#ifndef __LINUX_DCACHE_H
  #define __LINUX_DCACHE_H

  #include <asm/atomic.h>
  #include <linux/list.h>

  #include <linux/rculist.h>

  #include <linux/spinlock.h>
  #include <linux/cache.h>
  #include <linux/rcupdate.h>

  
  struct nameidata;

  struct path;

  struct vfsmount;
  
  /*
   * linux/include/linux/dcache.h
   *
   * Dirent cache data structures
   *
   * (C) Copyright 1997 Thomas Schoebel-Theuer,
   * with heavy changes by Linus Torvalds
   */
  
  #define IS_ROOT(x) ((x) == (x)->d_parent)
  
  /*
   * "quick string" -- eases parameter passing, but more importantly
   * saves "metadata" about the string (ie length and the hash).
   *
   * hash comes first so it snuggles against d_parent in the
   * dentry.
   */
  struct qstr {
  	unsigned int hash;
  	unsigned int len;
  	const unsigned char *name;
  };
  
  struct dentry_stat_t {
  	int nr_dentry;
  	int nr_unused;
  	int age_limit;          /* age in seconds */
  	int want_pages;         /* pages requested by system */
  	int dummy[2];
  };
  extern struct dentry_stat_t dentry_stat;
  
  /* Name hashing routines. Initial hash value */
  /* Hash courtesy of the R5 hash in reiserfs modulo sign bits */
  #define init_name_hash()		0
  
  /* partial hash update function. Assume roughly 4 bits per character */
  static inline unsigned long
  partial_name_hash(unsigned long c, unsigned long prevhash)
  {
  	return (prevhash + (c << 4) + (c >> 4)) * 11;
  }
  
  /*
   * Finally: cut down the number of bits to a int value (and try to avoid
   * losing bits)
   */
  static inline unsigned long end_name_hash(unsigned long hash)
  {
  	return (unsigned int) hash;
  }
  
  /* Compute the hash for a name string. */
  static inline unsigned int
  full_name_hash(const unsigned char *name, unsigned int len)
  {
  	unsigned long hash = init_name_hash();
  	while (len--)
  		hash = partial_name_hash(*name++, hash);
  	return end_name_hash(hash);
  }

  /*
   * Try to keep struct dentry aligned on 64 byte cachelines (this will
   * give reasonable cacheline footprint with larger lines without the
   * large memory footprint increase).
   */
  #ifdef CONFIG_64BIT
  #define DNAME_INLINE_LEN_MIN 32 /* 192 bytes */
  #else
  #define DNAME_INLINE_LEN_MIN 40 /* 128 bytes */
  #endif

  
  struct dentry {
  	atomic_t d_count;
  	unsigned int d_flags;		/* protected by d_lock */
  	spinlock_t d_lock;		/* per dentry lock */

  	int d_mounted;

  	struct inode *d_inode;		/* Where the name belongs to - NULL is
  					 * negative */
  	/*
  	 * The next three fields are touched by __d_lookup.  Place them here

  	 * so they all fit in a cache line.

  	 */

  	struct hlist_node d_hash;	/* lookup hash list */

  	struct dentry *d_parent;	/* parent directory */
  	struct qstr d_name;
  
  	struct list_head d_lru;		/* LRU list */

  	/*
  	 * d_child and d_rcu can share memory
  	 */
  	union {
  		struct list_head d_child;	/* child of parent list */
  	 	struct rcu_head d_rcu;
  	} d_u;

  	struct list_head d_subdirs;	/* our children */
  	struct list_head d_alias;	/* inode alias list */
  	unsigned long d_time;		/* used by d_revalidate */

  	const struct dentry_operations *d_op;

  	struct super_block *d_sb;	/* The root of the dentry tree */
  	void *d_fsdata;			/* fs-specific data */

  	unsigned char d_iname[DNAME_INLINE_LEN_MIN];	/* small names */
  };

  /*
   * dentry->d_lock spinlock nesting subclasses:
   *
   * 0: normal
   * 1: nested
   */
  enum dentry_d_lock_class
  {
  	DENTRY_D_LOCK_NORMAL, /* implicitly used by plain spin_lock() APIs. */
  	DENTRY_D_LOCK_NESTED
  };

  struct dentry_operations {
  	int (*d_revalidate)(struct dentry *, struct nameidata *);
  	int (*d_hash) (struct dentry *, struct qstr *);
  	int (*d_compare) (struct dentry *, struct qstr *, struct qstr *);
  	int (*d_delete)(struct dentry *);
  	void (*d_release)(struct dentry *);
  	void (*d_iput)(struct dentry *, struct inode *);

  	char *(*d_dname)(struct dentry *, char *, int);

  };
  
