(inode->i_state != (I_FREEING | I_CLEAR));
  	spin_unlock(&inode->i_lock);
  
  	destroy_inode(inode);
  }
  
  /*
   * dispose_list - dispose of the contents of a local list
   * @head: the head of the list to free
   *
   * 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)
  {
  	while (!list_empty(head)) {
  		struct inode *inode;
  
  		inode = list_first_entry(head, struct inode, i_lru);
  		list_del_init(&inode->i_lru);
  
  		evict(inode);
  	}
  }
  
  /**
   * evict_inodes	- evict all evictable inodes for a superblock
   * @sb:		superblock to operate on
   *
   * Make sure that no inodes with zero refcount are retained.  This is
   * called by superblock shutdown after having MS_ACTIVE flag removed,
   * so any inode reaching zero refcount during or after that call will
   * be immediately evicted.
   */
  void evict_inodes(struct super_block *sb)
  {
  	struct inode *inode, *next;
  	LIST_HEAD(dispose);
  
  	spin_lock(&inode_sb_list_lock);
  	list_for_each_entry_safe(inode, next, &sb->s_inodes, i_sb_list) {
  		if (atomic_read(&inode->i_count))
  			continue;
  
  		spin_lock(&inode->i_lock);
  		if (inode->i_state & (I_NEW | I_FREEING | I_WILL_FREE)) {
  			spin_unlock(&inode->i_lock);
  			continue;
  		}
  
  		inode->i_state |= I_FREEING;
  		inode_lru_list_del(inode);
  		spin_unlock(&inode->i_lock);
  		list_add(&inode->i_lru, &dispose);
  	}
  	spin_unlock(&inode_sb_list_lock);
  
  	dispose_list(&dispose);
  }
  
  /**
   * invalidate_inodes	- attempt to free all inodes on a superblock
   * @sb:		superblock to operate on
   * @kill_dirty: flag to guide handling of dirty inodes
   *
   * Attempts to free all inodes for a given superblock.  If there were any
   * busy inodes return a non-zero value, else zero.
   * If @kill_dirty is set, discard dirty inodes too, otherwise treat
   * them as busy.
   */
  int invalidate_inodes(struct super_block *sb, bool kill_dirty)
  {
  	int busy = 0;
  	struct inode *inode, *next;
  	LIST_HEAD(dispose);
  
  	spin_lock(&inode_sb_list_lock);
  	list_for_each_entry_safe(inode, next, &sb->s_inodes, i_sb_list) {
  		spin_lock(&inode->i_lock);
  		if (inode->i_state & (I_NEW | I_FREEING | I_WILL_FREE)) {
  			spin_unlock(&inode->i_lock);
  			continue;
  		}
  		if (inode->i_state & I_DIRTY && !kill_dirty) {
  			spin_unlock(&inode->i_lock);
  			busy = 1;
  			continue;
  		}
  		if (atomic_read(&inode->i_count)) {
  			spin_unlock(&inode->i_lock);
  			busy = 1;
  			continue;
  		}
  
  		inode->i_state |= I_FREEING;
  		inode_lru_list_del(inode);
  		spin_unlock(&inode->i_lock);
  		list_add(&inode->i_lru, &dispose);
  	}
  	spin_unlock(&inode_sb_list_lock);
  
  	dispose_list(&dispose);
  
  	return busy;
  }
  
  static int can_unuse(struct inode *inode)
  {
  	if (inode->i_state & ~I_REFERENCED)
  		return 0;
  	if (inode_has_buffers(inode))
  		return 0;
  	if (atomic_read(&inode->i_count))
  		return 0;
  	if (inode->i_data.nrpages)
  		return 0;
  	return 1;
  }
  
  /*
   * Walk the superblock inode LRU for freeable inodes and attempt to free them.
   * This is called from the superblock shrinker function with a number of inodes
   * to trim from the LRU. Inodes to be freed are moved to a temporary list and
   * then are freed outside inode_lock by dispose_list().
   *
   * Any inodes which are pinned purely because of attached pagecache have their
   * pagecache removed.  If the inode has metadata buffers attached to
   * mapping->private_list then try to remove them.
   *
   * If the inode has the I_REFERENCED flag set, then it means that it has been
   * used recently - the flag is set in iput_final(). When we encounter such an
   * inode, clear the flag and move it to the back of the LRU so it gets another
   * pass through the LRU before it gets reclaimed. This is necessary because of
   * the fact we are doing lazy LRU updates to minimise lock contention so the
   * LRU does not have strict ordering. Hence we don't want to reclaim inodes
   * with this flag set because they are the inodes that are out of order.
   */
  void prune_icache_sb(struct super_block *sb, int nr_to_scan)
  {
  	LIST_HEAD(freeable);
  	int nr_scanned;
  	unsigned long reap = 0;
  
  	spin_lock(&sb->s_inode_lru_lock);
  	for (nr_scanned = nr_to_scan; nr_scanned >= 0; nr_scanned--) {
  		struct inode *inode;
  
  		if (list_empty(&sb->s_inode_lru))
  			break;
  
  		inode = list_entry(sb->s_inode_lru.prev, struct inode, i_lru);
  
