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DEFINITIONS
This source file includes following definitions.
- get_from_free_list
- idr_layer_rcu_free
- free_layer
- __move_to_free_list
- move_to_free_list
- idr_mark_full
- idr_pre_get
- sub_alloc
- idr_get_empty_slot
- idr_get_new_above_int
- idr_get_new_above
- idr_get_new
- idr_remove_warning
- sub_remove
- idr_remove
- idr_remove_all
- idr_destroy
- idr_find
- idr_for_each
- idr_replace
- idr_cache_ctor
- idr_init_cache
- idr_init
- free_bitmap
- ida_pre_get
- ida_get_new_above
- ida_get_new
- ida_remove
- ida_destroy
- ida_init
/*
* 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.
*
* Modified by Nadia Derbey to make it RCU safe.
*
* 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/err.h>
#include <linux/string.h>
#include <linux/idr.h>
static struct kmem_cache *idr_layer_cache;
static struct idr_layer *get_from_free_list(struct idr *idp)
{
struct idr_layer *p;
unsigned long flags;
spin_lock_irqsave(&idp->lock, flags);
if ((p = idp->id_free)) {
idp->id_free = p->ary[0];
idp->id_free_cnt--;
p->ary[0] = NULL;
}
spin_unlock_irqrestore(&idp->lock, flags);
return(p);
}
static void idr_layer_rcu_free(struct rcu_head *head)
{
struct idr_layer *layer;
layer = container_of(head, struct idr_layer, rcu_head);
kmem_cache_free(idr_layer_cache, layer);
}
static inline void free_layer(struct idr_layer *p)
{
call_rcu(&p->rcu_head, idr_layer_rcu_free);
}
/* only called when idp->lock is held */
static void __move_to_free_list(struct idr *idp, struct idr_layer *p)
{
p->ary[0] = idp->id_free;
idp->id_free = p;
idp->id_free_cnt++;
}
static void move_to_free_list(struct idr *idp, struct idr_layer *p)
{
unsigned long flags;
/*
* Depends on the return element being zeroed.
*/
spin_lock_irqsave(&idp->lock, flags);
__move_to_free_list(idp, p);
spin_unlock_irqrestore(&idp->lock, flags);
}
static void idr_mark_full(struct idr_layer **pa, int id)
{
struct idr_layer *p = pa[0];
int l = 0;
__set_bit(id & IDR_MASK, &p->bitmap);
/*
* 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.
*/
while (p->bitmap == IDR_FULL) {
if (!(p = pa[++l]))
break;
id = id >> IDR_BITS;
__set_bit((id & IDR_MASK), &p->bitmap);
}
}
/**
* 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
* idr_get_new* functions. 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, gfp_t 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);
move_to_free_list(idp, new);
}
return 1;
}
EXPORT_SYMBOL(idr_pre_get);
static int sub_alloc(struct idr *idp, int *starting_id, struct idr_layer **pa)
{
int n, m, sh;
struct idr_layer *p, *new;
int l, id, oid;
unsigned long bm;
id = *starting_id;
restart:
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++;
oid = id;
id = (id | ((1 << (IDR_BITS * l)) - 1)) + 1;
/* if already at the top layer, we need to grow */
if (!(p = pa[l])) {
*starting_id = id;
return IDR_NEED_TO_GROW;
}
/* If we need to go up one layer, continue the
* loop; otherwise, restart from the top.
*/
sh = IDR_BITS * (l + 1);
if (oid >> sh == id >> sh)
continue;
else
goto restart;
}
if (m != n) {
sh = IDR_BITS*l;
id = ((id >> sh) ^ n ^ m) << sh;
}
if ((id >= MAX_ID_BIT) || (id < 0))
return IDR_NOMORE_SPACE;
if (l == 0)
break;
/*
* Create the layer below if it is missing.
*/
if (!p->ary[m]) {
new = get_from_free_list(idp);
if (!new)
return -1;
rcu_assign_pointer(p->ary[m], new);
p->count++;
}
pa[l--] = p;
p = p->ary[m];
}
pa[l] = p;
return id;
}
static int idr_get_empty_slot(struct idr *idp, int starting_id,
struct idr_layer **pa)
{
struct idr_layer *p, *new;
int layers, v, id;
unsigned long flags;
id = starting_id;
build_up:
p = idp->top;
layers = idp->layers;
if (unlikely(!p)) {
if (!(p = get_from_free_list(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 = get_from_free_list(idp))) {
/*
* The allocation failed. If we built part of
* the structure tear it down.
