| #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 **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 **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 **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 **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 **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 **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 **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); |