#include <linux/bitmap.h>
#include <linux/export.h>
#include <linux/idr.h>
#include <linux/slab.h>
#include <linux/spinlock.h>
DEFINE_PER_CPU(struct ida_bitmap *, ida_bitmap);
static DEFINE_SPINLOCK(simple_ida_lock);
/**
* idr_alloc - allocate an id
* @idr: idr handle
* @ptr: pointer to be associated with the new id
* @start: the minimum id (inclusive)
* @end: the maximum id (exclusive)
* @gfp: memory allocation flags
*
* Allocates an unused ID in the range [start, end). Returns -ENOSPC
* if there are no unused IDs in that range.
*
* 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.
*
* Simultaneous modifications to the @idr are not allowed and should be
* prevented by the user, usually with a lock. idr_alloc() may be called
* concurrently with read-only accesses to the @idr, such as idr_find() and
* idr_for_each_entry().
*/
int idr_alloc(struct idr *idr, void *ptr, int start, int end, gfp_t gfp)
{
void __rcu **slot;
struct radix_tree_iter iter;
if (WARN_ON_ONCE(start < 0))
return -EINVAL;
if (WARN_ON_ONCE(radix_tree_is_internal_node(ptr)))
return -EINVAL;
radix_tree_iter_init(&iter, start);
slot = idr_get_free(&idr->idr_rt, &iter, gfp, end);
if (IS_ERR(slot))
return PTR_ERR(slot);
radix_tree_iter_replace(&idr->idr_rt, &iter, slot, ptr);
radix_tree_iter_tag_clear(&idr->idr_rt, &iter, IDR_FREE);
return iter.index;
}
EXPORT_SYMBOL_GPL(idr_alloc);
/**
* idr_alloc_cyclic - allocate new idr entry in a cyclical fashion
* @idr: idr handle
* @ptr: pointer to be associated with the new id
* @start: the minimum id (inclusive)
* @end: the maximum id (exclusive)
* @gfp: memory allocation flags
*
* Allocates an ID larger than the last ID allocated if one is available.
* If not, it will attempt to allocate the smallest ID that is larger or
* equal to @start.
*/
int idr_alloc_cyclic(struct idr *idr, void *ptr, int start, int end, gfp_t gfp)
{
int id, curr = idr->idr_next;
if (curr < start)
curr = start;
id = idr_alloc(idr, ptr, curr, end, gfp);
if ((id == -ENOSPC) && (curr > start))
id = idr_alloc(idr, ptr, start, curr, gfp);
if (id >= 0)
idr->idr_next = id + 1U;
return id;
}
EXPORT_SYMBOL(idr_alloc_cyclic);
/**
* idr_for_each - iterate through all stored pointers
* @idr: idr handle
* @fn: function to be called for each pointer
* @data: data passed to callback function
*
* The callback function will be called for each entry in @idr, passing
* the id, the pointer and the data pointer passed to this function.
*
* If @fn returns anything other than %0, the iteration stops and that
* value is returned from this function.
*
* idr_for_each() can be called concurrently with idr_alloc() and
* idr_remove() if protected by RCU. Newly added entries may not be
* seen and deleted entries may be seen, but adding and removing entries
* will not cause other entries to be skipped, nor spurious ones to be seen.
*/
int idr_for_each(const struct idr *idr,
int (*fn)(int id, void *p, void *data), void *data)
{
struct radix_tree_iter iter;
void __rcu **slot;
radix_tree_for_each_slot(slot, &idr->idr_rt, &iter, 0) {
int ret = fn(iter.index, rcu_dereference_raw(*slot), data);
if (ret)
return ret;
}
return 0;
}
EXPORT_SYMBOL(idr_for_each);
/**
* idr_get_next - Find next populated entry
* @idr: idr handle
* @nextid: Pointer to lowest possible ID to return
*
* Returns the next populated entry in the tree with an ID greater than
* or equal to the value pointed to by @nextid. On exit, @nextid is updated
* to the ID of the found value. To use in a loop, the value pointed to by
* nextid must be incremented by the user.
*/
void *idr_get_next(struct idr *idr, int *nextid)
{
struct radix_tree_iter iter;
void __rcu **slot;
slot = radix_tree_iter_find(&idr->idr_rt, &iter, *nextid);
if (!slot)
return NULL;
*nextid = iter.index;
return rcu_dereference_raw(*slot);
}
EXPORT_SYMBOL(idr_get_next);
/**
* idr_replace - replace pointer for given id
* @idr: idr handle
* @ptr: New pointer to associate with the ID
* @id: Lookup key
*
* Replace the pointer registered with an ID and return the old value.
* This function can be called under the RCU read lock concurrently with
* idr_alloc() and idr_remove() (as long as the ID being removed is not
* the one being replaced!).
*
* Returns: 0 on success. %-ENOENT indicates that @id was not found.
