/*
* 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.
*/
#ifndef TEST // to test in user space...
#include <linux/slab.h>
#include <linux/init.h>
#include <linux/export.h>
#endif
#include <linux/err.h>
#include <linux/string.h>
#include <linux/idr.h>
#include <linux/spinlock.h>
#include <linux/percpu.h>
#define MAX_IDR_SHIFT (sizeof(int) * 8 - 1)
#define MAX_IDR_BIT (1U << MAX_IDR_SHIFT)
/* 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)
static struct kmem_cache *idr_layer_cache;
static DEFINE_PER_CPU(struct idr_layer *, idr_preload_head);
static DEFINE_PER_CPU(int, idr_preload_cnt);
static DEFINE_SPINLOCK(simple_ida_lock);
/* the maximum ID which can be allocated given idr->layers */
static int idr_max(int layers)
{
int bits = min_t(int, layers * IDR_BITS, MAX_IDR_SHIFT);
return (1 << bits) - 1;
}
/*
* Prefix mask for an idr_layer at @layer. For layer 0, the prefix mask is
* all bits except for the lower IDR_BITS. For layer 1, 2 * IDR_BITS, and
* so on.
*/
static int idr_layer_prefix_mask(int layer)
{
return ~idr_max(layer + 1);
}
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);
}
/**
* idr_layer_alloc - allocate a new idr_layer
* @gfp_mask: allocation mask
* @layer_idr: optional idr to allocate from
*
* If @layer_idr is %NULL, directly allocate one using @gfp_mask or fetch
* one from the per-cpu preload buffer. If @layer_idr is not %NULL, fetch
* an idr_layer from @idr->id_free.
*
* @layer_idr is to maintain backward compatibility with the old alloc
* interface - idr_pre_get() and idr_get_new*() - and will be removed
* together with per-pool preload buffer.
*/
static struct idr_layer *idr_layer_alloc(gfp_t gfp_mask, struct idr *layer_idr)
{
struct idr_layer *new;
/* this is the old path, bypass to get_from_free_list() */
if (layer_idr)
return get_from_free_list(layer_idr);
/*
* Try to allocate directly from kmem_cache. We want to try this
* before preload buffer; otherwise, non-preloading idr_alloc()
* users will end up taking advantage of preloading ones. As the
* following is allowed to fail for preloaded cases, suppress
* warning this time.
*/
new = kmem_cache_zalloc(idr_layer_cache, gfp_mask | __GFP_NOWARN);
if (new)
return new;
/*
* Try to fetch one from the per-cpu preload buffer if in process
* context. See idr_preload() for details.
*/
if (!in_interrupt()) {
preempt_disable();
new = __this_cpu_read(idr_preload_head);
if (new) {
__this_cpu_write(idr_preload_head, new->ary[0]);
__this_cpu_dec(idr_preload_cnt);
new->ary[0] = NULL;
}
preempt_enable();
if (new)
return new;
}
/*
* Both failed. Try kmem_cache again w/o adding __GFP_NOWARN so
* that memory allocation failure warning is printed as intended.
*/
return kmem_cache_zalloc(idr_layer_cache, gfp_mask);
}
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 *idr, struct idr_layer *p)
{
if (idr->hint == p)
RCU_INIT_POINTER(idr->hint, NULL);
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 (bitmap_full(p->bitmap, IDR_SIZE)) {
if (!(p = pa[++l]))
break;
id = id >> IDR_BITS;
__set_bit((id & IDR_MASK), p->bitmap);
}
}
static int __idr_pre_get(struct idr *idp, gfp_t gfp_mask)
{
while (idp->id_free_cnt < MAX_IDR_FREE) {
struct idr_layer *new;
new = kmem_cache_zalloc(idr_layer_cache, gfp_mask);
if (new == NULL)
return (0);
move_to_free_list(idp, new);
}
return 1;
}
/**
* sub_alloc - try to allocate an id without growing the tree depth
* @idp: idr handle
* @starting_id: id to start search at
* @pa: idr_layer[MAX_IDR_LEVEL] used as backtrack buffer
* @gfp_mask: allocation mask for idr_layer_alloc()
* @layer_idr: optional idr passed to idr_layer_alloc()
*
* Allocate an id in range [@starting_id, INT_MAX] from @idp without
* growing its depth. Returns
*
* the allocated id >= 0 if successful,
* -EAGAIN if the tree needs to grow for allocation to succeed,
* -ENOSPC if the id space is exhausted,
* -ENOMEM if more idr_layers need to be allocated.
