#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);