root/include/linux/dcache.h

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INCLUDED FROM

DEFINITIONS

This source file includes following definitions.
  1. partial_name_hash
  2. end_name_hash
  3. d_add
  4. d_add_unique
  5. d_count
  6. dget_dlock
  7. dget
  8. d_unhashed
  9. d_unlinked
  10. cant_mount
  11. dont_mount
  12. d_managed
  13. d_mountpoint
  14. __d_set_type
  15. __d_clear_type
  16. d_set_type
  17. __d_entry_type
  18. d_can_lookup
  19. d_is_autodir
  20. d_is_dir
  21. d_is_symlink
  22. d_is_file
  23. d_is_negative
  24. d_is_positive
  25. vfs_pressure_ratio
#ifndef __LINUX_DCACHE_H
#define __LINUX_DCACHE_H

#include <linux/atomic.h>
#include <linux/list.h>
#include <linux/rculist.h>
#include <linux/rculist_bl.h>
#include <linux/spinlock.h>
#include <linux/seqlock.h>
#include <linux/cache.h>
#include <linux/rcupdate.h>
#include <linux/lockref.h>

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)

/* The hash is always the low bits of hash_len */
#ifdef __LITTLE_ENDIAN
 #define HASH_LEN_DECLARE u32 hash; u32 len;
 #define bytemask_from_count(cnt)       (~(~0ul << (cnt)*8))
#else
 #define HASH_LEN_DECLARE u32 len; u32 hash;
 #define bytemask_from_count(cnt)       (~(~0ul >> (cnt)*8))
#endif

/*
 * "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 {
        union {
                struct {
                        HASH_LEN_DECLARE;
                };
                u64 hash_len;
        };
        const unsigned char *name;
};

#define QSTR_INIT(n,l) { { { .len = l } }, .name = n }
#define hashlen_hash(hashlen) ((u32) (hashlen))
#define hashlen_len(hashlen)  ((u32)((hashlen) >> 32))
#define hashlen_create(hash,len) (((u64)(len)<<32)|(u32)(hash))

struct dentry_stat_t {
        long nr_dentry;
        long nr_unused;
        long age_limit;          /* age in seconds */
        long want_pages;         /* pages requested by system */
        long 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. */
extern unsigned int full_name_hash(const unsigned char *, unsigned int);

/*
 * 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 32 /* 192 bytes */
#else
# ifdef CONFIG_SMP
#  define DNAME_INLINE_LEN 36 /* 128 bytes */
# else
#  define DNAME_INLINE_LEN 40 /* 128 bytes */
# endif
#endif

#define d_lock  d_lockref.lock

struct dentry {
        /* RCU lookup touched fields */
        unsigned int d_flags;           /* protected by d_lock */
        seqcount_t d_seq;               /* per dentry seqlock */
        struct hlist_bl_node d_hash;    /* lookup hash list */
        struct dentry *d_parent;        /* parent directory */
        struct qstr d_name;
        struct inode *d_inode;          /* Where the name belongs to - NULL is
                                         * negative */
        unsigned char d_iname[DNAME_INLINE_LEN];        /* small names */

        /* Ref lookup also touches following */
        struct lockref d_lockref;       /* per-dentry lock and refcount */
        const struct dentry_operations *d_op;
        struct super_block *d_sb;       /* The root of the dentry tree */
        unsigned long d_time;           /* used by d_revalidate */
        void *d_fsdata;                 /* fs-specific data */

        struct list_head d_lru;         /* LRU list */
        struct list_head d_child;       /* child of parent list */
        struct list_head d_subdirs;     /* our children */
        /*
         * d_alias and d_rcu can share memory
         */
        union {
                struct hlist_node d_alias;      /* inode alias list */
                struct rcu_head d_rcu;
        } d_u;
};

/*
 * 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 *, unsigned int);
        int (*d_weak_revalidate)(struct dentry *, unsigned int);
        int (*d_hash)(const struct dentry *, struct qstr *);
        int (*d_compare)(const struct dentry *, const struct dentry *,
                        unsigned int, const char *, const struct qstr *);
        int (*d_delete)(const struct dentry *);
        void (*d_release)(struct dentry *);
        void (*d_prune)(struct dentry *);
        void (*d_iput)(struct dentry *, struct inode *);
        char *(*d_dname)(struct dentry *, char *, int);
        struct vfsmount *(*d_automount)(struct path *);
        int (*d_manage)(struct dentry *, bool);
} ____cacheline_aligned;

/*
 * 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_OP_HASH                  0x00000001
#define DCACHE_OP_COMPARE               0x00000002
#define DCACHE_OP_REVALIDATE            0x00000004
#define DCACHE_OP_DELETE                0x00000008
#define DCACHE_OP_PRUNE                 0x00000010

#define DCACHE_DISCONNECTED             0x00000020
     /* 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               0x00000040 /* Recently used, don't discard. */
#define DCACHE_RCUACCESS                0x00000080 /* Entry has ever been RCU-visible */

#define DCACHE_CANT_MOUNT               0x00000100
#define DCACHE_GENOCIDE                 0x00000200
#define DCACHE_SHRINK_LIST              0x00000400

#define DCACHE_OP_WEAK_REVALIDATE       0x00000800

#define DCACHE_NFSFS_RENAMED            0x00001000
     /* this dentry has been "silly renamed" and has to be deleted on the last
      * dput() */
#define DCACHE_COOKIE                   0x00002000 /* For use by dcookie subsystem */
#define DCACHE_FSNOTIFY_PARENT_WATCHED  0x00004000
     /* Parent inode is watched by some fsnotify listener */