*/
static int sub_alloc(struct idr *idp, int *starting_id, struct idr_layer **pa,
gfp_t gfp_mask, struct idr *layer_idr)
{
int n, m, sh;
struct idr_layer *p, *new;
int l, id, oid;
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;
m = find_next_zero_bit(p->bitmap, 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 (id > idr_max(idp->layers)) {
*starting_id = id;
return -EAGAIN;
}
p = pa[l];
BUG_ON(!p);
/* 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_IDR_BIT) || (id < 0))
return -ENOSPC;
if (l == 0)
break;
/*
* Create the layer below if it is missing.
*/
if (!p->ary[m]) {
new = idr_layer_alloc(gfp_mask, layer_idr);
if (!new)
return -ENOMEM;
new->layer = l-1;
new->prefix = id & idr_layer_prefix_mask(new->layer);
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, gfp_t gfp_mask,
struct idr *layer_idr)
{
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 = idr_layer_alloc(gfp_mask, layer_idr)))
return -ENOMEM;
p->layer = 0;
layers = 1;
}
/*
* Add a new layer to the top of the tree if the requested
* id is larger than the currently allocated space.
*/
while (id > idr_max(layers)) {
layers++;
if (!p->count) {
/* special case: if the tree is currently empty,
* then we grow the tree by moving the top node
* upwards.
*/
p->layer++;
WARN_ON_ONCE(p->prefix);
continue;
}
if (!(new = idr_layer_alloc(gfp_mask, layer_idr))) {
/*
* 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->count = 0;
bitmap_clear(new->bitmap, 0, IDR_SIZE);
__move_to_free_list(idp, new);
}
spin_unlock_irqrestore(&idp->lock, flags);
return -ENOMEM;
}
new->ary[0] = p;
new->count = 1;
new->layer = layers-1;
new->prefix = id & idr_layer_prefix_mask(new->layer);
if (bitmap_full(p->bitmap, IDR_SIZE))
__set_bit(0, new->bitmap);
p = new;
}
rcu_assign_pointer(idp->top, p);
idp->layers = layers;
v = sub_alloc(idp, &id, pa, gfp_mask, layer_idr);
if (v == -EAGAIN)
goto build_up;
return(v);
}
/*
* @id and @pa are from a successful allocation from idr_get_empty_slot().
* Install the user pointer @ptr and mark the slot full.
*/
static void idr_fill_slot(struct idr *idr, void *ptr, int id,
struct idr_layer **pa)
{
/* update hint used for lookup, cleared from free_layer() */
rcu_assign_pointer(idr->hint, pa[0]);
rcu_assign_pointer(pa[0]->ary[id & IDR_MASK], (struct idr_layer *)ptr);
pa[0]->count++;
idr_mark_full(pa, id);
}
/**
* idr_preload - preload for idr_alloc()
* @gfp_mask: allocation mask to use for preloading
*
* Preload per-cpu layer buffer for idr_alloc(). Can only be used from
* process context and each idr_preload() invocation should be matched with
* idr_preload_end(). Note that preemption is disabled while preloaded.
*
* The first idr_alloc() in the preloaded section can be treated as if it
* were invoked with @gfp_mask used for preloading. This allows using more
* permissive allocation masks for idrs protected by spinlocks.
*
* For example, if idr_alloc() below fails, the failure can be treated as
* if idr_alloc() were called with GFP_KERNEL rather than GFP_NOWAIT.
*
* idr_preload(GFP_KERNEL);
* spin_lock(lock);
*
* id = idr_alloc(idr, ptr, start, end, GFP_NOWAIT);
*
* spin_unlock(lock);
* idr_preload_end();
* if (id < 0)
* error;
*/
void idr_preload(gfp_t gfp_mask)
{
/*
* Consuming preload buffer from non-process context breaks preload
* allocation guarantee. Disallow usage from those contexts.
