Linux-2.6.12-rc2
Initial git repository build. I'm not bothering with the full history, even though we have it. We can create a separate "historical" git archive of that later if we want to, and in the meantime it's about 3.2GB when imported into git - space that would just make the early git days unnecessarily complicated, when we don't have a lot of good infrastructure for it. Let it rip!
This commit is contained in:
Linus Torvalds
408
lib/idr.c
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408
lib/idr.c
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/*
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* 2002-10-18 written by Jim Houston jim.houston@ccur.com
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* Copyright (C) 2002 by Concurrent Computer Corporation
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* Distributed under the GNU GPL license version 2.
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*
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* Modified by George Anzinger to reuse immediately and to use
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* find bit instructions. Also removed _irq on spinlocks.
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*
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* Small id to pointer translation service.
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*
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* It uses a radix tree like structure as a sparse array indexed
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* by the id to obtain the pointer. The bitmap makes allocating
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* a new id quick.
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*
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* You call it to allocate an id (an int) an associate with that id a
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* pointer or what ever, we treat it as a (void *). You can pass this
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* id to a user for him to pass back at a later time. You then pass
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* that id to this code and it returns your pointer.
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* You can release ids at any time. When all ids are released, most of
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* the memory is returned (we keep IDR_FREE_MAX) in a local pool so we
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* don't need to go to the memory "store" during an id allocate, just
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* so you don't need to be too concerned about locking and conflicts
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* with the slab allocator.
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*/
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#ifndef TEST // to test in user space...
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#include <linux/slab.h>
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#include <linux/init.h>
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#include <linux/module.h>
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#endif
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#include <linux/string.h>
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#include <linux/idr.h>
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static kmem_cache_t *idr_layer_cache;
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static struct idr_layer *alloc_layer(struct idr *idp)
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{
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struct idr_layer *p;
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spin_lock(&idp->lock);
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if ((p = idp->id_free)) {
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idp->id_free = p->ary[0];
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idp->id_free_cnt--;
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p->ary[0] = NULL;
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}
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spin_unlock(&idp->lock);
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return(p);
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}
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static void free_layer(struct idr *idp, struct idr_layer *p)
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{
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/*
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* Depends on the return element being zeroed.
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*/
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spin_lock(&idp->lock);
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p->ary[0] = idp->id_free;
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idp->id_free = p;
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idp->id_free_cnt++;
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spin_unlock(&idp->lock);
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}
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/**
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* idr_pre_get - reserver resources for idr allocation
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* @idp: idr handle
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* @gfp_mask: memory allocation flags
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*
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* This function should be called prior to locking and calling the
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* following function. It preallocates enough memory to satisfy
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* the worst possible allocation.
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*
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* If the system is REALLY out of memory this function returns 0,
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* otherwise 1.
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*/
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int idr_pre_get(struct idr *idp, unsigned gfp_mask)
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{
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while (idp->id_free_cnt < IDR_FREE_MAX) {
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struct idr_layer *new;
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new = kmem_cache_alloc(idr_layer_cache, gfp_mask);
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if(new == NULL)
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return (0);
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free_layer(idp, new);
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}
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return 1;
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}
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EXPORT_SYMBOL(idr_pre_get);
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static int sub_alloc(struct idr *idp, void *ptr, int *starting_id)
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{
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int n, m, sh;
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struct idr_layer *p, *new;
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struct idr_layer *pa[MAX_LEVEL];
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int l, id;
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long bm;
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id = *starting_id;
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p = idp->top;
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l = idp->layers;
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pa[l--] = NULL;
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while (1) {
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/*
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* We run around this while until we reach the leaf node...
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*/
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n = (id >> (IDR_BITS*l)) & IDR_MASK;
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bm = ~p->bitmap;
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m = find_next_bit(&bm, IDR_SIZE, n);
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if (m == IDR_SIZE) {
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/* no space available go back to previous layer. */
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l++;
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id = (id | ((1 << (IDR_BITS*l))-1)) + 1;
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if (!(p = pa[l])) {
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*starting_id = id;
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return -2;
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}
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continue;
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}
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if (m != n) {
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sh = IDR_BITS*l;
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id = ((id >> sh) ^ n ^ m) << sh;
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}
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if ((id >= MAX_ID_BIT) || (id < 0))
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return -3;
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if (l == 0)
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break;
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/*
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* Create the layer below if it is missing.
