diff options
Diffstat (limited to 'kernel/lib/idr.c')
| -rw-r--r-- | kernel/lib/idr.c | 1177 |
1 files changed, 1177 insertions, 0 deletions
diff --git a/kernel/lib/idr.c b/kernel/lib/idr.c new file mode 100644 index 000000000..d0681a357 --- /dev/null +++ b/kernel/lib/idr.c @@ -0,0 +1,1177 @@ +/* + * 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> +#include <linux/locallock.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); +} + +#ifdef CONFIG_PREEMPT_RT_FULL +static DEFINE_LOCAL_IRQ_LOCK(idr_lock); + +static inline void idr_preload_lock(void) +{ + local_lock(idr_lock); +} + +static inline void idr_preload_unlock(void) +{ + local_unlock(idr_lock); +} + +void idr_preload_end(void) +{ + idr_preload_unlock(); +} +EXPORT_SYMBOL(idr_preload_end); +#else +static inline void idr_preload_lock(void) +{ + preempt_disable(); +} + +static inline void idr_preload_unlock(void) +{ + preempt_enable(); +} +#endif + +/** + * 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(gfp_mask & __GFP_WAIT); + + idr_preload_lock(); + + /* + * 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; + + idr_preload_unlock(); + new = kmem_cache_zalloc(idr_layer_cache, gfp_mask); + idr_preload_lock(); + 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(gfp_mask & __GFP_WAIT); + + /* 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. + * + * @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. + * + * 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. + */ +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); |