* %-EINVAL indicates that @id or @ptr were not valid.
*/
void *idr_replace(struct idr *idr, void *ptr, int id)
{
struct radix_tree_node *node;
void __rcu **slot = NULL;
void *entry;
if (WARN_ON_ONCE(id < 0))
return ERR_PTR(-EINVAL);
if (WARN_ON_ONCE(radix_tree_is_internal_node(ptr)))
return ERR_PTR(-EINVAL);
entry = __radix_tree_lookup(&idr->idr_rt, id, &node, &slot);
if (!slot || radix_tree_tag_get(&idr->idr_rt, id, IDR_FREE))
return ERR_PTR(-ENOENT);
__radix_tree_replace(&idr->idr_rt, node, slot, ptr, NULL, NULL);
return entry;
}
EXPORT_SYMBOL(idr_replace);
/**
* DOC: IDA description
*
* The IDA is an ID allocator which does not provide the ability to
* associate an ID with a pointer. As such, it only needs to store one
* bit per ID, and so is more space efficient than an IDR. To use an IDA,
* define it using DEFINE_IDA() (or embed a &struct ida in a data structure,
* then initialise it using ida_init()). To allocate a new ID, call
* ida_simple_get(). To free an ID, call ida_simple_remove().
*
* If you have more complex locking requirements, use a loop around
* ida_pre_get() and ida_get_new() to allocate a new ID. Then use
* ida_remove() to free an ID. You must make sure that ida_get_new() and
* ida_remove() cannot be called at the same time as each other for the
* same IDA.
*
* You can also use ida_get_new_above() if you need an ID to be allocated
* above a particular number. ida_destroy() can be used to dispose of an
* IDA without needing to free the individual IDs in it. You can use
* ida_is_empty() to find out whether the IDA has any IDs currently allocated.
*
* IDs are currently limited to the range [0-INT_MAX]. If this is an awkward
* limitation, it should be quite straightforward to raise the maximum.
*/
/*
* Developer's notes:
*
* The IDA uses the functionality provided by the IDR & radix tree to store
* bitmaps in each entry. The IDR_FREE tag means there is at least one bit
* free, unlike the IDR where it means at least one entry is free.
*
* I considered telling the radix tree that each slot is an order-10 node
* and storing the bit numbers in the radix tree, but the radix tree can't
* allow a single multiorder entry at index 0, which would significantly
* increase memory consumption for the IDA. So instead we divide the index
* by the number of bits in the leaf bitmap before doing a radix tree lookup.
*
* As an optimisation, if there are only a few low bits set in any given
* leaf, instead of allocating a 128-byte bitmap, we use the 'exceptional
* entry' functionality of the radix tree to store BITS_PER_LONG - 2 bits
* directly in the entry. By being really tricksy, we could store
* BITS_PER_LONG - 1 bits, but there're diminishing returns after optimising
* for 0-3 allocated IDs.
*
* We allow the radix tree 'exceptional' count to get out of date. Nothing
* in the IDA nor the radix tree code checks it. If it becomes important
* to maintain an accurate exceptional count, switch the rcu_assign_pointer()
* calls to radix_tree_iter_replace() which will correct the exceptional
* count.
*
* The IDA always requires a lock to alloc/free. If we add a 'test_bit'
* equivalent, it will still need locking. Going to RCU lookup would require
* using RCU to free bitmaps, and that's not trivial without embedding an
* RCU head in the bitmap, which adds a 2-pointer overhead to each 128-byte
* bitmap, which is excessive.
*/
#define IDA_MAX (0x80000000U / IDA_BITMAP_BITS)
/**
* ida_get_new_above - allocate new ID above or equal to a start id
* @ida: ida handle
* @start: id to start search at
* @id: pointer to the allocated handle
*
* Allocate new ID above or equal to @start. It should be called
* with any required locks to ensure that concurrent calls to
* ida_get_new_above() / ida_get_new() / ida_remove() are not allowed.
* Consider using ida_simple_get() if you do not have complex locking
* requirements.
*
* 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. On success, it will return 0.
*
* @id returns a value in the range @start ... %0x7fffffff.