  		/*
  		 * we are inverting the sb->s_inode_lru_lock/inode->i_lock here,
  		 * so use a trylock. If we fail to get the lock, just move the
  		 * inode to the back of the list so we don't spin on it.
  		 */
  		if (!spin_trylock(&inode->i_lock)) {
  			list_move(&inode->i_lru, &sb->s_inode_lru);
  			continue;
  		}
  
  		/*
  		 * Referenced or dirty inodes are still in use. Give them
  		 * another pass through the LRU as we canot reclaim them now.
  		 */
  		if (atomic_read(&inode->i_count) ||
  		    (inode->i_state & ~I_REFERENCED)) {
  			list_del_init(&inode->i_lru);
  			spin_unlock(&inode->i_lock);
  			sb->s_nr_inodes_unused--;
  			this_cpu_dec(nr_unused);
  			continue;
  		}
  
  		/* recently referenced inodes get one more pass */
  		if (inode->i_state & I_REFERENCED) {
  			inode->i_state &= ~I_REFERENCED;
  			list_move(&inode->i_lru, &sb->s_inode_lru);
  			spin_unlock(&inode->i_lock);
  			continue;
  		}
  		if (inode_has_buffers(inode) || inode->i_data.nrpages) {
  			__iget(inode);
  			spin_unlock(&inode->i_lock);
  			spin_unlock(&sb->s_inode_lru_lock);
  			if (remove_inode_buffers(inode))
  				reap += invalidate_mapping_pages(&inode->i_data,
  								0, -1);
  			iput(inode);
  			spin_lock(&sb->s_inode_lru_lock);
  
  			if (inode != list_entry(sb->s_inode_lru.next,
  						struct inode, i_lru))
  				continue;	/* wrong inode or list_empty */
  			/* avoid lock inversions with trylock */
  			if (!spin_trylock(&inode->i_lock))
  				continue;
  			if (!can_unuse(inode)) {
  				spin_unlock(&inode->i_lock);
  				continue;
  			}
  		}
  		WARN_ON(inode->i_state & I_NEW);
  		inode->i_state |= I_FREEING;
  		spin_unlock(&inode->i_lock);
  
  		list_move(&inode->i_lru, &freeable);
  		sb->s_nr_inodes_unused--;
  		this_cpu_dec(nr_unused);
  	}
  	if (current_is_kswapd())
  		__count_vm_events(KSWAPD_INODESTEAL, reap);
  	else
  		__count_vm_events(PGINODESTEAL, reap);
  	spin_unlock(&sb->s_inode_lru_lock);
  	if (current->reclaim_state)
  		current->reclaim_state->reclaimed_slab += reap;
  
  	dispose_list(&freeable);
  }
  
  static void __wait_on_freeing_inode(struct inode *inode);
  /*
   * Called with the inode lock held.
   */
  static struct inode *find_inode(struct super_block *sb,
  				struct hlist_head *head,
  				int (*test)(struct inode *, void *),
  				void *data)
  {
  	struct inode *inode = NULL;
  
  repeat:
  	hlist_for_each_entry(inode, head, i_hash) {
  		spin_lock(&inode->i_lock);
  		if (inode->i_sb != sb) {
  			spin_unlock(&inode->i_lock);
  			continue;
  		}
  		if (!test(inode, data)) {
  			spin_unlock(&inode->i_lock);
  			continue;
  		}
  		if (inode->i_state & (I_FREEING|I_WILL_FREE)) {
  			__wait_on_freeing_inode(inode);
  			goto repeat;
  		}
  		__iget(inode);
  		spin_unlock(&inode->i_lock);
  		return inode;
  	}
  	return NULL;
  }
  
  /*
   * 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 hlist_head *head, unsigned long ino)
  {
  	struct inode *inode = NULL;
  
  repeat:
  	hlist_for_each_entry(inode, head, i_hash) {
  		spin_lock(&inode->i_lock);
  		if (inode->i_ino != ino) {
  			spin_unlock(&inode->i_lock);
  			continue;
  		}
  		if (inode->i_sb != sb) {
  			spin_unlock(&inode->i_lock);
  			continue;
  		}
  		if (inode->i_state & (I_FREEING|I_WILL_FREE)) {
  			__wait_on_freeing_inode(inode);
  			goto repeat;
  		}
  		__iget(inode);
  		spin_unlock(&inode->i_lock);
  		return inode;
  	}
  	return NULL;
  }
  
  /*
   * Each cpu owns a range of LAST_INO_BATCH numbers.
   * 'shared_last_ino' is dirtied only once out of LAST_INO_BATCH allocations,
   * to renew the exhausted range.
   *
   * This does not significantly increase overflow rate because every CPU can
   * consume at most LAST_INO_BATCH-1 unused inode numbers. So there is
   * NR_CPUS*(LAST_INO_BATCH-1) wastage. At 4096 and 1024, this is ~0.1% of the
   * 2^32 range, and is a worst-case. Even a 50% wastage would only increase
   * overflow rate by 2x, which does not seem too significant.
   *
   * On a 32bit, non LFS stat() call, glibc will generate an EOVERFLOW
   * error if st_ino won't fit in target struct field. Use 32bit counter
   * here to attempt to avoid that.
   */
  #define LAST_INO_BATCH 1024
  static DEFINE_PER_CPU(unsigned int, last_ino);
  
  unsigned int get_next_ino(void)
  {
  	unsigned int *p = &get_cpu_var(last_ino);
  	unsigned int res = *p;
  