#define DCACHE_DENTRY_KILLED            0x00008000

#define DCACHE_MOUNTED                  0x00010000 /* is a mountpoint */
#define DCACHE_NEED_AUTOMOUNT           0x00020000 /* handle automount on this dir */
#define DCACHE_MANAGE_TRANSIT           0x00040000 /* manage transit from this dirent */
#define DCACHE_MANAGED_DENTRY \
        (DCACHE_MOUNTED|DCACHE_NEED_AUTOMOUNT|DCACHE_MANAGE_TRANSIT)

#define DCACHE_LRU_LIST                 0x00080000

#define DCACHE_ENTRY_TYPE               0x00700000
#define DCACHE_MISS_TYPE                0x00000000 /* Negative dentry */
#define DCACHE_DIRECTORY_TYPE           0x00100000 /* Normal directory */
#define DCACHE_AUTODIR_TYPE             0x00200000 /* Lookupless directory (presumed automount) */
#define DCACHE_SYMLINK_TYPE             0x00300000 /* Symlink */
#define DCACHE_FILE_TYPE                0x00400000 /* Other file type */

#define DCACHE_MAY_FREE                 0x00800000

extern seqlock_t rename_lock;

/*
 * 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 int d_instantiate_no_diralias(struct dentry *, struct inode *);
extern void __d_drop(struct dentry *dentry);
extern void d_drop(struct dentry *dentry);
extern void d_delete(struct dentry *);
extern void d_set_d_op(struct dentry *dentry, const struct dentry_operations *op);

/* allocate/de-allocate */
extern struct dentry * d_alloc(struct dentry *, const struct qstr *);
extern struct dentry * d_alloc_pseudo(struct super_block *, 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_find_any_alias(struct inode *inode);
extern struct dentry * d_obtain_alias(struct inode *);
extern struct dentry * d_obtain_root(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 void d_invalidate(struct dentry *);

/* only used at mount-time */
extern struct dentry * d_make_root(struct inode *);

/* <clickety>-<click> the ramfs-type tree */
extern void d_genocide(struct dentry *);

extern void d_tmpfile(struct dentry *, struct inode *);

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 void d_exchange(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(const struct dentry *, const struct qstr *);
extern struct dentry *d_hash_and_lookup(struct dentry *, struct qstr *);
extern struct dentry *__d_lookup(const struct dentry *, const struct qstr *);
extern struct dentry *__d_lookup_rcu(const struct dentry *parent,
                                const struct qstr *name, unsigned *seq);

static inline unsigned d_count(const struct dentry *dentry)
{
        return dentry->d_lockref.count;
}

/* 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 *simple_dname(struct dentry *, char *, int);

extern char *__d_path(const struct path *, const struct path *, char *, int);
extern char *d_absolute_path(const struct path *, char *, int);
extern char *d_path(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_lockref.count++;
        return dentry;
}

static inline struct dentry *dget(struct dentry *dentry)
{
        if (dentry)
                lockref_get(&dentry->d_lockref);
        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(const struct dentry *dentry)
{
        return hlist_bl_unhashed(&dentry->d_hash);
}

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

static inline int cant_mount(const 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 bool d_managed(const struct dentry *dentry)
{
        return dentry->d_flags & DCACHE_MANAGED_DENTRY;
}

static inline bool d_mountpoint(const struct dentry *dentry)
{
        return dentry->d_flags & DCACHE_MOUNTED;
}

/*
 * Directory cache entry type accessor functions.
 */
static inline void __d_set_type(struct dentry *dentry, unsigned type)
{
        dentry->d_flags = (dentry->d_flags & ~DCACHE_ENTRY_TYPE) | type;
}

static inline void __d_clear_type(struct dentry *dentry)
{
        __d_set_type(dentry, DCACHE_MISS_TYPE);
}

static inline void d_set_type(struct dentry *dentry, unsigned type)
{
        spin_lock(&dentry->d_lock);
        __d_set_type(dentry, type);
        spin_unlock(&dentry->d_lock);
}

static inline unsigned __d_entry_type(const struct dentry *dentry)
{
        return dentry->d_flags & DCACHE_ENTRY_TYPE;
}

static inline bool d_can_lookup(const struct dentry *dentry)
{
        return __d_entry_type(dentry) == DCACHE_DIRECTORY_TYPE;
}

static inline bool d_is_autodir(const struct dentry *dentry)
{
        return __d_entry_type(dentry) == DCACHE_AUTODIR_TYPE;
}

static inline bool d_is_dir(const struct dentry *dentry)
{
        return d_can_lookup(dentry) || d_is_autodir(dentry);
}

static inline bool d_is_symlink(const struct dentry *dentry)
{
        return __d_entry_type(dentry) == DCACHE_SYMLINK_TYPE;
}

static inline bool d_is_file(const struct dentry *dentry)
{
        return __d_entry_type(dentry) == DCACHE_FILE_TYPE;
}

static inline bool d_is_negative(const struct dentry *dentry)
{
        return __d_entry_type(dentry) == DCACHE_MISS_TYPE;
}

static inline bool d_is_positive(const struct dentry *dentry)
{
        return !d_is_negative(dentry);
}

extern int sysctl_vfs_cache_pressure;

static inline unsigned long vfs_pressure_ratio(unsigned long val)
{
        return mult_frac(val, sysctl_vfs_cache_pressure, 100);
}
#endif  /* __LINUX_DCACHE_H */
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