  /* the dentry parameter passed to d_hash and d_compare is the parent
   * directory of the entries to be compared. It is used in case these
   * functions need any directory specific information for determining
   * equivalency classes.  Using the dentry itself might not work, as it
   * might be a negative dentry which has no information associated with
   * it */
  
  /*
  locking rules:
  		big lock	dcache_lock	d_lock   may block
  d_revalidate:	no		no		no       yes
  d_hash		no		no		no       yes
  d_compare:	no		yes		yes      no
  d_delete:	no		yes		no       no
  d_release:	no		no		no       yes
  d_iput:		no		no		no       yes
   */
  
  /* d_flags entries */
  #define DCACHE_AUTOFS_PENDING 0x0001    /* autofs: "under construction" */
  #define DCACHE_NFSFS_RENAMED  0x0002    /* this dentry has been "silly
  					 * renamed" and has to be
  					 * deleted on the last dput()
  					 */
  #define	DCACHE_DISCONNECTED 0x0004
       /* This dentry is possibly not currently connected to the dcache tree,
        * in which case its parent will either be itself, or will have this
        * flag as well.  nfsd will not use a dentry with this bit set, but will
        * first endeavour to clear the bit either by discovering that it is
        * connected, or by performing lookup operations.   Any filesystem which
        * supports nfsd_operations MUST have a lookup function which, if it finds
        * a directory inode with a DCACHE_DISCONNECTED dentry, will d_move
        * that dentry into place and return that dentry rather than the passed one,
        * typically using d_splice_alias.
        */
  
  #define DCACHE_REFERENCED	0x0008  /* Recently used, don't discard. */
  #define DCACHE_UNHASHED		0x0010	

  #define DCACHE_INOTIFY_PARENT_WATCHED	0x0020 /* Parent inode is watched by inotify */

  #define DCACHE_COOKIE		0x0040	/* For use by dcookie subsystem */

  #define DCACHE_FSNOTIFY_PARENT_WATCHED	0x0080 /* Parent inode is watched by some fsnotify listener */

  #define DCACHE_CANT_MOUNT	0x0100

  extern spinlock_t dcache_lock;

  extern seqlock_t rename_lock;

  
  /**
   * d_drop - drop a dentry
   * @dentry: dentry to drop
   *
   * d_drop() unhashes the entry from the parent dentry hashes, so that it won't
   * be found through a VFS lookup any more. Note that this is different from
   * deleting the dentry - d_delete will try to mark the dentry negative if
   * possible, giving a successful _negative_ lookup, while d_drop will
   * just make the cache lookup fail.
   *
   * d_drop() is used mainly for stuff that wants to invalidate a dentry for some
   * reason (NFS timeouts or autofs deletes).
   *
   * __d_drop requires dentry->d_lock.
   */
  
  static inline void __d_drop(struct dentry *dentry)
  {
  	if (!(dentry->d_flags & DCACHE_UNHASHED)) {
  		dentry->d_flags |= DCACHE_UNHASHED;
  		hlist_del_rcu(&dentry->d_hash);
  	}
  }
  
  static inline void d_drop(struct dentry *dentry)
  {
  	spin_lock(&dcache_lock);
  	spin_lock(&dentry->d_lock);
   	__d_drop(dentry);
  	spin_unlock(&dentry->d_lock);
  	spin_unlock(&dcache_lock);
  }
  
  static inline int dname_external(struct dentry *dentry)
  {
  	return dentry->d_name.name != dentry->d_iname;
  }
  
  /*
   * These are the low-level FS interfaces to the dcache..
   */
  extern void d_instantiate(struct dentry *, struct inode *);
  extern struct dentry * d_instantiate_unique(struct dentry *, struct inode *);

  extern struct dentry * d_materialise_unique(struct dentry *, struct inode *);

  extern void d_delete(struct dentry *);
  
  /* allocate/de-allocate */
  extern struct dentry * d_alloc(struct dentry *, const struct qstr *);

  extern struct dentry * d_splice_alias(struct inode *, struct dentry *);

  extern struct dentry * d_add_ci(struct dentry *, struct inode *, struct qstr *);

  extern struct dentry * d_obtain_alias(struct inode *);

  extern void shrink_dcache_sb(struct super_block *);
  extern void shrink_dcache_parent(struct dentry *);

  extern void shrink_dcache_for_umount(struct super_block *);

  extern int d_invalidate(struct dentry *);
  
  /* only used at mount-time */
  extern struct dentry * d_alloc_root(struct inode *);
  
  /* <clickety>-<click> the ramfs-type tree */
  extern void d_genocide(struct dentry *);
  
  extern struct dentry *d_find_alias(struct inode *);
  extern void d_prune_aliases(struct inode *);
  
