[linux-2.6-block.git] / include / 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/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 */

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

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

extern int sysctl_vfs_cache_pressure;

#endif	/* __LINUX_DCACHE_H */
Commit	Line	Data
1da177e4 LT	1	#ifndef __LINUX_DCACHE_H
	2	#define __LINUX_DCACHE_H
	3
1da177e4 LT	4	#include <asm/atomic.h>
1da177e4 LT	5	#include <linux/list.h>
82524746	6	#include <linux/rculist.h>
1da177e4 LT	7	#include <linux/spinlock.h>
	8	#include <linux/cache.h>
	9	#include <linux/rcupdate.h>
1da177e4 LT	10
1da177e4 LT	11	struct nameidata;
cf28b486	12	struct path;
1da177e4 LT	13	struct vfsmount;
	14
	15	/*
	16	* linux/include/linux/dcache.h
	17	*
	18	* Dirent cache data structures
	19	*
	20	* (C) Copyright 1997 Thomas Schoebel-Theuer,
	21	* with heavy changes by Linus Torvalds
	22	*/
	23
	24	#define IS_ROOT(x) ((x) == (x)->d_parent)
	25
	26	/*
	27	* "quick string" -- eases parameter passing, but more importantly
	28	* saves "metadata" about the string (ie length and the hash).
	29	*
	30	* hash comes first so it snuggles against d_parent in the
	31	* dentry.
	32	*/
	33	struct qstr {
	34	unsigned int hash;
	35	unsigned int len;
	36	const unsigned char *name;
	37	};
	38
	39	struct dentry_stat_t {
	40	int nr_dentry;
	41	int nr_unused;
	42	int age_limit; /* age in seconds */
	43	int want_pages; /* pages requested by system */
	44	int dummy[2];
	45	};
	46	extern struct dentry_stat_t dentry_stat;
	47
	48	/* Name hashing routines. Initial hash value */
	49	/* Hash courtesy of the R5 hash in reiserfs modulo sign bits */
	50	#define init_name_hash() 0
	51
	52	/* partial hash update function. Assume roughly 4 bits per character */
	53	static inline unsigned long
	54	partial_name_hash(unsigned long c, unsigned long prevhash)
	55	{
	56	return (prevhash + (c << 4) + (c >> 4)) * 11;
	57	}
	58
	59	/*
	60	* Finally: cut down the number of bits to a int value (and try to avoid
	61	* losing bits)
	62	*/
	63	static inline unsigned long end_name_hash(unsigned long hash)
	64	{
	65	return (unsigned int) hash;
	66	}
	67
	68	/* Compute the hash for a name string. */
	69	static inline unsigned int
	70	full_name_hash(const unsigned char *name, unsigned int len)
	71	{
	72	unsigned long hash = init_name_hash();
	73	while (len--)
	74	hash = partial_name_hash(*name++, hash);
	75	return end_name_hash(hash);
	76	}
77
c2452f32 NP	78	/*
	79	* Try to keep struct dentry aligned on 64 byte cachelines (this will
	80	* give reasonable cacheline footprint with larger lines without the
	81	* large memory footprint increase).
	82	*/
	83	#ifdef CONFIG_64BIT
	84	#define DNAME_INLINE_LEN_MIN 32 /* 192 bytes */
	85	#else
	86	#define DNAME_INLINE_LEN_MIN 40 /* 128 bytes */
	87	#endif
1da177e4 LT	88
	89	struct dentry {
	90	atomic_t d_count;
	91	unsigned int d_flags; /* protected by d_lock */
	92	spinlock_t d_lock; /* per dentry lock */
c2452f32	93	int d_mounted;
1da177e4 LT	94	struct inode d_inode; / Where the name belongs to - NULL is
	95	* negative */
	96	/*
	97	* The next three fields are touched by __d_lookup. Place them here
3f4bb1f4	98	* so they all fit in a cache line.