*/
spin_lock_irqsave(&idp->lock, flags);
for (new = p; p && p != idp->top; new = p) {
p = p->ary[0];
new->ary[0] = NULL;
new->bitmap = new->count = 0;
__move_to_free_list(idp, new);
}
spin_unlock_irqrestore(&idp->lock, flags);
return -1;
}
new->ary[0] = p;
new->count = 1;
if (p->bitmap == IDR_FULL)
__set_bit(0, &new->bitmap);
p = new;
}
rcu_assign_pointer(idp->top, p);
idp->layers = layers;
v = sub_alloc(idp, &id, pa);
if (v == IDR_NEED_TO_GROW)
goto build_up;
return(v);
}
static int idr_get_new_above_int(struct idr *idp, void *ptr, int starting_id)
{
struct idr_layer *pa[MAX_LEVEL];
int id;
id = idr_get_empty_slot(idp, starting_id, pa);
if (id >= 0) {
/*
* Successfully found an empty slot. Install the user
* pointer and mark the slot full.
*/
rcu_assign_pointer(pa[0]->ary[id & IDR_MASK],
(struct idr_layer *)ptr);
pa[0]->count++;
idr_mark_full(pa, id);
}
return id;
}
/**
* 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)
return _idr_rc_to_errno(rv);
*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)
return _idr_rc_to_errno(rv);
*id = rv;
return 0;
}
EXPORT_SYMBOL(idr_get_new);
static void idr_remove_warning(int id)
{
printk(KERN_WARNING
"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];
struct idr_layer *to_free;
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);
rcu_assign_pointer(p->ary[n], NULL);
to_free = NULL;
while(*paa && ! --((**paa)->count)){
if (to_free)
free_layer(to_free);
to_free = **paa;
**paa-- = NULL;
}
if (!*paa)
idp->layers = 0;
if (to_free)
free_layer(to_free);
} else
idr_remove_warning(id);
}
/**
* idr_remove - remove the given id and free it's slot
* @idp: idr handle
* @id: unique key
*/
void idr_remove(struct idr *idp, int id)
{
struct idr_layer *p;
struct idr_layer *to_free;
/* 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]) {
/*
* Single child at leftmost slot: we can shrink the tree.
* This level is not needed anymore since when layers are
* inserted, they are inserted at the top of the existing
* tree.
*/
to_free = idp->top;
p = idp->top->ary[0];
rcu_assign_pointer(idp->top, p);
--idp->layers;
to_free->bitmap = to_free->count = 0;
free_layer(to_free);
}
while (idp->id_free_cnt >= IDR_FREE_MAX) {
p = get_from_free_list(idp);
/*
* Note: we don't call the rcu callback here, since the only
* layers that fall into the freelist are those that have been
* preallocated.
*/
kmem_cache_free(idr_layer_cache, p);
}
return;
}
EXPORT_SYMBOL(idr_remove);
/**
* idr_remove_all - remove all ids from the given idr tree
* @idp: idr handle
*
* idr_destroy() only frees up unused, cached idp_layers, but this
* function will remove all id mappings and leave all idp_layers
* unused.
*
* A typical clean-up sequence for objects stored in an idr tree, will
* use idr_for_each() to free all objects, if necessay, then
* idr_remove_all() to remove all ids, and idr_destroy() to free
* up the cached idr_layers.
*/
void idr_remove_all(struct idr *idp)
{
int n, id, max;
struct idr_layer *p;
struct idr_layer *pa[MAX_LEVEL];
struct idr_layer **paa = &pa[0];
n = idp->layers * IDR_BITS;
p = idp->top;
max = 1 << n;
id = 0;
while (id < max) {
while (n > IDR_BITS && p) {
n -= IDR_BITS;
*paa++ = p;
p = p->ary[(id >> n) & IDR_MASK];
}
id += 1 << n;
while (n < fls(id)) {
if (p)
free_layer(p);
n += IDR_BITS;
p = *--paa;
}
}
rcu_assign_pointer(idp->top, NULL);
idp->layers = 0;
}
EXPORT_SYMBOL(idr_remove_all);
/**
* idr_destroy - release all cached layers within an idr tree
* idp: idr handle
*/
void idr_destroy(struct idr *idp)
{
while (idp->id_free_cnt) {
struct idr_layer *p = get_from_free_list(idp);
kmem_cache_free(idr_layer_cache, p);
}
}
EXPORT_SYMBOL(idr_destroy);
/**
* 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().
*
* This function can be called under rcu_read_lock(), given that the leaf
* pointers lifetimes are correctly managed.
*/
void *idr_find(struct idr *idp, int id)
{
int n;
struct idr_layer *p;
n = idp->layers * IDR_BITS;
p = rcu_dereference(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 = rcu_dereference(p->ary[(id >> n) & IDR_MASK]);
}
return((void *)p);
}
EXPORT_SYMBOL(idr_find);
/**
* idr_for_each - iterate through all stored pointers
* @idp: idr handle
* @fn: function to be called for each pointer
* @data: data passed back to callback function
*
* Iterate over the pointers registered with the given idr. The
* callback function will be called for each pointer currently
* registered, passing the id, the pointer and the data pointer passed
* to this function. It is not safe to modify the idr tree while in
* the callback, so functions such as idr_get_new and idr_remove are
* not allowed.
