/*
- * linux/kernel/id.c
- *
* 2002-10-18 written by Jim Houston jim.houston@ccur.com
* Copyright (C) 2002 by Concurrent Computer Corporation
* Distributed under the GNU GPL license version 2.
*
+ * Modified by George Anzinger to reuse immediately and to use
+ * find bit instructions. Also removed _irq on spinlocks.
+ *
* Small id to pointer translation service.
*
* It uses a radix tree like structure as a sparse array indexed
* by the id to obtain the pointer. The bitmap makes allocating
* a new id quick.
-
- * Modified by George Anzinger to reuse immediately and to use
- * find bit instructions. Also removed _irq on spinlocks.
-
- * So here is what this bit of code does:
-
+ *
* 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
* 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.
-
- * A word on reuse. We reuse empty id slots as soon as we can, always
- * using the lowest one available. But we also merge a counter in the
- * high bits of the id. The counter is RESERVED_ID_BITS (8 at this time)
- * long. This means that if you allocate and release the same id in a
- * loop we will reuse an id after about 256 times around the loop. The
- * word about is used here as we will NOT return a valid id of -1 so if
- * you loop on the largest possible id (and that is 24 bits, wow!) we
- * will kick the counter to avoid -1. (Paranoid? You bet!)
- *
- * What you need to do is, since we don't keep the counter as part of
- * id / ptr pair, to keep a copy of it in the pointed to structure
- * (or else where) so that when you ask for a ptr you can varify that
- * the returned ptr is correct by comparing the id it contains with the one
- * you asked for. In other words, we only did half the reuse protection.
- * Since the code depends on your code doing this check, we ignore high
- * order bits in the id, not just the count, but bits that would, if used,
- * index outside of the allocated ids. In other words, if the largest id
- * currently allocated is 32 a look up will only look at the low 5 bits of
- * the id. Since you will want to keep this id in the structure anyway
- * (if for no other reason than to be able to eliminate the id when the
- * structure is found in some other way) this seems reasonable. If you
- * really think otherwise, the code to check these bits here, it is just
- * disabled with a #if 0.
-
-
- * So here are the complete details:
-
- * include <linux/idr.h>
-
- * void idr_init(struct idr *idp)
-
- * This function is use to set up the handle (idp) that you will pass
- * to the rest of the functions. The structure is defined in the
- * header.
-
- * int idr_pre_get(struct idr *idp, unsigned gfp_mask)
-
- * This function should be called prior to locking and calling the
- * following function. It pre allocates enough memory to satisfy the
- * worst possible allocation. Unless gfp_mask is GFP_ATOMIC, it can
- * sleep, so must not be called with any spinlocks held. If the system is
- * REALLY out of memory this function returns 0, other wise 1.
-
- * int idr_get_new(struct idr *idp, void *ptr);
-
- * This is the allocate id function. It should be called with any
- * required locks. In fact, in the SMP case, you MUST lock prior to
- * calling this function to avoid possible out of memory problems. If
- * memory is required, it will return a -1, in which case you should
- * unlock and go back to the idr_pre_get() call. ptr is the pointer
- * you want associated with the id. In other words:
-
- * void *idr_find(struct idr *idp, int id);
-
- * returns the "ptr", given the id. A NULL return indicates that the
- * id is not valid (or you passed NULL in the idr_get_new(), shame on
- * you). This function must be called with a spinlock that prevents
- * calling either idr_get_new() or idr_remove() or idr_find() while it
- * is working.
-
- * void idr_remove(struct idr *idp, int id);
-
- * removes the given id, freeing that slot and any memory that may
- * now be unused. See idr_find() for locking restrictions.
-
*/
-
-
#ifndef TEST // to test in user space...
#include <linux/slab.h>
#include <linux/init.h>
#include <linux/string.h>
#include <linux/idr.h>
-
static kmem_cache_t *idr_layer_cache;
-
-
static struct idr_layer *alloc_layer(struct idr *idp)
{
struct idr_layer *p;
spin_lock(&idp->lock);
- if (!(p = idp->id_free))
- BUG();
- idp->id_free = p->ary[0];
- idp->id_free_cnt--;
- p->ary[0] = 0;
+ if ((p = idp->id_free)) {
+ idp->id_free = p->ary[0];
+ idp->id_free_cnt--;
+ p->ary[0] = NULL;
+ }
spin_unlock(&idp->lock);
return(p);
}
spin_unlock(&idp->lock);
}
+/**
+ * idr_pre_get - reserver resources for idr allocation
+ * @idp: idr handle
+ * @gfp_mask: memory allocation flags
+ *
+ * This function should be called prior to locking and calling the
+ * following function. It preallocates enough memory to satisfy
+ * the worst possible allocation.
+ *
+ * If the system is REALLY out of memory this function returns 0,
+ * otherwise 1.
+ */
int idr_pre_get(struct idr *idp, unsigned gfp_mask)
{
while (idp->id_free_cnt < IDR_FREE_MAX) {
sh = IDR_BITS*l;
id = ((id >> sh) ^ n ^ m) << sh;
}
- if (id >= MAX_ID_BIT)
- return -1;
+ if ((id >= MAX_ID_BIT) || (id < 0))
+ return -3;
if (l == 0)
break;
/*
return(id);
}
-int idr_get_new_above(struct idr *idp, void *ptr, int starting_id)
+static int idr_get_new_above_int(struct idr *idp, void *ptr, int starting_id)
{
struct idr_layer *p, *new;
int layers, v, id;
* Add a new layer to the top of the tree if the requested
* id is larger than the currently allocated space.