1da177e4	99	*/
3f4bb1f4	100	struct hlist_node d_hash; /* lookup hash list */
1da177e4 LT	101	struct dentry d_parent; / parent directory */
	102	struct qstr d_name;
	103
	104	struct list_head d_lru; /* LRU list */
5160ee6f ED	105	/*
	106	* d_child and d_rcu can share memory
	107	*/
	108	union {
	109	struct list_head d_child; /* child of parent list */
	110	struct rcu_head d_rcu;
	111	} d_u;
1da177e4 LT	112	struct list_head d_subdirs; /* our children */
	113	struct list_head d_alias; /* inode alias list */
	114	unsigned long d_time; /* used by d_revalidate */
e56980d4	115	const struct dentry_operations *d_op;
1da177e4 LT	116	struct super_block d_sb; / The root of the dentry tree */
1da177e4 LT	117	void d_fsdata; / fs-specific data */
c2452f32	118
1da177e4 LT	119	unsigned char d_iname[DNAME_INLINE_LEN_MIN]; /* small names */
	120	};
	121
a90b9c05 IM	122	/*
	123	* dentry->d_lock spinlock nesting subclasses:
	124	*
	125	* 0: normal
	126	* 1: nested
	127	*/
	128	enum dentry_d_lock_class
	129	{
	130	DENTRY_D_LOCK_NORMAL, /* implicitly used by plain spin_lock() APIs. */
	131	DENTRY_D_LOCK_NESTED
	132	};
	133
1da177e4 LT	134	struct dentry_operations {
	135	int (d_revalidate)(struct dentry , struct nameidata *);
	136	int (d_hash) (struct dentry , struct qstr *);
	137	int (d_compare) (struct dentry , struct qstr , struct qstr );
	138	int (d_delete)(struct dentry );
	139	void (d_release)(struct dentry );
	140	void (d_iput)(struct dentry , struct inode *);
c23fbb6b	141	char (d_dname)(struct dentry , char , int);
1da177e4 LT	142	};
	143
	144	/* the dentry parameter passed to d_hash and d_compare is the parent
	145	* directory of the entries to be compared. It is used in case these
	146	* functions need any directory specific information for determining
	147	* equivalency classes. Using the dentry itself might not work, as it
	148	* might be a negative dentry which has no information associated with
	149	* it */
	150
	151	/*
	152	locking rules:
	153	big lock dcache_lock d_lock may block
	154	d_revalidate: no no no yes
	155	d_hash no no no yes
	156	d_compare: no yes yes no
	157	d_delete: no yes no no
	158	d_release: no no no yes
	159	d_iput: no no no yes
	160	*/
	161
	162	/* d_flags entries */
	163	#define DCACHE_AUTOFS_PENDING 0x0001 /* autofs: "under construction" */
	164	#define DCACHE_NFSFS_RENAMED 0x0002 /* this dentry has been "silly
	165	* renamed" and has to be
	166	* deleted on the last dput()
	167	*/
	168	#define DCACHE_DISCONNECTED 0x0004
	169	/* This dentry is possibly not currently connected to the dcache tree,
	170	* in which case its parent will either be itself, or will have this
	171	* flag as well. nfsd will not use a dentry with this bit set, but will
	172	* first endeavour to clear the bit either by discovering that it is
	173	* connected, or by performing lookup operations. Any filesystem which
	174	* supports nfsd_operations MUST have a lookup function which, if it finds
	175	* a directory inode with a DCACHE_DISCONNECTED dentry, will d_move
	176	* that dentry into place and return that dentry rather than the passed one,
	177	* typically using d_splice_alias.