*/
WARN_ON_ONCE(in_interrupt());
might_sleep_if(gfpflags_allow_blocking(gfp_mask));
preempt_disable();
/*
* idr_alloc() is likely to succeed w/o full idr_layer buffer and
* return value from idr_alloc() needs to be checked for failure
* anyway. Silently give up if allocation fails. The caller can
* treat failures from idr_alloc() as if idr_alloc() were called
* with @gfp_mask which should be enough.
*/
while (__this_cpu_read(idr_preload_cnt) < MAX_IDR_FREE) {
struct idr_layer *new;
preempt_enable();
new = kmem_cache_zalloc(idr_layer_cache, gfp_mask);
preempt_disable();
if (!new)
break;
/* link the new one to per-cpu preload list */
new->ary[0] = __this_cpu_read(idr_preload_head);
__this_cpu_write(idr_preload_head, new);
__this_cpu_inc(idr_preload_cnt);
}
}
EXPORT_SYMBOL(idr_preload);
/**
* idr_alloc - allocate new idr entry
* @idr: the (initialized) idr
* @ptr: pointer to be associated with the new id
* @start: the minimum id (inclusive)
* @end: the maximum id (exclusive, <= 0 for max)
* @gfp_mask: memory allocation flags
*
* Allocate an id in [start, end) and associate it with @ptr. If no ID is
* available in the specified range, returns -ENOSPC. On memory allocation
* failure, returns -ENOMEM.
*
* Note that @end is treated as max when <= 0. This is to always allow
* using @start + N as @end as long as N is inside integer range.
*
* The user is responsible for exclusively synchronizing all operations
* which may modify @idr. However, read-only accesses such as idr_find()
* or iteration can be performed under RCU read lock provided the user
* destroys @ptr in RCU-safe way after removal from idr.
*/
int idr_alloc(struct idr *idr, void *ptr, int start, int end, gfp_t gfp_mask)
{
int max = end > 0 ? end - 1 : INT_MAX; /* inclusive upper limit */
struct idr_layer *pa[MAX_IDR_LEVEL + 1];
int id;
might_sleep_if(gfpflags_allow_blocking(gfp_mask));
/* sanity checks */
if (WARN_ON_ONCE(start < 0))
return -EINVAL;
if (unlikely(max < start))
return -ENOSPC;
/* allocate id */
id = idr_get_empty_slot(idr, start, pa, gfp_mask, NULL);
if (unlikely(id < 0))
return id;
if (unlikely(id > max))
return -ENOSPC;
idr_fill_slot(idr, ptr, id, pa);
return id;
}
EXPORT_SYMBOL_GPL(idr_alloc);
/**
* idr_alloc_cyclic - allocate new idr entry in a cyclical fashion
* @idr: the (initialized) idr
* @ptr: pointer to be associated with the new id
* @start: the minimum id (inclusive)
* @end: the maximum id (exclusive, <= 0 for max)
* @gfp_mask: memory allocation flags
*
* Essentially the same as idr_alloc, but prefers to allocate progressively
* higher ids if it can. If the "cur" counter wraps, then it will start again
* at the "start" end of the range and allocate one that has already been used.
*/
int idr_alloc_cyclic(struct idr *idr, void *ptr, int start, int end,
gfp_t gfp_mask)
{
int id;
id = idr_alloc(idr, ptr, max(start, idr->cur), end, gfp_mask);
if (id == -ENOSPC)
id = idr_alloc(idr, ptr, start, end, gfp_mask);
if (likely(id >= 0))
idr->cur = id + 1;
return id;
}
EXPORT_SYMBOL(idr_alloc_cyclic);
static void idr_remove_warning(int id)
{
WARN(1, "idr_remove called for id=%d which is not allocated.\n", id);
}
static void sub_remove(struct idr *idp, int shift, int id)
{
struct idr_layer *p = idp->top;
struct idr_layer **pa[MAX_IDR_LEVEL + 1];
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_INIT_POINTER(p->ary[n], NULL);
to_free = NULL;
while(*paa && ! --((**paa)->count)){
if (to_free)
free_layer(idp, to_free);
to_free = **paa;
**paa-- = NULL;
}
if (!*paa)
idp->layers = 0;
if (to_free)
free_layer(idp, to_free);
} else
idr_remove_warning(id);
}
/**
* idr_remove - remove the given id and free its slot
* @idp: idr handle
* @id: unique key
*/
