#include <linux/bitmap.h> #include <linux/bug.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_u32() - Allocate an ID. * @idr: IDR handle. * @ptr: Pointer to be associated with the new ID. * @nextid: Pointer to an ID. * @max: The maximum ID to allocate (inclusive). * @gfp: Memory allocation flags. * * Allocates an unused ID in the range specified by @nextid and @max. * Note that @max is inclusive whereas the @end parameter to idr_alloc() * is exclusive. The new ID is assigned to @nextid before the pointer * is inserted into the IDR, so if @nextid points into the object pointed * to by @ptr, a concurrent lookup will not find an uninitialised ID. * * The caller should provide their own locking to ensure that two * concurrent modifications to the IDR are not possible. Read-only * accesses to the IDR may be done under the RCU read lock or may * exclude simultaneous writers. * * Return: 0 if an ID was allocated, -ENOMEM if memory allocation failed, * or -ENOSPC if no free IDs could be found. If an error occurred, * @nextid is unchanged. */ int idr_alloc_u32(struct idr *idr, void *ptr, u32 *nextid, unsigned long max, gfp_t gfp) { struct radix_tree_iter iter; void __rcu **slot; int base = idr->idr_base; int id = *nextid; if (WARN_ON_ONCE(radix_tree_is_internal_node(ptr))) return -EINVAL; if (WARN_ON_ONCE(!(idr->idr_rt.gfp_mask & ROOT_IS_IDR))) idr->idr_rt.gfp_mask |= IDR_RT_MARKER; id = (id < base) ? 0 : id - base; radix_tree_iter_init(&iter, id); slot = idr_get_free(&idr->idr_rt, &iter, gfp, max - base); if (IS_ERR(slot)) return PTR_ERR(slot); *nextid = iter.index + base; /* there is a memory barrier inside radix_tree_iter_replace() */ radix_tree_iter_replace(&idr->idr_rt, &iter, slot, ptr); radix_tree_iter_tag_clear(&idr->idr_rt, &iter, IDR_FREE); return 0; } EXPORT_SYMBOL_GPL(idr_alloc_u32); /** * 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 specified by @start and @end. If * @end is <= 0, it is treated as one larger than %INT_MAX. This allows * callers to use @start + N as @end as long as N is within integer range. * * The caller should provide their own locking to ensure that two * concurrent modifications to the IDR are not possible. Read-only * accesses to the IDR may be done under the RCU read lock or may * exclude simultaneous writers. * * Return: The newly allocated ID, -ENOMEM if memory allocation failed, * or -ENOSPC if no free IDs could be found. */ int idr_alloc(struct idr *idr, void *ptr, int start, int end, gfp_t gfp) { u32 id = start; int ret; if (WARN_ON_ONCE(start < 0)) return -EINVAL; ret = idr_alloc_u32(idr, ptr, &id, end > 0 ? end - 1 : INT_MAX, gfp); if (ret) return ret; return id; } EXPORT_SYMBOL_GPL(idr_alloc); /** * idr_alloc_cyclic() - Allocate an ID cyclically. * @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 specified by @nextid and @end. If * @end is <= 0, it is treated as one larger than %INT_MAX. This allows * callers to use @start + N as @end as long as N is within integer range. * The search for an unused ID will start at the last ID allocated and will * wrap around to @start if no free IDs are found before reaching @end. * * The caller should provide their own locking to ensure that two * concurrent modifications to the IDR are not possible. Read-only * accesses to the IDR may be done under the RCU read lock or may * exclude simultaneous writers. * * Return: The newly allocated ID, -ENOMEM if memory allocation failed, * or -ENOSPC if no free IDs could be found. */ int idr_alloc_cyclic(struct idr *idr, void *ptr, int start, int end, gfp_t gfp) { u32 id = idr->idr_next; int err, max = end > 0 ? end - 1 : INT_MAX; if ((int)id < start) id = start; err = idr_alloc_u32(idr, ptr, &id, max, gfp); if ((err == -ENOSPC) && (id > start)) { id = start; err = idr_alloc_u32(idr, ptr, &id, max, gfp); } if (err) return err; idr->idr_next = id + 1; return id; } EXPORT_SYMBOL(idr_alloc_cyclic); /** * idr_remove() - Remove an ID from the IDR. * @idr: IDR handle. * @id: Pointer ID. * * Removes this ID from the IDR. If the ID was not previously in the IDR, * this function returns %NULL. * * Since this function modifies the IDR, the caller should provide their * own locking to ensure that concurrent modification of the same IDR is * not possible. * * Return: The pointer formerly associated with this ID. */ void *idr_remove(struct idr *idr, unsigned long id) { return radix_tree_delete_item(&idr->idr_rt, id - idr->idr_base, NULL); } EXPORT_SYMBOL_GPL(idr_remove); /** * idr_find() - Return pointer for given ID. * @idr: IDR handle. * @id: Pointer ID. * * Looks up the pointer associated with this ID. A %NULL pointer may * indicate that @id is not allocated or that the %NULL pointer was * associated with this ID. * * This function can be called under rcu_read_lock(), given that the leaf * pointers lifetimes are correctly managed. * * Return: The pointer associated with this ID. */ void *idr_find(const struct idr *idr, unsigned long id) { return radix_tree_lookup(&idr->idr_rt, id - idr->idr_base); } EXPORT_SYMBOL_GPL(idr_find); /** * 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 entry and @data. * * 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; int base = idr->idr_base; radix_tree_for_each_slot(slot, &idr->idr_rt, &iter, 0) { int ret; if (WARN_ON_ONCE(iter.index > INT_MAX)) break; ret = fn(iter.index + base, 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 an ID. * * 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; int base = idr->idr_base; int id = *nextid; id = (id < base) ? 0 : id - base; slot = radix_tree_iter_find(&idr->idr_rt, &iter, id); if (!slot) return NULL; id = iter.index + base; if (WARN_ON_ONCE(id > INT_MAX)) return NULL; *nextid = id; return rcu_dereference_raw(*slot); } EXPORT_SYMBOL(idr_get_next); /** * idr_get_next_ul() - Find next populated entry. * @idr: IDR handle. * @nextid: Pointer to an ID. * * 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_ul(struct idr *idr, unsigned long *nextid) { struct radix_tree_iter iter; void __rcu **slot; unsigned long base = idr->idr_base; unsigned long id = *nextid; id = (id < base) ? 0 : id - base; slot = radix_tree_iter_find(&idr->idr_rt, &iter, id); if (!slot) return NULL; *nextid = iter.index + base; return rcu_dereference_raw(*slot); } EXPORT_SYMBOL(idr_get_next_ul); /** * idr_replace() - replace pointer for given ID. * @idr: IDR handle. * @ptr: New pointer to associate with the ID. * @id: ID to change. * * 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: the old value on success. %-ENOENT indicates that @id was not * found. %-EINVAL indicates that @ptr was not valid. */ void *idr_replace(struct idr *idr, void *ptr, unsigned long id) { struct radix_tree_node *node; void __rcu **slot = NULL; void *entry; if (WARN_ON_ONCE(radix_tree_is_internal_node(ptr))) return ERR_PTR(-EINVAL); id -= idr->idr_base; 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); 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 - 1) /** * 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);