*
* We check the return of @fn each time. If it returns anything other
* than 0, we break out and return that value.
*
* The caller must serialize idr_for_each() vs idr_get_new() and idr_remove().
*/
int idr_for_each(struct idr *idp,
int (*fn)(int id, void *p, void *data), void *data)
{
int n, id, max, error = 0;
struct idr_layer *p;
struct idr_layer *pa[MAX_LEVEL];
struct idr_layer **paa = &pa[0];
n = idp->layers * IDR_BITS;
p = rcu_dereference(idp->top);
max = 1 << n;
id = 0;
while (id < max) {
while (n > 0 && p) {
n -= IDR_BITS;
*paa++ = p;
p = rcu_dereference(p->ary[(id >> n) & IDR_MASK]);
}
if (p) {
error = fn(id, (void *)p, data);
if (error)
break;
}
id += 1 << n;
while (n < fls(id)) {
n += IDR_BITS;
p = *--paa;
}
}
return error;
}
EXPORT_SYMBOL(idr_for_each);
/**
* idr_replace - replace pointer for given id
* @idp: idr handle
* @ptr: pointer you want associated with the id
* @id: lookup key
*
* Replace the pointer registered with an id and return the old value.
* A -ENOENT return indicates that @id was not found.
* A -EINVAL return indicates that @id was not within valid constraints.
*
* The caller must serialize with writers.
*/
void *idr_replace(struct idr *idp, void *ptr, int id)
{
int n;
struct idr_layer *p, *old_p;
n = idp->layers * IDR_BITS;
p = idp->top;
id &= MAX_ID_MASK;
if (id >= (1 << n))
return ERR_PTR(-EINVAL);
n -= IDR_BITS;
while ((n > 0) && p) {
p = p->ary[(id >> n) & IDR_MASK];
n -= IDR_BITS;
}
n = id & IDR_MASK;
if (unlikely(p == NULL || !test_bit(n, &p->bitmap)))
return ERR_PTR(-ENOENT);
old_p = p->ary[n];
rcu_assign_pointer(p->ary[n], ptr);
return old_p;
}
EXPORT_SYMBOL(idr_replace);
static void idr_cache_ctor(void *idr_layer)
{
memset(idr_layer, 0, sizeof(struct idr_layer));
}
void __init idr_init_cache(void)
{
idr_layer_cache = kmem_cache_create("idr_layer_cache",
sizeof(struct idr_layer), 0, SLAB_PANIC,
idr_cache_ctor);
}
/**
* 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)
{
memset(idp, 0, sizeof(struct idr));
spin_lock_init(&idp->lock);
}
EXPORT_SYMBOL(idr_init);
/*
* IDA - IDR based ID allocator
*
* this is id allocator without id -> pointer translation. Memory
* usage is much lower than full blown idr because each id only
* occupies a bit. ida uses a custom leaf node which contains
* IDA_BITMAP_BITS slots.
*
* 2007-04-25 written by Tejun Heo <htejun@gmail.com>
*/
static void free_bitmap(struct ida *ida, struct ida_bitmap *bitmap)
{
unsigned long flags;
if (!ida->free_bitmap) {
spin_lock_irqsave(&ida->idr.lock, flags);
if (!ida->free_bitmap) {
ida->free_bitmap = bitmap;
bitmap = NULL;
}
spin_unlock_irqrestore(&ida->idr.lock, flags);
}
kfree(bitmap);
}
/**
* ida_pre_get - reserve resources for ida allocation
* @ida: ida handle
* @gfp_mask: memory allocation flag
*
* 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 ida_pre_get(struct ida *ida, gfp_t gfp_mask)
{
/* allocate idr_layers */
if (!idr_pre_get(&ida->idr, gfp_mask))
return 0;
/* allocate free_bitmap */
if (!ida->free_bitmap) {
struct ida_bitmap *bitmap;
bitmap = kmalloc(sizeof(struct ida_bitmap), gfp_mask);
if (!bitmap)
return 0;
free_bitmap(ida, bitmap);
}
return 1;
}
EXPORT_SYMBOL(ida_pre_get);
/**
* ida_get_new_above - allocate new ID above or equal to a start id
* @ida: ida handle
* @staring_id: id to start search at
* @p_id: pointer to the allocated handle
*
* Allocate new ID above or equal to @ida. It should be called with
* any required locks.
*
* If memory is required, it will return -EAGAIN, you should unlock
* and go back to the ida_pre_get() call. If the ida is full, it will
* return -ENOSPC.