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*/
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if (!p->ary[m]) {
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if (!(new = alloc_layer(idp)))
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return -1;
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p->ary[m] = new;
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p->count++;
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}
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pa[l--] = p;
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p = p->ary[m];
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}
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/*
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* We have reached the leaf node, plant the
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* users pointer and return the raw id.
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*/
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p->ary[m] = (struct idr_layer *)ptr;
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__set_bit(m, &p->bitmap);
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p->count++;
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/*
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* If this layer is full mark the bit in the layer above
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* to show that this part of the radix tree is full.
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* This may complete the layer above and require walking
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* up the radix tree.
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*/
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n = id;
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while (p->bitmap == IDR_FULL) {
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if (!(p = pa[++l]))
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break;
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n = n >> IDR_BITS;
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__set_bit((n & IDR_MASK), &p->bitmap);
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}
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return(id);
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}
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static int idr_get_new_above_int(struct idr *idp, void *ptr, int starting_id)
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{
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struct idr_layer *p, *new;
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int layers, v, id;
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id = starting_id;
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build_up:
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p = idp->top;
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layers = idp->layers;
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if (unlikely(!p)) {
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if (!(p = alloc_layer(idp)))
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return -1;
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layers = 1;
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}
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/*
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* Add a new layer to the top of the tree if the requested
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* id is larger than the currently allocated space.
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*/
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while ((layers < MAX_LEVEL) && (id >= (1 << (layers*IDR_BITS)))) {
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layers++;
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if (!p->count)
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continue;
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if (!(new = alloc_layer(idp))) {
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/*
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* The allocation failed. If we built part of
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* the structure tear it down.
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*/
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for (new = p; p && p != idp->top; new = p) {
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p = p->ary[0];
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new->ary[0] = NULL;
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new->bitmap = new->count = 0;
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free_layer(idp, new);
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}
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return -1;
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}
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new->ary[0] = p;
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new->count = 1;
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if (p->bitmap == IDR_FULL)
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__set_bit(0, &new->bitmap);
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p = new;
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}
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idp->top = p;
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idp->layers = layers;
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v = sub_alloc(idp, ptr, &id);
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if (v == -2)
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goto build_up;
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return(v);
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}
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/**
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* idr_get_new_above - allocate new idr entry above a start id
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* @idp: idr handle
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* @ptr: pointer you want associated with the ide
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* @start_id: id to start search at
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* @id: pointer to the allocated handle
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*
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* This is the allocate id function. It should be called with any
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* required locks.
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*
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* If memory is required, it will return -EAGAIN, you should unlock
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* and go back to the idr_pre_get() call. If the idr is full, it will
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* return -ENOSPC.
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*
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* @id returns a value in the range 0 ... 0x7fffffff
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*/
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int idr_get_new_above(struct idr *idp, void *ptr, int starting_id, int *id)
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{
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int rv;
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rv = idr_get_new_above_int(idp, ptr, starting_id);
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/*
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* This is a cheap hack until the IDR code can be fixed to
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* return proper error values.
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*/
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if (rv < 0) {
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if (rv == -1)
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return -EAGAIN;
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else /* Will be -3 */
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return -ENOSPC;
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}
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*id = rv;
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return 0;
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}
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EXPORT_SYMBOL(idr_get_new_above);
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/**
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* idr_get_new - allocate new idr entry
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* @idp: idr handle
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* @ptr: pointer you want associated with the ide
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* @id: pointer to the allocated handle
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*
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* This is the allocate id function. It should be called with any
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* required locks.
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*
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* If memory is required, it will return -EAGAIN, you should unlock
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* and go back to the idr_pre_get() call. If the idr is full, it will
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* return -ENOSPC.
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*
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* @id returns a value in the range 0 ... 0x7fffffff
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*/
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int idr_get_new(struct idr *idp, void *ptr, int *id)
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{
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int rv;
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rv = idr_get_new_above_int(idp, ptr, 0);
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/*
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* This is a cheap hack until the IDR code can be fixed to
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* return proper error values.