  #ifdef CONFIG_SMP
  	if (unlikely((res & (LAST_INO_BATCH-1)) == 0)) {
  		static atomic_t shared_last_ino;
  		int next = atomic_add_return(LAST_INO_BATCH, &shared_last_ino);
  
  		res = next - LAST_INO_BATCH;
  	}
  #endif
  
  	*p = ++res;
  	put_cpu_var(last_ino);
  	return res;
  }
  EXPORT_SYMBOL(get_next_ino);
  
  /**
   *	new_inode_pseudo 	- obtain an inode
   *	@sb: superblock
   *
   *	Allocates a new inode for given superblock.
   *	Inode wont be chained in superblock s_inodes list
   *	This means :
   *	- fs can't be unmount
   *	- quotas, fsnotify, writeback can't work
   */
  struct inode *new_inode_pseudo(struct super_block *sb)
  {
  	struct inode *inode = alloc_inode(sb);
  
  	if (inode) {
  		spin_lock(&inode->i_lock);
  		inode->i_state = 0;
  		spin_unlock(&inode->i_lock);
  		INIT_LIST_HEAD(&inode->i_sb_list);
  	}
  	return inode;
  }
  
  /**
   *	new_inode 	- obtain an inode
   *	@sb: superblock
   *
   *	Allocates a new inode for given superblock. The default gfp_mask
   *	for allocations related to inode->i_mapping is GFP_HIGHUSER_MOVABLE.
   *	If HIGHMEM pages are unsuitable or it is known that pages allocated
   *	for the page cache are not reclaimable or migratable,
   *	mapping_set_gfp_mask() must be called with suitable flags on the
   *	newly created inode's mapping
   *
   */
  struct inode *new_inode(struct super_block *sb)
  {
  	struct inode *inode;
  
  	spin_lock_prefetch(&inode_sb_list_lock);
  
  	inode = new_inode_pseudo(sb);
  	if (inode)
  		inode_sb_list_add(inode);
  	return inode;
  }
  EXPORT_SYMBOL(new_inode);
  
  #ifdef CONFIG_DEBUG_LOCK_ALLOC
  void lockdep_annotate_inode_mutex_key(struct inode *inode)
  {
  	if (S_ISDIR(inode->i_mode)) {
  		struct file_system_type *type = inode->i_sb->s_type;
  
  		/* Set new key only if filesystem hasn't already changed it */
  		if (lockdep_match_class(&inode->i_mutex, &type->i_mutex_key)) {
  			/*
  			 * ensure nobody is actually holding i_mutex
  			 */
  			mutex_destroy(&inode->i_mutex);
  			mutex_init(&inode->i_mutex);
  			lockdep_set_class(&inode->i_mutex,
  					  &type->i_mutex_dir_key);
  		}
  	}
  }
  EXPORT_SYMBOL(lockdep_annotate_inode_mutex_key);
  #endif
  
  /**
   * unlock_new_inode - clear the I_NEW state and wake up any waiters
   * @inode:	new inode to unlock
   *
   * Called when the inode is fully initialised to clear the new state of the
   * inode and wake up anyone waiting for the inode to finish initialisation.
   */
  void unlock_new_inode(struct inode *inode)
  {
  	lockdep_annotate_inode_mutex_key(inode);
  	spin_lock(&inode->i_lock);
  	WARN_ON(!(inode->i_state & I_NEW));
  	inode->i_state &= ~I_NEW;
  	smp_mb();
  	wake_up_bit(&inode->i_state, __I_NEW);
  	spin_unlock(&inode->i_lock);
  }
  EXPORT_SYMBOL(unlock_new_inode);
  
  /**
   * iget5_locked - obtain an inode from a mounted file system
   * @sb:		super block of file system
   * @hashval:	hash value (usually inode number) to get
   * @test:	callback used for comparisons between inodes
   * @set:	callback used to initialize a new struct inode
   * @data:	opaque data pointer to pass to @test and @set
   *
   * Search for the inode specified by @hashval and @data in the inode cache,
   * and if present it is return it with an increased reference count. This is
   * a generalized version of iget_locked() for file systems where the inode
   * number is not sufficient for unique identification of an inode.
   *
   * If the inode is not in cache, allocate a new inode and return it locked,
   * hashed, and with the I_NEW flag set. The file system gets to fill it in
   * before unlocking it via unlock_new_inode().
   *
   * Note both @test and @set are called with the inode_hash_lock held, so can't
   * sleep.
   */
  struct inode *iget5_locked(struct super_block *sb, unsigned long hashval,
  		int (*test)(struct inode *, void *),
  		int (*set)(struct inode *, void *), void *data)
  {
  	struct hlist_head *head = inode_hashtable + hash(sb, hashval);
  	struct inode *inode;
  
  	spin_lock(&inode_hash_lock);
  	inode = find_inode(sb, head, test, data);
  	spin_unlock(&inode_hash_lock);
  
  	if (inode) {
  		wait_on_inode(inode);
  		return inode;
  	}
  
  	inode = alloc_inode(sb);
  	if (inode) {
  		struct inode *old;
  
  		spin_lock(&inode_hash_lock);
  		/* We released the lock, so.. */
  		old = find_inode(sb, head, test, data);
  		if (!old) {
  			if (set(inode, data))
  				goto set_failed;
  
  			spin_lock(&inode->i_lock);
  			inode->i_state = I_NEW;
  			hlist_add_head(&inode->i_hash, head);
  			spin_unlock(&inode->i_lock);
  			inode_sb_list_add(inode);
  			spin_unlock(&inode_hash_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.
  		 */
  		spin_unlock(&inode_hash_lock);
  		destroy_inode(inode);
  		inode = old;
  		wait_on_inode(inode);
  	}
  	return inode;
  
  set_failed:
  	spin_unlock(&inode_hash_lock);
  	destroy_inode(inode);
  	return NULL;
  }
  EXPORT_SYMBOL(iget5_locked);
  