  /* test whether we have any submounts in a subdir tree */
  extern int have_submounts(struct dentry *);
  
  /*
   * This adds the entry to the hash queues.
   */
  extern void d_rehash(struct dentry *);
  
  /**
   * d_add - add dentry to hash queues
   * @entry: dentry to add
   * @inode: The inode to attach to this dentry
   *
   * This adds the entry to the hash queues and initializes @inode.
   * The entry was actually filled in earlier during d_alloc().
   */
   
  static inline void d_add(struct dentry *entry, struct inode *inode)
  {
  	d_instantiate(entry, inode);
  	d_rehash(entry);
  }
  
  /**
   * d_add_unique - add dentry to hash queues without aliasing
   * @entry: dentry to add
   * @inode: The inode to attach to this dentry
   *
   * This adds the entry to the hash queues and initializes @inode.
   * The entry was actually filled in earlier during d_alloc().
   */
  static inline struct dentry *d_add_unique(struct dentry *entry, struct inode *inode)
  {
  	struct dentry *res;
  
  	res = d_instantiate_unique(entry, inode);
  	d_rehash(res != NULL ? res : entry);
  	return res;
  }
  
  /* used for rename() and baskets */
  extern void d_move(struct dentry *, struct dentry *);

  extern struct dentry *d_ancestor(struct dentry *, struct dentry *);

  
  /* appendix may either be NULL or be used for transname suffixes */
  extern struct dentry * d_lookup(struct dentry *, struct qstr *);
  extern struct dentry * __d_lookup(struct dentry *, struct qstr *);

  extern struct dentry * d_hash_and_lookup(struct dentry *, struct qstr *);

  
  /* validate "insecure" dentry pointer */
  extern int d_validate(struct dentry *, struct dentry *);

  /*
   * helper function for dentry_operations.d_dname() members
   */
  extern char *dynamic_dname(struct dentry *, char *, int, const char *, ...);

  extern char *__d_path(const struct path *path, struct path *root, char *, int);

  extern char *d_path(const struct path *, char *, int);

  extern char *d_path_with_unreachable(const struct path *, char *, int);

  extern char *__dentry_path(struct dentry *, char *, int);

  extern char *dentry_path(struct dentry *, char *, int);

  /* Allocation counts.. */
  
  /**
   *	dget, dget_locked	-	get a reference to a dentry
   *	@dentry: dentry to get a reference to
   *
   *	Given a dentry or %NULL pointer increment the reference count
   *	if appropriate and return the dentry. A dentry will not be 
   *	destroyed when it has references. dget() should never be
   *	called for dentries with zero reference counter. For these cases
   *	(preferably none, functions in dcache.c are sufficient for normal
   *	needs and they take necessary precautions) you should hold dcache_lock
   *	and call dget_locked() instead of dget().
   */
   
  static inline struct dentry *dget(struct dentry *dentry)
  {
  	if (dentry) {
  		BUG_ON(!atomic_read(&dentry->d_count));
  		atomic_inc(&dentry->d_count);
  	}
  	return dentry;
  }
  
  extern struct dentry * dget_locked(struct dentry *);
  
  /**
   *	d_unhashed -	is dentry hashed
   *	@dentry: entry to check
   *
   *	Returns true if the dentry passed is not currently hashed.
   */
   
  static inline int d_unhashed(struct dentry *dentry)
  {
  	return (dentry->d_flags & DCACHE_UNHASHED);
  }

  static inline int d_unlinked(struct dentry *dentry)
  {
  	return d_unhashed(dentry) && !IS_ROOT(dentry);
  }

  static inline int cant_mount(struct dentry *dentry)
  {
  	return (dentry->d_flags & DCACHE_CANT_MOUNT);
  }
  
  static inline void dont_mount(struct dentry *dentry)
  {
  	spin_lock(&dentry->d_lock);
  	dentry->d_flags |= DCACHE_CANT_MOUNT;
  	spin_unlock(&dentry->d_lock);
  }

  static inline struct dentry *dget_parent(struct dentry *dentry)
  {
  	struct dentry *ret;
  
  	spin_lock(&dentry->d_lock);
  	ret = dget(dentry->d_parent);
  	spin_unlock(&dentry->d_lock);
  	return ret;
  }
  
  extern void dput(struct dentry *);
  
  static inline int d_mountpoint(struct dentry *dentry)
  {
  	return dentry->d_mounted;
  }

  extern struct vfsmount *lookup_mnt(struct path *);

  extern struct dentry *lookup_create(struct nameidata *nd, int is_dir);
  
  extern int sysctl_vfs_cache_pressure;

  #endif	/* __LINUX_DCACHE_H */