diff options
Diffstat (limited to 'lib/idr.c')
| -rw-r--r-- | lib/idr.c | 599 |
1 files changed, 599 insertions, 0 deletions
diff --git a/lib/idr.c b/lib/idr.c new file mode 100644 index 0000000000..da36054c3c --- /dev/null +++ b/lib/idr.c @@ -0,0 +1,599 @@ +// SPDX-License-Identifier: GPL-2.0-only +#include <linux/bitmap.h> +#include <linux/bug.h> +#include <linux/export.h> +#include <linux/idr.h> +#include <linux/slab.h> +#include <linux/spinlock.h> +#include <linux/xarray.h> + +/** + * 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; + unsigned int base = idr->idr_base; + unsigned int id = *nextid; + + if (WARN_ON_ONCE(!(idr->idr_rt.xa_flags & ROOT_IS_IDR))) + idr->idr_rt.xa_flags |= 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 @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 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; + unsigned long id = iter.index + base; + + if (WARN_ON_ONCE(id > INT_MAX)) + break; + ret = fn(id, rcu_dereference_raw(*slot), data); + if (ret) + return ret; + } + + return 0; +} +EXPORT_SYMBOL(idr_for_each); + +/** + * 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; + void *entry = NULL; + unsigned long base = idr->idr_base; + unsigned long id = *nextid; + + id = (id < base) ? 0 : id - base; + radix_tree_for_each_slot(slot, &idr->idr_rt, &iter, id) { + entry = rcu_dereference_raw(*slot); + if (!entry) + continue; + if (!xa_is_internal(entry)) + break; + if (slot != &idr->idr_rt.xa_head && !xa_is_retry(entry)) + break; + slot = radix_tree_iter_retry(&iter); + } + if (!slot) + return NULL; + + *nextid = iter.index + base; + return entry; +} +EXPORT_SYMBOL(idr_get_next_ul); + +/** + * 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) +{ + unsigned long id = *nextid; + void *entry = idr_get_next_ul(idr, &id); + + if (WARN_ON_ONCE(id > INT_MAX)) + return NULL; + *nextid = id; + return entry; +} +EXPORT_SYMBOL(idr_get_next); + +/** + * 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; + + 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); + + 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_alloc(), ida_alloc_min(), ida_alloc_max() or ida_alloc_range(). + * To free an ID, call ida_free(). + * + * 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. + * + * The IDA handles its own locking. It is safe to call any of the IDA + * functions without synchronisation in your code. + * + * 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 XArray to store bitmaps in + * each entry. The XA_FREE_MARK is only cleared when all bits in the bitmap + * have been set. + * + * I considered telling the XArray that each slot is an order-10 node + * and indexing by bit number, but the XArray can't allow a single multi-index + * entry in the head, 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 store the bits + * as a value entry. Value entries never have the XA_FREE_MARK cleared + * because we can always convert them into a bitmap entry. + * + * It would be possible to optimise further; once we've run out of a + * single 128-byte bitmap, we currently switch to a 576-byte node, put + * the 128-byte bitmap in the first entry and then start allocating extra + * 128-byte entries. We could instead