  /**
   * iget_locked - obtain an inode from a mounted file system
   * @sb:		super block of file system
   * @ino:	inode number to get
   *
   * Search for the inode specified by @ino in the inode cache and if present
   * return it with an increased reference count. This is for file systems
   * where the inode number is sufficient for unique identification of an inode.
   *
   * If the inode is not in cache, allocate a new inode and return it locked,
   * hashed, and with the I_NEW flag set.  The file system gets to fill it in
   * before unlocking it via unlock_new_inode().
   */
  struct inode *iget_locked(struct super_block *sb, unsigned long ino)
  {
  	struct hlist_head *head = inode_hashtable + hash(sb, ino);
  	struct inode *inode;
  
  	spin_lock(&inode_hash_lock);
  	inode = find_inode_fast(sb, head, ino);
  	spin_unlock(&inode_hash_lock);
  	if (inode) {
  		wait_on_inode(inode);
  		return inode;
  	}
  
  	inode = alloc_inode(sb);
  	if (inode) {
  		struct inode *old;
  
  		spin_lock(&inode_hash_lock);
  		/* We released the lock, so.. */
  		old = find_inode_fast(sb, head, ino);
  		if (!old) {
  			inode->i_ino = ino;
  			spin_lock(&inode->i_lock);
  			inode->i_state = I_NEW;
  			hlist_add_head(&inode->i_hash, head);
  			spin_unlock(&inode->i_lock);
  			inode_sb_list_add(inode);
  			spin_unlock(&inode_hash_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.
  		 */
  		spin_unlock(&inode_hash_lock);
  		destroy_inode(inode);
  		inode = old;
  		wait_on_inode(inode);
  	}
  	return inode;
  }
  EXPORT_SYMBOL(iget_locked);
  
  /*
   * search the inode cache for a matching inode number.
   * If we find one, then the inode number we are trying to
   * allocate is not unique and so we should not use it.
   *
   * Returns 1 if the inode number is unique, 0 if it is not.
   */
  static int test_inode_iunique(struct super_block *sb, unsigned long ino)
  {
  	struct hlist_head *b = inode_hashtable + hash(sb, ino);
  	struct inode *inode;
  
  	spin_lock(&inode_hash_lock);
  	hlist_for_each_entry(inode, b, i_hash) {
  		if (inode->i_ino == ino && inode->i_sb == sb) {
  			spin_unlock(&inode_hash_lock);
  			return 0;
  		}
  	}
  	spin_unlock(&inode_hash_lock);
  
  	return 1;
  }
  
  /**
   *	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)
  {
  	/*
  	 * On a 32bit, non LFS stat() call, glibc will generate an EOVERFLOW
  	 * error if st_ino won't fit in target struct field. Use 32bit counter
  	 * here to attempt to avoid that.
  	 */
  	static DEFINE_SPINLOCK(iunique_lock);
  	static unsigned int counter;
  	ino_t res;
  
  	spin_lock(&iunique_lock);
  	do {
  		if (counter <= max_reserved)
  			counter = max_reserved + 1;
  		res = counter++;
  	} while (!test_inode_iunique(sb, res));
  	spin_unlock(&iunique_lock);
  
  	return res;
  }
  EXPORT_SYMBOL(iunique);
  
  struct inode *igrab(struct inode *inode)
  {
  	spin_lock(&inode->i_lock);
  	if (!(inode->i_state & (I_FREEING|I_WILL_FREE))) {
  		__iget(inode);
  		spin_unlock(&inode->i_lock);
  	} else {
  		spin_unlock(&inode->i_lock);
  		/*
  		 * 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;
  	}
  	return inode;
  }
  EXPORT_SYMBOL(igrab);
  
  /**
   * ilookup5_nowait - search for an inode in the inode cache
   * @sb:		super block of file system to search
   * @hashval:	hash value (usually inode number) to search for
   * @test:	callback used for comparisons between inodes
   * @data:	opaque data pointer to pass to @test
   *
   * Search for the inode specified by @hashval and @data in the inode cache.
   * If the inode is in the cache, the inode is returned with an incremented
   * reference count.
   *
   * Note: I_NEW is not waited upon so you have to be very careful what you do
   * with the returned inode.  You probably should be using ilookup5() instead.
   *
   * Note2: @test is called with the inode_hash_lock held, so can't sleep.
   */
  struct inode *ilookup5_nowait(struct super_block *sb, unsigned long hashval,
  		int (*test)(struct inode *, void *), void *data)
  {
  	struct hlist_head *head = inode_hashtable + hash(sb, hashval);
  	struct inode *inode;
  
  	spin_lock(&inode_hash_lock);
  	inode = find_inode(sb, head, test, data);
  	spin_unlock(&inode_hash_lock);
  
  	return inode;
  }
  EXPORT_SYMBOL(ilookup5_nowait);
  