*/
- while (id >= (1 << (layers*IDR_BITS))) {
+ while ((layers < MAX_LEVEL) && (id >= (1 << (layers*IDR_BITS)))) {
layers++;
if (!p->count)
continue;
*/
for (new = p; p && p != idp->top; new = p) {
p = p->ary[0];
- new->ary[0] = 0;
+ new->ary[0] = NULL;
new->bitmap = new->count = 0;
free_layer(idp, new);
}
v = sub_alloc(idp, ptr, &id);
if (v == -2)
goto build_up;
- if ( likely(v >= 0 )) {
- idp->count++;
- v += (idp->count << MAX_ID_SHIFT);
- if ( unlikely( v == -1 ))
- v += (1L << MAX_ID_SHIFT);
- }
return(v);
}
+
+/**
+ * idr_get_new_above - allocate new idr entry above a start id
+ * @idp: idr handle
+ * @ptr: pointer you want associated with the ide
+ * @start_id: id to start search at
+ * @id: pointer to the allocated handle
+ *
+ * This is the allocate id function. It should be called with any
+ * required locks.
+ *
+ * If memory is required, it will return -EAGAIN, you should unlock
+ * and go back to the idr_pre_get() call. If the idr is full, it will
+ * return -ENOSPC.
+ *
+ * @id returns a value in the range 0 ... 0x7fffffff
+ */
+int idr_get_new_above(struct idr *idp, void *ptr, int starting_id, int *id)
+{
+ int rv;
+ rv = idr_get_new_above_int(idp, ptr, starting_id);
+ /*
+ * This is a cheap hack until the IDR code can be fixed to
+ * return proper error values.
+ */
+ if (rv < 0) {
+ if (rv == -1)
+ return -EAGAIN;
+ else /* Will be -3 */
+ return -ENOSPC;
+ }
+ *id = rv;
+ return 0;
+}
EXPORT_SYMBOL(idr_get_new_above);
-int idr_get_new(struct idr *idp, void *ptr)
+/**
+ * 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)
{
- return idr_get_new_above(idp, ptr, 0);
+ int rv;
+ rv = idr_get_new_above_int(idp, ptr, 0);
+ /*
+ * This is a cheap hack until the IDR code can be fixed to
+ * return proper error values.
+ */
+ if (rv < 0) {
+ if (rv == -1)
+ return -EAGAIN;
+ else /* Will be -3 */
+ return -ENOSPC;
+ }
+ *id = rv;
+ return 0;
}
EXPORT_SYMBOL(idr_get_new);
+static void idr_remove_warning(int id)
+{
+ printk("idr_remove called for id=%d which is not allocated.\n", id);
+ dump_stack();
+}
static void sub_remove(struct idr *idp, int shift, int id)
{
struct idr_layer *p = idp->top;
struct idr_layer **pa[MAX_LEVEL];
struct idr_layer ***paa = &pa[0];
+ int n;
*paa = NULL;
*++paa = &idp->top;
while ((shift > 0) && p) {
- int n = (id >> shift) & IDR_MASK;
+ n = (id >> shift) & IDR_MASK;
__clear_bit(n, &p->bitmap);
*++paa = &p->ary[n];
p = p->ary[n];
shift -= IDR_BITS;
}
- if (likely(p != NULL)){
- int n = id & IDR_MASK;
+ n = id & IDR_MASK;
+ if (likely(p != NULL && test_bit(n, &p->bitmap))){
__clear_bit(n, &p->bitmap);
p->ary[n] = NULL;
while(*paa && ! --((**paa)->count)){
}
if ( ! *paa )
idp->layers = 0;
+ } else {
+ idr_remove_warning(id);
}
}
+
+/**
+ * idr_remove - remove the given id and free it's slot
+ * idp: idr handle
+ * id: uniqueue key
+ */
void idr_remove(struct idr *idp, int id)
{
struct idr_layer *p;
+ /* Mask off upper bits we don't use for the search. */
+ id &= MAX_ID_MASK;
+
sub_remove(idp, (idp->layers - 1) * IDR_BITS, id);
if ( idp->top && idp->top->count == 1 &&
(idp->layers > 1) &&
}
EXPORT_SYMBOL(idr_remove);
+/**
+ * idr_find - return pointer for given id
+ * @idp: idr handle
+ * @id: lookup key
+ *
+ * Return the pointer given the id it has been registered with. A %NULL
+ * return indicates that @id is not valid or you passed %NULL in
+ * idr_get_new().
+ *
+ * The caller must serialize idr_find() vs idr_get_new() and idr_remove().
+ */
void *idr_find(struct idr *idp, int id)
{
int n;
n = idp->layers * IDR_BITS;
p = idp->top;
-#if 0
- /*
- * This tests to see if bits outside the current tree are
- * present. If so, tain't one of ours!
- */
- if ( unlikely( (id & ~(~0 << MAX_ID_SHIFT)) >> (n + IDR_BITS)))
- return NULL;
-#endif
+
+ /* Mask off upper bits we don't use for the search. */
+ id &= MAX_ID_MASK;
+
+ if (id >= (1 << n))
+ return NULL;
+
while (n > 0 && p) {
n -= IDR_BITS;
p = p->ary[(id >> n) & IDR_MASK];
{
if (!idr_layer_cache)
idr_layer_cache = kmem_cache_create("idr_layer_cache",
- sizeof(struct idr_layer), 0, 0, idr_cache_ctor, 0);
+ sizeof(struct idr_layer), 0, 0, idr_cache_ctor, NULL);
return 0;
}
+/**
+ * idr_init - initialize idr handle
+ * @idp: idr handle
+ *
+ * This function is use to set up the handle (@idp) that you will pass
+ * to the rest of the functions.
+ */
void idr_init(struct idr *idp)
{
init_id_cache();
spin_lock_init(&idp->lock);
}
EXPORT_SYMBOL(idr_init);
-
git://git.onelab.eu / linux-2.6.git / blobdiff