use the 512 bytes of the node's + * data as a bitmap before moving to that scheme. I do not believe this + * is a worthwhile optimisation; Rasmus Villemoes surveyed the current + * users of the IDA and almost none of them use more than 1024 entries. + * Those that do use more than the 8192 IDs that the 512 bytes would + * provide. + * + * The IDA always uses 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. + */ + +/** + * ida_alloc_range() - Allocate an unused ID. + * @ida: IDA handle. + * @min: Lowest ID to allocate. + * @max: Highest ID to allocate. + * @gfp: Memory allocation flags. + * + * Allocate an ID between @min and @max, inclusive. The allocated ID will + * not exceed %INT_MAX, even if @max is larger. + * + * Context: Any context. It is safe to call this function without + * locking in your code. + * Return: The allocated ID, or %-ENOMEM if memory could not be allocated, + * or %-ENOSPC if there are no free IDs. + */ +int ida_alloc_range(struct ida *ida, unsigned int min, unsigned int max, + gfp_t gfp) +{ + XA_STATE(xas, &ida->xa, min / IDA_BITMAP_BITS); + unsigned bit = min % IDA_BITMAP_BITS; + unsigned long flags; + struct ida_bitmap *bitmap, *alloc = NULL; + + if ((int)min < 0) + return -ENOSPC; + + if ((int)max < 0) + max = INT_MAX; + +retry: + xas_lock_irqsave(&xas, flags); +next: + bitmap = xas_find_marked(&xas, max / IDA_BITMAP_BITS, XA_FREE_MARK); + if (xas.xa_index > min / IDA_BITMAP_BITS) + bit = 0; + if (xas.xa_index * IDA_BITMAP_BITS + bit > max) + goto nospc; + + if (xa_is_value(bitmap)) { + unsigned long tmp = xa_to_value(bitmap); + + if (bit < BITS_PER_XA_VALUE) { + bit = find_next_zero_bit(&tmp, BITS_PER_XA_VALUE, bit); + if (xas.xa_index * IDA_BITMAP_BITS + bit > max) + goto nospc; + if (bit < BITS_PER_XA_VALUE) { + tmp |= 1UL << bit; + xas_store(&xas, xa_mk_value(tmp)); + goto out; + } + } + bitmap = alloc; + if (!bitmap) + bitmap = kzalloc(sizeof(*bitmap), GFP_NOWAIT); + if (!bitmap) + goto alloc; + bitmap->bitmap[0] = tmp; + xas_store(&xas, bitmap); + if (xas_error(&xas)) { + bitmap->bitmap[0] = 0; + goto out; + } + } + + if (bitmap) { + bit = find_next_zero_bit(bitmap->bitmap, IDA_BITMAP_BITS, bit); + if (xas.xa_index * IDA_BITMAP_BITS + bit > max) + goto nospc; + if (bit == IDA_BITMAP_BITS) + goto next; + + __set_bit(bit, bitmap->bitmap); + if (bitmap_full(bitmap->bitmap, IDA_BITMAP_BITS)) + xas_clear_mark(&xas, XA_FREE_MARK); + } else { + if (bit < BITS_PER_XA_VALUE) { + bitmap = xa_mk_value(1UL << bit); + } else { + bitmap = alloc; + if (!bitmap) + bitmap = kzalloc(sizeof(*bitmap), GFP_NOWAIT); + if (!bitmap) + goto alloc; + __set_bit(bit, bitmap->bitmap); + } + xas_store(&xas, bitmap); + } +out: + xas_unlock_irqrestore(&xas, flags); + if (xas_nomem(&xas, gfp)) { + xas.xa_index = min / IDA_BITMAP_BITS; + bit = min % IDA_BITMAP_BITS; + goto retry; + } + if (bitmap != alloc) + kfree(alloc); + if (xas_error(&xas)) + return xas_error(&xas); + return xas.xa_index * IDA_BITMAP_BITS + bit; +alloc: + xas_unlock_irqrestore(&xas, flags); + alloc = kzalloc(sizeof(*bitmap), gfp); + if (!alloc) + return -ENOMEM; + xas_set(&xas, min / IDA_BITMAP_BITS); + bit = min % IDA_BITMAP_BITS; + goto retry; +nospc: + xas_unlock_irqrestore(&xas, flags); + kfree(alloc); + return -ENOSPC; +} +EXPORT_SYMBOL(ida_alloc_range); + +/** + * ida_free() - Release an allocated ID. + * @ida: IDA handle. + * @id: Previously allocated ID. + * + * Context: Any context. It is safe to call this function without + * locking in your code. + */ +void ida_free(struct ida *ida, unsigned int id) +{ + XA_STATE(xas, &ida->xa, id / IDA_BITMAP_BITS); + unsigned bit = id % IDA_BITMAP_BITS; + struct ida_bitmap *bitmap; + unsigned long flags; + + if ((int)id < 0) + return; + + xas_lock_irqsave(&xas, flags); + bitmap = xas_load(&xas); + + if (xa_is_value(bitmap)) { + unsigned long v = xa_to_value(bitmap); + if (bit >= BITS_PER_XA_VALUE) + goto err; + if (!(v & (1UL << bit))) + goto err; + v &= ~(1UL << bit); + if (!v) + goto delete; + xas_store(&xas, xa_mk_value(v)); + } else { + if (!bitmap || !test_bit(bit, bitmap->bitmap)) + goto err; + __clear_bit(bit, bitmap->bitmap); + xas_set_mark(&xas, XA_FREE_MARK); + if (bitmap_empty(bitmap->bitmap, IDA_BITMAP_BITS)) { + kfree(bitmap); +delete: + xas_store(&xas, NULL); + } + } + xas_unlock_irqrestore(&xas, flags); + return; + err: + xas_unlock_irqrestore(&xas, flags); + WARN(1, "ida_free called for id=%d which is not allocated.\n", id); +} +EXPORT_SYMBOL(ida_free); + +/** + * ida_destroy() - Free all IDs. + * @ida: IDA handle. + * + * Calling this function frees all IDs and releases all resources used + * by an IDA. When this call returns, the IDA is empty and can be reused + * or freed. If the IDA is already empty, there is no need to call this + * function. + * + * Context: Any context. It is safe to call this function without + * locking in your code. + */ +void ida_destroy(struct ida *ida) +{ + XA_STATE(xas, &ida->xa, 0); + struct ida_bitmap *bitmap; + unsigned long flags; + + xas_lock_irqsave(&xas, flags); + xas_for_each(&xas, bitmap, ULONG_MAX) { + if (!xa_is_value(bitmap)) + kfree(bitmap); + xas_store(&xas, NULL); + } + xas_unlock_irqrestore(&xas, flags); +} +EXPORT_SYMBOL(ida_destroy); + +#ifndef __KERNEL__ +extern void xa_dump_index(unsigned long index, unsigned int shift); +#define IDA_CHUNK_SHIFT ilog2(IDA_BITMAP_BITS) + +static void ida_dump_entry(void *entry, unsigned long index) +{ + unsigned long i; + + if (!entry) + return; + + if (xa_is_node(entry)) { + struct xa_node *node = xa_to_node(entry); + unsigned int shift = node->shift + IDA_CHUNK_SHIFT + + XA_CHUNK_SHIFT; + + xa_dump_index(index * IDA_BITMAP_BITS, shift); + xa_dump_node(node); + for (i = 0; i < XA_CHUNK_SIZE; i++) + ida_dump_entry(node->slots[i], + index | (i << node->shift)); + } else if (xa_is_value(entry)) { + xa_dump_index(index * IDA_BITMAP_BITS, ilog2(BITS_PER_LONG)); + pr_cont("value: data %lx [%px]\n", xa_to_value(entry), entry); + } else { + struct ida_bitmap *bitmap = entry; + + xa_dump_index(index * IDA_BITMAP_BITS, IDA_CHUNK_SHIFT); + pr_cont("bitmap: %p data", bitmap); + for (i = 0; i < IDA_BITMAP_LONGS; i++) + pr_cont(" %lx", bitmap->bitmap[i]); + pr_cont("\n"); + } +} + +static void ida_dump(struct ida *ida) +{ + struct xarray *xa = &ida->xa; + pr_debug("ida: %p node %p free %d\n", ida, xa->xa_head, + xa->xa_flags >> ROOT_TAG_SHIFT); + ida_dump_entry(xa->xa_head, 0); +} +#endif |