  /**
   * ilookup5 - search for an inode in the inode cache
   * @sb:		super block of file system to search
   * @hashval:	hash value (usually inode number) to search for
   * @test:	callback used for comparisons between inodes
   * @data:	opaque data pointer to pass to @test
   *
   * Search for the inode specified by @hashval and @data in the inode cache,
   * and if the inode is in the cache, return the inode with an incremented
   * reference count.  Waits on I_NEW before returning the inode.
   * returned with an incremented reference count.
   *
   * This is a generalized version of ilookup() for file systems where the
   * inode number is not sufficient for unique identification of an inode.
   *
   * Note: @test is called with the inode_hash_lock held, so can't sleep.
   */
  struct inode *ilookup5(struct super_block *sb, unsigned long hashval,
  		int (*test)(struct inode *, void *), void *data)
  {
  	struct inode *inode = ilookup5_nowait(sb, hashval, test, data);
  
  	if (inode)
  		wait_on_inode(inode);
  	return inode;
  }
  EXPORT_SYMBOL(ilookup5);
  
  /**
   * ilookup - search for an inode in the inode cache
   * @sb:		super block of file system to search
   * @ino:	inode number to search for
   *
   * Search for the inode @ino in the inode cache, and if the inode is in the
   * cache, the inode is returned with an incremented reference count.
   */
  struct inode *ilookup(struct super_block *sb, unsigned long ino)
  {
  	struct hlist_head *head = inode_hashtable + hash(sb, ino);
  	struct inode *inode;
  
  	spin_lock(&inode_hash_lock);
  	inode = find_inode_fast(sb, head, ino);
  	spin_unlock(&inode_hash_lock);
  
  	if (inode)
  		wait_on_inode(inode);
  	return inode;
  }
  EXPORT_SYMBOL(ilookup);
  
  int insert_inode_locked(struct inode *inode)
  {
  	struct super_block *sb = inode->i_sb;
  	ino_t ino = inode->i_ino;
  	struct hlist_head *head = inode_hashtable + hash(sb, ino);
  
  	while (1) {
  		struct inode *old = NULL;
  		spin_lock(&inode_hash_lock);
  		hlist_for_each_entry(old, head, i_hash) {
  			if (old->i_ino != ino)
  				continue;
  			if (old->i_sb != sb)
  				continue;
  			spin_lock(&old->i_lock);
  			if (old->i_state & (I_FREEING|I_WILL_FREE)) {
  				spin_unlock(&old->i_lock);
  				continue;
  			}
  			break;
  		}
  		if (likely(!old)) {
  			spin_lock(&inode->i_lock);
  			inode->i_state |= I_NEW;
  			hlist_add_head(&inode->i_hash, head);
  			spin_unlock(&inode->i_lock);
  			spin_unlock(&inode_hash_lock);
  			return 0;
  		}
  		__iget(old);
  		spin_unlock(&old->i_lock);
  		spin_unlock(&inode_hash_lock);
  		wait_on_inode(old);
  		if (unlikely(!inode_unhashed(old))) {
  			iput(old);
  			return -EBUSY;
  		}
  		iput(old);
  	}
  }
  EXPORT_SYMBOL(insert_inode_locked);
  
  int insert_inode_locked4(struct inode *inode, unsigned long hashval,
  		int (*test)(struct inode *, void *), void *data)
  {
  	struct super_block *sb = inode->i_sb;
  	struct hlist_head *head = inode_hashtable + hash(sb, hashval);
  
  	while (1) {
  		struct inode *old = NULL;
  
  		spin_lock(&inode_hash_lock);
  		hlist_for_each_entry(old, head, i_hash) {
  			if (old->i_sb != sb)
  				continue;
  			if (!test(old, data))
  				continue;
  			spin_lock(&old->i_lock);
  			if (old->i_state & (I_FREEING|I_WILL_FREE)) {
  				spin_unlock(&old->i_lock);
  				continue;
  			}
  			break;
  		}
  		if (likely(!old)) {
  			spin_lock(&inode->i_lock);
  			inode->i_state |= I_NEW;
  			hlist_add_head(&inode->i_hash, head);
  			spin_unlock(&inode->i_lock);
  			spin_unlock(&inode_hash_lock);
  			return 0;
  		}
  		__iget(old);
  		spin_unlock(&old->i_lock);
  		spin_unlock(&inode_hash_lock);
  		wait_on_inode(old);
  		if (unlikely(!inode_unhashed(old))) {
  			iput(old);
  			return -EBUSY;
  		}
  		iput(old);
  	}
  }
  EXPORT_SYMBOL(insert_inode_locked4);
  
  
  int generic_delete_inode(struct inode *inode)
  {
  	return 1;
  }
  EXPORT_SYMBOL(generic_delete_inode);
  
  /*
   * Called when we're dropping the last reference
   * to an inode.
   *
   * Call the FS "drop_inode()" function, defaulting to
   * the legacy UNIX filesystem behaviour.  If it tells
   * us to evict inode, do so.  Otherwise, retain inode
   * in cache if fs is alive, sync and evict if fs is
   * shutting down.
   */
  static void iput_final(struct inode *inode)
  {
  	struct super_block *sb = inode->i_sb;
  	const struct super_operations *op = inode->i_sb->s_op;
  	int drop;
  