	178	*/
	179
	180	#define DCACHE_REFERENCED 0x0008 /* Recently used, don't discard. */
	181	#define DCACHE_UNHASHED 0x0010
	182
c32ccd87 NP	183	#define DCACHE_INOTIFY_PARENT_WATCHED 0x0020 /* Parent inode is watched */
c32ccd87 NP	184
c2452f32 NP	185	#define DCACHE_COOKIE 0x0040 /* For use by dcookie subsystem */
c2452f32 NP	186
1da177e4	187	extern spinlock_t dcache_lock;
74c3cbe3	188	extern seqlock_t rename_lock;
1da177e4 LT	189
	190	/**
	191	* d_drop - drop a dentry
	192	* @dentry: dentry to drop
	193	*
	194	* d_drop() unhashes the entry from the parent dentry hashes, so that it won't
	195	* be found through a VFS lookup any more. Note that this is different from
	196	* deleting the dentry - d_delete will try to mark the dentry negative if
	197	* possible, giving a successful _negative_ lookup, while d_drop will
	198	* just make the cache lookup fail.
	199	*
	200	* d_drop() is used mainly for stuff that wants to invalidate a dentry for some
	201	* reason (NFS timeouts or autofs deletes).
	202	*
	203	* __d_drop requires dentry->d_lock.
	204	*/
	205
	206	static inline void __d_drop(struct dentry *dentry)
	207	{
	208	if (!(dentry->d_flags & DCACHE_UNHASHED)) {
	209	dentry->d_flags \|= DCACHE_UNHASHED;
	210	hlist_del_rcu(&dentry->d_hash);
	211	}
	212	}
	213
	214	static inline void d_drop(struct dentry *dentry)
	215	{
	216	spin_lock(&dcache_lock);
	217	spin_lock(&dentry->d_lock);
	218	__d_drop(dentry);
	219	spin_unlock(&dentry->d_lock);
	220	spin_unlock(&dcache_lock);
	221	}
	222
	223	static inline int dname_external(struct dentry *dentry)
	224	{
	225	return dentry->d_name.name != dentry->d_iname;
	226	}
	227
	228	/*
	229	* These are the low-level FS interfaces to the dcache..
	230	*/
	231	extern void d_instantiate(struct dentry , struct inode );
	232	extern struct dentry * d_instantiate_unique(struct dentry , struct inode );
770bfad8	233	extern struct dentry * d_materialise_unique(struct dentry , struct inode );
1da177e4 LT	234	extern void d_delete(struct dentry *);
	235
	236	/* allocate/de-allocate */
	237	extern struct dentry * d_alloc(struct dentry , const struct qstr );
1da177e4	238	extern struct dentry * d_splice_alias(struct inode , struct dentry );
e45b590b	239	extern struct dentry * d_add_ci(struct dentry , struct inode , struct qstr *);
4ea3ada2	240	extern struct dentry * d_obtain_alias(struct inode *);
1da177e4 LT	241	extern void shrink_dcache_sb(struct super_block *);
1da177e4 LT	242	extern void shrink_dcache_parent(struct dentry *);
c636ebdb	243	extern void shrink_dcache_for_umount(struct super_block *);
1da177e4 LT	244	extern int d_invalidate(struct dentry *);
	245
	246	/* only used at mount-time */
	247	extern struct dentry * d_alloc_root(struct inode *);
	248
	249	/* <clickety>-<click> the ramfs-type tree */
	250	extern void d_genocide(struct dentry *);
	251
	252	extern struct dentry d_find_alias(struct inode );
	253	extern void d_prune_aliases(struct inode *);
	254
	255	/* test whether we have any submounts in a subdir tree */
	256	extern int have_submounts(struct dentry *);
	257
	258	/*
	259	* This adds the entry to the hash queues.
	260	*/
	261	extern void d_rehash(struct dentry *);
	262
	263	/**
	264	* d_add - add dentry to hash queues
	265	* @entry: dentry to add
	266	* @inode: The inode to attach to this dentry
	267	*
	268	* This adds the entry to the hash queues and initializes @inode.
	269	* The entry was actually filled in earlier during d_alloc().
