/*
* 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.
*
* Modified by George Anzinger to reuse immediately and to use
* find bit instructions. Also removed _irq on spinlocks.
*
* Small id to pointer translation service.
*
* It uses a radix tree like structure as a sparse array indexed
* by the id to obtain the pointer. The bitmap makes allocating
* a new id quick.
*
* You call it to allocate an id (an int) an associate with that id a
* pointer or what ever, we treat it as a (void *). You can pass this
* id to a user for him to pass back at a later time. You then pass
* that id to this code and it returns your pointer.
* You can release ids at any time. When all ids are released, most of
* the memory is returned (we keep IDR_FREE_MAX) in a local pool so we
* don't need to go to the memory "store" during an id allocate, just
* so you don't need to be too concerned about locking and conflicts
* with the slab allocator.
*/
#ifndef TEST // to test in user space...
#include <linux/slab.h>
#include <linux/init.h>
#include <linux/module.h>
#endif
#include <linux/string.h>
#include <linux/idr.h>
static kmem_cache_t *idr_layer_cache;
static struct idr_layer *alloc_layer(struct idr *idp)
{
struct idr_layer *p;
spin_lock(&idp->lock);
if ((p = idp->id_free)) {
idp->id_free = p->ary[0];
idp->id_free_cnt--;
p->ary[0] = NULL;
}
spin_unlock(&idp->lock);
return(p);
}
static void free_layer(struct idr *idp, struct idr_layer *p)
{
/*
* Depends on the return element being zeroed.
*/
spin_lock(&idp->lock);
p->ary[0] = idp->id_free;
idp->id_free = p;
idp->id_free_cnt++;
spin_unlock(&idp->lock);
}
/**
* idr_pre_get - reserver resources for idr allocation
* @idp: idr handle
* @gfp_mask: memory allocation flags
*
* This function should be called prior to locking and calling the
* following function. It preallocates enough memory to satisfy
* the worst possible allocation.
*
* If the system is REALLY out of memory this function returns 0,
* otherwise 1.
*/
int idr_pre_get(struct idr *idp, unsigned gfp_mask)
{
while (idp->id_free_cnt < IDR_FREE_MAX) {
struct idr_layer *new;
new = kmem_cache_alloc(idr_layer_cache, gfp_mask);
if(new == NULL)
return (0);
free_layer(idp, new);
}
return 1;
}
EXPORT_SYMBOL(idr_pre_get);
static int sub_alloc(struct idr *idp, void *ptr, int *starting_id)
{
int n, m, sh;
struct idr_layer *p, *new;
struct idr_layer *pa[MAX_LEVEL];
int l, id;
long bm;
id = *starting_id;
p = idp->top;
l = idp->layers;
pa[l--] = NULL;
while (1) {
/*
* We run around this while until we reach the leaf node...
*/
n = (id >> (IDR_BITS*l)) & IDR_MASK;
bm = ~p->bitmap;
m = find_next_bit(&bm, IDR_SIZE, n);
if (m == IDR_SIZE) {
/* no space available go back to previous layer. */
l++;
id = (id | ((1 << (IDR_BITS*l))-1)) + 1;
if (!(p = pa[l])) {
*starting_id = id;
return -2;
}
continue;
}
if (m != n) {
sh = IDR_BITS*l;
id = ((id >> sh) ^ n ^ m) << sh;
}
if ((id >= MAX_ID_BIT) || (id < 0))
return -3;
if (l == 0)
break;
/*
* Create the layer below if it is missing.
*/
if (!p->ary[m]) {
if (!(new = alloc_layer(idp)))
return -1;
p->ary[m] = new;
p->count++;
}
pa[l--] = p;
p = p->ary[m];
}
/*
* We have reached the leaf node, plant the
* users pointer and return the raw id.
*/
p->ary[m] = (struct idr_layer *)ptr;
__set_bit(m, &p->bitmap);
p->count++;
/*
* If this layer is full mark the bit in the layer above
* to show that this part of the radix tree is full.
* This may complete the layer above and require walking
* up the radix tree.
*/
n = id;
while (p->bitmap == IDR_FULL) {
if (!(p = pa[++l]))
break;
n = n >> IDR_BITS;
__set_bit((n & IDR_MASK), &p->bitmap);
}
return(id);
}
static int idr_get_new_above_int(struct idr *idp, void *ptr, int starting_id)
{
struct idr_layer *p, *new;
int layers, v, id;
id = starting_id;
build_up:
p = idp->top;
layers = idp->layers;
if (unlikely(!p)) {
if (!(p = alloc_layer(idp)))
return -1;
layers = 1;
}
/*
* Add a new layer to the top of the tree if the requested
* id is larger than the currently allocated space.
*/
while ((layers < (MAX_LEVEL - 1)) && (id >= (1 << (layers*IDR_BITS)))) {
layers++;
if (!p->count)
continue;
if (!(new = alloc_layer(idp))) {
/*
* The allocation failed. If we built part of
* the structure tear it down.
*/
for (new = p; p && p != idp->top; new = p) {
p = p->ary[0];
new->ary[0] = NULL;
new->bitmap = new->count = 0;
free_layer(idp, new);
}
return -1;
}
new->ary[0] = p;
new->count = 1;
if (p->bitmap == IDR_FULL)
__set_bit(0, &new->bitmap);
p = new;
}
idp->top = p;
idp->layers = layers;
v = sub_alloc(idp, ptr, &id);
if (v == -2)
goto build_up;
return(v);
}
/**
* idr_get_new_above - allocate new idr entry above or equal to a start id
* @idp: idr handle
* @ptr: pointer you want associated with the ide
* @start_id: id to start search at
* @id: pointer to the allocated handle
*
* This is the allocate id function. It should be called with any
* required locks.