  	WARN_ON(inode->i_state & I_NEW);
  
  	if (op->drop_inode)
  		drop = op->drop_inode(inode);
  	else
  		drop = generic_drop_inode(inode);
  
  	if (!drop && (sb->s_flags & MS_ACTIVE)) {
  		inode->i_state |= I_REFERENCED;
  		inode_add_lru(inode);
  		spin_unlock(&inode->i_lock);
  		return;
  	}
  
  	if (!drop) {
  		inode->i_state |= I_WILL_FREE;
  		spin_unlock(&inode->i_lock);
  		write_inode_now(inode, 1);
  		spin_lock(&inode->i_lock);
  		WARN_ON(inode->i_state & I_NEW);
  		inode->i_state &= ~I_WILL_FREE;
  	}
  
  	inode->i_state |= I_FREEING;
  	if (!list_empty(&inode->i_lru))
  		inode_lru_list_del(inode);
  	spin_unlock(&inode->i_lock);
  
  	evict(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 then freed and may also be destroyed.
   *
   *	Consequently, iput() can sleep.
   */
  void iput(struct inode *inode)
  {
  	if (inode) {
  		BUG_ON(inode->i_state & I_CLEAR);
  
  		if (atomic_dec_and_lock(&inode->i_count, &inode->i_lock))
  			iput_final(inode);
  	}
  }
  EXPORT_SYMBOL(iput);
  
  /**
   *	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.
   */
  sector_t bmap(struct inode *inode, sector_t block)
  {
  	sector_t res = 0;
  	if (inode->i_mapping->a_ops->bmap)
  		res = inode->i_mapping->a_ops->bmap(inode->i_mapping, block);
  	return res;
  }
  EXPORT_SYMBOL(bmap);
  
  /*
   * With relative atime, only update atime if the previous atime is
   * earlier than either the ctime or mtime or if at least a day has
   * passed since the last atime update.
   */
  static int relatime_need_update(struct vfsmount *mnt, struct inode *inode,
  			     struct timespec now)
  {
  
  	if (!(mnt->mnt_flags & MNT_RELATIME))
  		return 1;
  	/*
  	 * Is mtime younger than atime? If yes, update atime:
  	 */
  	if (timespec_compare(&inode->i_mtime, &inode->i_atime) >= 0)
  		return 1;
  	/*
  	 * Is ctime younger than atime? If yes, update atime:
  	 */
  	if (timespec_compare(&inode->i_ctime, &inode->i_atime) >= 0)
  		return 1;
  
  	/*
  	 * Is the previous atime value older than a day? If yes,
  	 * update atime:
  	 */
  	if ((long)(now.tv_sec - inode->i_atime.tv_sec) >= 24*60*60)
  		return 1;
  	/*
  	 * Good, we can skip the atime update:
  	 */
  	return 0;
  }
  
  /*
   * This does the actual work of updating an inodes time or version.  Must have
   * had called mnt_want_write() before calling this.
   */
  static int update_time(struct inode *inode, struct timespec *time, int flags)
  {
  	if (inode->i_op->update_time)
  		return inode->i_op->update_time(inode, time, flags);
  
  	if (flags & S_ATIME)
  		inode->i_atime = *time;
  	if (flags & S_VERSION)
  		inode_inc_iversion(inode);
  	if (flags & S_CTIME)
  		inode->i_ctime = *time;
  	if (flags & S_MTIME)
  		inode->i_mtime = *time;
  	mark_inode_dirty_sync(inode);
  	return 0;
  }
  
  /**
   *	touch_atime	-	update the access time
   *	@path: the &struct path to update
   *
   *	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 touch_atime(struct path *path)
  {
  	struct vfsmount *mnt = path->mnt;
  	struct inode *inode = path->dentry->d_inode;
  	struct timespec now;
  
  	if (inode->i_flags & S_NOATIME)
  		return;
  	if (IS_NOATIME(inode))
  		return;
  	if ((inode->i_sb->s_flags & MS_NODIRATIME) && S_ISDIR(inode->i_mode))
  		return;
  
  	if (mnt->mnt_flags & MNT_NOATIME)
  		return;
  	if ((mnt->mnt_flags & MNT_NODIRATIME) && S_ISDIR(inode->i_mode))
  		return;
  
  	now = current_fs_time(inode->i_sb);
  
  	if (!relatime_need_update(mnt, inode, now))
  		return;
  
  	if (timespec_equal(&inode->i_atime, &now))
  		return;
  
  	if (!sb_start_write_trylock(inode->i_sb))
  		return;
  
  	if (__mnt_want_write(mnt))
  		goto skip_update;
  	/*
  	 * File systems can error out when updating inodes if they need to
  	 * allocate new space to modify an inode (such is the case for
  	 * Btrfs), but since we touch atime while walking down the path we
  	 * really don't care if we failed to update the atime of the file,
  	 * so just ignore the return value.
  	 * We may also fail on filesystems that have the ability to make parts
  	 * of the fs read only, e.g. subvolumes in Btrfs.
  	 */
  	update_time(inode, &now, S_ATIME);
  	__mnt_drop_write(mnt);
  skip_update:
  	sb_end_write(inode->i_sb);
  }
  EXPORT_SYMBOL(touch_atime);
  