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*/
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if (rv < 0) {
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if (rv == -1)
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return -EAGAIN;
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else /* Will be -3 */
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return -ENOSPC;
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}
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*id = rv;
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return 0;
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}
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EXPORT_SYMBOL(idr_get_new);
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static void idr_remove_warning(int id)
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{
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printk("idr_remove called for id=%d which is not allocated.\n", id);
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dump_stack();
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}
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static void sub_remove(struct idr *idp, int shift, int id)
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{
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struct idr_layer *p = idp->top;
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struct idr_layer **pa[MAX_LEVEL];
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struct idr_layer ***paa = &pa[0];
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int n;
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*paa = NULL;
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*++paa = &idp->top;
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while ((shift > 0) && p) {
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n = (id >> shift) & IDR_MASK;
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__clear_bit(n, &p->bitmap);
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*++paa = &p->ary[n];
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p = p->ary[n];
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shift -= IDR_BITS;
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}
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n = id & IDR_MASK;
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if (likely(p != NULL && test_bit(n, &p->bitmap))){
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__clear_bit(n, &p->bitmap);
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p->ary[n] = NULL;
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while(*paa && ! --((**paa)->count)){
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free_layer(idp, **paa);
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**paa-- = NULL;
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}
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if ( ! *paa )
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idp->layers = 0;
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} else {
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idr_remove_warning(id);
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}
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}
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/**
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* idr_remove - remove the given id and free it's slot
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* idp: idr handle
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* id: uniqueue key
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*/
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void idr_remove(struct idr *idp, int id)
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{
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struct idr_layer *p;
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/* Mask off upper bits we don't use for the search. */
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id &= MAX_ID_MASK;
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sub_remove(idp, (idp->layers - 1) * IDR_BITS, id);
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if ( idp->top && idp->top->count == 1 &&
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(idp->layers > 1) &&
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idp->top->ary[0]){ // We can drop a layer
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p = idp->top->ary[0];
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idp->top->bitmap = idp->top->count = 0;
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free_layer(idp, idp->top);
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idp->top = p;
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--idp->layers;
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}
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while (idp->id_free_cnt >= IDR_FREE_MAX) {
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p = alloc_layer(idp);
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kmem_cache_free(idr_layer_cache, p);
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return;
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}
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}
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EXPORT_SYMBOL(idr_remove);
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/**
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* idr_find - return pointer for given id
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* @idp: idr handle
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* @id: lookup key
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*
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* Return the pointer given the id it has been registered with. A %NULL
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* return indicates that @id is not valid or you passed %NULL in
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* idr_get_new().
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*
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* The caller must serialize idr_find() vs idr_get_new() and idr_remove().
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*/
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void *idr_find(struct idr *idp, int id)
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{
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int n;
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struct idr_layer *p;
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n = idp->layers * IDR_BITS;
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p = idp->top;
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/* Mask off upper bits we don't use for the search. */
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id &= MAX_ID_MASK;
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if (id >= (1 << n))
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return NULL;
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while (n > 0 && p) {
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n -= IDR_BITS;
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p = p->ary[(id >> n) & IDR_MASK];
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}
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return((void *)p);
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}
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EXPORT_SYMBOL(idr_find);
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static void idr_cache_ctor(void * idr_layer,
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kmem_cache_t *idr_layer_cache, unsigned long flags)
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{
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memset(idr_layer, 0, sizeof(struct idr_layer));
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}
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static int init_id_cache(void)
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{
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if (!idr_layer_cache)
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idr_layer_cache = kmem_cache_create("idr_layer_cache",
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sizeof(struct idr_layer), 0, 0, idr_cache_ctor, NULL);
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return 0;
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}
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/**
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* idr_init - initialize idr handle
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* @idp: idr handle
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*
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* This function is use to set up the handle (@idp) that you will pass
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* to the rest of the functions.
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*/
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void idr_init(struct idr *idp)
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{
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init_id_cache();
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memset(idp, 0, sizeof(struct idr));
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spin_lock_init(&idp->lock);
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}
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EXPORT_SYMBOL(idr_init);
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Block a user