void idr_remove(struct idr *idp, int id)
{
struct idr_layer *p;
struct idr_layer *to_free;
if (id < 0)
return;
if (id > idr_max(idp->layers)) {
idr_remove_warning(id);
return;
}
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->count = 0;
bitmap_clear(to_free->bitmap, 0, IDR_SIZE);
free_layer(idp, to_free);
}
}
EXPORT_SYMBOL(idr_remove);
static void __idr_remove_all(struct idr *idp)
{
int n, id, max;
int bt_mask;
struct idr_layer *p;
struct idr_layer *pa[MAX_IDR_LEVEL + 1];
struct idr_layer **paa = &pa[0];
n = idp->layers * IDR_BITS;
*paa = idp->top;
RCU_INIT_POINTER(idp->top, NULL);
max = idr_max(idp->layers);
id = 0;
while (id >= 0 && id <= max) {
p = *paa;
while (n > IDR_BITS && p) {
n -= IDR_BITS;
p = p->ary[(id >> n) & IDR_MASK];
*++paa = p;
}
bt_mask = id;
id += 1 << n;
/* Get the highest bit that the above add changed from 0->1. */
while (n < fls(id ^ bt_mask)) {
if (*paa)
free_layer(idp, *paa);
n += IDR_BITS;
--paa;
}
}
idp->layers = 0;
}
/**
* idr_destroy - release all cached layers within an idr tree
* @idp: idr handle
*
* Free all id mappings and all idp_layers. After this function, @idp is
* completely unused and can be freed / recycled. The caller is
* responsible for ensuring that no one else accesses @idp during or after
* idr_destroy().
*
* A typical clean-up sequence for objects stored in an idr tree will use
* idr_for_each() to free all objects, if necessary, then idr_destroy() to
* free up the id mappings and cached idr_layers.
*/
void idr_destroy(struct idr *idp)
{
__idr_remove_all(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);
void *idr_find_slowpath(struct idr *idp, int id)
{
int n;
struct idr_layer *p;
if (id < 0)
return NULL;
p = rcu_dereference_raw(idp->top);
if (!p)
return NULL;
n = (p->layer+1) * IDR_BITS;
if (id > idr_max(p->layer + 1))
return NULL;
BUG_ON(n == 0);
while (n > 0 && p) {
n -= IDR_BITS;
BUG_ON(n != p->layer*IDR_BITS);
p = rcu_dereference_raw(p->ary[(id >> n) & IDR_MASK]);
}
return((void *)p);
}
EXPORT_SYMBOL(idr_find_slowpath);
/**
* 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_IDR_LEVEL + 1];
struct idr_layer **paa = &pa[0];
n = idp->layers * IDR_BITS;
*paa = rcu_dereference_raw(idp->top);
max = idr_max(idp->layers);
id = 0;
while (id >= 0 && id <= max) {
p = *paa;
while (n > 0 && p) {
n -= IDR_BITS;
p = rcu_dereference_raw(p->ary[(id >> n) & IDR_MASK]);
*++paa = p;
}
if (p) {
error = fn(id, (void *)p, data);
if (error)
break;
}
id += 1 << n;
while (n < fls(id)) {
n += IDR_BITS;
--paa;
}
}
return error;
}
EXPORT_SYMBOL(idr_for_each);
/**
* idr_get_next - lookup next object of id to given id.
* @idp: idr handle
* @nextidp: pointer to lookup key
*
* Returns pointer to registered object with id, which is next number to
* given id. After being looked up, *@nextidp will be updated for the next
* iteration.
*
* This function can be called under rcu_read_lock(), given that the leaf
* pointers lifetimes are correctly managed.
*/
void *idr_get_next(struct idr *idp, int *nextidp)
{
struct idr_layer *p, *pa[MAX_IDR_LEVEL + 1];
struct idr_layer **paa = &pa[0];
int id = *nextidp;
int n, max;
/* find first ent */
p = *paa = rcu_dereference_raw(idp->top);
if (!p)
return NULL;
n = (p->layer + 1) * IDR_BITS;
max = idr_max(p->layer + 1);
while (id >= 0 && id <= max) {
p = *paa;
while (n > 0 && p) {
n -= IDR_BITS;
p = rcu_dereference_raw(p->ary[(id >> n) & IDR_MASK]);
*++paa = p;
}
if (p) {
*nextidp = id;
return p;
}
/*
* Proceed to the next layer at the current level. Unlike
* idr_for_each(), @id isn't guaranteed to be aligned to
* layer boundary at this point and adding 1 << n may
* incorrectly skip IDs. Make sure we jump to the
* beginning of the next layer using round_up().