  /*
   * The logic we want is
   *
   *	if suid or (sgid and xgrp)
   *		remove privs
   */
  int should_remove_suid(struct dentry *dentry)
  {
  	umode_t mode = dentry->d_inode->i_mode;
  	int kill = 0;
  
  	/* suid always must be killed */
  	if (unlikely(mode & S_ISUID))
  		kill = ATTR_KILL_SUID;
  
  	/*
  	 * sgid without any exec bits is just a mandatory locking mark; leave
  	 * it alone.  If some exec bits are set, it's a real sgid; kill it.
  	 */
  	if (unlikely((mode & S_ISGID) && (mode & S_IXGRP)))
  		kill |= ATTR_KILL_SGID;
  
  	if (unlikely(kill && !capable(CAP_FSETID) && S_ISREG(mode)))
  		return kill;
  
  	return 0;
  }
  EXPORT_SYMBOL(should_remove_suid);
  
  static int __remove_suid(struct dentry *dentry, int kill)
  {
  	struct iattr newattrs;
  
  	newattrs.ia_valid = ATTR_FORCE | kill;
  	return notify_change(dentry, &newattrs);
  }
  
  int file_remove_suid(struct file *file)
  {
  	struct dentry *dentry = file->f_path.dentry;
  	struct inode *inode = dentry->d_inode;
  	int killsuid;
  	int killpriv;
  	int error = 0;
  
  	/* Fast path for nothing security related */
  	if (IS_NOSEC(inode))
  		return 0;
  
  	killsuid = should_remove_suid(dentry);
  	killpriv = security_inode_need_killpriv(dentry);
  
  	if (killpriv < 0)
  		return killpriv;
  	if (killpriv)
  		error = security_inode_killpriv(dentry);
  	if (!error && killsuid)
  		error = __remove_suid(dentry, killsuid);
  	if (!error && (inode->i_sb->s_flags & MS_NOSEC))
  		inode->i_flags |= S_NOSEC;
  
  	return error;
  }
  EXPORT_SYMBOL(file_remove_suid);
  
  /**
   *	file_update_time	-	update mtime and ctime time
   *	@file: file accessed
   *
   *	Update the mtime and ctime members of an inode and mark the inode
   *	for writeback.  Note that this function is meant exclusively for
   *	usage in the file write path of filesystems, and filesystems may
   *	choose to explicitly ignore update via this function with the
   *	S_NOCMTIME inode flag, e.g. for network filesystem where these
   *	timestamps are handled by the server.  This can return an error for
   *	file systems who need to allocate space in order to update an inode.
   */
  
  int file_update_time(struct file *file)
  {
  	struct inode *inode = file_inode(file);
  	struct timespec now;
  	int sync_it = 0;
  	int ret;
  
  	/* First try to exhaust all avenues to not sync */
  	if (IS_NOCMTIME(inode))
  		return 0;
  
  	now = current_fs_time(inode->i_sb);
  	if (!timespec_equal(&inode->i_mtime, &now))
  		sync_it = S_MTIME;
  
  	if (!timespec_equal(&inode->i_ctime, &now))
  		sync_it |= S_CTIME;
  
  	if (IS_I_VERSION(inode))
  		sync_it |= S_VERSION;
  
  	if (!sync_it)
  		return 0;
  
  	/* Finally allowed to write? Takes lock. */
  	if (__mnt_want_write_file(file))
  		return 0;
  
  	ret = update_time(inode, &now, sync_it);
  	__mnt_drop_write_file(file);
  
  	return ret;
  }
  EXPORT_SYMBOL(file_update_time);
  
  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);
  
  int inode_wait(void *word)
  {
  	schedule();
  	return 0;
  }
  EXPORT_SYMBOL(inode_wait);
  
  /*
   * If we try to find an inode in the inode hash while it is being
   * deleted, we have to wait until the filesystem completes its
   * deletion before reporting that it isn't found.  This function waits
   * until the deletion _might_ have completed.  Callers are responsible
   * to recheck inode state.
   *
   * It doesn't matter if I_NEW is not set initially, a call to
   * wake_up_bit(&inode->i_state, __I_NEW) after removing from the hash list
   * will DTRT.
   */
  static void __wait_on_freeing_inode(struct inode *inode)
  {
  	wait_queue_head_t *wq;
  	DEFINE_WAIT_BIT(wait, &inode->i_state, __I_NEW);
  	wq = bit_waitqueue(&inode->i_state, __I_NEW);
  	prepare_to_wait(wq, &wait.wait, TASK_UNINTERRUPTIBLE);
  	spin_unlock(&inode->i_lock);
  	spin_unlock(&inode_hash_lock);
  	schedule();
  	finish_wait(wq, &wait.wait);
  	spin_lock(&inode_hash_lock);
  }
  
  static __initdata unsigned long ihash_entries;
  static int __init set_ihash_entries(char *str)
  {
  	if (!str)
  		return 0;
  	ihash_entries = simple_strtoul(str, &str, 0);
  	return 1;
  }
  __setup("ihash_entries=", set_ihash_entries);
  
  /*
   * Initialize the waitqueues and inode hash table.
   */
  void __init inode_init_early(void)
  {
  	unsigned int loop;
  