	270	*/
	271
	272	static inline void d_add(struct dentry entry, struct inode inode)
	273	{
	274	d_instantiate(entry, inode);
	275	d_rehash(entry);
	276	}
	277
	278	/**
	279	* d_add_unique - add dentry to hash queues without aliasing
	280	* @entry: dentry to add
	281	* @inode: The inode to attach to this dentry
	282	*
	283	* This adds the entry to the hash queues and initializes @inode.
	284	* The entry was actually filled in earlier during d_alloc().
	285	*/
	286	static inline struct dentry d_add_unique(struct dentry entry, struct inode *inode)
	287	{
	288	struct dentry *res;
	289
	290	res = d_instantiate_unique(entry, inode);
	291	d_rehash(res != NULL ? res : entry);
	292	return res;
	293	}
	294
	295	/* used for rename() and baskets */
	296	extern void d_move(struct dentry , struct dentry );
e2761a11	297	extern struct dentry d_ancestor(struct dentry , struct dentry *);
1da177e4 LT	298
	299	/* appendix may either be NULL or be used for transname suffixes */
	300	extern struct dentry * d_lookup(struct dentry , struct qstr );
	301	extern struct dentry * __d_lookup(struct dentry , struct qstr );
3e7e241f	302	extern struct dentry * d_hash_and_lookup(struct dentry , struct qstr );
1da177e4 LT	303
	304	/* validate "insecure" dentry pointer */
	305	extern int d_validate(struct dentry , struct dentry );
	306
c23fbb6b ED	307	/*
	308	* helper function for dentry_operations.d_dname() members
	309	*/
	310	extern char dynamic_dname(struct dentry , char , int, const char , ...);
	311
9d1bc601	312	extern char __d_path(const struct path path, struct path root, char , int);
20d4fdc1	313	extern char d_path(const struct path , char *, int);
6092d048	314	extern char dentry_path(struct dentry , char *, int);
cf28b486	315
1da177e4 LT	316	/* Allocation counts.. */
	317
	318	/**
	319	* dget, dget_locked - get a reference to a dentry
	320	* @dentry: dentry to get a reference to
	321	*
	322	* Given a dentry or %NULL pointer increment the reference count
	323	* if appropriate and return the dentry. A dentry will not be
	324	* destroyed when it has references. dget() should never be
	325	* called for dentries with zero reference counter. For these cases
	326	* (preferably none, functions in dcache.c are sufficient for normal
	327	* needs and they take necessary precautions) you should hold dcache_lock
	328	* and call dget_locked() instead of dget().
	329	*/
	330
	331	static inline struct dentry dget(struct dentry dentry)
	332	{
	333	if (dentry) {
	334	BUG_ON(!atomic_read(&dentry->d_count));
	335	atomic_inc(&dentry->d_count);
	336	}
	337	return dentry;
	338	}
	339
	340	extern struct dentry * dget_locked(struct dentry *);
	341
	342	/**
	343	* d_unhashed - is dentry hashed
	344	* @dentry: entry to check
	345	*
	346	* Returns true if the dentry passed is not currently hashed.
	347	*/
	348
	349	static inline int d_unhashed(struct dentry *dentry)
	350	{
	351	return (dentry->d_flags & DCACHE_UNHASHED);
	352	}
	353
	354	static inline struct dentry dget_parent(struct dentry dentry)
	355	{
	356	struct dentry *ret;
	357
	358	spin_lock(&dentry->d_lock);
	359	ret = dget(dentry->d_parent);
	360	spin_unlock(&dentry->d_lock);
	361	return ret;
	362	}
	363
	364	extern void dput(struct dentry *);
	365
	366	static inline int d_mountpoint(struct dentry *dentry)
	367	{
	368	return dentry->d_mounted;
	369	}
	370
	371	extern struct vfsmount lookup_mnt(struct vfsmount , struct dentry *);
	372	extern struct dentry lookup_create(struct nameidata nd, int is_dir);
	373
	374	extern int sysctl_vfs_cache_pressure;
	375
1da177e4	376	#endif /* __LINUX_DCACHE_H */