*/
id = round_up(id + 1, 1 << n);
while (n < fls(id)) {
n += IDR_BITS;
--paa;
}
}
return NULL;
}
EXPORT_SYMBOL(idr_get_next);
/**
* 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;
if (id < 0)
return ERR_PTR(-EINVAL);
p = idp->top;
if (!p)
return ERR_PTR(-ENOENT);
if (id > idr_max(p->layer + 1))
return ERR_PTR(-ENOENT);
n = p->layer * 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);
void __init idr_init_cache(void)
{
idr_layer_cache = kmem_cache_create("idr_layer_cache",
sizeof(struct idr_layer), 0, SLAB_PANIC, NULL);
}
/**
* 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);
static int idr_has_entry(int id, void *p, void *data)
{
return 1;
}
bool idr_is_empty(struct idr *idp)
{
return !idr_for_each(idp, idr_has_entry, NULL);
}
EXPORT_SYMBOL(idr_is_empty);
/**
* DOC: IDA description
* 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
* @starting_id: id to start search at
* @p_id: pointer to the allocated handle
*
* Allocate new ID above or equal to @starting_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 ida_pre_get() call. If the ida is full, it will
* return %-ENOSPC.
*
* Note that callers must ensure that concurrent access to @ida is not possible.
* See ida_simple_get() for a varaint which takes care of locking.
*
* @p_id returns a value in the range @starting_id ... %0x7fffffff.
*/
int ida_get_new_above(struct ida *ida, int starting_id, int *p_id)
{
struct idr_layer *pa[MAX_IDR_LEVEL + 1];
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, 0, &ida->idr);
if (t < 0)
return t == -ENOMEM ? -EAGAIN : t;
if (t * IDA_BITMAP_BITS >= MAX_IDR_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_IDR_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_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;
if (idr_id > idr_max(ida->idr.layers))
goto err;
/* 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 (!bitmap || !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:
WARN(1, "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_simple_get - get a new id.
* @ida: the (initialized) ida.
* @start: the minimum id (inclusive, < 0x8000000)
* @end: the maximum id (exclusive, < 0x8000000 or 0)
* @gfp_mask: memory allocation flags
*
* Allocates an id in the range start <= id < end, or returns -ENOSPC.
* On memory allocation failure, returns -ENOMEM.
*
* Compared to ida_get_new_above() this function does its own locking, and
* should be used unless there are special requirements.
*
* Use ida_simple_remove() to get rid of an id.
*/
int ida_simple_get(struct ida *ida, unsigned int start, unsigned int end,
gfp_t gfp_mask)
{
int ret, id;
unsigned int max;
unsigned long flags;
BUG_ON((int)start < 0);
BUG_ON((int)end < 0);
if (end == 0)
max = 0x80000000;
else {
BUG_ON(end < start);
max = end - 1;
}
again:
if (!ida_pre_get(ida, gfp_mask))
return -ENOMEM;
spin_lock_irqsave(&simple_ida_lock, flags);
ret = ida_get_new_above(ida, start, &id);
if (!ret) {
if (id > max) {
ida_remove(ida, id);
ret = -ENOSPC;
} else {
ret = id;
}
}
spin_unlock_irqrestore(&simple_ida_lock, flags);
if (unlikely(ret == -EAGAIN))
goto again;
return ret;
}
EXPORT_SYMBOL(ida_simple_get);
/**
* ida_simple_remove - remove an allocated id.
* @ida: the (initialized) ida.
* @id: the id returned by ida_simple_get.
*
* Use to release an id allocated with ida_simple_get().
*
* Compared to ida_remove() this function does its own locking, and should be
* used unless there are special requirements.
*/
void ida_simple_remove(struct ida *ida, unsigned int id)
{
unsigned long flags;
BUG_ON((int)id < 0);
spin_lock_irqsave(&simple_ida_lock, flags);
ida_remove(ida, id);
spin_unlock_irqrestore(&simple_ida_lock, flags);
}
EXPORT_SYMBOL(ida_simple_remove);
/**
* 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);