root/include/linux/idr.h

INCLUDED FROM

/*
 * include/linux/idr.h
 * 
 * 2002-10-18  written by Jim Houston jim.houston@ccur.com
 *      Copyright (C) 2002 by Concurrent Computer Corporation
 *      Distributed under the GNU GPL license version 2.
 *
 * Small id to pointer translation service avoiding fixed sized
 * tables.
 */

#ifndef __IDR_H__
#define __IDR_H__

#include <linux/types.h>
#include <linux/bitops.h>
#include <linux/init.h>
#include <linux/rcupdate.h>

#if BITS_PER_LONG == 32
# define IDR_BITS 5
# define IDR_FULL 0xfffffffful
/* We can only use two of the bits in the top level because there is
   only one possible bit in the top level (5 bits * 7 levels = 35
   bits, but you only use 31 bits in the id). */
# define TOP_LEVEL_FULL (IDR_FULL >> 30)
#elif BITS_PER_LONG == 64
# define IDR_BITS 6
# define IDR_FULL 0xfffffffffffffffful
/* We can only use two of the bits in the top level because there is
   only one possible bit in the top level (6 bits * 6 levels = 36
   bits, but you only use 31 bits in the id). */
# define TOP_LEVEL_FULL (IDR_FULL >> 62)
#else
# error "BITS_PER_LONG is not 32 or 64"
#endif

#define IDR_SIZE (1 << IDR_BITS)
#define IDR_MASK ((1 << IDR_BITS)-1)

#define MAX_ID_SHIFT (sizeof(int)*8 - 1)
#define MAX_ID_BIT (1U << MAX_ID_SHIFT)
#define MAX_ID_MASK (MAX_ID_BIT - 1)

/* Leave the possibility of an incomplete final layer */
#define MAX_LEVEL (MAX_ID_SHIFT + IDR_BITS - 1) / IDR_BITS

/* Number of id_layer structs to leave in free list */
#define IDR_FREE_MAX MAX_LEVEL + MAX_LEVEL

struct idr_layer {
        unsigned long            bitmap; /* A zero bit means "space here" */
        struct idr_layer        *ary[1<<IDR_BITS];
        int                      count;  /* When zero, we can release it */
        struct rcu_head          rcu_head;
};

struct idr {
        struct idr_layer *top;
        struct idr_layer *id_free;
        int               layers;
        int               id_free_cnt;
        spinlock_t        lock;
};

#define IDR_INIT(name)                                          \
{                                                               \
        .top            = NULL,                                 \
        .id_free        = NULL,                                 \
        .layers         = 0,                                    \
        .id_free_cnt    = 0,                                    \
        .lock           = __SPIN_LOCK_UNLOCKED(name.lock),      \
}
#define DEFINE_IDR(name)        struct idr name = IDR_INIT(name)

/* Actions to be taken after a call to _idr_sub_alloc */
#define IDR_NEED_TO_GROW -2
#define IDR_NOMORE_SPACE -3

#define _idr_rc_to_errno(rc) ((rc) == -1 ? -EAGAIN : -ENOSPC)

/**
 * idr synchronization (stolen from radix-tree.h)
 *
 * idr_find() is able to be called locklessly, using RCU. The caller must
 * ensure calls to this function are made within rcu_read_lock() regions.
 * Other readers (lock-free or otherwise) and modifications may be running
 * concurrently.
 *
 * It is still required that the caller manage the synchronization and
 * lifetimes of the items. So if RCU lock-free lookups are used, typically
 * this would mean that the items have their own locks, or are amenable to
 * lock-free access; and that the items are freed by RCU (or only freed after
 * having been deleted from the idr tree *and* a synchronize_rcu() grace
 * period).
 */

/*
 * This is what we export.
 */

void *idr_find(struct idr *idp, int id);
int idr_pre_get(struct idr *idp, gfp_t gfp_mask);
int idr_get_new(struct idr *idp, void *ptr, int *id);
int idr_get_new_above(struct idr *idp, void *ptr, int starting_id, int *id);
int idr_for_each(struct idr *idp,
                 int (*fn)(int id, void *p, void *data), void *data);
void *idr_replace(struct idr *idp, void *ptr, int id);
void idr_remove(struct idr *idp, int id);
void idr_remove_all(struct idr *idp);
void idr_destroy(struct idr *idp);
void idr_init(struct idr *idp);


/*
 * IDA - IDR based id allocator, use when translation from id to
 * pointer isn't necessary.
 */
#define IDA_CHUNK_SIZE          128     /* 128 bytes per chunk */
#define IDA_BITMAP_LONGS        (128 / sizeof(long) - 1)
#define IDA_BITMAP_BITS         (IDA_BITMAP_LONGS * sizeof(long) * 8)

struct ida_bitmap {
        long                    nr_busy;
        unsigned long           bitmap[IDA_BITMAP_LONGS];
};

struct ida {
        struct idr              idr;
        struct ida_bitmap       *free_bitmap;
};

#define IDA_INIT(name)          { .idr = IDR_INIT(name), .free_bitmap = NULL, }
#define DEFINE_IDA(name)        struct ida name = IDA_INIT(name)

int ida_pre_get(struct ida *ida, gfp_t gfp_mask);
int ida_get_new_above(struct ida *ida, int starting_id, int *p_id);
int ida_get_new(struct ida *ida, int *p_id);
void ida_remove(struct ida *ida, int id);
void ida_destroy(struct ida *ida);
void ida_init(struct ida *ida);

void __init idr_init_cache(void);

#endif /* __IDR_H__ */