include/linux/dcache.h - linux - Git at Google

 #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/seqlock.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 {
 	unsigned int d_count;		/* protected by d_lock */
 	unsigned int d_flags;		/* protected by d_lock */
 	spinlock_t d_lock;		/* per dentry lock */
 	seqcount_t d_seq;		/* per dentry seqlock */
 	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)(const struct dentry *, const struct inode *,
 			struct qstr *);
 	int (*d_compare)(const struct dentry *, const struct inode *,
 			const struct dentry *, const struct inode *,
 			unsigned int, const char *, const struct qstr *);
 	int (*d_delete)(const struct dentry *);
 	void (*d_release)(struct dentry *);
 	void (*d_iput)(struct dentry *, struct inode *);
 	char *(*d_dname)(struct dentry *, char *, int);
 };

 /*
  * Locking rules for dentry_operations callbacks are to be found in
  * Documentation/filesystems/Locking. Keep it updated!
  *
  * FUrther descriptions are found in Documentation/filesystems/vfs.txt.
  * Keep it updated too!
  */

 /* 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
 #define DCACHE_GENOCIDE		0x0200
 #define DCACHE_MOUNTED		0x0400	/* is a mountpoint */


 extern spinlock_t dcache_inode_lock;
 extern seqlock_t rename_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_drop(struct dentry *dentry);
 extern void d_drop(struct dentry *dentry);
 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;
 }

 extern void dentry_update_name_case(struct dentry *, struct qstr *);

 /* 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_hash_and_lookup(struct dentry *, struct qstr *);
 extern struct dentry *__d_lookup(struct dentry *, struct qstr *);
 extern struct dentry *__d_lookup_rcu(struct dentry *parent, struct qstr *name,
 				unsigned *seq, struct inode **inode);

 /**
  * __d_rcu_to_refcount - take a refcount on dentry if sequence check is ok
  * @dentry: dentry to take a ref on
  * @seq: seqcount to verify against
  * @Returns: 0 on failure, else 1.
  *
  * __d_rcu_to_refcount operates on a dentry,seq pair that was returned
  * by __d_lookup_rcu, to get a reference on an rcu-walk dentry.
  */
 static inline int __d_rcu_to_refcount(struct dentry *dentry, unsigned seq)
 {
 	int ret = 0;

 	assert_spin_locked(&dentry->d_lock);
 	if (!read_seqcount_retry(&dentry->d_seq, seq)) {
 		ret = 1;
 		dentry->d_count++;
 	}

 	return ret;
 }

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

 /* Allocation counts.. */

 /**
  *	dget, dget_dlock -	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.
  */
 static inline struct dentry *dget_dlock(struct dentry *dentry)
 {
 	if (dentry)
 		dentry->d_count++;
 	return dentry;
 }

 static inline struct dentry *dget(struct dentry *dentry)
 {
 	if (dentry) {
 		spin_lock(&dentry->d_lock);
 		dget_dlock(dentry);
 		spin_unlock(&dentry->d_lock);
 	}
 	return dentry;
 }

 extern struct dentry *dget_parent(struct dentry *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);
 }

 extern void dput(struct dentry *);

 static inline int d_mountpoint(struct dentry *dentry)
 {
 	return dentry->d_flags & DCACHE_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 */
	#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/seqlock.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 {
	unsigned int d_count; /* protected by d_lock */
	unsigned int d_flags; /* protected by d_lock */
	spinlock_t d_lock; /* per dentry lock */
	seqcount_t d_seq; /* per dentry seqlock */
	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)(const struct dentry , const struct inode *,
	struct qstr *);
	int (d_compare)(const struct dentry , const struct inode *,
	const struct dentry , const struct inode ,
	unsigned int, const char , const struct qstr );
	int (d_delete)(const struct dentry );
	void (d_release)(struct dentry );
	void (d_iput)(struct dentry , struct inode *);
	char (d_dname)(struct dentry , char , int);
	};

	/*
	* Locking rules for dentry_operations callbacks are to be found in
	* Documentation/filesystems/Locking. Keep it updated!
	*
	* FUrther descriptions are found in Documentation/filesystems/vfs.txt.
	* Keep it updated too!
	*/

	/* 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
	#define DCACHE_GENOCIDE 0x0200
	#define DCACHE_MOUNTED 0x0400 /* is a mountpoint */


	extern spinlock_t dcache_inode_lock;
	extern seqlock_t rename_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_drop(struct dentry *dentry);
	extern void d_drop(struct dentry *dentry);
	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;
	}

	extern void dentry_update_name_case(struct dentry , struct qstr );

	/* 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_hash_and_lookup(struct dentry , struct qstr *);
	extern struct dentry __d_lookup(struct dentry , struct qstr *);
	extern struct dentry __d_lookup_rcu(struct dentry parent, struct qstr *name,
	unsigned seq, struct inode *inode);

	/**
	* __d_rcu_to_refcount - take a refcount on dentry if sequence check is ok
	* @dentry: dentry to take a ref on
	* @seq: seqcount to verify against
	* @Returns: 0 on failure, else 1.
	*
	* __d_rcu_to_refcount operates on a dentry,seq pair that was returned
	* by __d_lookup_rcu, to get a reference on an rcu-walk dentry.
	*/
	static inline int __d_rcu_to_refcount(struct dentry *dentry, unsigned seq)
	{
	int ret = 0;

	assert_spin_locked(&dentry->d_lock);
	if (!read_seqcount_retry(&dentry->d_seq, seq)) {
	ret = 1;
	dentry->d_count++;
	}

	return ret;
	}

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

	/* Allocation counts.. */

	/**
	* dget, dget_dlock - 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.
	*/
	static inline struct dentry dget_dlock(struct dentry dentry)
	{
	if (dentry)
	dentry->d_count++;
	return dentry;
	}

	static inline struct dentry dget(struct dentry dentry)
	{
	if (dentry) {
	spin_lock(&dentry->d_lock);
	dget_dlock(dentry);
	spin_unlock(&dentry->d_lock);
	}
	return dentry;
	}

	extern struct dentry dget_parent(struct dentry 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);
	}

	extern void dput(struct dentry *);

	static inline int d_mountpoint(struct dentry *dentry)
	{
	return dentry->d_flags & DCACHE_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 */