*
* If memory is required, it will return -EAGAIN, you should unlock
* and go back to the idr_pre_get() call. If the idr is full, it will
* return -ENOSPC.
*
* @id returns a value in the range 0 ... 0x7fffffff
*/
int idr_get_new_above(struct idr *idp, void *ptr, int starting_id, int *id)
{
int rv;
rv = idr_get_new_above_int(idp, ptr, starting_id);
/*
* This is a cheap hack until the IDR code can be fixed to
* return proper error values.
*/
if (rv < 0) {
if (rv == -1)
return -EAGAIN;
else /* Will be -3 */
return -ENOSPC;
}
*id = rv;
return 0;
}
EXPORT_SYMBOL(idr_get_new_above);
/**
* idr_get_new - allocate new idr entry
* @idp: idr handle
* @ptr: pointer you want associated with the ide
* @id: pointer to the allocated handle
*
* This is the allocate id function. It should be called with any
* required locks.
*
* If memory is required, it will return -EAGAIN, you should unlock
* and go back to the idr_pre_get() call. If the idr is full, it will
* return -ENOSPC.
*
* @id returns a value in the range 0 ... 0x7fffffff
*/
int idr_get_new(struct idr *idp, void *ptr, int *id)
{
int rv;
rv = idr_get_new_above_int(idp, ptr, 0);
/*
* This is a cheap hack until the IDR code can be fixed to
* return proper error values.
*/
if (rv < 0) {
if (rv == -1)
return -EAGAIN;
else /* Will be -3 */
return -ENOSPC;
}
*id = rv;
return 0;
}
EXPORT_SYMBOL(idr_get_new);
static void idr_remove_warning(int id)
{
printk("idr_remove called for id=%d which is not allocated.\n", id);
dump_stack();
}
static void sub_remove(struct idr *idp, int shift, int id)
{
struct idr_layer *p = idp->top;
struct idr_layer **pa[MAX_LEVEL];
struct idr_layer ***paa = &pa[0];
int n;
*paa = NULL;
*++paa = &idp->top;
while ((shift > 0) && p) {
n = (id >> shift) & IDR_MASK;
__clear_bit(n, &p->bitmap);
*++paa = &p->ary[n];
p = p->ary[n];
shift -= IDR_BITS;
}
n = id & IDR_MASK;
if (likely(p != NULL && test_bit(n, &p->bitmap))){
__clear_bit(n, &p->bitmap);
p->ary[n] = NULL;
while(*paa && ! --((**paa)->count)){
free_layer(idp, **paa);
**paa-- = NULL;
}
if ( ! *paa )
idp->layers = 0;
} else {
idr_remove_warning(id);
}
}
/**
* idr_remove - remove the given id and free it's slot
* idp: idr handle
* id: uniqueue key
*/
void idr_remove(struct idr *idp, int id)
{
struct idr_layer *p;
/* Mask off upper bits we don't use for the search. */
id &= MAX_ID_MASK;
sub_remove(idp, (idp->layers - 1) * IDR_BITS, id);
if ( idp->top && idp->top->count == 1 &&
(idp->layers > 1) &&
idp->top->ary[0]){ // We can drop a layer
p = idp->top->ary[0];
idp->top->bitmap = idp->top->count = 0;
free_layer(idp, idp->top);
idp->top = p;
--idp->layers;
}
while (idp->id_free_cnt >= IDR_FREE_MAX) {
p = alloc_layer(idp);
kmem_cache_free(idr_layer_cache, p);
return;
}
}
EXPORT_SYMBOL(idr_remove);
/**
* idr_find - return pointer for given id
* @idp: idr handle
* @id: lookup key
*
* Return the pointer given the id it has been registered with. A %NULL
* return indicates that @id is not valid or you passed %NULL in
* idr_get_new().
*
* The caller must serialize idr_find() vs idr_get_new() and idr_remove().
*/
void *idr_find(struct idr *idp, int id)
{
int n;
struct idr_layer *p;
n = idp->layers * IDR_BITS;
p = idp->top;
/* Mask off upper bits we don't use for the search. */
id &= MAX_ID_MASK;
if (id >= (1 << n))
return NULL;
while (n > 0 && p) {
n -= IDR_BITS;
p = p->ary[(id >> n) & IDR_MASK];
}
return((void *)p);
}
EXPORT_SYMBOL(idr_find);
static void idr_cache_ctor(void * idr_layer,
kmem_cache_t *idr_layer_cache, unsigned long flags)
{
memset(idr_layer, 0, sizeof(struct idr_layer));
}
static int init_id_cache(void)
{
if (!idr_layer_cache)
idr_layer_cache = kmem_cache_create("idr_layer_cache",
sizeof(struct idr_layer), 0, 0, idr_cache_ctor, NULL);
return 0;
}
/**
* idr_init - initialize idr handle
* @idp: idr handle
*
* This function is use to set up the handle (@idp) that you will pass
* to the rest of the functions.
*/
void idr_init(struct idr *idp)
{
init_id_cache();
memset(idp, 0, sizeof(struct idr));
spin_lock_init(&idp->lock);
}
EXPORT_SYMBOL(idr_init);