*/
int ida_get_new_above(struct ida *ida, int start, int *id)
{
struct radix_tree_root *root = &ida->ida_rt;
void __rcu **slot;
struct radix_tree_iter iter;
struct ida_bitmap *bitmap;
unsigned long index;
unsigned bit, ebit;
int new;
index = start / IDA_BITMAP_BITS;
bit = start % IDA_BITMAP_BITS;
ebit = bit + RADIX_TREE_EXCEPTIONAL_SHIFT;
slot = radix_tree_iter_init(&iter, index);
for (;;) {
if (slot)
slot = radix_tree_next_slot(slot, &iter,
RADIX_TREE_ITER_TAGGED);
if (!slot) {
slot = idr_get_free(root, &iter, GFP_NOWAIT, IDA_MAX);
if (IS_ERR(slot)) {
if (slot == ERR_PTR(-ENOMEM))
return -EAGAIN;
return PTR_ERR(slot);
}
}
if (iter.index > index) {
bit = 0;
ebit = RADIX_TREE_EXCEPTIONAL_SHIFT;
}
new = iter.index * IDA_BITMAP_BITS;
bitmap = rcu_dereference_raw(*slot);
if (radix_tree_exception(bitmap)) {
unsigned long tmp = (unsigned long)bitmap;
ebit = find_next_zero_bit(&tmp, BITS_PER_LONG, ebit);
if (ebit < BITS_PER_LONG) {
tmp |= 1UL << ebit;
rcu_assign_pointer(*slot, (void *)tmp);
*id = new + ebit - RADIX_TREE_EXCEPTIONAL_SHIFT;
return 0;
}
bitmap = this_cpu_xchg(ida_bitmap, NULL);
if (!bitmap)
return -EAGAIN;
memset(bitmap, 0, sizeof(*bitmap));
bitmap->bitmap[0] = tmp >> RADIX_TREE_EXCEPTIONAL_SHIFT;
rcu_assign_pointer(*slot, bitmap);
}
if (bitmap) {
bit = find_next_zero_bit(bitmap->bitmap,
IDA_BITMAP_BITS, bit);
new += bit;
if (new < 0)
return -ENOSPC;
if (bit == IDA_BITMAP_BITS)
continue;
__set_bit(bit, bitmap->bitmap);
if (bitmap_full(bitmap->bitmap, IDA_BITMAP_BITS))
radix_tree_iter_tag_clear(root, &iter,
IDR_FREE);
} else {
new += bit;
if (new < 0)
return -ENOSPC;
if (ebit < BITS_PER_LONG) {
bitmap = (void *)((1UL << ebit) |
RADIX_TREE_EXCEPTIONAL_ENTRY);
radix_tree_iter_replace(root, &iter, slot,
bitmap);
*id = new;
return 0;
}
bitmap = this_cpu_xchg(ida_bitmap, NULL);
if (!bitmap)
return -EAGAIN;
memset(bitmap, 0, sizeof(*bitmap));
__set_bit(bit, bitmap->bitmap);
radix_tree_iter_replace(root, &iter, slot, bitmap);
}
*id = new;
return 0;
}
}
EXPORT_SYMBOL(ida_get_new_above);
/**
* ida_remove - Free the given ID
* @ida: ida handle
* @id: ID to free
*
* This function should not be called at the same time as ida_get_new_above().
*/
void ida_remove(struct ida *ida, int id)
{
unsigned long index = id / IDA_BITMAP_BITS;
unsigned offset = id % IDA_BITMAP_BITS;
struct ida_bitmap *bitmap;
unsigned long *btmp;
struct radix_tree_iter iter;
void __rcu **slot;
slot = radix_tree_iter_lookup(&ida->ida_rt, &iter, index);
if (!slot)
goto err;
bitmap = rcu_dereference_raw(*slot);
if (radix_tree_exception(bitmap)) {
btmp = (unsigned long *)slot;
offset += RADIX_TREE_EXCEPTIONAL_SHIFT;
if (offset >= BITS_PER_LONG)
goto err;
} else {
btmp = bitmap->bitmap;
}
if (!test_bit(offset, btmp))
goto err;
__clear_bit(offset, btmp);
radix_tree_iter_tag_set(&ida->ida_rt, &iter, IDR_FREE);
if (radix_tree_exception(bitmap)) {
if (rcu_dereference_raw(*slot) ==
(void *)RADIX_TREE_EXCEPTIONAL_ENTRY)
radix_tree_iter_delete(&ida->ida_rt, &iter, slot);
} else if (bitmap_empty(btmp, IDA_BITMAP_BITS)) {
kfree(bitmap);
radix_tree_iter_delete(&ida->ida_rt, &iter, slot);
}
return;
err:
WARN(1, "ida_remove called for id=%d which is not allocated.\n", id);
}
EXPORT_SYMBOL(ida_remove);
/**
* ida_destroy - Free the contents of an ida
* @ida: ida handle
*
* Calling this function releases all resources associated with an IDA. When
* this call returns, the IDA is empty and can be reused or freed. The caller
* should not allow ida_remove() or ida_get_new_above() to be called at the
* same time.
*/
void ida_destroy(struct ida *ida)
{
struct radix_tree_iter iter;
void __rcu **slot;
radix_tree_for_each_slot(slot, &ida->ida_rt, &iter, 0) {
struct ida_bitmap *bitmap = rcu_dereference_raw(*slot);
if (!radix_tree_exception(bitmap))
kfree(bitmap);
radix_tree_iter_delete(&ida->ida_rt, &iter, slot);
}
}
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);