  	/* If hashes are distributed across NUMA nodes, defer
  	 * hash allocation until vmalloc space is available.
  	 */
  	if (hashdist)
  		return;
  
  	inode_hashtable =
  		alloc_large_system_hash("Inode-cache",
  					sizeof(struct hlist_head),
  					ihash_entries,
  					14,
  					HASH_EARLY,
  					&i_hash_shift,
  					&i_hash_mask,
  					0,
  					0);
  
  	for (loop = 0; loop < (1U << i_hash_shift); loop++)
  		INIT_HLIST_HEAD(&inode_hashtable[loop]);
  }
  
  void __init inode_init(void)
  {
  	unsigned int loop;
  
  	/* inode slab cache */
  	inode_cachep = kmem_cache_create("inode_cache",
  					 sizeof(struct inode),
  					 0,
  					 (SLAB_RECLAIM_ACCOUNT|SLAB_PANIC|
  					 SLAB_MEM_SPREAD),
  					 init_once);
  
  	/* Hash may have been set up in inode_init_early */
  	if (!hashdist)
  		return;
  
  	inode_hashtable =
  		alloc_large_system_hash("Inode-cache",
  					sizeof(struct hlist_head),
  					ihash_entries,
  					14,
  					0,
  					&i_hash_shift,
  					&i_hash_mask,
  					0,
  					0);
  
  	for (loop = 0; loop < (1U << i_hash_shift); loop++)
  		INIT_HLIST_HEAD(&inode_hashtable[loop]);
  }
  
  void init_special_inode(struct inode *inode, umode_t mode, dev_t rdev)
  {
  	inode->i_mode = mode;
  	if (S_ISCHR(mode)) {
  		inode->i_fop = &def_chr_fops;
  		inode->i_rdev = rdev;
  	} else if (S_ISBLK(mode)) {
  		inode->i_fop = &def_blk_fops;
  		inode->i_rdev = rdev;
  	} else if (S_ISFIFO(mode))
  		inode->i_fop = &pipefifo_fops;
  	else if (S_ISSOCK(mode))
  		inode->i_fop = &bad_sock_fops;
  	else
  		printk(KERN_DEBUG "init_special_inode: bogus i_mode (%o) for"
  				  " inode %s:%lu\n", mode, inode->i_sb->s_id,
  				  inode->i_ino);
  }
  EXPORT_SYMBOL(init_special_inode);
  
  /**
   * inode_init_owner - Init uid,gid,mode for new inode according to posix standards
   * @inode: New inode
   * @dir: Directory inode
   * @mode: mode of the new inode
   */
  void inode_init_owner(struct inode *inode, const struct inode *dir,
  			umode_t mode)
  {
  	inode->i_uid = current_fsuid();
  	if (dir && dir->i_mode & S_ISGID) {
  		inode->i_gid = dir->i_gid;
  		if (S_ISDIR(mode))
  			mode |= S_ISGID;
  	} else
  		inode->i_gid = current_fsgid();
  	inode->i_mode = mode;
  }
  EXPORT_SYMBOL(inode_init_owner);
  
  /**
   * inode_owner_or_capable - check current task permissions to inode
   * @inode: inode being checked
   *
   * Return true if current either has CAP_FOWNER in a namespace with the
   * inode owner uid mapped, or owns the file.
   */
  bool inode_owner_or_capable(const struct inode *inode)
  {
  	struct user_namespace *ns;
  
  	if (uid_eq(current_fsuid(), inode->i_uid))
  		return true;
  
  	ns = current_user_ns();
  	if (ns_capable(ns, CAP_FOWNER) && kuid_has_mapping(ns, inode->i_uid))
  		return true;
  	return false;
  }
  EXPORT_SYMBOL(inode_owner_or_capable);
  
  /*
   * Direct i/o helper functions
   */
  static void __inode_dio_wait(struct inode *inode)
  {
  	wait_queue_head_t *wq = bit_waitqueue(&inode->i_state, __I_DIO_WAKEUP);
  	DEFINE_WAIT_BIT(q, &inode->i_state, __I_DIO_WAKEUP);
  
  	do {
  		prepare_to_wait(wq, &q.wait, TASK_UNINTERRUPTIBLE);
  		if (atomic_read(&inode->i_dio_count))
  			schedule();
  	} while (atomic_read(&inode->i_dio_count));
  	finish_wait(wq, &q.wait);
  }
  
  /**
   * inode_dio_wait - wait for outstanding DIO requests to finish
   * @inode: inode to wait for
   *
   * Waits for all pending direct I/O requests to finish so that we can
   * proceed with a truncate or equivalent operation.
   *
   * Must be called under a lock that serializes taking new references
   * to i_dio_count, usually by inode->i_mutex.
   */
  void inode_dio_wait(struct inode *inode)
  {
  	if (atomic_read(&inode->i_dio_count))
  		__inode_dio_wait(inode);
  }
  EXPORT_SYMBOL(inode_dio_wait);
  
  /*
   * inode_dio_done - signal finish of a direct I/O requests
   * @inode: inode the direct I/O happens on
   *
   * This is called once we've finished processing a direct I/O request,
   * and is used to wake up callers waiting for direct I/O to be quiesced.
   */
  void inode_dio_done(struct inode *inode)
  {
  	if (atomic_dec_and_test(&inode->i_dio_count))
  		wake_up_bit(&inode->i_state, __I_DIO_WAKEUP);
  }
  EXPORT_SYMBOL(inode_dio_done);
  