*
* @p_id returns a value in the range 0 ... 0x7fffffff.
*/
int ida_get_new_above(struct ida *ida, int starting_id, int *p_id)
{
struct idr_layer *pa[MAX_LEVEL];
struct ida_bitmap *bitmap;
unsigned long flags;
int idr_id = starting_id / IDA_BITMAP_BITS;
int offset = starting_id % IDA_BITMAP_BITS;
int t, id;
restart:
/* get vacant slot */
t = idr_get_empty_slot(&ida->idr, idr_id, pa);
if (t < 0)
return _idr_rc_to_errno(t);
if (t * IDA_BITMAP_BITS >= MAX_ID_BIT)
return -ENOSPC;
if (t != idr_id)
offset = 0;
idr_id = t;
/* if bitmap isn't there, create a new one */
bitmap = (void *)pa[0]->ary[idr_id & IDR_MASK];
if (!bitmap) {
spin_lock_irqsave(&ida->idr.lock, flags);
bitmap = ida->free_bitmap;
ida->free_bitmap = NULL;
spin_unlock_irqrestore(&ida->idr.lock, flags);
if (!bitmap)
return -EAGAIN;
memset(bitmap, 0, sizeof(struct ida_bitmap));
rcu_assign_pointer(pa[0]->ary[idr_id & IDR_MASK],
(void *)bitmap);
pa[0]->count++;
}
/* lookup for empty slot */
t = find_next_zero_bit(bitmap->bitmap, IDA_BITMAP_BITS, offset);
if (t == IDA_BITMAP_BITS) {
/* no empty slot after offset, continue to the next chunk */
idr_id++;
offset = 0;
goto restart;
}
id = idr_id * IDA_BITMAP_BITS + t;
if (id >= MAX_ID_BIT)
return -ENOSPC;
__set_bit(t, bitmap->bitmap);
if (++bitmap->nr_busy == IDA_BITMAP_BITS)
idr_mark_full(pa, idr_id);
*p_id = id;
/* Each leaf node can handle nearly a thousand slots and the
* whole idea of ida is to have small memory foot print.
* Throw away extra resources one by one after each successful
* allocation.
*/
if (ida->idr.id_free_cnt || ida->free_bitmap) {
struct idr_layer *p = get_from_free_list(&ida->idr);
if (p)
kmem_cache_free(idr_layer_cache, p);
}
return 0;
}
EXPORT_SYMBOL(ida_get_new_above);
/**
* ida_get_new - allocate new ID
* @ida: idr handle
* @p_id: pointer to the allocated handle
*
* Allocate new ID. 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 ida_get_new(struct ida *ida, int *p_id)
{
return ida_get_new_above(ida, 0, p_id);
}
EXPORT_SYMBOL(ida_get_new);
/**
* ida_remove - remove the given ID
* @ida: ida handle
* @id: ID to free
*/
void ida_remove(struct ida *ida, int id)
{
struct idr_layer *p = ida->idr.top;
int shift = (ida->idr.layers - 1) * IDR_BITS;
int idr_id = id / IDA_BITMAP_BITS;
int offset = id % IDA_BITMAP_BITS;
int n;
struct ida_bitmap *bitmap;
/* clear full bits while looking up the leaf idr_layer */
while ((shift > 0) && p) {
n = (idr_id >> shift) & IDR_MASK;
__clear_bit(n, &p->bitmap);
p = p->ary[n];
shift -= IDR_BITS;
}
if (p == NULL)
goto err;
n = idr_id & IDR_MASK;
__clear_bit(n, &p->bitmap);
bitmap = (void *)p->ary[n];
if (!test_bit(offset, bitmap->bitmap))
goto err;
/* update bitmap and remove it if empty */
__clear_bit(offset, bitmap->bitmap);
if (--bitmap->nr_busy == 0) {
__set_bit(n, &p->bitmap); /* to please idr_remove() */
idr_remove(&ida->idr, idr_id);
free_bitmap(ida, bitmap);
}
return;
err:
printk(KERN_WARNING
"ida_remove called for id=%d which is not allocated.\n", id);
}
EXPORT_SYMBOL(ida_remove);
/**
* ida_destroy - release all cached layers within an ida tree
* ida: ida handle
*/
void ida_destroy(struct ida *ida)
{
idr_destroy(&ida->idr);
kfree(ida->free_bitmap);
}
EXPORT_SYMBOL(ida_destroy);
/**
* ida_init - initialize ida handle
* @ida: ida handle
*
* This function is use to set up the handle (@ida) that you will pass
* to the rest of the functions.
*/
void ida_init(struct ida *ida)
{
memset(ida, 0, sizeof(struct ida));
idr_init(&ida->idr);
}
EXPORT_SYMBOL(ida_init);