idr.h

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/*
 * include/linux/idr.h
 * 
 * 2002-10-18  written by Jim Houston [email protected]
 *  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_IDR_SHIFT (sizeof(int)*8 - 1)
#define MAX_IDR_BIT (1U << MAX_IDR_SHIFT)
#define MAX_IDR_MASK (MAX_IDR_BIT - 1)

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

/* Number of id_layer structs to leave in free list */
#define MAX_IDR_FREE (MAX_IDR_LEVEL * 2)

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

struct idr {
    struct idr_layer __rcu *top;
    struct idr_layer *id_free;
    int       layers; /* only valid without concurrent changes */
    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)

/*
 * 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_get_next(struct idr *idp, int *nextid);
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.
 *
 * IDA_BITMAP_LONGS is calculated to be one less to accommodate
 * ida_bitmap->nr_busy so that the whole struct fits in 128 bytes.
 */
#define IDA_CHUNK_SIZE      128 /* 128 bytes per chunk */
#define IDA_BITMAP_LONGS    (IDA_CHUNK_SIZE / 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);

int ida_simple_get(struct ida *ida, unsigned int start, unsigned int end,
           gfp_t gfp_mask);
void ida_simple_remove(struct ida *ida, unsigned int id);

void __init idr_init_cache(void);

#endif /* __IDR_H__ */